Neuro anatomy🧠 Flashcards

Question

What are the parts of the brainstem?

Answer 1

-Midbrain -Pons -Medulla oblongata

Answer 2

The most superior part of the brainstem where the crus cerebri are located.

Answer 3

The large, bulbous, central part of the brainstem

Answer 4

The most inferior part of the brainstem that tapers down to become the spinal cord inferiorly.

Answer 5

Most posteriorly in the frontal lobe is the primary motor cortex which is located immediately anterior to the central sulcus. This part of the cortex is involved in execution of motor function (movement).

Answer 6

Immediately anterior to the primary motor cortex is the premotor cortex which is responsible for preparation and planning of movements.

Answer 7

More anterior than the premotor cortex. This area is involved in personality, behaviour, problem solving, impulse control and inhibition, and social and sexual behaviour.

Answer 8

Broca’s area is found at the inferior frontal lobe of the dominant hemisphere (normally the left) and is important for spoken language production

Answer 9

The parietal lobe extends from the central sulcus (anteriorly) to the parietooccipital fissure (posteriorly).

Answer 10

Immediately posterior to the central sulcus It is responsible for interpretation of sensory information

Answer 11

The dominant parietal lobe (normally the left) is important for perception, and mathematical and language operations

Answer 12

The non-dominant parietal lobe (normally the right) is important for visuospatial functions.

Answer 13

Immediately below the lateral sulcus in the temporal lobe is the primary auditory cortex which is responsible for interpretation of auditory information

Answer 14

Inferior and medially in the temporal lobe is the hippocampus which is instrumental in the formation of memory.

Answer 15

The amygdala is also located deep within the temporal lobe, and it has a role in the perception of fear

Answer 16

Wernicke’s area is located in the most superior and posterior part of the dominant temporal lobe. It is important in understanding and coordinating spoken language.

Answer 17

The most posterior part of the cerebrum is the occipital lobe, and it contains the primary visual cortex

Answer 18

Responsible for interpreting visual information received via the optic nerves giving us the perception of sight.

Answer 19

The limbic system is a group of structures found in the medial margins of the hemispheres including the hippocampus, amygdala and various parts of the cortex. It also includes parts of the diencephalon

Answer 20

As a group, they are involved in emotion, memory and behaviour. It has influence over the endocrine functions of the body and parts of it are specifically related to the sensations of fear, pleasure and rewarding behaviours

Answer 21

Being aware of the functions of each lobe of the brain allows clinicians to localise a problem within a patient’s brain before confirming this with neuroimaging (such as CT or MRI scans). For example, if a patient is suspected to have suffered a stroke (disruption to blood supply to a part of the brain) and one of their symptoms is blindness, this could indicate that the occipital lobe is affected. Similarly, if their symptoms are paralysis of their right side and slurring of speech, this may indicate the left frontal lobe is affected.

Answer 22

Within the primary motor and sensory cortices, different parts of the body are represented by different parts of the gyri. When displayed pictorially, this ‘mapping’ of specific parts of the body to parts of the cortex is called a homunculus. There is a homunculus for the motor and sensory cortices, but they are largely similar.

Answer 23

On the lateral aspects of the primary motor and somatosensory cortices

Answer 24

The most superior part of the cortex.

Answer 25

Most medial parts of the cortices (deep in the longitudinal fissure)

Answer 26

It is relevant when discussing lesions affecting the cortex, such as a stroke, which may only affect the lateral aspect of the hemisphere, instead of the superior or medial aspects, for example.

Answer 27

The meninges are three layers of tissue that envelop the brain and spinal cord. Their full names include ‘mater’ but clinically, they are often referred to by just their first part.

Answer 28

Most external, lying against the skull. It is fibrous, thick and does not stretch.

Answer 29

The intermediate layer, it is much thinner and more flexible and resembles a spider’s web, hence the name

Answer 30

Most internal, it lies on the surface of the brain. It is very thin such that it cannot be seen with the naked eye.

Answer 31

* The outer endosteal layer is adherent to the interior of the skull. * The inner meningeal layer completely envelops the brain and spinal cord.

Answer 32

The meningeal layer peels away from the endosteal layer in certain places and folds down into the brain to form a double layer of dura that separates certain parts of the brain.

Answer 33

A double layer of folded dura lying in the longitudinal fissure that separates the two cerebral hemispheres.

Answer 34

The tentorium cerebelli is a double layer of folded dura that separates the occipital lobe from the cerebellum

Answer 35

The falx cerebelli, like the falx cerebri, separates the two lobes the cerebellum. It is, however, much less pronounced

Answer 36

There are small channels where the outer endosteal layer and inner meningeal layer of the dura are briefly apart from each other, or where the inner meningeal layer folds back on itself leaving a small space. These channels are filled with venous blood

Answer 37

Formed in the space between the two layers of the dura, this sinus is located superiorly and runs the along the top of the brain in the sagittal plane.

Answer 38

This is a smaller version of the superior sagittal sinus and runs in the same direction but is located inferior to it. It is formed as the meningeal layer of dura that forms the falx cerebri folds back on itself in the longitudinal fissure. It lies on top of the corpus callosum.

Answer 39

This dural venous sinus is found where the falx cerebri connects to the tentorium cerebelli posteriorly and allows venous blood to drain backwards from the inferior sagittal sinus.

Answer 40

Found on both lateral aspects extending from the tentorium cerebelli around the side of the skull.

Answer 41

These s-shaped sinuses connect the transverse sinuses to the internal jugular veins outside the skull to drain venous blood from the brain

Answer 42

Where the straight sinus meets the transverse sinuses and the superior sagittal sinus. It is found at the most posterior aspect of the skull and often leaves an impression in the internal aspect of the skull.

Answer 43

These ‘cave-like’ sinuses are found anteriorly, either side of the sella turcica of the sphenoid bone. The internal carotid artery passes through it, along with some important nerves.

Answer 44

The arachnoid is a single layer that loosely follows the contours of the meningeal layer of the dura. During dissection, it resembles a very thin, transparent layer of cling film.

Answer 45

Between the arachnoid and the pia below is the subarachnoid space which contains cerebrospinal fluid (CSF).

Answer 46

In some areas, the arachnoid spans between the gyri of the brain, leaving a covering over the sulcus. This forms a sealed space filled with CSF. These spaces are known as ‘cisterns’.

Answer 47

As mentioned, the pia is so thin it cannot be seen without a microscope. It is tightly adhered to the brain and spinal cord and plays a vital role in forming the blood-brain barrier

Answer 48

At the capillary level, the pia fuses with the endothelial cells of the capillaries, forming a specialised layer of pia and endothelial cells known as the blood-brain barrier It limits the passage of certain molecules into the brain and spinal cord to protect them from harmful substances

Answer 49

1. The endothelial cells are tightly bonded together to prevent molecules passing between them. 2. The basement membrane of the capillaries in the brain and spinal cord lacks fenestrations (small holes) that are found elsewhere in the body. 3. Further specialised cells known as ‘pericytes’ wrap around the endothelial cells to regulate blood flow and permeability. 4. CNS cells called ‘astrocytes’ have specialised projections called ‘end feet’ that further wrap around the capillaries to restrict flow of certain molecules.

Answer 50

Inflammation of the meningeal layers is called meningitis. It is often caused by infection due to a viral or bacterial organism. Symptoms include headache, stiffness of the neck and photophobia (bright lights causing discomfort). Viral meningitis usually causes more mild symptoms and resolves on its own. Bacterial meningitis is much more serious and requires treatment with intravenous antibiotics. To confirm the diagnosis, a sample of CSF is required to be tested. To collect this, a small needle is inserted into the subarachnoid space in the lumbar region of the spine. This is known as a lumbar puncture or ‘spinal tap’.

Answer 51

Spontaneously, or after head trauma, bleeding can occur between the meningeal layers. The three main types of bleeds are: Extradural haemorrage Subdural haematoma Subarachnoid haemorrhage

Answer 52

Blood is located outside the dura, but inside the skull. The characteristic pattern on a CT scan is that of an oval or convex shape, often located at the lateral aspect of the brain. The reason the blood forms this shape is because the endosteal layer of the dura is tightly stuck to the inside of the skull, meaning blood trapped outside of it bulges inwards and cannot spread around the side of the brain. Extradural blood is arterial, and a common cause of an extradural haemorrhage is traumatic damage to the middle meningeal artery located on the lateral aspects of the skull. This region is sometimes referred to as the ‘temple’

Answer 53

Blood is located deep to the dura, but superficial to the arachnoid. The characteristic pattern on a CT scan is that of a crescent or concave shape, often located at the lateral aspect of the brain. Unlike in the extradural space, the arachnoid and dura are not adherent to each other, so blood can easily spread around the sides of the brain causing the crescent appearance. Subdural blood is venous, and bleeding is often caused because of stretching of bridging veins that are carrying venous blood from the brain to the dural venous sinuses. Any process or illness that causes the brain to shrink in size causes these bridging veins to become stretched, which is why subdural haematomas are more common in the elderly or patients suffering from alcoholism.

Answer 54

Blood is located deep to the arachnoid, but superficial to the pia. Blood leaks into the subarachnoid cisterns, mixing with the CSF, sometimes causing a white star-shaped pattern on a CT scan. Subarachnoid blood is usually arterial and may be caused by a traumatic head injury or rupture of an aneurysm of one of the cerebral arteries. The classic symptom at presentation of spontaneous subarachnoid haemorrhage is sudden-onset severe headache, often termed a ‘thunderclap’ headache. Diagnosis may be confirmed by CT scan or by the presence of blood in the CSF. This can be sampled with a lumbar puncture.

Answer 55

A haemorrhage is an active bleed, whereas a haematoma is a collection of blood without active bleeding

Answer 56

The main complication of bleeding inside the skull is the resultant increase in intracranial pressure. As the skull is a fixed size in adults, and cannot expand, if there is a build-up of blood inside it, the brain becomes compressed. Eventually, this will lead to impairment of functions of the brain, and ultimately, death

Answer 57

The classic presentation of an extradural haemorrhage, for example, is that of a patient who sustains a head injury, and then retains consciousness for a ‘lucid’ period, before becoming comatose. This is explained by the brain initially compensating for the bleed by becoming compressed, but eventually, it reaches its limit of compensation, and the patient loses consciousness. If a collection of blood or another space-occupying lesion, such as a tumour, is causing compression of the brain, you may be able to see a deviated falx cerebri or compressed lateral ventricle on at CT scan

Answer 58

As intracranial contents are compressed by the build-up of pressure inside the skull, parts of the brain may be pushed aside and can herniate into other areas.

Answer 59

For example, part of the temporal lobe called the uncus may be forced under the tentorium cerebelli (uncal herniation), or certain parts of the cerebellum called tonsils may be forced out of the foramen magnum (tonsillar herniation).

Answer 60

This pressure will restrict blood supply to compressed parts of the brain, and is often fatal if not treated promptly

Answer 61

The arterial supply to the brain comes from two pairs of arteries: the internal carotid arteries, and the vertebral arteries The vertebral arteries supply approximately 20% of blood to the brain, mainly the posterior parts such as the occipital lobe, cerebellum and brainstem. The internal carotid arteries supply the remaining 80% including the rest of the cerebrum and diencephalon.

Answer 62

The internal carotid and vertebral arteries ascend in the neck and enter the skull, they form a circular network known as the circle of Willis, or cerebral arterial circle This network of arteries can be seen on the inferior surface of the brain lying on the brainstem and frontal lobe

Answer 63

ascending upwards from the neck.

Answer 64

Ascending upwards through the cervical vertebrae

Answer 65

A singular artery formed by the unison of the two vertebral arteries. It gives off small pontine arteries to supply the brainstem as it travels along its surface

Answer 66

Formed by the bifurcation of the basilar artery, these arteries pass posteriorly after their formation

Answer 67

The continuation of the internal carotid arteries after they have entered the skull. These arteries pass into the lateral sulcus and give off many branches to both superficial and deep brain tissue.

Answer 68

Branches of the internal carotid arteries as they enter the skull. These arteries pass anteriorly and then wrap backwards over the corpus callosum.

Answer 69

Branches of the internal carotid arteries as they enter the skull. These arteries pass anteriorly and then wrap backwards over the corpus callosum.

Answer 70

Joins the left and right anterior cerebral arteries

Answer 71

o Anterior inferior cerebellar arteries (AICA). o Posterior inferior cerebellar arteries (PICA). o Superior cerebellar arteries (SCA).

