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Neuro Anatomy Flashcards

1
Q

What are the two anatomical sub-divisions of the nervous system? What are they made up of?

A
  • The central nervous system (CNS):
    brain and spinal cord.
  • The peripheral nervous system
    (PNS): everything other than CNS
    e.g. cranial, spinal and autonomic
    nerves.
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2
Q

What are the two functional sub-divisions of the nervous system? What do they control?

A
  • Somatic nervous system: voluntary
    activities, under conscious control.
  • Autonomic nervous system:
    involuntary activities, not under
    conscious control.
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3
Q

What are the two components of the somatic nervous system? What are each responsible for?

A
  • The motor component: controls voluntary
    contraction of skeletal muscle. E.g. movement of limbs or face.
  • The sensory component: carries information aboutperipheral stimuli from receptors to CNS, reaching conscious perception. E.g. pain, temperature, touch.
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4
Q

What are the two components of the autonomic nervous system? What are each responsible for?

A
  • The motor component: controls smooth muscle,
    glands, and cardiac muscle. Two parts: sympathetic
    and parasympathetic.
  • The sensory component: conveys internal sensory
    information from viscera to CNS, doesn’t reach
    conscious perception. E.g. blood pressure
    monitoring.
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5
Q

Describe the cerebrum.

A
  • Largest part of the brain.
  • Composed of left and right cerebral
    hemispheres.
  • Surface is called cerebral cortex, this
    is folded, grey matter.
  • Each cerebral hemisphere is divided
    into four lobes: frontal, parietal,
    occipital and temporal.
  • White matter and nuclei.
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6
Q

Describe the cerebellum.

A
  • Inferior to the posterior of the cerebrum.
  • Composed of left and right
    hemispheres.
  • Folded cortex.
  • Contains white matter and nuclei.
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7
Q

Describe the brainstem.

A
  • Three parts: midbrain, pons, and
    medulla.
  • Inferior to cerebrum and anterior to
    cerebellum.
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8
Q

Describe the spinal cord.

A
  • Continuous with the medulla.
  • Protected by the vertebral column, but shorter than
    it (ends at L1-L2).
  • Cord = grey matter, surrounded by white matter
    containing tracts (bundles of axons).
  • 31 pairs of spinal nerves attached, each pair
    corresponding to a segment.
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9
Q

How are the pairs of spinal nerves divided?

A
  • 8 pairs of cervical spinal nerves (C1 - C8).
  • 12 pairs of thoracic (T1 - T12).
  • 5 pairs of lumbar (L1 - L5).
  • 5 pairs of sacral (S1 - S5).
  • 1 pair of coccygeal (Co1).
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10
Q

What do spinal nerves carry and which gaps do they pass through?

A
  • Somatic motor fibres (CNS -> body), somatic sensory
    fibres (body -> CNS), and sympathetic fibres (CNS ->
    body).
  • Pass through the intervertebral foramina.
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11
Q

What are ventricles and what are they filled with? How many are there?

A
  • Cavities in the brain which are continuous with each other and filled with cerebrospinal fluid (CSF).
  • Four interconnected in the brain, and a channel in
    the spinal cord.
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12
Q

What does CSF do?

A
  • Provides nutrients to the brain.
  • Creates a cushion around the brain, protecting it
    from trauma.
  • Prevents nerves and vessels being compressed
    between the brain and the skull.
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13
Q

What are the three meningeal layers called? How are they arranged and what are their properties?

A
  • The dura mater: inner surface of skull/vertebral
    column, thick and strong.
  • The arachnoid mater: deep to the dura, thin.
  • The pia mater: deep to the arachnoid, adhered to
    the brain/spinal cord, very thin.
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14
Q

Which two pairs of arteries supply the brain?

A
  • Left and right internal carotid arteries.
  • Left and right vertebral arteries.
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15
Q

What is the ‘Circle of Willis’ an example of? Why is this arrangement useful theoretically?

A
  • Anastomosis: branches from separate arteries unite,
    in this case forming an interconnected ring.
  • Theoretically allows blood supply to an area to be
    maintained if one of the supplying vessels is blocked.
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16
Q

What does the sympathetic system prepare the body for, and how?

A
  • The four F’s: fight, flight, fright, and freeze.
  • Heart rate increases.
  • Bronchi dilate.
  • Peripheral blood vessels constrict, diverting blood to
    the skeletal muscles in preparation for activity.
  • Pupils dilate.
  • Hair stands on end.
  • Sweat glands are stimulated.
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17
Q

What does the parasympathetic system prepare the body for, and how?

A
  • Rest and digest.
  • Heart rate decreases.
  • Bronchi constrict.
  • Glands and gut activity are stimulated.
  • Pupils constrict.
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18
Q

Describe the similarities in the anatomical arrangements of the sympathetic and parasympathetic systems.

A
  • First neuron cell bodies lie in the CNS, their axons
    leave the CNS and synapse with a second neuron,
    whose cell body lies in a ganglion.
  • Therefore, first neuron = preganglionic/presynaptic,
    and second neuron = postganglionic/postsynaptic.
  • Postganglionic fibres travel to target organs.
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19
Q

Describe the differences in the anatomical arrangements of the sympathetic and parasympathetic systems.

A
  • The first neuron cell bodies in the sympathetic
    system lie in T1 - L2/3.
  • The first neuron cell bodies in the parasympathetic
    system lie in the brainstem and S2 - S4.
  • Sympathetic ganglia = closer to CNS, preganglionic
    axons = short, postganglionic = long.
  • Parasympathetic ganglia = closer to / within target
    organs, preganglionic axons = long, postganglionic =
    short.
  • Sympathetic system is more widely distributed.
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20
Q

What is a dermatome?

A

An area of skin innervated by a single spinal nerve.

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21
Q

What is a myotome?

A

A group of muscles innervated by a single spinal nerve.

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22
Q

Describe cranial nerves.

A
  • Arise from cerebrum and brainstem.
  • 12 pairs numbered I -> XII, individually named.
  • Part of the peripheral nervous system.
  • Mainly serve the head and neck, exit the skull via
    foramina.
  • Carry many different types of nerve fibres (never
    sympathetic fibres).
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23
Q

Embryologically, what were the first 3 divisions of the brain called?

A

Forebrain - prosencephalon.
Midbrain - mesencephalon.
Hindbrain - rhombencephalon.

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24
Q

Embryologically, what were the 5 further subdivisions of the brain called, and which were their primary divisions?

A

Telencephalon (prosencephalon).
Diencephalon (“ “).
Mesencephalon.
Metencephalon (rhombencephalon).
Myelencephalon (“ “).