Answer 72

The major arteries of the circle of Willis supply a specific area of the brain. It is important to know which parts they supply as this can help identify which artery is likely to be compromised if certain neurological functions are lost in patients who have suffered a stroke

Answer 73

These vessels supply the medial aspects of the frontal and parietal lobes, and a strip of cortex on the superior aspect. This includes the motor and somatosensory cortex responsible for the lower limbs. They also supply some of the anterior structures of the diencephalon

Answer 74

These large vessels supply the vast majority of the lateral aspects (outside) and deep parts of the hemispheres. This includes the parts of the motor and somatosensory cortices responsible for the face, arms and trunk, and a structure called the internal capsule that transmits all fibres to and from the cortices. The MCA also supplies some of the structures of the diencephalon.

Answer 75

These vessels mainly supply the occipital lobe which contains the visual cortex, but also a small portion of the inferior temporal lobe.

Answer 76

This large singular vessel carries arterial blood from the vertebral arteries to the circle of Willis. It gives off small branches to supply the pons. As the pons forms part of the pathway of between the brain and spinal cord, disruption of the basilar artery can potentially threaten the function of all ascending and descending fibres including all motor control and sensation from the neck down.

Answer 77

These vessels mainly supply the cerebellum, but in addition to the basilar artery, they also supply parts of the brainstem.

Answer 78

including the anterior and middle cerebral arteries

Answer 79

Including the posterior cerebral, basilar and cerebellar arteries

Answer 80

A stroke is an interruption to the blood supply of part of the brain leading to a neurological deficit that lasts longer than 24 hours. Strokes may be ischaemic (caused by obstruction of a vessel by a thrombus or embolus and subsequent downstream ischaemia) or haemorrhagic (caused by rupture of a blood vessel leading to compression of nearby structures by the accumulation of blood).

Answer 81

Aneurysms are deformities in arterial vessel walls causing them to balloon and make them prone to rupture. Berry aneurysms, named after their characteristic appearance, may be found in the cerebral circulation on the sides of cerebral arteries. They are often asymptomatic until they rupture. A ruptured berry aneurysm most often causes a subarachnoid haemorrhage, leaking arterial blood into the subarachnoid space. Symptoms include a severe, sudden-onset headache, vomiting or a reduction in a patient’s conscious level.

Answer 82

The venous drainage of the brain is unique in that venous blood is drained from smaller cerebral veins into large dural venous sinuses before passing back into veins to be returned to the heart

Answer 83

* Cerebral venous blood first drains into internal cerebral veins, which are located deep within the brain tissue. * The internal cerebral veins then drain into larger external cerebral veins which can be seen on the surface of the brain. * The external cerebral veins then drain into the dural venous sinuses * The dural venous sinuses can drain the blood into extracranial veins

Answer 84

o The sigmoid sinuses become the internal jugular veins as they exit the skull. o Emissary veins cross the endosteal layer of dura and drain the venous blood into the bones of the skull.

Answer 85

One of the dural venous sinuses that is found behind the orbit (eye socket) on both sides is called the cavernous sinus.

Answer 86

It is clinically relevant because the internal carotid artery and several important nerves pass through it: the oculomotor nerve (CN III), trochlear nerve (CN IV), ophthalmic nerve (CN V1), maxillary nerve (CN V2) and abducens nerve (CN VI). Venous blood draining from the face can potentially drain into the cavernous sinus, thereby providing a connection for superficial infection of the face to reach intracranial structures. Infection in the cavernous sinus can lead to meningitis or thrombosis. A thrombosis here will cause an increase in pressure and compress these nerves leading to problems with eye movements and sensation over the face.

Answer 87

Just like other vessels in the body, blood can clot within the dural venous sinuses. If this occurs, drainage of venous blood will be compromised, meaning there will be an increase in intracranial pressure causing a headache and potentially a significant and devastating compression of intracranial structures

Answer 88

There are central cavities within the brain that are filled with cerebrospinal fluid (CSF). These cavities are called ventricles and are joined to each other. They are continuous with the subarachnoid space meaning the CSF can surround the brain and spinal cord.

Answer 89

It means the brain is submerged in a thin layer of CSF which provides a degree of physical protection, and mechanism for transfer of certain substances in and out of the brain tissue.

Answer 90

CSF is primarily produced in the lateral ventricles by a group of specialised cells called the choroid plexus. The lateral ventricles are located within the cerebral hemispheres

Answer 91

It then flows out of the lateral ventricles via the interventricular foramen to reach the third ventricle. The third ventricle is a very thin chamber in the midline separating the two sides of the diencephalon.

Answer 92

CSF then passes out of the third ventricle via the cerebral aqueduct into the fourth ventricle which is diamond-shaped and located posterior to the brainstem, but anterior to the cerebellum

Answer 93

Leaves the ventricular system either by passing inferiorly via the central canal to fill the subarachnoid space around the spinal cord, or posteriorly and laterally (via the median aperture of Magendie and lateral apertures of Luschka, respectively) to enter the subarachnoid space that surrounds the brain.

Answer 94

In certain areas around the brainstem and diencephalon, there are larger pockets of CSF in the subarachnoid space called subarachnoid cisterns On a CT scan, blood may be identified in the subarachnoid cisterns if there is bleeding into the subarachnoid space.

Answer 95

These are outpouchings similar in shape to a mushroom, that push out of the subarachnoid space around the brain into the dural venous sinuses. CSF diffuses across the wall of the arachnoid granulations to enter the bloodstream here.

Answer 96

Hindbrain- pons and medulla Midbrain Forebrain- Telencephalon and diencephalon

Answer 97

Caudal (hind) -> rostral (neck) Horizontal, sagittal (through nose), coronal ( thru ears)

Answer 98

Axons and myelin (made of fat

Answer 99

Remain within 1 hemisphere Group of fibres that communicate within the hemisphere

Answer 100

Cross between hemispheres anterior commisure- helps with identifying site of interest Corpus callosum- main communiscto

Answer 101

Go down into spinal cord and then up

Answer 102

1+2. Input from other cortical areas 3. Projects to other cortical areas 4. Input from thalamus 5. Projects to brainstem and spinal cord 6. Projects to thalamus

Answer 103

Back of brain does sensory stuff Front of brain does output stuff

Answer 104

Frontal petalia is only on right occipital petalia is only on the left (ADD TO THIS)

Answer 105

Falx cerebri Tentorium cerebelli Tentorial incisure Straight sinus Inferior sagittal sinus Superior sagittal sinus Transverse sinuses Falx cerebelli

Answer 106

The faint streak which is the earliest trace of the embryo in the fertilized ovum of a higher vertebrate

Answer 107

White matter is insulated by Oligodendrocytes\Schwann cells Allows the electrical signals to travel faster Your myelinated brain stem keeps you breathing Unless you have an abnormal PHOX2B gene

Answer 108

Neurons arise in the germinal matrix Migrate to cortical sub plate and wait

Answer 109

Is only about 1.3 kg in weight Thus only about 2.3% of you body mass Uses 20% of blood supply and oxygen Generates about 23 watts (Joules/second) The neo-cortex and language centres are 76% of your brain

Answer 110

Rooting Reflex: turn head and mouth in direction of stroking of cheek Sucking Reflex: babies will suck object that touches the lips Moro (Startle) Reflex: back arches, legs and arms are flung out and then brought back toward chest into a hugging motion Grasping (Palmar) Reflex: babies grasp objects pressed against palms Stepping Reflex: babies will mimic walking when help upright Babinski Reflex: infant fans toes when feet are stroked Tonic-Neck Reflex: infant turns head to one side, extending arm and leg

Answer 111

Best see objects 7 to 9 inches from eyes Lack peripheral vision Able to track movement within one day of birth Convergence does not occur until 7 or 8 weeks Cones less developed than rods at birth, but at 3 months, can see most visible colours

Answer 112

Middle and inner ear mature in shape and size. So hear remarkably well Show preference for mothers’ voice

Answer 113

Smell well developed at birth Demonstrate facial expressions to different odours Aversion for noxious and preference for pleasant odours Recognize familiar odours Learned preference for mother

Answer 114

Tastes sensitive at birth Discriminate between salty, sour, and bitter tastes Prefers sweet – works as an analgesic

Answer 115

Cranial to caudal Proximal to distal Simple to complex Ambidextrous until 3 years old

Answer 116

Verbal, Speaking, Reading, Thinking, Reasoning, Processes information sequentially, One piece of information at a time

Answer 117

Nonverbal, Spatial relationships, Patterns/Drawing recognition, Music, Emotional expression, Processes information holistically

Answer 118

smooth brain, neuronal migration disorder

Answer 119

Around 80% of babies less than 32 weeks have a normal scan Around 14% have small bleeds Around 6% of babies less than 32 weeks have scans like these Neonatal brains display significant plasticity

Answer 120

Syndromic children/Dysmorphisms History of brain injury Any loss of skills at any age Visually not fixing or following an object Hearing loss Low or High muscle tone Squint after 3 to 4 months (6th nerve) Cannot hold object placed in hand at 5 months

Answer 121

Can’t sit unsupported by 12 months Boys not walking by 18 months Girls not walking by 2 years Persistent toe walking No speech by 18 months Can’t point at object to share interest with others by 2 years Handedness before 3 years old

Answer 122

Plain X-rays Computed Tomography – CT Magnetic Resonance Imaging – MRI Cerebral Angiography Myelography Nuclear Medicine

Answer 123

Dose of Radiation 1 CT head = 100 chest X-rays Limited anatomical detail Acquired in axial plane Volume data May require iodinated contrast media Potential for allergic reaction Better than MRI for demonstrating bone & calcification (craniopharyngioma/meningioma) Seconds

Answer 124

Multiple planes possible Excellent anatomical detail Contrast injection may required Strong magnetic field – in some patients MRI is contraindicated Noisy & claustrophobic Longer scan times than CT No ionising radiation

Answer 125

Ring enhancing lesion- could be a brain tumour, plaque of de-myelination or abscess MS active inflammation incomplete ring enhancement Neuroborrelosis- Lyme disease

Answer 126

Low grade glioma High grade glioma Oligodendroglioma Leukaemic deposit Meningioma Metastases from other cancers

Answer 127

Outer ear- air Middle ear- air Inner ear- fluid Central auditory pathways

Answer 128

Ear shape is unique to ppl folds collect soundwaves and channel into external- auditory canal Filters out low frequency sound instead of high frequency sounds

Answer 129

Contains bones- malleus, incus, stapes Contains muscles- Tensor tympani and stapedius Tubes- eustachian tube

Answer 130

Set of fluid filled scs cochlear- hraring labyrinth: balance Innervation: vestibulocochlear nerve

Answer 131

2.5 turns fluid filled bony tube

Answer 132

Narrow at base- wide at apex Stiff at base- floppy at apex High frequencies detected at base Low frequencies at apex Concept called tonotopy

Answer 133

Neurons and glia

Answer 134

Specialised

Answer 135

Myofibres arranged in fascicles Connective tissue Basement membrane Vascular supply Innervation Myotendinous junction

Answer 136

Epimysium Perimysium Endomysium

Answer 137

Surrounds individual myofibres Collagen, glycoproteins and proteoglycans Roles in tensile strength, regeneration, development

Answer 138

Transmits force of muscle contraction to the tendon

Answer 139

Each fibre innervated by one nerve, with cell bodies in anterior horn of spinal cord or brainstem One neuron innervates multiple muscle fibres – motor unit Neuromuscular junction Proprioception – length and tension

Answer 140

Synapse – rapid transmission of depolarising impulse Acetyl choline – binds post-synaptic AChR

Answer 141

length and tension Muscle spindles – encapsulated intrafusal fibres. Mediate stretch reflexes and proprioception Golgi tendon organs - tension

Answer 142

MND Peripheral neuropathy Neuromuscular transmission defects Primary muscle disease

Answer 143

Can be studied by muscle biopsy Requires the use of frozen sections and good orientation EM Molecular tests

Answer 144

Enzyme histochemistry- reveals different fibre types It is why it has to be fresh Incl. NADH and ATPase

Answer 145

-Slow twitch (red fibres) – type 1, oxidative, fatigue resistant -Fast twitch – fatigue rapidly but generate a large peak of muscle tension -2A – glycolytic and oxidative (intermediate) -2B – glycolytic (white)

Answer 146

-Motor neuron (lower) and the fibres it innervates -Neuron and its fibres of same type -Fibre type dependent on neuron -Size of motor unit varies between muscles

Answer 147

-Loss of innervation causes fibre atrophy -Collateral sprouting from adjacent motor units allows reinnervation -Larger motor units result – this can be detected electrophysiologically -Conversion of fibres results in fibre type grouping

Answer 148

Sarcomere – basic unit of contraction Repeating arrangement of thick (myosin) and thin filaments (actin)

Answer 149

-alpha-actinin -Titin -Nebulin -Desmin (links myofibrils to each other and the sarcolemma)

Answer 150

-Troponin/tropomyosin complex – Calcium regulation

Answer 151

- Myosin heads bind actin - Binding of ATP allows release and hydrolysis to ADP allows movement of myosin head. ADP released during power stroke. - Sarcomeric shortening due to sliding of the filaments NOT change in length of either actin or myosin - Initiated by increased cytosolic Ca2+ - Accessory proteins

Answer 152

-Troponin/tropomyosin – mediate Ca2+ regulation -Maintaining architecture of the filament – e.g. nebulin, titin

Answer 153

High energy requirement from ATP Creatine phosphate a short term energy store CP replenished by creatine kinase (CK) CK is released on muscle fibre damage Measurement of serum CK clinically useful

Answer 154

Mitochondrial DNA - Circular ds DNA, Maternally inherited Diverse clinical presentations with an emphasis on CNS E.g. MERRF, MELAS, CPEO Mutations in either mitochondrial or nuclear DNA Mitochondrial mutations – maternal inheritance Heteroplasmy

Answer 155

-Ragged red fibres -Electron transport chain deficits – cytochrome oxidase negative fibres -Abnormal mitochondrial morphology -Gene defects

Answer 156

Ragged red fibres

Answer 157

Distrophin

Answer 158

-Dystrophies are genetically determined, destructive and mainly progressive disorders of muscle -There are many types of dystrophy -Defects of proteins that confer stability to the sarcolemma are one group of causes.

Answer 159

-A large protein encoded by a 2.4 million bp gene on Xp21 -Confers stability to the muscle cell membrane -Deletion resulting in disruption of the reading frame results in Duchenne -In Becker’s, and in-frame deletion results in a truncated product

Answer 160

Nerve impulse results in the release of acetyl choline from synaptic vesicles ACh binds to its receptor Cation entry results in depolarisation, the end-plate potential An action potential travels across the muscle cell membrane and into the T-tubule system Calcium is released from the sarcoplasmic reticulum leading to activation of contraction Dissociated ACh is hydrolysed by acetyl cholinesterase in the NMJ

Answer 161

-Myasthenia gravis – variable weakness, progressive with sustained effort, eye signs – ptosis -Autoimmune disease -Anti-AChR antibodies resulting in a reduction in ACh receptors -Acetyl cholinesterase inhibitors can improve muscle function

Answer 162

In the PNS, the Schwann cell is responsible for the myelin sheath Each Schwann cell is responsible for one segment of myelin Nodes of Ranvier lie between adjacent myelin segments The node is where depolarisation of the membrane occurs Myelination allows saltatory conduction

Answer 163

-Damage to motor or sensory neurons – neuronopathies -Damage to axons – axonopathies -Selective damage to myelin sheaths - demyelination

Answer 164

Fascicles of perineurium surrounded by fatty connective epineurium

Answer 165

-Injury to axon – distal fragmentation -Globules of myelin and axon debris form, initially within Schwann cell -Axonal sprouts form from proximal part of damaged axon and grow along columns of proliferating Schwann cells -Regenerated axons can remyelinate

Answer 166

The base of the skull is formed from several individual bones joined by fibrous joints known as sutures. Several of the names of the bones match the lobes of the brain that are in contact with them.

Answer 167

Depressions in the base of the skull - Anterior cranial fossa - Middle cranial fossa - Posterior cranial fossa

Answer 168

Within each cranial fossa are several small holes which allow nerves, arteries and veins to pass in and out of the skull. These are known as cranial foramina (singular: foramen).

Answer 169

he frontal lobes rest in the anterior cranial fossa, and it is formed of 3 bones: - Orbital part of frontal bone - Cribriform plate - Lesser wings of sphenoid bone

Answer 170

The two rounded elevations are the spherical cavities of the bony orbits, where the eyes are located.

Answer 171

The cribriform plate (meaning ‘sieve-like’) has many small holes for passage of olfactory nerves. The crista galli (meaning ‘rooster’s crest’) is the vertical protrusion in its centre.

Answer 172

The sphenoid bone (meaning ‘wedge-shaped’) has smaller (lesser) superior wings, a body in its centre and larger (greater) inferior wings.

Answer 173

Cribriform plate – transmits olfactory fibres that allow our sense of smell.

Answer 174

The temporal lobes rest in the middle cranial fossa, and it is formed of two bones: - Petrous and squamous parts of the temporal bone - Greater wing and body of the sphenoid bone

Answer 175

The petrous (meaning ‘rock-like’) is the very hard and bulbous inferior and medial part of the temporal bone. The inner and middle ear cavities are located inside it. The squamous (meaning ‘scale-like’) is the flat, lateral part of the temporal bone.

Answer 176

The body of the sphenoid bone includes a small, rounded cavity about the size of the end of your finger called the pituitary fossa. It is also known as the sella turcica (meaning ‘turkish saddle’) and it is where the pituitary gland is located

Answer 177

- Optic canal - Superior orbital fissure - Foramen rotundum - Foramen ovale - Foramen lacerum - Foramen spinosum

Answer 178

Transmits the optic nerve into the bony orbit.

Answer 179

Transmits several nerves that provide motor innervation (oculomotor, trochlear and abducens nerves) and sensation (ophthalmic branch of the trigeminal nerve) to the orbital region.

Answer 180

Transmits the maxillary branch of the trigeminal nerve.

Answer 181

transmits the mandibular branch of the trigeminal nerve.

Answer 182

The internal carotid artery exits the carotid canal through this foramen to enter the skull.

Answer 183

Transmits the middle meningeal artery.

Answer 184

- Internal auditory meatus - Jugular foramen - Hypoglossal canal - Foramen magnum

Answer 185

Transmits the vestibulocochlear and facial nerves into the inner ear cavity.

Answer 186

Transmits the glossopharyngeal, vagus and accessory nerves, and the internal jugular vein.

Answer 187

Transmits the hypoglossal nerve

Answer 188

This central singular foramen is very large and allows central nervous system fibres to leave the skull and become the spinal cord.

Answer 189

· The brain itself could be directly damaged by the force. · The fracture could extend through some of the foramina and damage the structures passing through them. · The dura and arachnoid meninges may be damaged which could cause CSF to leak out. Clinically, this may be suspected if a clear liquid is seen to be leaking from the patient’s nose or ears after a head injury. · Significant bleeding may occur from the fractured bone or due to damage to intracranial arteries, veins or dural venous sinuses.

Answer 190

The pterion is an area of the skull often referred to as the ‘temple’ and it is located just lateral and posterior to the eyebrow. It is a shallow depression where four bones of the skull converge: the frontal, temporal, sphenoid and parietal bones. Because of this, it is considered to be the weakest part of the skull and prone to fracture if struck. Unfortunately, the middle meningeal artery lies immediately behind the pterion, therefore traumatic injuries to this area may cause an extradural haemorrhage.

Answer 191

The sutures (joints between the bones) of the skull do not completely fuse until a child is around two years old. This allows the brain to increase in size as the child grows quickly in infancy. If certain sutures of the skull fuse together too early, as the brain continues to grow it will cause the skull to become misshapen and this is called craniosynostosis. The skull may be elongated in the longitudinal, transverse or oblique planes, depending on which sutures fuse before they are supposed to.

Answer 192

If there is a build-up of pressure within the fixed confines of the skull, this must be relieved, or the brain will eventually be compressed which can lead to death. Common causes of a build of pressure in this way may include intracranial bleeding (such as an extradural haemorrhage) or a brain tumour. To relieve the pressure quickly, a small hole (about 10-15 mm diameter) can be drilled into the skull. This allows the brain to expand enough to relieve the pressure, or it can be used to directly drain the bleeding that’s causing the pressure build-up.

Answer 193

To perform surgery on the brain, a larger hole may be needed. This is called a craniotomy, and a circular piece of the skull is removed. This may be replaced later, or a prosthetic implant may be used to close the craniotomy instead.

Answer 194

The two orbits are shaped like cones, with a broad opening at the front, tapering to a narrow part at the back. They are formed of several bones: the larger frontal, sphenoid, zygomatic and maxillary bones, and the smaller ethmoid and lacrimal bones.

Answer 195

- Eye - Extraocular muscles - Nerves - Fat - Lacrimal gland

Answer 196

Six small but distinct muscles that move the eye to direct our vision where we want it, and a seventh muscle responsible for retracting the upper eyelid.

Answer 197

Including the optic nerve for vision, the oculomotor, trochlear and abducens nerves that control the extraocular muscles, and the ophthalmic branch of the trigeminal nerve which supplies sensation to eye and forehead.

Answer 198

Found in the superior and lateral part of the orbit, this gland produces tears to lubricate the anterior surface of the eye.

Answer 199

Optic canal, superior orbital fissure and inferior orbital fissure.

Answer 200

There are seven extraocular muscles. All have distinct functions and two have a unique nerve supply. Some muscles have additional actions on the eye due to the angle at which they attach to the eye. The dysfunction of one of the muscles or nerves supplying them will produce characteristic findings when examining the patient.

Answer 201

LR6SO4 – lateral rectus is supplied by cranial nerve 6, superior oblique is supplied by cranial nerve 4. The rest of muscles are supplied by cranial nerve 3

Answer 202

· Elevation – to look up. · Depression – to look down. · Adduction – to look medially. · Abduction – to look laterally. · Extorsion – to rotate the eye, so the top of the eye rotates laterally. · Intorsion – to rotate the eye, so the top of the eye rotates medially.

Answer 203

Both eyes do not necessarily perform the same movement when you change where you look. For example, to look to your left with both eyes, your left eye needs to abduct, but your right eye will need to adduct. This is known as conjugate eye movements.

Answer 204

Nerve supply- Oculomotor nerve (CN III) Action on eye- Elevate superior eyelid Findings if non-functional- Ptosis (drooping eyelid)

Answer 205

Nerve supply- Oculomotor nerve (CN III) Action on eye- Elevate, intort, adduct Findings if non-functional- unable to elevate

Answer 206

Nerve supply- Oculomotor nerve (CN III) Action on eye- Depress, extort, adduct Findings if non-functional- unable to depress

Answer 207

Nerve supply- Oculomotor nerve (CN III) Action on eye- Adduct Findings if non-functional- Unable to adduct

Answer 208

Nerve supply- Abducens nerve (CN VI) Action on eye- Abduct Findings if non-functional- Unable to abduct

Answer 209

Nerve supply- Trochlear nerve (CN IV) Action on eye- Intort, depress, abduct Findings if non-functional- Unable to depress if eye is adducted

Answer 210

Nerve supply- Oculomotor nerve (CN III) Action on eye- Extort, elevate, abduct Findings if non-functional- Unable to elevate if eye is adducted

Answer 211

The four recti extraocular muscles originate at the back of the orbit on a fibrous ring known as the common tendinous ring (or annular tendon, or annulus of Zinn)

Answer 212

The additional functions of intorsion, extorsion and adduction are secondary effects caused by the angle at which these two muscles pull on the eye. When looking at the orbits from above, if you draw a line through the centre of both orbits (which represents the angle at which these muscles pull on the eye) you’ll notice these two lines are not parallel and they do not point directly forwards. They diverge off to each side. However, the eye is normally angled to point directly forwards. This means that when the superior or inferior recti act on the eye, they are not only pulling it upwards or downwards, but they are also causing it to intort or extort and adduct.

Answer 213

The superior oblique muscle originates at the back of the eye but passes through a fibrous sling called the trochlea, which is located in the superior and medial corner of the orbit. The muscle then inserts onto the top of the eye, so it’s action will pull the top of the eye medially, causing it to rotate. The top of the eye rotating inwards is called intorsion.

Answer 214

The inferior oblique muscle originates from the medial orbital wall and inserts on the bottom of the eye. Its action will pull the bottom of the eye medially, also causing it to rotate, but in the opposite direction. With the top of the eye rotating outwards, this is called extorsion.

Answer 215

The reason that the eye needs the oblique muscles to be able to intort and extort is to counter the secondary effects of extorsion and intorsion caused by the inferior and superior recti muscles respectively. This helps maintain steady vision when looking up or down.

Answer 216

The eye is responsible for providing us with sight. As light enters the eye, it is focused to converge onto the retina where it is detected by specialised cells (rods and cones). These cells generate nerve impulses which are transmitted along the optic nerve and optic tracts towards the primary visual cortex in the occipital lobe.