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25
What are the 5 further subdivisions of the brain known as in modern terms?
Telencephalon = cerebrum. Diencephalon = diencephalon. Mesencephalon = midbrain. Metencephalon = pons and cerebellum. Myelencephalon = medulla oblangata.
26
Describe white matter.
Nerve cell axons, appear white due to presence of myelin around axons (which speeds up conduction).
27
Describe grey matter.
Primarily nerve cell bodies, including their nuclei. Also consists of astrocytes, oligodendrocytes, or unmyelinated axons.
28
Where is grey matter found in the cerebrum?
Outer surface mostly.
29
Where is white matter found in the cerebrum?
Deeper parts of the cerebrum.
30
Where is grey matter found in the spinal cord?
In a H-shape at the centre of the cord.
31
Where is white matter found in the spinal cord?
Outer parts of the tract.
32
Describe the cortex.
Outer part of the cerebrum and cerebellum, mainly grey matter.
33
What is a nucleus?
A group of functionally similar or anatomically related nerve cells.
34
What is a tract?
A pathway of nerve fibres - can be a single group with no synapses, or could be two or three nerve fibres which synapse along the tract.
35
What is a fossa?
An indentation or shallow depression.
36
What is a foramen?
An opening, hole or passage.
37
What are the broad four parts of the brain?
- Cerebrum. - Cerebellum. - Diencephalon. - Brainstem.
38
Describe the cerebrum.
- Largest part of the brain. - Covers superior and lateral aspects of the brain. - Covered in folds of tissue. - 2 hemispheres, each divided into 4 lobes.
39
Describe the cerebellum.
- Smaller, bulbous structure under posterior part of the cerebrum.
40
Describe the diencephalon.
- Deep within the brain. - Beneath the cerebrum, but above the brainstem.
41
Describe the brainstem.
- Connects cerebrum and diencephalon to the spinal cord.
42
Briefly describe the four features and functions of the frontal lobe.
Contains the primary motor cortex: - Involved in executing conscious movement. Also contains the premotor cortex: - Responsible for planning and preparation of movements. Also contains the prefrontal cortex: - Involved in behaviour, personality and decision making. Also contains Broca's area: - Important for spoken language production.
43
Briefly describe the four features and functions of the temporal lobe.
Contains the primary auditory cortex: - Responsible for processing auditory information. Also contains the hippocampus: - Involved in the formation of memories. Also contains the amygdala: - Has a role in the perception of fear. Also contains Wernicke's area: - Important in understanding and coordinating spoken language.
44
Briefly describe the three features and functions of the parietal lobe.
Contains the primary somatosensory cortex: - Involved in processing sensory information. One dominant lobe: - Important for perception, and mathematical and language operations One non-dominant lobe: - Important for visuospatial functions.
45
Briefly describe the features and functions of the occipital lobe.
- Contains the primary visual cortex. - Responsible for processing visual information.
46
Briefly describe the functions of the cerebellum.
- Helps maintain posture and balance. - Corrects fine movements.
47
Briefly describe the features and functions of the brainstem.
- Connects rest of the brain to the spinal cord. - Contains nuclei of cranial nerves. - Contains vital centres for regulating breathing and cardiovascular function.
48
What are gyri?
Folds of tissue which you can find on the exterior aspect of the brain. Some have specific names and functions.
49
What are sulci?
The grooves between the gyri.
50
What is a central sulcus and where can one be found?
- Large sulcus running in coronal plane. - Separates the frontal and parietal lobes. - There is a central sulcus on both hemispheres.
51
What is a lateral sulcus and where can one be found?
- Large sulcus that runs in the transverse plane. - Separates the temporal lobe from the frontal and parietal lobes above it. - There is a lateral sulcus on both hemispheres. - AKA the 'Sylvian fissure'.
52
What two structures can be identified if the lateral sulcus is gently teased apart? Briefly describe these.
- Insula (sometimes considered to be the fifth lobe). - Opercula (refers to parts of the frontal, parietal and temporal lobes that cover the insula like lips around a mouth).
53
What is the longitudinal fissure?
The large groove that separates the two hemispheres, can be seen from a superior view.
54
What structure can be identified by gently separating the longitudinal fissure? Briefly describe this structure.
- Corpus callosum. - Large bundle of white matter (axons) that connects the two hemispheres.
55
Describe the olfactory tracts.
- Nerve fibres carrying information about smell from the nasal cavity. - Run along the inferior surface of the frontal lobes on both sides.
56
Describe the optic nerves.
- Carry visual information from the retinas of the eyes. - Run along the inferior surface of the frontal lobes, pass posteriorly and medially. - Partly cross over each other (optic chiasm).
57
Describe the mammilary bodies.
- Rounded structures. - Found just behind the optic chiasm and pituitary gland. - Part of the diencephalon.
58
Describe the hypothalamus.
- Part of the diencephalon. - Only just visible behind the optic chiasm. - Mammillary bodies are located on its most inferior surface.
59
Describe the crus cerebri.
- Means 'feet of the brain'. - Pillars of white matter that connect the rest of the brain to the brainstem. - Next to the mammillary bodies. - Form part of the cerebral peduncles (a part of the midbrain).
60
Describe the interpeduncular fossa.
- The fossa between the cerebral peduncles. - May have a layer of arachnoid mater overlying it.
61
What are the 3 parts of the brainstem.
- Midbrain. - Pons. - Medulla oblongata.
62
Describe the midbrain.
- Most superior part of the brainstem. - Where the crus cerebri are located.
63
Describe the pons.
Large, bulbous, central part of the brainstem.
64
Describe the medulla oblongata.
- Most inferior part of the brainstem. - Tapers down to become the spinal cord inferiorly.
65
List the four key areas of the frontal lobe in terms of position.
Most posterior -> most anterior: - Primary motor cortex. - Premotor cortex. - Prefrontal crotex. Broca's area = inferior frontal lobe.
66
Name the parts of the limbic system.
- Hippocampus. - Amygdala. - Various parts of the cortex. - Parts of the diencephalon.
67
What three things is the limbic system involved in?
- Emotion. - Memory. - Behaviour.
68
What is the clinical relevance of the parts of the brain and their functions?
Symptoms can indicate which lobe may be affected before scans are even taken. E.g. blindness = occipital lobe.
69
What are the meninges, how many are there, and what are they called?
- Layers of tissue that envelop the brain and spinal cord. - Three layers. - Dura mater, arachnoid mater, and pia mater.
70
Describe the dura mater.
- Most external, lying against the skull. - Fibrous, thick and does not stretch.
71
Describe the arachnoid mater.
- The intermediate layer. - Much thinner and more flexible. - Resembles a spiders web.
72
Describe the pia mater.
- Most internal, lies on the surface of the brain. - Very thin. - Cannot be seen with the naked eye.
73
How many layers is the dura mater made up of? What are they called?
2: - Outer endosteal layer. - Inner meningeal layer.
74
Describe the two layers of the dura mater.
Outer endosteal layer: - Adherent to interior of the skull. Inner meningeal layer: - Completely envelops brain and spinal cord. - Peels away from outer layer in certain places and folds down into the brain to form a double layer of dura, separating certain parts of the brain.
75
What is the falx cerebri?
A double layer of folded dura lying in the longitudinal fissure that separates the two cerebral hemispheres.
76
What is the tentorium cerebelli?
A double layer of folded dura that separates the occipital lobe from the cerebellum.
77
What is the falx cerebelli?
A double layer of folded dura that separates the two lobes of the cerebellum.
78
What are the dural venous sinuses?
Small channels where the outer endosteal layer and inner meningeal layer of the dura mater are briefly apart from each other. These channels are filled with venous blood.
79
Name some of the dural venous sinuses.
- Superior sagittal sinus. - Inferior sagittal sinus. - Straight sinus. - Transverse sinuses. - Sigmoid sinuses. - Confluence of sinuses. - Cavernous sinuses.
80
Describe the superior sagittal sinus.
- Formed in the space between the two layers of the dura. - Located superiorly. - Runs along the top of the brain in the sagittal plane.
81
Describe the inferior sagittal sinus.
- Small version of the superior sagittal sinus, runs in the same direction but inferior to it. - Formed as the meningeal layer of dura that forms the falx cerebri folds back on itself in the longitudinal fissure. - Lies on top of the corpus callosum.
82
Describe the straight sinus.
- Found where the falx cerebri connects to the tentorium cerebelli posteriorly. - Allows venous blood to drain backwards from the inferior sagittal sinus.
83
Describe the transverse sinuses.
- Found on both lateral aspects extending from the tentorium cerebelli around the side of the skull.
84
Describe the sigmoid sinuses.
- S-shaped sinuses. - Connect transverse sinuses to the internal jugular veins outside the skull to drain venous blood from the brain.
85
Describe the confluence of sinuses.
- Where the straight sinus meets the transverse sinuses and the superior sagittal sinus. - Found at the most posterior aspect of the skull. - Often leaves an impression in the internal aspect of the skull.
86
Describe the cavernous sinuses.
- Cave-like sinuses. - Found anteriorly, either side of the sella turcica of the sphenoid bone. - Internal carotid artery passes through it, along with some important nerves.
87
What is the space between the arachnoid mater and the pia mater called? What does this contain?
- Subarachnoid space. - Cerebrospinal fluid (CSF).
88
What is a cistern?
A sealed space filled with CSF, where the arachnoid spans between the gyri, leaving a covering over the sulcus.
89
Which meninge plays a vital role in the blood-brain barrier?
Pia mater.
90
Where are the arteries that supply the brain located in relation to the meninges?
In the subarachnoid space.
91
What is the blood-brain barrier?
A specialised layer of pia and endothelial cells.
92
What does the blood-brain barrier do?
Limits the passage of certain molecules into the brain and spinal cord, to protect them from harmful substances.
93
Explain the four features that allow the blood-brain barrier to be effective.
1. Endothelial cells are tightly bonded so molecules cannot pass between them. 2. Basement membrane of the capillaries in the brain and spinal cord lack fenestrations which are found elsewhere in the body. 3. Pericytes wrap around the endothelial cells to regulate blood flow and permeability. 4. Astrocytes have specialised projections called 'end feet' that further wrap around capillaries to restrict flow of certain molecules.