Answer 217

To achieve good vision, the eye must be able to focus light to varying amounts depending on how far away the object is that is being visualised

Answer 218

To achieve this, the eye adjusts the thickness of the lens within it. A thicker lens will cause greater refraction of light and is useful for looking at near objects. A thinner lens will cause less refraction of light and is useful for looking at distant objects.

Answer 219

The ciliary muscles are responsible for adjusting the thickness of the lens. They are supplied by parasympathetic fibres that travel within the oculomotor nerve (CN III). Because of this, accommodation is an autonomic function that we are unable to control.

Answer 220

To protect the retina from over-exposure to light, the eye must be able to limit how much light enters the eye. To achieve this, a circular muscle within the iris known as constrictor pupillae will constrict the pupil when too much light is detected on the retina.

Answer 221

This muscle is also supplied by parasympathetic fibres that travel within the oculomotor nerve (CN III). Because of this, pupillary construction is another autonomic function that we are unable to control.

Answer 222

Conversely, when it is dark, the eye must be able to allow more light in to allow us to see adequately. To achieve this, a radial muscle within the iris known as dilator pupillae will dilate the pupil when not enough light is detected on the retina

Answer 223

This muscle is supplied by sympathetic fibres that originate from the sympathetic chain and enter the skull alongside the internal carotid artery. Because of this, pupillary dilation is another autonomic function that we are unable to control.

Answer 224

When there is stimulation of the body’s parasympathetic or sympathetic nervous systems, the pupils may change size. For example, in states of fear, excitement or pleasure, the sympathetic nervous system is highly active, and the pupils will dilate. In states of resting, the parasympathetic nervous system is active, and pupils will constrict

Answer 225

The pupillary light reflex, which is responsible for automatically adjusting the amount of light entering the eye, has an afferent (sensory) and efferent (motor) nerve

Answer 226

The afferent nerve is the optic nerve, and it carries information about the amount of light being detected on the retina to the midbrain. Here, there is a synapse with the Edinger-Westphal nucleus, which instructs the efferent nerve (the oculomotor nerve) to initiate constriction of the constrictor pupillae muscle in the iris, thereby narrowing the pupil and reducing the amount of light entering the eye.

Answer 227

When a light is shone in one eye of a healthy patient, both pupils will constrict. The constriction of the pupil which is having a light shone into it is called the direct pupillary respons

Answer 228

when the pupil that doesn't have the light shining in it also contracts

Answer 229

The reason that the other pupil constricts as well is because there is a connection between the right and left Edinger-Westphal nuclei such that if one side is activated, then both sides are activated.

Answer 230

The lacrimal gland produces tears to lubricate and moisten the surface of the eye. It is located in the superior and lateral corner of the orbit.

Answer 231

The tears flow across the eye and drain into the lacrimal ducts in the inferior and medial corner of the orbit. Through here, they then drain into the nasal cavity via the nasolacrimal duct. This is why our nose runs when we cry

Answer 232

The secretomotor nerve supply to the lacrimal gland is via the parasympathetic fibres within the facial nerve (CN VII).

Answer 233

Direct traumatic blows to the eye (as may be sustained during a fist fight) may fracture the walls of the orbit. These are known as ‘blow out’ fractures and a fracture of the inferior orbital wall is most common. The inferior rectus muscle can become trapped inside the fracture, tethering the eye in position and patients will be unable to look up.

Answer 234

A cataract is a common ocular condition characterised by clouding of the lens that is responsible for focusing light onto the retina. Cataracts develop slowly and painlessly, and whilst they cannot be prevented, they are relatively easily treated surgically, by removing the affected lens and replacing it with a new and clear intraocular lens.

Answer 235

If the oculomotor nerve is not functioning on one side, it produces a very characteristic set of findings on clinical examination. The affected eye will rest in a ‘down-and-out’ position (depressed and abducted). This is because the lateral rectus and superior oblique muscles are unopposed so pull the eye into that position at rest. The affected eye’s pupil will also be dilated due to loss of parasympathetic nerve supply to the constrictor pupillae, leaving dilator pupillae unopposed. Finally, due to the loss of motor nerve supply to levator palpebrae superioris, the eyelid will droop. This is known as ptosis. Additionally, on asking the patient to look left and right, the affected side will be unable to adduct.

Answer 236

If the abducens nerve is not functioning on one side, the affected eye will be unable to abduct as the lateral rectus muscle is no longer working. The lateral rectus muscle may be overpowered by the medial rectus, which is still functional, to pull the eye medially at rest causing strabismus (sometime referred to as a ‘squint’).

Answer 237

Testing the different movements of the eye is a vital part of a neurological examination of the cranial nerves. The do this, a clinician may ask the patient to follow their finger as they draw the shape of the letter ‘H’ in front of the patient. The clinician observes the patient’s eyes to ensure they are moving together and asks the patient if they are experiencing any diplopia (double vision).

Answer 238

Certain therapeutic and recreational drugs will cause changes to the size of the pupil. Opiates, for example, such as morphine and heroin (diamorphine), will cause pupillary constriction in higher doses. Sympathomimetics, such as ecstasy (MDMA) and cocaine will cause pupillary dilation. The size of the pupil can help clinicians during assessment of unconscious patients.

Answer 239

If a patient suffers a significant head injury and has bleeding inside the skull (for example, an extradural haemorrhage), intracranial pressure will rise. This may lead to compression of the oculomotor nerve on one or both sides. If compressed, the oculomotor nerve may be unable to function properly and an early sign of this is dilation of the ipsilateral pupil. This is another reason why clinicians often check the size of a patient’s pupils during clinical examination of unconscious patients. A fixed and dilated pupil is a concerning sign.

Answer 240

The most external part of the ear consists of the pinna (or ‘auricle’), the ear canal (or external acoustic meatus) and the tympanic membrane (eardrum). The pinna is shaped to gather sound waves and direct them into the ear canal. The ear canal directs these sound waves towards the tympanic membrane. When sounds waves strike the tympanic membrane, it vibrates like the surface of a drum and transmits them deeper into the ear towards the cochlea.

Answer 241

Immediately behind the tympanic membrane is the middle ear cavity. Within it, are the ossicles. The ossicles are three of the smallest bones in the body and they carry the sound waves to the oval window which conveys it into the cochlea.

Answer 242

The first ossicle rests against the tympanic membrane. It is shaped like a hammer, from which its name is derived. The handle of the ‘hammer’ rests against the tympanic membrane and can be seen through the membrane during otoscopy (looking in a patient’s ear). The head of the hammer connects to the incus.

Answer 243

The second ossicle’s name means ‘anvil’. As the ‘hammer’ (malleus) strikes the ‘anvil’ (incus), sound waves are transmitted, eventually reaching the stapes.

Answer 244

The third and final ossicle’s name means ‘stirrup’, which it clearly resembles. It receives sound wave vibrations from the incus and transmits them onto the oval window which marks the boundary of the middle and inner ear cavities.

Answer 245

The superior opening of the auditory tube (also known as the Eustachian tube) is also located in the middle ear cavity.

Answer 246

The inferior opening of the auditory tube is in the posterior and inferior part of the nasal cavity. It therefore provides a connection of airflow between the external environment and the middle ear cavity via the nasal cavity. This connection is vital to maintain equal air pressure on either side of the tympanic membrane.

Answer 247

Without it, air pressure would build up on the inside or outside of the tympanic membrane, causing pain and potentially rupture.

Answer 248

This pressure can be felt when descending in an aeroplane from a significant height, or when diving underwater. As you descend deeper, air (or water) pressure outside the tympanic membrane increases and causes the membrane to bulge inwards. To counter this, air is allowed to pass up through the auditory tube to increase air pressure on the inside of the tympanic membrane. Sometimes, if the pressure correction occurs suddenly, you can feel a ‘pop’ in your ear.

Answer 249

- Tensor tympani - Stapedius Act to dampen sound vibrations and reduce perceived volume.

Answer 250

Inserts on the malleus and when it contracts, it increases tension in the tympanic membrane, reducing how much it can vibrate. Tensor tympani is supplied by the mandibular branch of the trigeminal nerve (CN V).

Answer 251

The stapedius muscle inserts on the stapes and acts in similar way. When it contracts, it dampens the vibrations of the stapes. Stapedius is supplied by the facial nerve (CN VII)

Answer 252

1. Endothelial cell tight junctions 2. Lack of BM fenestrations 3. Astrocytic end feet 4. Pericytes

Answer 253

Area supplied by middle cerebral artery as it is the closest to the internal carotid artery

Answer 254

If you block off one artery the area can still be perfused by other smaller blood vessels This is the case in the circle of Willis

Answer 255

The bifurcation point of the common carotid artery

Answer 256

Anterior- internal carotid artery Posterior- Vertebral artery

Answer 257

Watershed regions In between the vascular territories

Answer 258

Along the top of the brain in the falx cerebri

Answer 259

anterior spinal vein and anterior spinal artery on anterior side posterior spinal vein, posterior spinal arteries and posterolateral spinal veins on the posterior side

Answer 260

Lateral ventricles (I&II) Interventricular foramen 3rd ventricle Cerebral aqueduct 4th ventricle foramen magandie

Answer 261

Ependymal cells- glial cells Look like epithelial cells Cillia to beat and move CSF

Answer 262

Choroid plexus- highly vascularised

Answer 263

Interstitial fluid drains → CSF via perivascular channels. CSF drains via arachnoid granulations peripheral nerves to lymphatics Importantly: nasal mucosa lymphatics → deep cervical lymph nodes

Answer 264

Lymphoid immune surveillance Assessing for infection in brain

Answer 265

Sensory innervation of the nose

Answer 266

Sensory innervation of the eyes

Answer 267

Motor innervation of the superior oblique muscle

Answer 268

Motor innervation of all eye muscles except lateral rectus and superior oblique

Answer 269

Part of the olivo-cerebellar system and is mainly involved in cerebellar motor-learning and function.

Answer 270

Bulbopontine sulcus

Answer 271

Middle cerebellar peduncles

Answer 272

Forms floor of the 4th ventricle

Answer 273

Carry joint position sense- position of limbs

Answer 274

Back of midbrain Visual sensory area

Answer 275

Auditory sensory area

Answer 276

Tectum- everything in front of the cerebral aqueduct Tegmentum- everything behind the cerebral aqueduct

Answer 277

Initiates movement contains neuromelanin Parkinsons damages this

Answer 278

Archicerebellum Paleocerebellum Neo cerebellum

Answer 279

Floculonodular lobe: balance. Connected to vesibular nuclei and reticular nuclei.

Answer 280

Muscle tone and posture Afferent: dorsal spinocerebellar tracts via inf cerebellar peduncle and ventral SC tract via superior CP Efferent: Globose and emboliform nuclei to red nucleus to rubrospinal tract

Answer 281

(more fancy movements, coordination, muscle tone) Afferent: Cerebral cortex to pontocerebellar fibres (decussate) via MCP Efferent: Purks to dentate to red nucleus & ventral thalamus via SCP

Answer 282

Mossy fibres from cortex (ponto cerebellar pathway), vestibular nucleus, spinal cord, reticular formation, deep cerebellar nuclei (feedback)

Answer 283

Major output pathway of the hippocampus

Answer 284

Laying down memory Lose the ability to make new memories if removed

Answer 285

Deep grey structures contains internal capsule- white streak

Answer 286

3 main groups of nuclei: sensory relays cerebellar and basal ganglia relays to motor frontal lobe connected to associative and limbic areas of cerebral cortex Damage causes loss of sensation, pain, or movement disorders

Answer 287

Deep grey structures that aren't the thalamus

Answer 288

Hippocampus Amygdala Circulating blood

Answer 289

Pituitary -> hormones -> homeostasis

Answer 290

Part of limbic system

Answer 291

Around L1 Means you can take some csf from there without damaging spinal cord

Answer 292

Same as the rest of the brain Dura mater- aka thika Arachnoid Pia

Answer 293

sensory info fewer neuronal cell bodies

Answer 294

Now usually done percutaneously For treatment of intractable pain. Side effects include sleep apnoea due to reticulospinal tract damage

Answer 295

Crude touch, Pain Temperature cross then up

Answer 296

Vibration Joint position up then cross

Answer 297

Dorsal root -> afferent (affected by the world- sensory) Ventral root -> efferent (having an effect on the world- motor)

Answer 298

Contain caudal part of the reticular formation ("little net"): low level sensorimotor control – e.g. balance Involved in variety of vital functions: Sleep/Wakefulness Motor Plant: movement, maintenance of muscle tone Various cardiac, circulatory, respiratory, excretory reflexes Contains tracts carrying signals between the rest of the brain and the body.

Answer 299

Relay from cortex and midbrain to the cerebellum Contains millions of neuronal fibers Pontine reticular formation (pattern generators) – e.g. for walking

Answer 300

Smaller than the brain but contains as many neurons as all the rest of the CNS. “Motor errors” between intended movement and actual movement – adjusts synaptic weights to eliminate error. Online correction can take place during the movement : motor learning. Thought exclusive for motor coordin-ation – recently implicated in cognitive and affective/emotional function.

Answer 301

Tegmentum and tectum

Answer 302

Visual/spatial and auditory frequency maps

Answer 303

Superior colliculus- Sensitive to sensory change – orienting/defensive movements Inferior colliculus- similar but for auditory events

Answer 304

Periaqueductal grey Red nucleus Substantia nigra

Answer 305

Role in pain (ascending and descending signals) Role in defensive behavior Role in reproduction

Answer 306

Role in pre-cortical motor control (especially arms and legs Target of cortex and cerebellum, projects to spinal cord

Answer 307

Substantia nigra pars reticulata – basal ganglia output Substantia nigra pars compacta (Dopamine cells) – basal ganglia Input…Parkinson’s disease

Answer 308

Relay structure Specific nuclei : relay signals to cortex/limbic system for all sensations (but smell...). Non-specific nuclei : Role in regulating state of sleep and wakefulness and levels of arousal Important relays from basal ganglia and cerebellum back to cortex

Answer 309

Regulates the pituitary gland which regulates hormonal secretion: interface between brain and hormones Role in hormonal control of motivated behavior …including hunger, thirst, temperature, pain, pleasure and sex

Answer 310

Basal Ganglia Limbic system

Answer 311

Group of structures Loop organization These structures thought to be involved in motor function since involved in movement disorders However: work in Sheffield has been key to newer understanding of fundamental roles in action selection and reinforcement learning

Answer 312

Group of structures These structures involved in emotion, motivation and emotional association with memory The limbic system influences the formation of memory by integrating emotional states with stored memories of physical sensations

Answer 313

White matter: fibers / axons Gray matter (6 layers) : cell bodies

Answer 314

Contain the precentral gyrus from which motor instructions (particularly for fine motor control) that are sent to muscles controlling hands and feet. Primary motor cortex: contains many of the cells giving origin to the descending motor pathways - it is involved in the initiation of voluntary movements. Premotor and supplementary motor areas: higher level motor plans and initiation of voluntary movements.

Answer 315

Involved in - i.e. lesions disrupt…. “Executive" planning – generating models of the consequences of actions Judgmental roles Emotional modulation Working memory: short-term information (rather than long-term factual data) Control of behavior that depends upon context or setting Prefrontal cortex: generating sophisticated behavioural options that are mindful of consequences

Answer 316

As sound waves and vibrations travel through fluid within the cochlea, they are converted into electrical impulses which are passed via the cochlear nerve to the auditory cortex. This allows us to perceive sound

Answer 317

The sound waves first enter the cochlea via the oval window (which the stapes is in contact with). The round window is located nearby and bulges in and out to allow the fluid within the cochlea to move.

Answer 318

Consists of the semicircular canals, utricle and saccule. The vestibular system contains fluid, which flows when we move our heads

Answer 319

The movement of this fluid is detected by specialised cells causing them to produce electrical impulses. These impulses are passed along the vestibular nerve towards various parts of the brain including the cerebellum, thalamus and certain cranial nerve nuclei

Answer 320

The three semicircular canals, positioned perpendicular to each other in three dimensions, allow us to perceive movement.

Answer 321

Perceive linear acceleration

Answer 322

Impulses from the cochlea and vestibular system are carried by the vestibulocochlear nerve (CN VIII), through the internal auditory meatus towards the nuclei of the vestibulocochlear nerve in the pons.

Answer 323

In the nuclei of the vestibulocochlear nerve there are connections to other brainstem nuclei of the oculomotor, trochlear and abducens nerves which control eye movements. Because of these connections, we are able to maintain fixed gaze whilst moving our head. This is called the oculocephalic reflex.

Answer 324

Vertigo is the symptom of being able to perceive movement when there is none. This is commonly perceived and recreated if you spin around several times and then stop suddenly. The perception of the world continuing to spin around you, or the floor moving unevenly beneath you, is vertigo. There are various causes of vertigo, but a common presentation to clinical practice is a disorder of the vestibular system. Inflammation, infections, endo/perilymph disorders or cancers of the vestibular system or nerves may cause vertigo.

Answer 325

Also known as an acoustic neuroma, this is a benign tumour of the Schwann cells surrounding the vestibulocochlear nerve. As it grows, it gradually leads to symptoms of unilateral hearing loss, tinnitus, a feeling of fullness in the ear and vertigo. If it grows large enough, it will start to compress the other cranial nerves that leave the brainstem around the same position. This position is known as the cerebellopontine angle, and other cranial nerves leaving the brainstem here are the trigeminal (CN V) and facial (CN VII) nerves.

Answer 326

Otitis media is the term for inflammation within the middle ear cavity. It is most often caused by a simple viral infection and is particularly common in young children. When a patient is suffering from an upper respiratory tract infection, the inflammation can spread throughout the upper respiratory tract from the nose and pharynx to the middle ear cavity via the auditory tube. This can lead to accumulation of inflammatory fluid and pus in the middle ear cavity, impairing conduction of sound waves along the ossicles.

Answer 327

The auditory tube is relatively narrow in young children and therefore less effective at draining the middle ear cavity. Because of this, a build of pus behind the tympanic membrane can increase pressure significantly which can be painful. If the inflammation continues, the tympanic membrane may rupture due to the pressure. This may relieve the pain and allow drainage of the pus. The tympanic membrane will usually later heal on its own. However, more serious cases of otitis media can spread deeper into the ear and cause inflammation of the cochlea or vestibular system, mastoid process of the temporal bone or the meninges.

Answer 328

continues around the central sulcus

Answer 329

Motor innervation of the muscles of the face

Answer 330

Sensory innervation of the inner ear

Answer 331

Sensory innervation of face, sinuses, teeth ect Motor innervation of muscles of mastication

Answer 332

Motor innervation of the lateral rectus muscle

Answer 333

Motor innervation of the muscles of the face

Answer 334

Motor innervation of the pharyngeal musculature Sensory innervation of posterior 1/3 of tongue, tonsils and pharynx

Answer 335

Motor innervation of heart, lungs, bronchi and gi tract Sensory innervation of the heart, lungs, bronchi, trachea, pharynx, larynx, GI tract, ext ear

Answer 336

Motor innervation of sternocleidomastoid and trapezius muscles

Answer 337

Sensory innervation of muscles of the tongue

Answer 338

Motor innervation of the submandibular and sublingual glands Sensory innervation of the anterior 2/3rds of the tongue

Answer 339

Outer layer- sclera and cornea Middle layer- uvea Inner layer- retina

Answer 340

The sclera

Answer 341

Cartilage protects eye

Answer 342

Made of collagen- it is a barrier to trauma and infection It has to be transparent for light transmission It is responsible for 2/3 refractive power of the eye

Answer 343

Epithelium- can regenerate Bowman's layer Stroma Descemet's layer Endothelium- cannot regenerate

Answer 344

Made up of iris, ciliary body and choroid

Answer 345

Glandular epithelium produces aqueous humour Ciliary (smooth muscle) controls accommodation

Answer 346

Made up of: - Retina - Specialised organ of phototransduction - Many layers

Answer 347

Ganglion cells Bipolar neurons Rod cells Cone cells

Answer 348

Macula lutea- centre of the retina Fovea centralis- centre of the macula lutea Cones Rods

Answer 349

Made up of axons of ganglion cells

Answer 350

The midbrain sits at the very top of the brainstem and is often difficult to see on an undissected specimen. The optic chiasm obstructs most of the view of the anterior brainstem. It is divided broadly into two parts, one ventral (tegmentum) and one dorsal (tectum) to the cerebral aqueduct

Answer 351

this smaller part of the midbrain is located dorsally. It contains two pairs of rounded bumps, known as colliculi.

Answer 352

Involved in regulating eye movements and reflexes associated with visual stimuli, such as turning or moving the head quickly when something quickly enters our field of vision.

Answer 353

Involved sound location, pitch discrimination and reflexes associated with auditory stimuli, such as turning our head on hearing a loud noise.

Answer 354

This larger part of the midbrain is located ventrally. It contains the substantia nigra, cerebral peduncles and red nuclei

Answer 355

Important in motor control by producing dopamine.

Answer 356

On its most ventral surface which are large white matter bundles that connect the midbrain to the thalami,

Answer 357

Which are involved in supporting motor control of the limbs.

Answer 358

The midbrain contains the nuclei of the oculomotor (CN III) and trochlear (CN IV) nerves, and the Edinger-Westphal nuclei (involved in the pupillary light reflex).

Answer 359

The pons is the large, rounded, middle part of the brainstem. On its ventral surface lies the basilar artery and on its dorsal surface, it has large white matter connections to the cerebellum called the middle cerebellar peduncles. The fourth ventricle of the ventricular system is situated dorsal to the pons, between the two middle cerebellar peduncles

Answer 360

The pons contains the nuclei of the trigeminal (CN V), abducens (CN VI), facial (CN VII) and vestibulocochlear (CN VIII) nerves. It also contains the pneumotaxic and apneustic centres which are involved in the regulation of breathing

Answer 361

The medulla oblongata connects the pons to the spinal cord. It has a groove on its ventral surface known as the anterior median fissure. The medulla contains the two medullary pyramids, which form two distinct lumps of the ventral surface, separated by this fissure. Essential motor tracts known as the corticospinal tracts run inside the pyramids. Immediately lateral to the medullary pyramids are another pair of prominent ridges known as the medullary olives.

Answer 362

An important sensory pathway of nerves runs in the dorsal part of the medulla within two pairs of nerve bundles: fasciculus gracilis and fasciculus cuneatus. Fibres of both corticospinal and DCML tracts cross over to the contralateral side within the medulla

Answer 363

The medulla contains the nuclei of the glossopharyngeal (CN IX), vagus (CN X), accessory (CN XI) and hypoglossal (CN XII) nerves. The medulla also contains vital centres responsible for regulating respiration, heart rate and blood pressure, and initiating vomiting

Answer 364

This term refers to dysfunction of the cranial nerves that arise from the medulla (glossopharyngeal, vagus, accessory and hypoglossal). Symptoms include difficulty speaking and swallowing, excessive saliva production, wasting and fasciculations of the tongue and an absent gag reflex. Causes include diseases which affect peripheral nerves such as motor neurone disease and Guillain-Barré syndrome.

Answer 365

The cranial nerves are 12 pairs of named nerves that originate directly from the brain, instead of the spinal cord like other nerves. Each pair has its own function and leaves the skull via specific foramina. Understanding the individual characteristics of each pair of cranial nerves is important when testing them during a clinical examination.

Answer 366

Specialised nerve cells in the roof of the nasal cavity detect odour molecules and convey this information superiorly through the cribriform plate to the olfactory bulbs. The olfactory bulbs are located on the superior surface of the cribriform plate, either side of the crista galli. The olfactory tracts then carry smell information posteriorly along the underside of the frontal lobes towards the olfactory cortices in the temporal lobes.

Answer 367

The optic nerve carries sight information from the retina to the optic chiasm, where some fibres cross over

Answer 368

These nerves control the muscles that are responsible for movements of the eyes and diameter of the pupils

Answer 369

The trigeminal nerve is the largest cranial nerve and divides into three branches shortly after it exits the pons. The branches are often named V1, V2, and V3.

Answer 370

A purely sensory nerve that supplies the skin over the superior third of the face as far as the top of the of the head, and the anterior surface of the eye

Answer 371

Also a purely sensory nerve that supplies the middle third of the face, including most of the internal nasal cavity, upper teeth and palate.

Answer 372

A mixed motor and sensory nerve. The sensory fibres supply the inferior third of the face, including general sensation to the anterior 2/3 of the tongue, and the mandibular teeth and gums. The motor fibres of the mandibular nerve supply five muscles.

Answer 373

One is the tensor tympani in the middle ear and the other four are the ‘muscles of mastication’ which are responsible for moving our mandible to chew our food: o Temporalis o Masseter o Medial pterygoid o Lateral pterygoid.