94
Give 4 clinical relevancies of the meninges.
- Meningitis. - Extradural haemorrhage. - Subdural haemorrhage, - Subarachnoid haemorrhage.
95
What is meningitis?
Inflammation of the meningeal layers, often caused by infection
96
Give 3 symptoms of meningitis.
- Headache. - Stiffness of the neck. - Photophobia.
97
Describe the differences between viral and bacterial meningitis?
Viral = usually more mild symptoms, resolves on its own. Bacterial = much more serious symptoms, requires treatment with IV antibiotics.
98
How can meningitis be diagnosed?
Lumbar puncture (aka 'spinal tap') - small needle inserted into the subarachnoid space, in the lumbar region of the spine, to obtain a sample of CSF to test.
99
Describe an extradural haemorrhage. (Include location of blood, characteristic CR, type of blood and a common cause)
- Blood located outside the dura. - Oval/convex on CT, lateral aspect of brain. - Arterial blood. - Commonly due to traumatic damage to the middle meningeal artery (the 'temple' region).
100
Describe an subdural haematoma (Include location of blood, characteristic CR, type of blood and a common cause)
- Blood located deep to the dura, but superficial to the arachnoid. - Crescent/concave on CT, lateral aspect of brain. - Venous blood. - More common in elderly patients or those suffering with alcoholism, as these cause brain to shrink in size, which mean bridging veins stretch.
101
Describe an subarachnoid haemorrhage. (Include location of blood, characteristic CR, type of blood and a common cause)
- Blood located deep to the arachnoid, but superficial to the pia. - White star-shaped pattern on CT. - Usually arterial blood. - Can be caused by traumatic head injury or rupture of an aneurysm of one of the cerebral arteries.
102
What is the difference between a haemorrhage and a haematoma?
Haemorrhage - active bleed. Haematoma - collection of blood without active bleeding.
103
What is the main complication of bleeding inside the skull?
The resultant increase in intracranial pressure.
104
What can be the effects of increased intercranial pressure?
The brain becomes compressed, parts of the brain could herniate into other areas, impairment of the functions of the brain, and ultimately, death.
105
What % of blood to the brain is supplied by various arteries?
80% from internal carotid arteries. 20% from vertebral arteries.
106
Where can the Circle of Willis be found?
On the inferior surface of the brain, lying on the brainstem and frontal lobe.
107
List the arteries involved in the Circle of Willis.
- Internal carotid arteries (L+R). - Vertebral arteries (L+R). - Basilar artery -> pontine arteries. - Posterior cerebral arteries (L+R). - Middle cerebral arteries (L+R). - Anterior cerebral arteries (L+R). - Posterior communicating arteries (L+R). - Anterior communicating artery. - Anterior inferior cerebellar arteries. - Posterior inferior cerebellar arteries. - Superior cerebellar arteries.
108
What do the anterior cerebral arteries supply?
- Medial aspects of frontal and parietal lobes. - Strip of cortex on the superior aspect. - Some of the anterior structures of the diencephalon.
109
What do the middle cerebral arteries supply?
- Vast majority of the lateral aspects and deep parts of the hemispheres. - Some of the structures of the diencephalon.
110
What do the posterior cerebral arteries supply?
- Mainly the occipital lobe. - Also a small portion of the inferior temporal lobe.
111
What does the basilar artery supply?
- Carries arterial blood from the vertebral arteries to the Circle of Willis. - Gives off small branches to supply the pons.
112
What do the cerebellar arteries supply?
- Mainly the cerebellum. - Also supply part of the brainstem.
113
How is the basilar artery formed?
By the unison of the two vertebral arteries.
114
How are the posterior cerebral arteries formed?
By the bifurcation of the basilar artery.
115
How are the middle cerebral arteries formed?
Continuations of the internal carotid arteries after they have entered the skull.
116
How are the anterior cerebral arteries formed?
Branches of the internal carotid arteries as they enter the skull.
117
What two groups may the arterial supply to the brain be divided into?
Anterior circulation - including the anterior and middle cerebral arteries. Posterior circulation - including the posterior cerebral, basilar and cerebellar arteries.
118
Give 2 clinical relevancies of the blood supply to the brain.
- Stroke. - Berry aneurysms.
119
What is a stroke?
An interruption to the blood supply of part of the brain leading to a neurological deficit that lasts longer than 24 hours.
120
What are the 2 types of strokes? Describe the differences.
Ischaemic - caused by an obstruction of a vessel by a thrombus or embolus, leading to downstream ischaemia. Haemorrhagic - caused by a rupture of a blood vessel leading to compression of nearby structures by the accumulation of blood.
121
What are berry aneurysms?
Aneurysm = deformity in arterial vessel walls causing them to balloon, and therefore be more prone to rupture. Berry aneurysm = named after characteristic appearance, may be found on the sides of cerebral arteries.
122
Describe the symptoms of a berry aneurysm.
- Often asymptomatic until they rupture. - If they rupture: severe, sudden-onset headache, vomiting or a reduction in a patient's conscious level.
123
What happens when a berry aneurysm ruptures?
Most often causes a subarachnoid haemorrhage, leaking arterial blood into the subarachnoid space.
124
Briefly describe the stages of venous drainage of the brain.
Cerebral venous blood -> internal cerebral veins -> external cerebral veins -> dural venous sinuses -> extracranial veins via two routes. Route 1: sigmoid sinuses become internal jugular veins as they exit the skull. Route 2: emissary veins cross the endosteal layer of dura and drain the venous blood into the bones of the skull.
125
Give 2 clinical relevancies of the venous drainage of the brain.
- Infection of the cavernous sinus -> meningitis or thrombosis. - Venous sinus thrombosis.
126
Why is the cavernous sinus clinically relevant?
As the internal carotid artery and several important nerves (CN III, IV, V1, V2, VI) pass through it Venous blood from the face can drain into it, providing a connection for superficial infection of the face t reach intracranial structures.
127
Where is the cavernous sinus found?
Behind the orbit on both sides.
128
What would a thrombosis in the cavernous sinus cause?
An increase in pressure, compressing nerves which leads to problems with eye movements and sensation over the face.
129
Describe the effects of a venous sinus thrombosis.
Drainage of venous blood = compromised -> increase in intracranial pressure causing a headache and potential compression of intracranial structures.
130
Where is CSF primarily produced? By what?
In the lateral ventricles (in the cerebral hemispheres), by a group of specialised cells called the choroid plexus.
131
Describe CSFs journey through the ventricular system.
Lateral ventricles -> third ventricle (via interventricular foramen) -> fourth ventricle (via the cerebral aqueduct) -> leaves ventricular system in one of two ways.
132
Describe the three ways CSF can leave the ventricular system
Either by: - Passing inferiorly via the central canal to fill the subarachnoid space around the spinal cord. - Passing posteriorly via the median aperture of Magendie to enter the subarachnoid space surrounding the brain. - Passing laterally via the lateral apertures of Luschka to enter the subarachnoid space surrounding the brain.
133
What are arachnoid granulations and what do they do?
- Mushroom-shaped outpouchings that push out of the subarachnoid space around the brain into the dural venous sinuses. - CSF diffuses across the wall of the arachnoid granulations, thereby recycling CSF back into the bloodstream.
134
Give a clinical relevancy of the ventricular system and CSF.
Hydrocephalus.
135
What is hydrocephalus?
The accumulation of CSF, often characterised by enlarged lateral ventricles.
136
What may cause hydrocephalus, and what symptoms can it cause?
- Most often caused by a blockage to the flow of CSF through the ventricular system. - Compression of the rest of the brain can cause: headache, vomiting, drowsiness, reduced conscious level or seizures.
137
How can hydrocephalus be relieved?
By placing a 'shunt' - this diverts CSF around the obstruction. Common type = 'VP' (ventriculo-peritoneal) shunt, diverts CSF from cerebral ventricles -> peritoneal cavity in abdomen through a tube under the skin.
138
Describe the formation of the base of the skull.
- Several individual bones connected by fibrous joints known as sutures. - 3 distinct depressions when looking from above - the cranial fossae. - Within ease cranial fossa are several small holes for nerves, arteries and veins to pass in/out of the skull called cranial foramina.
139
Which lobes rest in the anterior cranial fossa, and how many bones form it?
- The frontal lobes. - Formed of 3 bones: orbital part of the frontal bone, cribriform plate and crista galli of the ethmoid bone, and lesser wings of the sphenoid bone.
140
Describe the orbital part of the frontal bone.
The two rounded elevations are spherical cavities of the bony orbit, where the eyes are located.
141
Describe the cribriform plate and crista galli of the ethmoid bone
Cribriform plate - many small holes (sieve-like). Crista galli - vertical protrusion in its centre.
142
Describe the lesser wings of the sphenoid bone.
Small, superior wings of the sphenoid bone.
143
How many foramina are located in the anterior cranial fossa?
One - the cribriform plate.
144
What is transmitted through the cribriform plate?
Olfactory fibres that allow our sense of smell.
145
Which lobes rest in the middle cranial fossa, and how many bones form it?
- The temporal lobes. - Formed from two bones: petrous and squamous parts of the temporal bone, and the greater wings and body of the sphenoid bone.
146
Describe the petrous and squamous parts of the temporal bone.
Petrous part - hard and bulbous inferior and medial part (inner and middle ear cavities inside). Squamous part - flat, lateral part.
147
Describe the greater wings and body of the sphenoid bone.
The body in its centre and the larger inferior wings.
148
How many foramina are located on each side of the middle cranial fossa?
Six: - Optic canal. - Superior orbital fissure. - Foramen rotundum. - Foramen ovale. - Foramen lacerum. - Foramen spinosum.
149
What is transmitted through the optic canal?
Optic nerve into the bony orbit.
150
What is transmitted through the superior orbital fissure?
Several nerves that provide motor innervation (oculomotor, trochlear and abducens) and sensation (opthalmic branch of trigeminal) to the orbital region.
151
What is transmitted through the foramen rotundum?
Maxillary branch of the trigeminal nerve.
152
What is transmitted through the foramen ovale?
Mandibular branch of the trigeminal nerve.