Answer 374

Sensory CNS origin- Cerebrum Skull base foramen- Cribriform plate Function- Olfaction (smell)

Answer 375

Sensory CNS origin- Diencephalon Skull base foramen- Optic canal Function- Sight

Answer 376

Motor (+ parasympathetics) CNS origin- Midbrain Skull base foramen- Superior orbital fissure Function- Eye movements (SR, IR, MR, IO), eyelid opening (LPS), pupillary constriction and accommodation

Answer 377

Sensory and motor CNS origin- Pons Skull base foramen- V1- Ophthalmic superior orbital fissure, V2- Maxillary foramen rotundum, V3- mandibular foramen ovale Function- V1 – sensation from the upper third of face. V2 – sensation from the middle third of face. V3 – sensation from the lower third of face, motor to the muscles of mastication, motor to the tensor tympani muscle

Answer 378

Motor CNS origin- Pons Skull base foramen- Superior orbital fissure Function- Eye movements (LR)

Answer 379

The facial nerve takes an unusual route out of the skull. It first passes through the internal auditory meatus alongside the vestibulocochlear nerve (CN VIII). Shortly after this, it gives off a branch which supplies parasympathetic secretomotor function to the lacrimal gland.

Answer 380

As it progresses through the middle ear cavity, the facial nerve gives off a branch to the stapedius muscle and another branch known as the ‘chorda tympani’. This nerve supplies taste sensation to the anterior 2/3 of the tongue and parasympathetic secretomotor function to the submandibular and sublingual salivary glands

Answer 381

The facial nerve then leaves the temporal bone of the skull via the stylomastoid foramen which is located between the styloid and mastoid processes of the temporal bone, hence the name.

Answer 382

After exiting the skull, it gives of a small branch which carries sensory information from the ear and motor supply to some muscles of the scalp. The main body of the facial nerve then enters the substance of the parotid salivary gland (which it does not innervate), and within it, divides into five branches which spread out across the face to supply the muscles of facial expression.

Answer 383

Temporal, zygomatic, buccal, marginal mandibular and cervical branches.

Answer 384

Both (+parasympathetic) CNS origin- Pons Skull base foramen- Internal auditory meatus then stylomastoid foramen Function- Motor to the muscles of facial expression, motor to the stapedius muscle, sensation from the ear canal, secretomotor function to the submandibular and sublingual salivary glands and lacrimal gland, taste from the anterior 2/3 of the tongue.

Answer 385

Sensory CNS origin- Pons Skull base foramen- Internal auditory meatus Function- Balance and hearing

Answer 386

Sensory and motor (+ parasympathetics) CNS origin- medulla Skull base foramen- Jugular foramen Function- Motor to the stylopharyngeus muscle, sensation from the pharynx and posterior 1/3 of the tongue, sensation from the carotid baroreceptors, secretomotor function to the parotid salivary gland, taste from the posterior 1/3 of the tongue.

Answer 387

Sensory and motor (+ parasympathetic) CNS origin- Medulla Skull base foramen- jugular foramen Function- Motor to the muscles of the soft palate, pharyngeal muscles and internal laryngeal muscles, sensation from the external ear and ear canal, taste from the epiglottis and parasympathetics to the thoracic and abdominal organs.

Answer 388

Motor CNS origin- Spinal cord C1-5 Skull base foramen- Foramen magnum (in) and jugular foramen (out) Function- Motor to the trapezius and sternocleidomastoid muscles

Answer 389

Motor CNS outline- medulla Skull base foramen- hypoglossal canal Function- Motor to the muscles of the tongue

Answer 390

This purely sensory nerve carries information of the special senses hearing and equilibrium (balance) from the inner ear.

Answer 391

The glossopharyngeal nerve has numerous functions. It supplies motor function to one muscle, the stylopharyngeus, which assists with facilitating swallowing. It carries general sensation from the middle ear, auditory tube, majority of the pharynx and both general and taste sensation from the posterior 1/3 of the tongue. It provides parasympathetic secretomotor supply to the parotid salivary gland and finally, it carries unconscious sensory information from the carotid chemoreceptors and baroreceptors towards the medulla.

Answer 392

Some of the main functions of this nerve have been discussed in previous modules (parasympathetic supply to thoracic and abdominal organs, and motor and sensory innervation to the larynx). However, it also supplies motor innervation to the muscles of the soft palate, palatine folds and pharyngeal constrictors, and carries general sensation from the ear canal and pinna. Finally, it carries taste sensation from the epiglottis of the larynx.

Answer 393

This purely motor nerve follows an unusual route. It does not actually originate from the brain. Its fibres originate from the spinal cord levels C1-C5. They join each other to form the spinal accessory nerve and enter the skull through the foramen magnum, then leave the skull again via the jugular foramen. The accessory nerve only supplies two muscles: sternocleidomastoid which is responsible for turning the head and nodding, and trapezius which is a large muscle on the back of the torso responsible for shrugging and numerus movements of the scapula.

Answer 394

Finally, the hypoglossal nerve is a purely motor nerve. It leaves the skull as the only structure to pass through its named foramen, the hypoglossal canal, and supplies motor innervation to all intrinsic and extrinsic muscles of the tongue (except palatoglossus which is supplied by the vagus nerve). Damage to a unilateral hypoglossal nerve will cause that side of the tongue to be paralysed and atrophy, meaning the other side will overpower it. This leads to a characteristic finding of the tongue pointing towards the side of the lesion.

Answer 395

the clinician can simply ask the patient if their sense of smell has changed, or they can ensure the patient is able to identify certain strong-smelling compounds, such as coffee, chocolate, vanilla, or cinnamon.

Answer 396

This nerve is tested in several ways. Firstly, visual acuity is tested using a Snellen chart (a chart with letters of decreasing sizes). Visual fields (peripheral vision), accommodation to near and far objects, colour vision, and the pupillary light reflex also test the optic nerve

Answer 397

Tested by a clinician asking a patient to follow their finger as they move it across the patient’s field of vision. The clinician can observe the movements of the patient’s eyes to ensure they are moving as they should. The pupillary light reflex also tests the oculomotor nerve.

Answer 398

the motor and sensory parts of the trigeminal nerve are tested separately. Firstly, sensation is tested by simply ensuring the patient can feel a brush of cotton wool against their skin in the three regions of the face (forehead, cheek, jaw) on both sides. Sensation may be further tested by ensuring the patient is able to tell the difference between sharp and crude touch, or by testing the blink reflex when the cornea of the eye is touched. Motor function is tested by palpating a patient’s jaw muscles as they clench their teeth or asking the patient to forcibly open their mouth against resistance.

Answer 399

The motor function of the facial nerve is its only function that is routinely tested. This is achieved by asking the patient to perform a series of facial movements, such a raising their eyebrows, closing their eyes tightly, blowing their cheeks out or showing all their teeth. The clinician looks for any asymmetry in their movements.

Answer 400

the simplest way this nerve is tested is by blocking the one of the patient’s ears and whispering a number or word in the other ear and asking the patient to repeat it to check their hearing. The test is repeated with the other ear. The function of the ear, cochlear and vestibular system can be tested more thoroughly with other tests using tuning forks and dedicated equipment in specialist clinics.

Answer 401

This nerve is tested by assessing the patient’s gag reflex. A tongue-depressor (a blunt wooden ‘lolly-stick’) is pressed against the oropharynx and a normal finding would be the patient ‘gagging’ or looking like they will vomit. This tests the sensory function of this nerve

Answer 402

There are several ways to test the vagus nerve. The gag reflex above tests the motor function of the vagus nerve, but it can be further tested by asking the patient to open their mouth and say ‘ahhh’. This should cause elevation of the soft palate by muscles which are supplied by the vagus nerve. Coughing and swallowing also both require function of the vagus nerve.

Answer 403

To test the trapezius muscle, a clinician can ask the patient to shrug their shoulders, and to test the sternocleidomastoid, a clinician asks the patient to turn their head against resistance.

Answer 404

The hypoglossal nerve is tested by asking the patient to protrude their tongue. Deviation of the tongue to one side or the other may imply damage to one of the hypoglossal nerves

Answer 405

Light is detected by the retina within the eye and impulses are passed via the optic nerves, then optic tracts and finally the optic radiations before reaching the primary visual cortex in the occipital lobe. The fibres divide and cross over in a complex way

Answer 406

The areas of vision that we can see with each eye are known as the visual fields. Each visual field is divided into a temporal field and a nasal field.

Answer 407

The temporal field is the lateral half of the visual field, the nasal retina provides our temporal visual field

Answer 408

Nasal field is the medial half The temporal retina provides our nasal visual field.

Answer 409

Visual information from the retinas first travels along the right and left optic nerves to the optic chiasm. This structure is located immediately anterior to the midbrain and superior to the pituitary gland. At the optic chiasm, visual information from the temporal visual fields (nasal retinas) from each eye cross over, such that information about the temporal vision from the left eye now travels through the right side of the brain, and vice versa.

Answer 410

After the optic chiasm, the visual information travels along the optic tracts. When the tracts reach the thalamus, the majority of fibres synapse in the lateral geniculate nucleus. After they synapse, the fibres carrying the visual information towards the primary visual cortex divide into a superior and inferior pathway on each side, known as optic radiations

Answer 411

The superior optic radiation travels in the parietal lobe, and is therefore known as the parietal radiation

Answer 412

The inferior optic radiation travels in the temporal lobe, and is known as the temporal radiation, also known as ‘Meyer’s loop’.

Answer 413

The visual information within the parietal radiations is that which is received in the superior aspects of the retinas, and therefore constitutes the inferior fields of vision. Conversely, the information in the temporal radiation is from the inferior retinas, which is therefore from the superior parts of our field of vision.

Answer 414

They both also receive input from the optic tracts at the point close to where the fibres synapse in the lateral geniculate nucleus of the thalamus.

Answer 415

Because of how visual information is passed from the retinas to the primary visual cortex, damage to different parts of the pathway will cause a different area of the visual field to be lost

Answer 416

This defect is caused by damage to an optic nerve, meaning all vision is lost from the ipsilateral eye.

Answer 417

This term means ‘both – temporal – half – vison loss’ and is caused by damage to the optic chiasm. The fibres that cross at the optic chiasm are carrying visual information from the nasal retinas, and therefore information about the temporal visual fields.

Answer 418

This term means ‘same – half – vision loss’ and is caused by damage to an optic tract, between the optic chiasm and the lateral geniculate nucleus. If the left optic tract is damaged, information from the left temporal retina and right nasal retina is lost, meaning the left nasal visual field and the right temporal visual field are lost. This would mean the patient has lost the right side of their vision in both eyes, so would be termed a right homonymous hemianopia.

Answer 419

This term means ‘same – quarter – vision loss’ and is caused by damage to either the parietal or temporal optic radiation between the lateral geniculate nucleus and the primary visual cortex. This is a more complex field loss than the homonymous hemianopia but follows similar principles. If the left parietal optic radiation is damaged, information from the left superior temporal retina and right superior nasal retina is lost, meaning the left inferior nasal visual field and the right inferior temporal visual field are lost. This would mean the patient has lost the bottom-right corner of their vision in both eyes, so would be termed a right inferior homonymous hemianopia.

Answer 420

A tumour of the pituitary gland may cause it to enlarge. As it sits immediately beneath the optic chiasm, it can enlarge enough to compress the optic chiasm. This will cause the characteristic bitemporal hemianopia.

Answer 421

* Only the brain and spinal cord are ‘central’ nervous system*. Everything else is ‘peripheral’. * the olfactory and optic nerves (CN I and II) are considered extensions of the brain rather than specific ‘nerves’ so they are CNS structures.

Answer 422

Cerebellum means ‘little brain’ and it sits immediately beneath the occipital lobe. The Cerebellum is also located immediately posterior to the brainstem

Answer 423

Fold of dura that separates the cerebellum from the occipital lobe

Answer 424

Connect the cerebellum to the brainstem 3 pairs

Answer 425

The fourth ventricle is trapped in the space between the posterior pons and medulla (ventrally) and the cerebellum (dorsally).

Answer 426

Like the cerebrum, the cerebellum is divided into separate lobes by fissures. And like the cerebrum, the cerebellum has two hemispheres, a left and right Cerebellum also has gyri

Answer 427

The anterior lobe is found on the superior surface of the cerebellum and is divided from the larger posterior lobe by the primary fissure.

Answer 428

A horizontal fissure is present within the posterior lobe

Answer 429

The third lobe, the flocculonodular lobe, is located most ventrally and is made of the flocculus and nodule. The flocculus is located beneath the cerebellar peduncles, and the nodule is found in the midline.