153
What is transmitted through the foramen lacerum?
Internal carotid artery exits the carotid canal through this foramen to enter the skull.
154
What is transmitted through the foramen spinosum?
Middle meningeal artery.
155
Which lobes/areas rest in the posterior cranial fossa, and how many bones form it?
- The occipital lobes, cerebellum and brainstem. - Two bones: mostly the occipital bone, but part of the petrous part of the temporal bone.
156
How many foramina are located on each side of the posterior cranial fossa?
Four: - Internal auditory meatus. - Jugular foramen. - Hypoglossal canal. - Foramen magnum.
157
What is transmitted through the internal auditory meatus?
Vestibulocochlear and facial nerves into the inner ear cavity.
158
What is transmitted through the jugular foramen?
Glossopharyngeal, vagus and accessory nerves, and the internal jugular vein.
159
What is transmitted through the hypoglossal canal?
Hypoglossal nerve.
160
What is transmitted through the foramen magnum?
Large, central, singular foramen. CNS fibres to leave the skull and become the spinal cord.
161
Give 4 clinical relevancies of the base of the skull.
- Head injuries. - Pterion. - Craniosynostosis. - Burr holes and craniotomies.
162
Give 4 consequences of a fracture of the skull from head injury.
- Brain directly damaged by the force. - Fracture extends through foramina, damaging structures passing through them. - Dura and arachnoid meninges may be damaged -> CSF leak. - Significant bleeding.
163
What is the pterion?
- Often referred to as the 'temple'. - Shallow depression where frontal, temporal, sphenoid and parietal bones converge. - Weakest part of the skull, prone to fracture if struck.
164
What could be a consequence of a traumatic injury to the pterion? Why?
An extradural haemorrhage, as the middle meningeal artery lies immediately behind it.
165
What is craniosynostosis?
When certain sutures of the skull fuse together too early, so as the brain continues to grow the skull will become misshapen.
166
When do the sutures of the skull usually completely fuse?
When a child is around 2 years old.
167
What are burr holes? Why are they done?
Small holes (10-15mm diameter) drilled into the skull to relieve intracranial pressure.
168
What is a craniotomy?
When a larger, circular piece of the skull is removed to allow surgery. This may be replaced later, or a prosthetic implant may be used to close the craniotomy instead.
169
What are the shapes of the bony orbits?
Like cones, broad opening at the front, tapering to a narrow part at the back.
170
Which 6 bones are the orbits formed of?
- Frontal. - Sphenoid. - Zygomatic. - Maxillary. - Ethmoid. - Lacrimal.
171
What are the 5 structures found within the orbits?
- Eye (aka eyeball or globe). - Extraocular muscles. - Nerves. - Fat. - Lacrimal gland.
172
Which 3 foramina are found at the back of the orbit?
- Optic canal. - Superior orbital fissure. - Inferior orbital fissure.
173
How many extraocular muscles are there? What are they called?
Seven muscles: - Levator palpebrae superiosis. - Superior rectus. - Inferior rectus. - Medial rectus. - Lateral rectus. - Superior oblique. - Inferior oblique.
174
Which nerves supply the extraocular muscles?
LR6SO4: - Lateral rectus = CN VI. - Superior oblique = CN IV. - Rest = CN III.
175
Describe the levator palpebrae superiosis muscle. (Include nerve supply, action on the eye, and findings if non-functional)
Nerve - oculomotor nerve (CN III). Action - elevate the superior eyelid. Non-functional - ptosis (drooping eyelid).
176
Describe the superior rectus muscle. (Include nerve supply, action on the eye, and findings if non-functional)
Nerve - oculomotor nerve (CN III). Action - elevate, intort, adduct. Non-functional - unable to elevate.
177
Describe the inferior rectus muscle. (Include nerve supply, action on the eye, and findings if non-functional)
Nerve - oculomotor nerve (CN III). Action - depress, extort, adduct. Non-functional - unable to depress.
178
Describe the medial rectus muscle. (Include nerve supply, action on the eye, and findings if non-functional)
Nerve - oculomotor nerve (CN III). Action - adduct. Non-functional - unable to adduct.
179
Describe the lateral rectus muscle. (Include nerve supply, action on the eye, and findings if non-functional)
Nerve - abducens nerve (CN VI). Action - abduct. Non-functional - unable to abduct.
180
Describe the superior oblique muscle. (Include nerve supply, action on the eye, and findings if non-functional)
Nerve - trochlear nerve (CN IV). Action - intort, depress, abduct. Non-functional - unable to depress if eye is adducted.
181
Describe the inferior oblique muscle. (Include nerve supply, action on the eye, and findings if non-functional)
Nerve - oculomotor nerve (CN III). Action - extort, elevate, abduct. Non-functional - unable to elevate if eye is adducted.
182
What are conjugate eye movements?
When your eyes each perform different movements to look at the same thing. E.g. to look left; your left eye must abduct, but your right eye most adduct.
183
Where do the four recti extrocular muscles originate?
At the back of the orbit on a fibrous ring known as the common tendinous ring.
184
What happens as light enters the eye?
It is focussed 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 tract towards the primary visual cortex in the occipital lobe.
185
What is accommodation?
The eye being able to focus light to varying amounts depending on how far away the object being visualised is.
186
How does the eye achieve accommodation?
Adjusts the thickness of the lens within it: - Thicker = greater refraction of light = useful for near objects. - Thinner = lesser refraction of light = useful for distant objects.
187
How does the eye limit how much light enters it?
Constrictor pupillae (a circular muscle within the iris) constricts the pupil when too much light is detected on the retina.
188
Why would the eye limit how much light enters it?
To protect the retina from over-exposure to light.
189
Describe the innervation of the constrictor pupillae.
Parasympathetic fibres that travel within the oculomotor nerve (CN III), therefore autonomic.
190
How does the eye enable more light into it?
Dilator pupillae (a radial muscle within the iris) dilates the pupil when not enough light is detected on the retina.
191
Why would the eye allow more light to enter it?
To allow us to see adequately in the dark.
192
Describe the innervation of the dilator pupillae.
Sympathetic fibres that originate from the sympathetic chain, entering the skull alongside the internal carotid artery, therefore autonomic.
193
Does the pupillary response override stimulation of the parasympathetic or sympathetic nervous system's affects on the pupils?
Yes, even when in a state of stimulation, pupillary response will override.
194
What is the pupillary light reflex responsible for?
Automatically adjusting the amount of loght entering the eye.
195
What is the afferent (sensory) nerve of the pupillary light reflex?
The optic nerve.
196
What is the efferent (motor) nerve of the pupillayr light reflex?
The oculomotor nerve.
197
Describe the pupillary light reflex.
Optic nerve carries information about light detected on the retina -> midbrain. Synapse here with the Edinger-Westphal nucleus, which instructs the oculomotor nerve to initiate constriction of the constrictor pupillae muscle -> narrowing the pupil and reducing the light entering the eye.
198
Describe the direct pupillary responce and the consensual pupillary response.
Light shone into one eye - both constrict. Constriction of the pupil that the light is shone into = direct. Constriction of the other pupil = consensual.
199
Explain how consensual pupillary response occurs.
As there is a connection between the right and left Edinger-Westphal nuclei, if one side is activated, both sides are.
200
What does the lacrimal gland produce?
Tears.
201
Why are tears produced by the lacrimal gland?
To lubricate and moisten the surface of the eye.
202
Where can the lacrimal glands be found?
In the superior and lateral corner of the orbits.
203
Describe the movement of tears from the lacrimal gland -> nasal cavity.
Produced by lacrimal gland -> flow across eye and drain into lacrimal ducts -> drain into nasal cavity via nasolacrimal duct.
204
Where can the lacrimal ducts be found?
In the inferior and medial corner of the orbits.
205
Describe the innervation of the lacrimal gland.
Parasympathetic fibres within the facial nerve (CN VII).
206
Give 7 clinical relevancies of the orbit, extraocular muscle and the eye.
- Orbital wall fractures. - Cataracts. - Oculomotor nerve palsy. - Abducens nerve palsy. - Testing eye movements. - Drugs and the pupillary response. - Head injury and the pupillary response.
207
What can cause orbital wall fractures? Which wall is most common to fracture?
- Direct traumatic blows (e.g. in a fist fight). - Inferior orbital wall.
208
What may happen due to an orbital wall fracture?
Inferior rectus muscle may become trapped inside the fracture, tethering the eye in position and patients will be unable to look up.
209
What is a cataract?
A common ocular conditions characterised by clouding of the lens.
210
How do cataracts develop?
Slowly and painlessly.
211
Discuss cataract prevention and treatment.
- Cannot be prevented. - Relatively easy to treat via surgery, removing the affected lens and replacing it with a new and clear intraocular lens.
212
Describe oculomotor nerve palsy.
- Affected eye will be depressed and abducted due to lateral rectus and superior oblique muscles being unopposed. - Affected eye's pupil will also be dilated due to lack of parasympathetic nerve supply to the constrictor pupillae, leaving the dilator pupillae unopposed. - Affected eye will have ptosis (eyelid drooping) due to the loss of motor nerve supply to the levator palpebrae superiosis. - Affected eye will also be unable to adduct.
213
Describe abducens nerve palsy.
- Affected eye unable to abduct as the lateral rectus muscle is no longer working. - Affected eye may be pulled medially at rest causing strabismus (aka squint), as medial rectus may be still functional and overpower the lateral rectus.
214
Describe how a clinician may test the different eye movements and why.
- Ask the patient to follow their fingers as they draw the letter 'H' in front of them. - Vital part of neurological examination of the cranial nerves.
215
Give 2 drugs that will cause pupillary constriction.
- Morphine. - Heroin.
216
Give 2 drugs that will cause pupillary dilation.
- Ecstasy. - Cocaine.
217
In which scenario can the size of the pupil be particularly helpful for clinicians?
When assessing unconscious patients.
218
What is an early sign of oculomotor nerve compression after head injury?
Dilation of the ipsilateral pupil.
219
What does the outer ear consist of?
- The pinna. - The ear canal. - The tympanic membrane.
220
Describe the function of the pinna.
Shaped to gather sound waves and direct them into the ear canal.
221
Describe the function of the ear canal.
Directs sound waves towards the tympanic membrane.
222
Describe the function of the tympanic membrane.
When sound waves strike it, it vibrates like the surface of a drum, transmitting them deeper into the ear towards the cochlea.
223
What does the middle ear cavity consist of?
- The ossicles: malleus, incus and stapes. - The superior opening of the auditory tube (aka Eustachian tube). - The tensor tympani muscle and the stapedius muscle.
224
What are the ossicles and what do they do?
Three of the smallest bones in the body, they carry the sound waves to the oval window which conveys it into the cochlea.
225
Describe the malleus.
- First ossicle. - Rests against the tympanic membrane. - Hammer shaped (handle rests against tympanic membrane, head connects to the incus).
226
Describe the incus.
- Second ossicle. - Means 'anvil'. - As the hammer strikes the anvil sound waves are transmitted, eventually reaching the stapes.
227
Describe the stapes.
- Third ossicle. - Means 'stirrup', which it resembles. - Receives sound wave vibrations from incus, transmits them onto oval window.
228
What structure marks the boundary of the middle and inner ear cavities?
The oval window.
229
Where are the superior and inferior openings of the auditory tube located?
Superior - middle ear cavity. Inferior - posterior and inferior part of the nasal cavity.
230
What do the openings of the auditory tube allow?
A connection of airflow from the external environment and the middle ear cavity, via the nasal cavity.
231
Why is a connection of airflow from the external environment and the middle ear cavity vital?
To maintain equal air pressure on either side of the tympanic membrane, so air pressure does not build up on one side r the other - this could cause pain and potentially rupture.
232
Discuss descent in relation to the tympanic membrane.
- As you descend (in air or water), pressure increases outside the tympanic membrane causing it to bulge inwards. - To counter this, air passes up through the auditory tube to increase pressure on the inside. - Sometimes, if the pressure correction occurs suddenly, you feel a 'pop' in your ear.
233
What is the general role of the two small muscles of the muddle ear cavity?
To dampen sound vibrations and reduce perceived volume.
234
Describe the function of the tensor tympani muscle.
Inserts on the malleus and when it contracts it increases tension in the tympanic membrane - reducing how much it can vibrate.
235
Discuss the innervation of the tensor tympani muscle.
Supplied by the mandibular branch of the trigeminal nerve (CN V).
236
Describe the function of the stapedius muscle.
Inserts on the stapes, when it contracts it dampens its vibrations.
237
Discuss the innervation of the stapedius muscle.
Supplied by the facial nerve (CN VII).
238
What are the 2 main organs within the bony labyrinth of the inner ear cavity?
- Cochlea. - Vestibular system.
239
Describe the bony labyrinth of the inner ear.
Network of small bony passages within the petrous part of the temporal bone of the skull.
240
Describe the role and function of the cochlea.
- Sound waves and vibrations travel through fluid within the cochlea. - They are converted into electrical impulses which are passed to the auditory cortex via the cochlear nerve. - This allows us to perceive sound.
241
What does the vestibular system consist of?
- Semicircular canals. - The utricle. - The saccule.
242
Describe the role and function of the vestibular system.
- Contains fluid which flows when we move our heads. - Movement of fluid is detected by specialised cells, causing them to produce electrical impulses. - Impulses are passed along the vestibular nerve to various parts of the brain (e.g. cerebellum, thalamus, certain cranial nerve nuclei). - Semicircular canals allow us to perceive movement. - Utricle and saccule allow us to perceive linear acceleration.
243
What is the oculocephalic reflex?
The ability to maintain a fixed gaze whilst moving our head.
244
How does the oculocephalic reflex work?
- Impulses from cochlea and vestibular system carried by the vestibulocochlear nerve (CN VIII), through the internal auditory meatus, towards nuclei of CN VIII in the pons. - Here, there are other connections to other brainstem nuclei of the oculomotor, trochlear and abducens nerves which control eye movement. - These connections make the oculocephalic reflex possible.
245
Give 3 clinical relevancies of the ear.
- Vertigo. - Vestibular schwannoma. - Otitis media.
246
What is vertigo?
The symptom of being able to perceive movement when there is none.
247
What may cause vertigo?
- Many causes. - Common = disorder of the vestibular system. - E.g. inflammation, infections, endo/perilymph disorders, cancers of the vestibular system or nerves.
248
What is vestibular schwannoma?
- Benign tumour of Schwann cells surrounding the vestibulocochlear nerve. - AKA acoustic neuroma.
249
What symptoms may occur due to vestibular schwannoma?
- As the tumour grows, it can lead to unilateral hearing loss, tinnitus, a feeling of fullness in the ear, and vertigo.
250
What may happen if a vestibular schwannoma grows increasingly large?
- May compress the other cranial nerves leaving the brainstem at that position. - These are the trigeminal (CN V) and facial (CN VII) nerves. - This position is known as the cerebellopontine angle.
251
What is otitis media?
Inflammation within the middle ear cavity.
252
What may causes otitis media? Who is more likely to suffer with otitis media?
- Simple viral infections. - More common in young children. - Upper respiratory tract infections can lead to it (via nasal cavity and auditory tube), leading to inflammatory fluid and pus being present.
253
What can inflammatory fluid and pus in the middle ear cavity cause?
- Impaired conduction of sound waves along the ossicles. - Possible increased pressure behind the tympanic membrane = pain. - If inflammation continues, pressure increases, tympanic membrane may rupture (can heal itself later usually).
254
What may occur in more severe cases of otitis media?
Spreads deeper into the ear, causing inflammation of the cochlea or vestibular system, mastoid process of the temporal bone, or the meninges.
255
Where can the midbrain be found? Describe its parts.
- At the top of the brainstem. - Divided into two parts, either side of the cerebral aqueduct (the tectum and the tegmentum). - Tectum dorsally. - Tegmentum ventrally.
256
Which is smaller, the tectum or the tegmentum?
The tectum.
257
What important features does the tectum contain?
Two sets of colliculi - superior and inferior.
258
What are the superior colliculi involved in?
Regulating eye movements and reflexes associated with visual stimuli.
259
What are the inferior colliculi involved in?
Sound location, pitch discrimination, and reflexes associated with auditory stimuli.
260
What important features does the tegmentum contain?
- Substantia nigra. - Red nucleus. - Cerebral peduncles.
261
What is the substantia nigra involved in?
- Motor control, by producing dopamine.
262
What is the red nucleus involved in?
Supporting motor control of the limbs.
263
What are the cerebral peduncles? What do they do?
- Large white matter bundles on the ventral surface of the tegmentum. - Connect the midbrain to the thalami.
264
Which 3 important nuclei does the midbrain contain?
- Oculomotor nerve (CN III) nuclei. - Trochlear nerve (CN IV) nuclei. - Edinger-Westphal nuclei.
265
Where can the pons be found?
It is the large, rounded, middle part of the brainstem.
266
Describe the 3 main structures near the pons.
- Basilar artery: sits on its ventral surface. - Middle cerebellar peduncles: white matter bundles on its dorsal surface that connect it to the cerebellum. - Fourth ventricle: situated dorsal to the pons, between the middle cerebellar peduncles.
267
Which 4 important nuclei does the pons contain?
- Trigeminal nerve (CN V) nuclei. - Abducens nerve (CN VI) nuclei. - Facial nerve (CN VII) nuclei. - Vestibulocochlear nerve (CN VIII) nuclei.
268
Which 2 important centres does the pons contain? What are these for?
- Pneumotaxic and apneustic centres. - Involved in the regulation of breathing.
269
Where can the medulla oblongata be found?
Connects the pons to the spinal cord.
270
What is the name of the groove that runs on the surface of the medulla? Does this groove lie on its ventral or dorsal surface?
- Anterior median fissure. - On its ventral surface.
271
What does the anterior median fissure separate?
The two medullary pyramids.
272
What runs inside the medullary pyramids?
Corticospinal tracts.
273
What are the other pair of ridges, immediately lateral to the medullary pyramids, called?
The medullary olives.
274
What is the name of the important sensory pathway of nerves that runs in the dorsal part of the medulla?
The dorsal column medial lemniscus pathway (DCML).
275
What are the two pairs of nerve fibres which the DCML runs within?
- Fasciculus gracilis. - Fasciculus cuneatus.
276
Which 4 important nuclei does the medulla contain?
- Glossopharyngeal nerve (CN IX) nuclei. - Vagus nerve (CN X) nuclei. - Accessory nerve (CN XI) nuclei. - Hypoglossal nerve (CN XII) nuclei.
277
The medulla also contains vital centres for which functions?
Regulating respiration, heart rate and blood pressure, and initiating vomiting.
278
Define bulbar palsy.
Dysfunction of the cranial nerves that arise from the medulla (CN IX -> CN XII).
279
What are 5 symptoms of bulbar palsy?
- Difficulty speaking. - Difficulty swallowing. - Excessive saliva production. - Wasting and fasciculations of the tongue. - Absent gag reflex.
280
What can cause bulbar palsy? Give 2 examples.
- Diseases which affect peripheral nerves. - E.g. motor neurone disease, and Guillain-Barré syndrome.
281
Fact file of CN I. (Name, type of fibre, CNS origin, skull base foramen, and function).
- Olfactory nerve. - Sensory. - Cerebrum. - Cribriform plate. - Olfaction (smell).
282
Fact file of CN II. (Name, type of fibre, CNS origin, skull base foramen, and function).
- Optic nerve. - Sensory. - Diencephalon. - Optic canal. - Sight.
283
Fact file of CN III. (Name, type of fibre, CNS origin, skull base foramen, and function).
- Oculomotor nerve. - Motor (and parasympathetics). - Midbrain. - Superior orbital fissure. - Eye movements (SR, IR, MR, IO), eyelid opening (LPS), pupillary constriction and accommodation.
284
Fact file of CN IV. (Name, type of fibre, CNS origin, skull base foramen, and function).
- Trochlear nerve. - Motor. - Midbrain. - Superior orbital fissure. - Eye movements (SO).
285
Fact file of CN V. (Name, type of fibre, CNS origin, skull base foramen, and function).
- Trigeminal nerve. - Both. - Pons. - V1 = ophthalmic = superior orbital fissure, - V2 = maxillary = foramen rotundum. - V3 = mandibular = foramen ovale. - V1 = sensation for upper 1/3 of face. - V2 = sensation for middle 1/3 of face. - V3 = sensation for lower 1/3 of face, motor to muscles of mastication, motor to the tensor tympani muscle.
286
Fact file of CN VI. (Name, type of fibre, CNS origin, skull base foramen, and function).