Answer 430

They are divided by a midline structure called the vermis.

Answer 431

The cerebellum also has gyri, like the cerebrum, but they are much smaller and called folia.

Answer 432

The cerebellum has unique anatomical features and specific functions. Certain parts of the anatomy of the cerebellum correlate with certain functions and together, they are known as functional areas of the cerebellum. Each functional area sends and receives its fibres via a specific cerebellar peduncle.

Answer 433

Anatomical part- Vermis Primary input- Spinocerebellar tracts Cerebellar peduncle- Superior and inferior Function- Correction and modulation of fine movements

Answer 434

Anatomical part- Lateral hemispheres Primary input- Cerebral cortex Cerebellar peduncle- Middle Function- Planning of coordinated movements

Answer 435

Anatomical part- Flocculonodular lobe Primary input- Vestibular system (inner ear) Cerebellar peduncle- Inferior Function- Balance, posture, tone and stabilisation of eye movements

Answer 436

Superior cerebellar arteries (SCA) Anterior inferior cerebellar arteries (AICA) Posterior inferior cerebellar arteries (PICA) (All also supply the brainstem)

Answer 437

Branch from the most superior part of the basilar artery, just before it bifurcates into the posterior cerebral arteries.

Answer 438

Branch from the most inferior part of the basilar artery, just after it is formed from the vertebral arteries.

Answer 439

Branch from the vertebral arteries before they merge to form the basilar artery.

Answer 440

V-vertigo A-ataxia N-nystagmus I-intention tremor S-slurred speech H-hypotonia E-exaggerated past pointing D-dysdiadochokinesia

Answer 441

As the cerebellum receives and processes a large amount of input from the vestibular system such as our sense of balance and the perception of movement, vertigo may be caused if it is damaged.

Answer 442

This term means poor coordination. Typically, it is obvious when observing a patient’s gait, as the patient may appear unstable, with a very wide step to try to stabilise themselves.

Answer 443

This term refers to the subtle, rapid, backwards-and-forwards eye movements that can be observed when looking closely at a patient’s eyes at the extremes of their gaze. A small amount of horizontal nystagmus may be considered normal, but vertical or rotational nystagmus is almost always abnormal. There are other causes of nystagmus, but without a functioning cerebellum able to stabilise eye movements, patients may develop this symptom.

Answer 444

Tremors are features of various neurological diseases and vary in character. In contrast to a Parkinson’s disease tremor, a tremor caused by a cerebellar lesion is absent at rest and appears as the patient ‘intends’ to do something, such as put their arms outstretched, or pick something up. This is because the cerebellum is unable to correct and modulate fine movements to stabilise the arm and hand.

Answer 445

Coordination of fine movements is one of the functions of the cerebellum and this extends to the coordination of muscles involved in articulation of speech so cerebellar dysfunction may cause patients to have slurred speech

Answer 446

Maintenance of tone and posture are functions of the vestibulocerebellum and therefore, cerebellar dysfunction will cause lack of tone

Answer 447

This is observed when asking a patient to touch their own nose, then reach out to touch the tip of your finger as you hold it in front of them. Rapid correctional movements are coordinated by the cerebellum to ensure their finger touches the target. Patients with cerebellar dysfunction are unable to correct their movements, so often ‘overshoot’ your fingertip when reaching for it and ‘point past’ it.

Answer 448

Often abbreviated to DDK, this symptom is demonstrated by asking a patient to rapidly alternate between touching the palmar and dorsal parts of their fingers onto the opposite palm. Patients with cerebellar dysfunction will struggle to coordinate this movement smoothly and will have difficulty rapidly pronating and supinating their forearms or will miss the palm entirely.

Answer 449

The primary connection between the left and right hemispheres of the cerebrum. The corpus callosum is categorised as a group of commissural fibres (fibres that cross the commissure into the opposite cerebrum).

Answer 450

A very important, central structure that acts as a relay for numerous functions of the brain including motor, sensory, visual, auditory, cognitive and emotional pathways.

Answer 451

As its name would suggest, the hypothalamus sits immediately below the thalamus, and is key to homeostasis. It exerts control over numerous hormonal endocrine functions of the body and the autonomic nervous system

Answer 452

Located at the end of a stalk known as the infundibulum, the pituitary gland secretes numerous important hormones, often under direction from the hypothalamus. The pituitary gland sits in the pituitary fossa (sella turcica) of the sphenoid bone, and the optic chiasm is immediately superior to it.

Answer 453

Considered to be part of the diencephalon but located immediately posterior to the colliculi of the midbrain, the pineal gland secretes melatonin. This hormone controls our sleep-wake cycle.

Answer 454

Within this sulcus of the occipital lobe is the primary visual cortex.

Answer 455

The limbic system is a group of deep brain structures that play a significant role in numerous important functions including learning, memory, and emotional control

Answer 456

Fornix, mamillary bodies, hippocampus, parahippocampal gyri, cingulate gyrus and cingulate sulcus, cingulum, sections of the olfactory and insular cortex, thalamus, hypothalamus, and nucleus accumbens and amygdala (discussed in the next section).

Answer 457

Similar in shape to the corpus callosum, but much smaller.

Answer 458

Small, round nuclei located at the anterior tip of the fornix.

Answer 459

Located immediately inferior to the inferior horn of each lateral ventricle, the hippocampi are part of the temporal lobes and are integral in converting short-term to long-term memory. It’s named is derived from its shape, which resembles a seahorse

Answer 460

As their name suggests, these gyri of the temporal cortices are located next to the hippocampi

Answer 461

This is a large gyrus and associated sulcus that is superior to it which are located immediately superior to the corpus callosum on both sides of the cerebrum.

Answer 462

Fibres that travel from the cingulate gyrus to other parts of the limbic system, namely the parahippocampal gyrus, are called the cingulum. The cingulum is an example of a group of association fibres

Answer 463

Fibres that connect different parts of the same hemisphere

Answer 464

As the limbic system, and particularly the hippocampus, is responsible for formation of memory and conversion of short-term memory into long-term memory, a head injury or a disease which affects this area of the brain can cause amnesia. Amnesia can be classified into retrograde amnesia (meaning patients cannot recall events that took place prior to the onset of amnesia) or anterograde amnesia (meaning patients cannot create new memories after the onset but are able to recall long-term memories of things prior to the onset).

Answer 465

The basal ganglia are a group of deep nuclei of the brain that contribute to the coordination, control and inhibition of motor function. There are five main named parts to the basal ganglia. There is a left and right nucleus for each part of the basal ganglia.

Answer 466

They are spread throughout the cerebrum, diencephalon, and midbrain. They are located close to the thalamus. Very complex excitatory and inhibitory pathways exist between each nucleus of the basal ganglia,

Answer 467

A c-shaped structure that rest immediately medial to, and follows the curvature of, the lateral ventricle.

Answer 468

A triangular-shaped nucleus that can be divided into an internal and external part.

Answer 469

An oval-shaped nucleus found immediately lateral to the globus pallidus.

Answer 470

A black nucleus found in the midbrain. Notable for producing dopamine.

Answer 471

A small nucleus, located inferior to the thalamus, but superior to the substantia nigra.

Answer 472

* Lentiform nucleus – putamen and globus pallidus. * Striatum – caudate nucleus and lentiform nucleus.

Answer 473

Nucleus accumbens Amygdala

Answer 474

Located at the anterior junction between the caudate nucleus and putamen, this nucleus plays a role in reward systems and is a subject of research into addiction.

Answer 475

A small, spherical nucleus at the tip of the inferior horn of the caudate nucleus. It is involved in memory and emotional responses such as fear and anxiety.

Answer 476

Amongst the basal ganglia, between the globus pallidus and thalamus, is a bundle of white matter tracts known as the internal capsule. This very important structure forms part of the route of the majority of sensory and motor axons travelling to and from the cortex.

Answer 477

The fibres within the internal capsule are examples of projection fibres, as they connect the cortex to deeper structures

Answer 478

Damage to the internal capsule (for example, from a stroke) can cause significant contralateral motor and sensory dysfunction

Answer 479

The axons that pass from the internal capsule to the cortex form the corona radiata. These fibres are shaped such that they ‘radiate’ out of the internal capsule towards the cortex.

Answer 480

Parkinson’s disease is caused by degeneration of the dopamine-producing neurones of the substantia nigra. This leads to a reduction in the passage of impulses within the basal ganglia which impairs the initiation and inhibition of movement. The most characteristic symptom is a ‘pill-rolling’ resting tremor. Other symptoms include a shuffling gait with small steps which is difficult to initiate and difficult to stop, ‘cogwheel’ rigidity best seen in the upper limb muscles, micrographia (very small handwriting) and a ‘mask-like’ loss of facial expression. Dopamine can be replaced with an oral precursor drug called levodopa which can temporarily reduce the severity the symptoms.

Answer 481

The vertebral column, or ‘spine’ or ‘spinal column’ is a flexible column of bones running from the head to the pelvis.

Answer 482

* Protecting the spinal cord * Supporting the head and torso * Providing attachments for muscles and ribs * Site of haematopoesis.

Answer 483

It is made up of 33 vertebrae (singular: vertebra), although some of them are fused together: * 7 cervical vertebrae which are found in the neck. * 12 thoracic vertebrae which are found in the back of the thorax. * 5 lumbar vertebrae which are found in the lower back. * 5 sacral vertebrae which fuse to form the sacrum and are found in the pelvis. * 4 coccygeal vertebrae which fuse to form the coccyx and are found in pelvis, caudal to the sacrum

Answer 484

Individual vertebrae are named with a letter and a number. The letter represents its type (cervical, thoracic etc.) and the number represents its position within that type, from cranial to caudal. For example, the first cervical vertebra is called C1, followed by C2, C3, C4 etc. The first thoracic vertebra is called T1, followed by T2, T3 etc.

Answer 485

The vertebral column has several distinct curvatures, referred to as a lordosis or a kyphosis. Lordosis is an ‘inwards’ curvature and kyphosis is an ‘outwards’ curvature. * Cervical lordosis in the neck. * Thoracic kyphosis in the upper back. * Lumbar lordosis in the lower back.

Answer 486

Excessive lordosis or kyphosis may be caused by poor posture, muscle weakness, anatomical abnormalities, or injuries. A third type of curvature known as scoliosis is seen when the spine curves laterally. Scoliosis is not a normal feature of the spine.

Answer 487

The large, often cylindrical, structure that is located most anteriorly. It supports the weight of the vertebral column above it. Neighbouring vertebral bodies are separated from each other by intervertebral discs.

Answer 488

This part stems posteriorly from the vertebral body and forms the lateral wall of the spinal canal.

Answer 489

this part forms the posterior wall of the spinal canal. The spinous process stems from the lamina.

Answer 490

This is the hole formed by the body, pedicle and lamina. The spinal cord travels within the spinal canal.

Answer 491

These are lateral protrusions from the vertebra at the junction between the pedicle and lamina that provide an attachment for muscles. In the cervical spine, they form a canal for the vertebral arteries. In the thoracic spine, they form the primary site of articulation for the ribs.

Answer 492

These are vertical protrusions from the vertebrae that provide a site of attachment to the vertebrae above and below. These synovial articulations are called facet joints.

Answer 493

These holes at the side of each vertebra are formed by the spaces between the bodies and pedicles of neighbouring vertebrae. The spinal nerves leave the cord via these foramina.

Answer 494

The atlas (C1) is the first cervical vertebrae and articulates directly with the occipital bone of the skull. This joint allows us to nod our heads. The atlas is shaped like a ring, and instead of having a vertebral body, the atlas bone has a space where it should be. It also does not have a spinous process.

Answer 495

The axis (C2) has a body that protrudes vertically upwards. This is called the odontoid process and is sometimes referred to as the ‘peg’ or ‘dens’. The odontoid process takes the place of the body of the atlas above it, such that the atlas can spin around the axis. This joint allows us to turn our heads and is called the atlanto-axial joint. It is an example of a pivot joint

Answer 496

The other five cervical vertebrae are all similar in their shape but C7 has some slight differences. Cervical vertebrae have a smaller body than the other types as they support less weight. Their transverse processes have a hole in them – the transverse foramina – which transmits the vertebral arteries (except in C7) and they all have a bifid spinous process (meaning ‘two-pronged’) (except in C7). The spinous process of C7 much more prominent and is usually the most superior spinous process that you can palpate through the skin. For this reason, C7 is sometimes referred to as ‘vertebra prominens’.