- Abducens nerve. - Motor. - Pons. - Superior orbital fissure. - Eye movements (LR).
287
Fact file of CN VII. (Name, type of fibre, CNS origin, skull base foramen, and function).
- Facial nerve. - Both (and parasympathetics). - Pons. - Internal auditory meatus, then stylomastoid foramen. - Motor to muscles of facial expression, motor to stapedius muscle, sensation from ear canal, secretomotor function to submandibular and sublingual salivary glands and lacrimal gland, taste from anterior /3 of the tongue.
288
Fact file of CN VIII. (Name, type of fibre, CNS origin, skull base foramen, and function).
- Vestibulocochlear nerve. - Sensory. - Pons. - Internal auditory meatus. - Balance and hearing.
289
Fact file of CN IX. (Name, type of fibre, CNS origin, skull base foramen, and function).
- Glossopharyngeal nerve. - Both (and parasympathetics). - Medulla. - Jugular foramen. - Motor to the stylopharyngeus muscle, sensation from pharynx and posterior 1/3 of the tongue, sensation from carotid baroreceptors, secretomotor function to parotid salivary gland, taste from posterior 1/3 of tongue.
290
Fact file of CN X. (Name, type of fibre, CNS origin, skull base foramen, and function).
- Vagus nerve. - Both (and parasympathetics). - Medulla. - Jugular foramen. - Motor to muscles of the soft palate, pharyngeal muscles and internal laryngeal muscles, sensation from external ear and ear canal, taste from epiglottis, and parasympathetics to thoracic and abdominal regions.
291
Fact file of CN XI. (Name, type of fibre, CNS origin, skull base foramen, and function).
- Accessory nerve. - Motor. - Spinal cord C1 -> C5. - Foramen magnum (in) and jugular foramen (out). - Motor to the trapezius and sternocleidomastoid.
292
Fact file of CN XII. (Name, type of fibre, CNS origin, skull base foramen, and function).
- Hypoglossal nerve. - Motor. - Medulla. - Hypoglossal canal. - Motor to muscles of the tongue.
293
Of the 3 branches of the trigeminal nerve (CN V), which are purely sensor, and which is a mixed nerve?
V1 = purely sensory. V2 = purely sensory. V3 = mixed motor and sensory.
294
What are the 4 muscles of mastication?
- Temporalis. - Masseter. - Medial pterygoid. - Lateral pterygoid.
295
Where does the facial nerve divide into 5 branches?
In the parotid salivary gland (which it does not innervate).
296
What are the 5 branches of the facial nerve?
- Temporal. - Zygomatic. - Buccal. - Marginal mandibular. - Cervical.
297
What do the 5 branches of the facial nerve supply?
The muscles of facial expression.
298
Which muscles of the tongue does the hypoglossal nerve (CN XII) innervate?
All intrinsic and extrinsic muscles of the tongue, except palatoglossus, which is supplied by the vagus nerve (CN X).
299
What will occur if there is damage to a unilateral hypoglossal nerve?
- That side of the tongue will be paralysed and atrophy. - Other side will overpower it, leading to a finding of the tongue pointing towards the side of the lesion.
300
How is the olfactory nerve (CN I) tested in a patient with a neurological condition?
- Ask the patient if their sense of smell has changed. - Ensure the patient can identify strong-smelling compounds e.g. coffee, vanilla, cinnamon.
301
How is the optic nerve (CN II) tested in a patient with a neurological condition?
- Snellen chart. - Visual fields. - Accommodation to near and far objects. - Colour vision. - Pupillary light reflex.
302
How is the oculomotor nerve (CN III) tested in a patient with a neurological condition?
- Follow a finger as it moves across a patient's field of vision. - Tested alongside trochlear (CN IV) and abducens (CN VI) nerves. - Pupillary light reflex also.
303
How is the trochlear nerve (CN IV) tested in a patient with a neurological condition?
- Same test as CN III, following a finger.
304
How is the trigeminal nerve (CN V) tested in a patient with a neurological condition?
- Sensation tested by ensuring patients can feel a brush of cotton wool against 3 regions of the face (forehead, cheek, jaw) on both sides. - Can be further tested by identifying between sharp and crude touch, or by testing blink reflex when cornea is touched. - Motor is tested by palpating a patient's jaw muscles as they clench their teeth, or by asking a patient to forcibly open their mouth against resistance.
305
How is the abducens nerve (CN VI) tested in a patient with a neurological condition?
- Same test as CN III, following a finger.
306
How is the facial nerve (CN VII) tested in a patient with a neurological condition?
- Motor function = only function that is routinely tested. - Asking the patient to perform several facial movements e.g. raising eyebrows, closing eyes tightly, blowing cheeks out, showing all their teeth. - Clinicians look for asymmetry in their movements.
307
How is the vestibulocochlear nerve (CN VIII) tested in a patient with a neurological condition?
- Simplest way = block one ear, whisper a number or word in the other, ask the patient to repeat to check their hearing. Repeat with the opposite ear. - Can also use more thorough tests e.g. tuning forks.
308
How is the glossopharyngeal nerve (CN IX) tested in a patient with a neurological condition?
- Assess the patient's gag reflex by pressing a tongue depressor against the oropharynx (a normal patient would gag). - This tests the sensory function of the nerve.
309
How is the vagus nerve (CN X) tested in a patient with a neurological condition?
- Gag reflex test assesses motor function of the nerve. - Also, asking patients to open their mouth and say 'ahh', this should cause elevation of the soft palate by muscles supplied by the vagus nerve. - Coughing and swallowing also require function of the vagus nerve.
310
How is the accessory nerve (CN XI) tested in a patient with a neurological condition?
- Ask a patient to shrug their shoulders (tests the trapezius muscle). - Ask a patient to turn their head against resistance (tests the sternocleidomastoid muscle).
311
How is the hypoglossal nerve (CN XII) tested in a patient with a neurological condition?
- Ask the patient to protrude their tongue. - Deviation to one side or the other may imply damage to one of the hypoglossal nerves.
312
Describe the path of light to the primary visual cortex.
Light detected by retina -> impulses pass via optic nerves -> optic chiasm -> optic tracts -> optic radiation -> primary visual cortex.
313
What are the 2 parts of the visual field?
- Temporal field (lateral half of the visual field). - Nasal field (medial half of the visual field).
314
Describe the relationship between the halfs of the visual field and the retina.
- Light entering one half of the visual field, is received by the opposite half of the retina. - E.g. light enters lateral field = received by nasal retina, and vice versa.
315
Which part of the visual field does the nasal retina provide?
The temporal field.
316
Which part of the visual field does the lateral retina provide?
The nasal field.
317
Where can the optic chiasm be found?
- Immediately anterior to the midbrain. - Superior to the pituitary gland.
318
What occurs at the optic chiasm?
Visual information from the temporal field/nasal retina from each eye crosses over, to travel through the opposing side of the brain.
319
When the optic tracts reach the thalamus, where do the majority of fibres synapse?
In the lateral geniculate nucleus.
320
After fibres synapse in the lateral geniculate nucleus, what do they do?
Divide into a superior and inferior pathway on each side, known as optic radiations.
321
What are the 2 optic radiations called, and why?
Superior optic radiation = parietal radiation, as it travels in the parietal lobe. Inferior optic radiation = temporal radiation, as it travels in the temporal lobe.
322
Describe the visual information within the parietal radiations.
Received in superior aspects of the retinas, so therefore constitutes the inferior fields of vision.
323
Describe the visual information within the temporal radiations.
Received in inferior aspects of the retinas, so therefore constitutes the inferior fields of vision.
324
Name 4 visual field defects.
- Monocular vision loss. - Bitemporal hemianopia. - Homonymous hemianopia. - Homonymous quadrantanopia.
325
What is monocular vision loss? What causes it?
- All vision is lost from one eye. - Caused by damage to an optic nerve (ipsilateral one).
326
What is bitemporal hemianopia? What causes it?
- Loss of both temporal fields of vision. - Caused by damage to the optic chiasm, as fibres that cross over here are from the nasal retinas, therefore the temporal visual fields.
327
What is homonymous hemianopia? What causes it?
- Loss of the same side of vision from each eye (one temporal, one nasal). - Caused by damage to an optic tract, as, for example, if the left optic tract is damaged, it carries left temporal retina and right nasal retina information -> left nasal field and right temporal field lost = same side (this would be right homonymous hemianopia).
328
What is homonymous quadrantanopia? What causes it?
- Loss of the same quadrant of vision from each eye. - Caused by damage to an optic radiation, as, for example, if the left parietal optic radiation is damaged, it carries left superior temporal retina and right superior nasal retina information -> left inferior nasal visual field and right inferior temporal visual field lost = same quadrant (this would be right inferior homonymous quadrantanopia).
329
What type of brain tumour is significant in relation to vision? Why?
A tumour of the pituitary gland, as if it enlarges, it can compress the optic chiasm.
330
What will a compression of the optic chiasm cause in terms of visual field defect?
Bitemporal hemianopia.
331
What separates the cerebellum and the occipital lobe? What is this?
The tentorium cerebelli - a fold of dura.
332
How is the cerebellum connected to the brainstem?
Via 3 pairs of cerebellar peduncles (superior, middle, and inferior).
333
Where can the fourth ventricle be found?
Between the posterior pons and medulla (ventrally), and the cerebellum (dorsally).
334
How many lobes are there of the cerebellum? What are these called?
3 lobes: anterior, posterior and flocculonodular lobes.
335
What separates the anterior and posterior lobes of the cerebellum?
The primary fissure.
336
What fissure can be found in the posterior lobe of the cerebellun?
The horizontal fissure.
337
What is the flocculonodular lobe made up of? Where can these parts be found?
- The flocculus and the nodule. - The flocculus is located beneath the cerebellar peduncles. - The nodule is found in the midline.
338
What divides the two hemispheres of the cerebellun?
The vermis.
339
Describe the cerebellum's equivalent of gyri.
- Called folia. - Much smaller than gyri.
340
Fact file of spino-cerebellum (a functional area of the cerebellum). (Include anatomical part of the cerebellum, the primary input, which cerebellar peduncle is sends/receives fibres via, and its function).
Anatomical part = vermis. Primary input = spinocerebellar tracts. Cerebellar peduncle = superior and inferior. Function = correction and modulation of fine movements.
341
Fact file of cerebro-cerebellum (a functional area of the cerebellum). (Include anatomical part of the cerebellum, the primary input, which cerebellar peduncle is sends/receives fibres via, and its function).
Anatomical part = lateral hemispheres. Primary input = cerebral cortex. Cerebellar peduncle = middle. Function = planning of coordinated movements.
342
Fact file of vestibulo-cerebellum (a functional area of the cerebellum). (Include anatomical part of the cerebellum, the primary input, which cerebellar peduncle is sends/receives fibres via, and its function).
Anatomical part = flocculonodular lobe. Primary input = vestibular system (inner ear). Cerebellar peduncle = inferior. Function = balance, posture, tone and stabilisation of eye movements.
343
Which 3 paired arteries supply blood to the cerebellum?
- Superior cerebellar arteries (SCA). - Anterior inferior cerebellar arteries (AICA). - Posterior inferior cerebellar arteries (PICA).
344
What acronym can be used to remember the symptoms of cerebellar dysfunction?
VANISHED. V = vertigo. A = ataxia. N = nystagmus. I = intention tremor. S = slurred speech. H = hypotonia. E = exaggerated past-pointing. D = dysdiachokinesia (DDK).
345
What can cause disruption to the cerebellum's function?
- Heavy alcohol consumption. - Lesion of the cerebellum (e.g. stroke or tumour).
346
Why can cerebellar dysfunction cause vertigo?
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, therefore damage -> vertigo.
347
What is ataxia?
Poor coordination, can be seen by a patient's gait (may appear unstable, with a very wide step to try to stabilise themselves).
348
What is nystagmus?
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.
349
Describe an intention tremor and why it occurs with cerebellar dysfunction.
Absent at rest, and appears as a patient 'intends' to do something. This is because the cerebellum cannot correct and modulate the fine movements if damaged.
350
Why does cerebellar dysfunction cause slurred speech?
As the cerebellum is responsible for coordination of fine movements, including the coordination of muscles involved in articulating speech, therefore damage = slurred speech.
351
Why does cerebellar dyfunction cause hypotonia?
As maintenance of tone and posture are functions of the vestibulocerebellum, therefore cerebellar dysfunction = lack of tone.
352
Describe past-pointing in patients with cerebellar dysfunction.
Patients are unable to correct their movements, so often overshoot your fingertip when reaching for it - pointing past it.
353
What is dysdiadochokinesia?
Difficulty rapidly pronating and supinating their forearms, or missing the palm entirely when asked to rapidly alternate between touching the palmar and dorsal parts of their fingers onto the opposite palm.
354
Describe the corpus callosum.
- Primary connection between left and right hemispheres. - Categorised as a group of commissural fibres.
355
Describe the thalamus.
- Very important, central structure. - Acts as a relay for numerous brain functions including motor, sensory, visual, auditory, cognitive and emotional pathways.
356
Describe the hypothalamus.
- Sits immediately below the thalamus. - Key to homeostasis. - Exerts control over numerous hormonal endocrine functions of the body and the autonomic nervous system.
357
Describe the pituitary gland.
- Located at the end of the stalk known as the infundibulum. - Secretes numerous important hormones, often under direction from the hypothalamus. - Sits in the sella turcica (pituitary fossa) of the sphenoid bone. - Optic chiasm is immediately superior to it.
358
Describe the pineal gland.
- Considered to be part of the diencephalon, but located immediately posterior to the colliculi of the midbrain. - Secretes melatonin, which controls our sleep-wake cycle.
359
Describe the calcarine sulcus.
- Within this sulcus of the occipital lobe is the primary visual cortex.
360
Describe the limbic system.
Group of deep brain structures that play a significant role in numerous important functions such as learning, memory and emotional control.
361
Describe the fornix.
- Part of the limbic system. - Similar in shape to the corpus callosum, but much smaller.
362
Describe the mammillary bodies.
- Part of the limbic system. - Small, round nuclei located at the anterior tip of the fornix.
363
Describe the hippocampus.
- Part of the limbic system. - Part of the temporal lobes. - Integral in converting short-term to long-term memory. - Name is derived from its shape, which resembles a seahorse.
364
Describe the parahippocampal gyri.
- Part of the limbic system. - Gyri of the temporal cortices located next to the hippocampi.
365
Describe the cingulate gyrus and cingulate sulcus.
- Large gyrus and its associated sulcus that is superior to it. - Located immediately superior to the corpus callosum.
366
What are the fibres called that travel from the cingulate gyrus to other parts of the limbic system? What type of fibres are they?
- The cingulum. - Example of a group of association fibres.
367
Name some other parts of the limbic system
- Sections of the olfactory and insular cortex. - Thalamus. - Hypothalamus. - Nuclear accumbens. - Amygdala.
368
Give a clinical relevancy of the limbic system, particularly the hippocampus.
Amnesia.
369
How can amnesia be classified?
- Retrograde amnesia: meaning patients cannot recall events that took place prior to the onset of amnesia). - Anterograde amnesia: meaning patients cannot create new memories after the onset of amnesia, but are able to recall long-term memories of things prior to the onset).
370
What are the basal ganglia and what do they contribute to?
A group of deep nuclei of the brain that contribute to the coordination, control and inhibition of motor function.
371
What structure are the basal ganglia located very near to?
The thalamus.
372
How many parts are there to the basal ganglia?
5 parts, with a left and right nucleus for each.
373
What are the 5 parts of the basal ganglia?
- Caudate nucleus. - Globus pallidus. - Putamen. - Substantia nigra. - Subthalamic nucleus.
374
Describe the caudate nucleus.
A C-shaped structure that rests immediately medial to, and follows the curvature of, the lateral ventricle.
375
Describe the globus pallidus.
A triangular-shaped nucleus that can be divided into an internal and external part.
376
Describe the putamen.
An oval-shaped nucleus found immediately lateral to the globus pallidus.
377
Describe the substantia nigra.
A black nucleus found in the midbrain, notable for producing dopamine.
378
Describe the subthalamic nucleus.
A small nucleus, located inferior to the thalamus, but superior to the substantia nigra.
379
What is the lentiform nucleus made up of?
The putamen and globus pallidus.
380
What is the striatum made up of?
The caudate nucleus and lentiform nucleus.
381
Which 2 structures can be found very close to the basal ganglia but are not involved in its motor function, instead being part of the limbic system?
- The nucleus accumbens. - The amygdala.
382
Describe the nucleus accumbens.
- Located at the anterior junction between the caudate nucleus and putamen. - Plays a role in reward systems and is a subject of research into addiction.
383
Describe the amygdala.
A small, spherical nucleus at the tip of the inferior horn of the caudate nucleus. - Involved in memory and emotional responses such as fear and anxiety.
384
Where is the internal capsule found? What is it made up of?
- Between the globus pallidus and the thalamus. - A bundle of white matter tracts.
385
What type of fibres are those within the internal capsule?
Projection fibres.
386
Why is the internal capsule important?
As it forms part of the route of the majority of sensory and motor axons travelling to and from the cortex.
387
What do the axons that pass through the internal capsule to the cortex from?
The corona radiata.
388
Give 2 clinical relevancies of the basal ganglia and the internal capsule.
- Parkinson's disease. - Huntington's disease.
389
What causes Parkinson's Disease?
Degeneration of the dopamine-producing neurones of the substantia nigra. This leads to a reduction in the passage of impulses within the basal ganglia, impairing initiation and inhibition of movement.
390
What is the most characteristic symptom of Parkinson's Disease?
A 'pill-rolling' resting tremor.
391
Give 4 other symptoms of Parkinson's Disease.
- Shuffling gait with small steps which is difficult to both initiate and stop. - 'Cogwheel' rigidity best seen in the upper limb muscles. - Micrographia (small handwriting). - 'Mask-like' loss of facial expression.
392
What can help temporarily reduce the severity of the symptoms of Parkinson's Disease?
An oral precursor drug called levodopa, which replaces dopamine.
393
What causes Huntington's Disease?
An autosomal-dominant genetic disorder that leads to gradual damage to cells in various places within the brain.
394
What is the characteristic movement disorder of Huntington's Disease?
'Chorea', which involves sudden, jerky and uncontrollable movements of the face, arms and legs.
395
Give 3 other symptoms of Huntington's disease.
- Mood and personality changes. - Cognitive impairment. - Motor dysfunction.
396
What drug treatment can be used in Huntington's disease?
Dopamine receptor blockers = neuroleptics.
397
Describe the 33 vertebrae, their names and positions in the body, and what they form (if they form anything).
7 cervical vertebrae = neck. 12 thoracic vertebrae = back of the thorax. 5 lumbar vertebrae = lower back. 5 sacral vertebrae = pelvis, fuse to form the sacrum. 4 coccygeal = pelvis, fuse to form the coccyx.
398
What is a lordosis?
An 'inwards' curvature.
399
What is a kyphosis?
An 'outwards' curvature.
400
What are the 3 distinct curvatures of the vertebral column? Where can they be found?
- Cervical lordosis (neck). - Thoracic kyphosis (upper back). - Lumbar lordosis (lower back).
401
What is scoliosis?
- An abnormal feature of the spine. - The spine curves laterally.
402
What name is given to vertebrae C1?
Atlas.
403
What name is given to vertebrae C2?
Axis.
404
Which bone does the atlas (C1) articulate directly with? What does this joint allow?
- The occipital bone of the skull. - Allows us to nod our heads.
405
What is unique about the atlas?
- Shaped like a ring, with no vertebral body, but a gap where it should be. - Does not have a spinous process.
406
What is unique about the axis?
- Has a body that protrudes vertically upwards. - Called the odontoid process.
407
What does the odontoid process and the joint it forms allow us to do? What is the joint called? What type of joint is it?
- Takes the place of the body of the atlas. - Lets the atlas spin around the axis. - Joint allows us to turn our heads. - Called the atlanto-axial joint. - Example of a pivot joint.
408
What is unique about C7 in comparison to the other cervical vertebrae?
- Spinous process is much more prominent. - Usually the most superior spinous process that you can palpate through the skin. - Doe not have a bifid spinous process.
409
What is C7 sometimes called?
Vertebra prominens.
410