Answer 497

The 12 thoracic vertebrae are all similar in shape and become increasingly larger from superior to inferior, as the most inferior vertebrae must support more weight. The thoracic vertebrae are unique from the other types as they have additional articular surfaces for the ribs. The spinous processes are long, sharp and point downwards, allowing them to protect the spinal canal more effectively.

Answer 498

The five lumbar vertebrae are the largest individual vertebrae in the spine. They support more weight than thoracic vertebrae so have very large vertebral bodies. Their transverse processes project laterally and provide an attachment for additional muscles. The spinous processes are large and, in comparison to the thoracic vertebrae, they are relatively short and rectangular.

Answer 499

The five sacral vertebrae are fused to form the sacrum, a large triangular-shaped bone that is located in the centre of posterior part of the pelvis. It articulates with the pelvis at the sacroiliac joints. There is an anterior prominence at the top of the sacrum called the sacral promontory. The four coccygeal bones are also all fused into one bone, the coccyx, which attaches to the inferior aspect of the sacrum.

Answer 500

Vertebral body- Absent Spinous process- Absent Transverse processes- Transverse foramen Primary movements- Rotation at atlanto-axial joint

Answer 501

Vertebral body- Elongated vertically as the 'odontoid process' Spinous process- Bifid Transverse processes- Contains a transverse foramen Primary movements- Rotation at atlanto-axial joint

Answer 502

Vertebral body- Small Spinous process- Bifid (except C7) Transverse processes- contains a transverse foramen Primary movements- Flexion, extension and lateral flexion

Answer 503

Vertebral body- Medium sized and heart shaped Spinous process- Long, sharp and down-sloping Transverse processes- contain articulations for ribs Primary movements- Rotation

Answer 504

Vertebral body- very large Spinous process- Large, relatively short and rectangular Transverse processes- long, flat and directed laterally Primary movements- Flexion, extension and lateral flexion

Answer 505

Vertebral body- Fused Spinous process- Fused Transverse processes- None Primary movements- None

Answer 506

Vertebral body- Fused Spinous process- Fused Transverse processes- None Primary movements- None

Answer 507

Between the non-fused vertebrae of the spine are the intervertebral discs which are strong fibrocartilaginous structures able to withstand compression forces whilst also allowing flexibility and movement between each vertebra.

Answer 508

They are made of a central gelatinous core called the nucleus pulposus. Surrounding the nucleus pulposus is the annulus fibrosus which is made of concentric rings of collagen.

Answer 509

The intervertebral discs are separated from the vertebral bodies of the neighbouring vertebrae by a thin layer of hyaline cartilage on the surface of the vertebral bodies above and below. This joint structure of ‘bone – hyaline cartilage – fibrocartilage – hyaline cartilage – bone’ is an example of a secondary cartilaginous joint.

Answer 510

The vertebral column is supported by several ligaments that help maintain upright posture and prevent hyperflexion and hyperextension injuries. They are the Anterior longitudinal ligament; Posterior longitudinal ligament; ligamentum flavum; Interspinous ligament; Supraspinous ligament

Answer 511

Along the anterior surfaces of the vertebral bodies.

Answer 512

Along the posterior surfaces of the vertebral bodies, but anterior to the spinal canal.

Answer 513

Along the inside of the laminae. ‘Flavum’ is Latin for ‘yellow’ and this ligament appears yellow due to amount of the elastin protein within it

Answer 514

Between the spinous processes

Answer 515

Along the very tips of the spinous processes.

Answer 516

The muscles that support the vertebral column are numerous. A group of these muscles are together known as the erector spinae. These muscles form a column either side of the spinous processes. They contribute to maintaining an upright posture and can often be palpated either side of the lumbar spine whilst standing.

Answer 517

Disc herniation Repetitive compression of the intervertebral discs can lead to weakening of the annulus fibrosus and posterior herniation of the nucleus pulposus which can narrow the intervertebral foramina or spinal canal. If an intervertebral foramen is narrowed and the transiting spinal nerve is compressed, this can cause weakness in muscles supplied by that nerve or altered sensation in the dermatome. If the spinal cord or cauda equina is compressed by the herniated disc, this can cause significant neurological deficit below that level and is a surgical emergency.

Answer 518

This procedure involves sampling some CSF from the subarachnoid space in the lower vertebral canal. As the spinal cord terminates at L1/L2, a lumbar puncture (LP) must be performed lower than L2 to avoid damaging the cord. Below this level, the nerves of the cauda equina are simply pushed out of the way of the needle rather than being damaged by it.

Answer 519

To find an appropriate space between the vertebrae, the patient is positioned either sitting on the edge of a bed, or in the foetal position, and asked to push out their lower back to widen the space between the vertebrae. The L4/L5 space is in line with the intercristal plane (top of the iliac crests) so this is an appropriate space to aim for. As the needle reaches the subarachnoid space, the clinician can usually feel several gentle ‘pops’ when the needle pushes through the ligamentum flavum and dura mater. When CSF starts flowing out, the needle is in far enough.

Answer 520

Anaesthetic drugs may also be injected into the subarachnoid space through the same approach to give anaesthesia for surgery of the lower pelvis or lower limbs. This is known as spinal anaesthesia. A similar method involves injecting anaesthetic into the extradural space in the lower back and this is known as an ‘epidural’ anaesthetic.

Answer 521

At almost every vertebral level, a pair of spinal nerves leave the vertebral column via the intervertebral foramina (one on each side). Each pair of spinal nerves are named according to the vertebral level at which they leave the spine. For example, the spinal nerves that leave the spine at the level of the T4 vertebra are called the T4 spinal nerves.

Answer 522

In the cervical spine, the spinal nerves leave the spine directly above their corresponding vertebrae, as far as C7. There is an additional pair of spinal nerves that leave the vertebral column below the C7 vertebra, and these are called the C8 spinal nerves (note, there is no C8 vertebra).

Answer 523

After the C8 spinal nerves, all remaining spinal nerves leave the vertebral column directly below their corresponding vertebra. Finally, there is only one pair of coccygeal spinal nerves (Co1), so in total there are 31 pairs of spinal nerves.

Answer 524

At the level of approximately the L1-L2 junction, the spinal cord tapers off into a cone shape (called the conus medullaris) and terminates. The dura and arachnoid meninges continue down to the sacrum.

Answer 525

The pia mater thickens after the cord terminates to form a thin strand of fibrous tissue known as the filum terminale. This continues all the way to the coccyx where it helps tether the spinal cord in position.

Answer 526

Shortly before the cord terminates, it gives off all of its remaining spinal nerves that are yet to leave (L3-L5, S1-S5 and Co1) and these spinal nerves descend within the spinal canal until it is their designated level to the leave the vertebral column. This mass of spinal nerves dangling within the spinal canal resembles a horse’s tail and hence it is called the cauda equina, which means horse’s tail in Latin.

Answer 527

Each spinal nerve is formed of two roots that directly stem from the dorsal and ventral aspects of the spinal cord and are therefore named the dorsal and ventral roots.

Answer 528

The dorsal root carries sensory fibres into the spinal cord and contains a ganglion, known as the dorsal root ganglion.

Answer 529

The ventral root carries motor fibres out of the spinal cord and does not have ganglion on it. Sympathetic fibres that leave the cord also leave via the ventral root.

Answer 530

Within the spinal cord itself is the grey matter in the centre in an ‘H’ shape, and the white matter tracts around the outside. The grey matter forms two dorsal horns and two ventral horns.

Answer 531

Sensory neurones enter the cord via the dorsal root and pass through the dorsal horn. Motor neurones pass through the ventral horn and out via the ventral root.

Answer 532

Shortly after the spinal nerve is formed, it divides into two rami, a dorsal ramus that contains both sensory and motor fibres supplying dorsal structures (such as the skin over the back and paraspinal muscles), and a larger ventral ramus that carries sensory and motor fibres to ventral structures.

Answer 533

Intercostal nerves

Answer 534

To carry information along a long distance, such as from the brain to the distal limb, or from the limb to the brain, the pathway may be split into several neurones. The first neurone in the pathway is called the first order neurone. The second neurone is called the second order neurone and so on.

Answer 535

In ascending sensory pathways, there are typically three neurones: * First order neurone – from the receptor to the CNS (spinal cord or brainstem). The cell bodies of these neurones are in the dorsal root ganglion. * Second order neurone – from the spinal cord or brainstem to the thalamus. * Third order neurone – from the thalamus to the somatosensory cortex.

Answer 536

For descending motor pathways, there are typically two neurones: * First order neurone (upper motor neurone) – from the motor cortex to the ventral horn of the spinal cord. * Second order neurone (lower motor neurone) – from the spinal cord to the target muscle.

Answer 537

At some point along their path, a neurone in most of the ascending or descending tracts will cross over to the contralateral side. This crossing is known as the decussation. Different tracts decussate at different points.

Answer 538

Within the spinal cord, bundles of these neurones (axons) are organised into vertical columns within the peripheral white matter of the cord. These are known as spinal tracts. The tracts carry impulses from the brain to the periphery or vice versa.

Answer 539

These sensory tracts are located dorsally in the spinal cord and carry sensory information about fine touch, two-point discrimination, vibration and proprioception.

Answer 540

The first order neurones enter the spinal cord via the dorsal root and enter the ipsilateral dorsal columns.

Answer 541

The dorsal columns are divided into two distinct tracts on each side, the fasciculus gracilis (located medially) and the fasciculus cuneatus (located laterally). The fasciculus gracilis carries information from the lower limbs, whilst the fasciculus cuneatus carries sensory information from the upper limbs.

Answer 542

Once the first order neurones reach the medulla, they synapse at their named nuclei: the gracile and cuneate nuclei.

Answer 543

* After the synapse, the second order neurones decussate within the medulla, and the tract continues to the thalamus on the contralateral side. This part of the tract is called the medial lemniscus. Because of this, the whole tract is called the dorsal column medial lemniscus (DCML) pathway.

Answer 544

There is another synapse in the thalamus, and the third order neurones continue via the internal capsule to the primary somatosensory cortex in the parietal lobe

Answer 545

These sensory tracts are located antero-laterally in the spinal cord and carry sensory information about crude touch, pain and temperature.

Answer 546

Once the first order neurones enter the spinal cord via the dorsal root, they synapse within the dorsal horn.

Answer 547

After the synapse, the second order neurones decussate in the spinal cord, usually after travelling upwards one or two vertebral levels, and the tract continues to the thalamus on the contralateral side

Answer 548

There is another synapse in the thalamus, and the third order neurones continue via the internal capsule to the primary somatosensory cortex in the parietal lobe.

Answer 549

These motor tracts are located laterally in the spinal cord and carry motor impulses.

Answer 550

* The first order neurones (upper motor neurones) leave the motor cortex and pass through the internal capsule. They decussate within the medulla at the level of the medullary pyramids and continue contralaterally in the spinal cord. * Once the first order neurones reach the desired spinal cord level, they synapse within the ventral horn.

Answer 551

After the synapse, the second order neurones (lower motor neurones) leave the cord via the ventral root towards the target muscle.

Answer 552

These sensory tracts are located most laterally in the cord and carry unconscious proprioceptive information to the cerebellum.

Answer 553

The anterior, or ventral, spinocerebellar tract decussates twice, once at the level of entry into the cord, and again as soon as it enters the cerebellum through the superior peduncle. It therefore terminates ipsilaterally to side that it entered the cord.

Answer 554

The posterior, or dorsal, spinocerebellar tract does not decussate at all, so also reaches the cerebellum on the ipsilateral side.

Answer 555

This syndrome is caused by damage to one side of the cord only (hemisection of the cord). In clinical practice, it is quite a rare injury but causes characteristic findings on examination that explain the decussations of the tracts.

Answer 556

If a patient suffers damage to the left-hand side of their spinal cord, for example, then descending lateral corticospinal tract fibres are interrupted on the left side. Ascending dorsal column fibres on the left side are also interrupted. However, the ascending spinothalamic fibres that are interrupted on the left side had already decussated, therefore they were providing sensory information about the right side.

Answer 557

In this example, clinical examination below the level of the lesion would reveal loss of motor control of muscles on the left, loss of two-point discriminative touch, vibration and proprioception sensation on the left, but loss of pain and temperature sensation on the right from one or two levels below the lesion.

Answer 558

-Striatum -Putamen -Caudate nucleus -Globus pallidus -Internal segment (Gpi) -External segment (Gpe)

Answer 559

-Subthalamic nucleus -Substantia nigra

Answer 560

-Rostral (upper) part -Caudal (lower) part