Why do cervical vertebrae have a smaller body than the other types?
Support less weight.
411
What travels through the transverse foramina of the cervical vertebrae? What is the exception?
The vertebral arteries (except in C7).
412
What is the trend in size of the thoracic vertebrae? Why?
- Increasingly larger from superior to inferior. - As inferior support more weight.
413
What is unique about thoracic vertebrae?
- Additional articular surfaces for the ribs. - Spinous processes are long, sharp, and point downwards to protect the spinal canal more effectively.
414
Which are the largest individual vertebrae in the spine?
The lumbar vertebrae.
415
What is unique about lumbar vertebrae?
- Large vertebral bodies to support weight. - Transverse processes project laterally. - Spinous processes are relatively short and rectangular.
416
Describe the sacrum.
Large, triangular-shaped bone, located in the centre of posterior part of the pelvis.
417
Where does the sacrum articulate with the pelvis?
At the sacroiliac joints.
418
What is the sacral promontory?
An anterior prominence at the top of the sacrum.
419
Where is the coccyx found?
Attaches to the inferior aspect of the sacrum.
420
Fact file for atlas (C1). (Include: vertebral body, spinous process, transverse processes, primary movements).
- Vertebral body: absent. - Spinous process: absent. - Transverse processes: contains a transverse foramen. - Primary movements: rotation at atlanto-axial joint.
421
Fact file for axis (C2). (Include: vertebral body, spinous process, transverse processes, primary movements).
- Vertebral body: elongated vertically (odontoid process). - Spinous process: bifid. - Transverse processes: contains a transverse foramen. - Primary movements: rotation at atlanto-axial joint.
422
Fact file for cervical vertebrae (C3 -> 7). (Include: vertebral body, spinous process, transverse processes, primary movements).
- Vertebral body: small. - Spinous process: bifid (except C7). - Transverse processes: contains a transverse foramen. - Primary movements: flexion, extension and lateral flexion.
423
Fact file for thoracic vertebrae (T1 -> 12). (Include: vertebral body, spinous process, transverse processes, primary movements).
- Vertebral body: medium sized, heart-shaped. - Spinous process: long, sharp and down-sloping. - Transverse processes: contains articulation for the ribs. - Primary movements: rotation.
424
Fact file for lumbar vertebrae (L1 -> 5). (Include: vertebral body, spinous process, transverse processes, primary movements).
- 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.
425
Fact file for sacral vertebrae (S1 -> 5). (Include: vertebral body, spinous process, transverse processes, primary movements).
- Vertebral body: fused. - Spinous process: fused. - Transverse processes: none. - Primary movements: none.
426
Fact file for coccygeal vertebrae (Co1 -> Co4). (Include: vertebral body, spinous process, transverse processes, primary movements).
- Vertebral body: fused. - Spinous process: fused. - Transverse processes: none. - Primary movements: none.
427
What are the intervertebral discs?
Strong, fibrocartilaginous structures between the non-fused vertebrae of the spine.
428
What do the intervertebral discs withstand and allow?
- Withstand compression forces. - Allow flexibility and movement between each vertebra.
429
Describe the intervertebral discs make-up.
- Central gelatinous core called the nucleus pulposus. - Surrounding this is the annulus fibrosis, which is made of concentric rings of collagen.
430
Describe the joint structure of the vertebrae and intervertebral discs. What type of joint is this?
- Intervertebral discs separated from vertebral bodies of neighbouring vertebrae by a thin layer of hyaline cartilage. - Bone, hyaline cartilage, fibrocartilage, hyaline cartilage, bone. - A secondary cartilaginous joint.
431
What is the purpose of spinal ligaments?
- Help maintain upright posture. - Prevent hyperflexion and hyperextension injuries.
432
Name 5 spinal ligaments.
- Anterior longitudinal ligament. - Posterior longitudinal ligament. - Ligamentum flavum. - Interspinous ligament. - Supraspinous ligament.
433
What is the name of a group of muscles that support the vertebral column?
- The erector spinae.
434
Describe the erector spinae. What does it contribute to?
- Muscles that form a column either side of the spinous processes. - Contributes to maintaining an upright posture.
435
Give 2 clinical relevancies of the vertebral column.
- Disc herniation. - Lumbar puncture.
436
What can cause disc herniation? Explain this process.
Repetitive compression of the intervertebral discs -> weakening of the annulus fibrosus, and posterior herniation of the nucleus pulposus -> narrow the intervertebral foramina or the spinal canal.
437
What risks are there after disc herniation?
- If an intervertebral foramen is narrowed, the transiting spinal nerve is compressed = weakness in muscles supplied by that nerve, or altered sensation in the dermatome. - If the spinal cord/cauda equina is compressed -> neurological deficit below that level and is a surgical emergency.
438
What does a lumbar puncture involve?
Sampling some CSF from the subarachnoid space in the lower vertebral canal.
439
Where must a lumbar puncture be performed, and why?
- Lower than L2, as the spinal cord terminates at L1/2, so this avoids damaging the cord. - The cauda equina nerves are simply pushed out of the way of the needle rather than being damaged below this point.
440
What position is patient usually asked to be in for a lumbar puncture, and why?
- Sitting on the edge of the bed, or in the foetal position, and asked to push out their lower back. - This allows the space between the vertebrae to widen.
441
What is an appropriate space to aim for with a lumbar puncture, and why?
- L4/5 space as it is in line with the intercristal plane (top of the iliac crests).
442
How can a clinician know if the needle is in far enough for a lumbar puncture?
- Feel several gentle 'pops' as it reaches the subarachnoid space (as it passes through the ligamentum flavum and dura mater). - CSF starts flowing out.
443
What else may be injected into the subarachnoid space and why?
Anaesthetic drugs for surgery of the lower pelvis or lower limbs (aka spinal anaesthesia).
444
Where do pairs of spinal nerves leave the vertebral column?
At almost every vertebral level, via the intervertebral foramina (one on each side).
445
Where do the spinal nerves leave the cervical spine?
- Directly above their corresponding vertebrae, as far as C7. - An additional pair leave below the C7 vertebra, called the C8 spinal nerves.
446
Where do the remaining spinal nerves leave the vertebral column, other than the cervical spinal nerves?
Directly below their corresponding vertebra.
447
How many pairs of spinal nerves are there? Why?
31 pairs of spinal nerves, due to the extra C8 spinal nerves, and the fact there is only one pair of coccygeal spinal nerves (Co1).
448
What happens to the spinal cord at approx. the level of L1/2 junction?
Tapers off into a cone shape (the conus medullaris), and terminates.
449
What happens beneath the L1/2 junction where the spinal cord terminates?
- Dura and arachnoid meninges continue down to the sacrum. - Pia mater thickens to form a thin strand of fibrous tissue = filum terminale. - Filum terminale continues all the way to the coccyx where is helps tether the spinal cord in position.
450
What happens shortly before the spinal cord terminates?
It gives off all its remaining spinal nerves that are yet to leave, these descend within the spinal canal until it is their designated level to leave the vertebral column.
451
What is the name for the mass of spinal nerves dangling within the spinal canal? Why is it called this?
- The cauda equina. - Means 'horse tail' in Latin, which the dangling nerves resemble.
452
What is each spinal nerve formed from?
Two roots, stemming directly from the dorsal and ventral aspects of the spinal cord - therefore named the dorsal and ventral roots.
453
What does the dorsal root do?
- Carries sensory fibres into the spinal cord. - Contains a dorsal root ganglion.
454
What does the ventral root do?
- Carries motor fibres out of the spinal cord. - Does not have a ganglion on it. - Sympathetic fibres that leave the cord leave via the ventral root.
455
The grey matter of the spinal cord is in what shape? What does this shape therefore form?
- A H shape. - Forms two dorsal horns and two ventral horns.
456
What happens shortly after the spinal nerve is formed?
Divides into two rami - a dorsal ramus and a larger ventral ramus.
457
What do the rami do?
Dorsal - contains sensory and motor fibres supplying dorsal structures. Ventral - carries sensory and motor fibres to ventral structures.
458
Within the thoracic region, what are the thoracic ventral rami renamed as?
The intercostal nerves.
459
In ascending sensory pathways, how many neurones are their typically? Where are these?
3: - First order neurone: from receptor -> CNS, cell bodies in dorsal root ganglion. - Second order: from spinal cord/brainstem -> thalamus. - Third order: from thalamus -> somatosensory cortex.
460
In descending motor pathways, how many neurones are their typically? Where are these?
2: - First order neurone (UMN): from motor cortex -> ventral horn of the spinal cord. - Second order (LMN): spinal cord -> target muscle.
461
What is decussation?
A neurone crossing over to the contralateral side.
462
What are spinal tracts?
Bundles of axons organised into vertical columns within the peripheral white matter of the cord.
463
What do spinal tracts do?
Carry impulses from the brain -> periphery or vice vers.
464
What does DCML stand for?
Dorsal Columns Medial Lemniscus.
465
Where are the tracts of the DCML pathway found?
Dorsally in the spinal cord.
466
What does the DCML carry?
Sensory information about fine touch, two-point discrimination, vibration and proprioception.
467
How many tracts are the dorsal columns divided into? What are these called?
- Two distinct tracts on each side. - The fasciculus gracilis (medially) and the fasciculus cuneatus (laterally).
468
What information does the fasciculus gracilis carry?
Information about the lower limbs.
469
What information does the fasciculus cuneatus carry?
Information about the upper limbs.
470
Describe the journey of the first order neurones in the DCML.
- Enter spinal cord via dorsal root and enter ipsilateral dorsal columns. - Fasciculus gracilis and fasciculus cuneatus. - Reach the medulla, synapse at their names nuclei: gracile and cuneate nuclei.
471
Describe the journey of the second order neurones in the DCML.
- After the synapse, second order neurones decussate within the medulla, tract continues to thalamus on the contralateral side. - This part is called the medial lemniscus.
472
Describe the journey of the third order neurones in the DCML.
- Another synapse in the thalamus, third order neurones continue via the internal capsule -> primary somatosensory cortex (in the parietal lobe).
473
Where is the spinothalamic tract located?
Antero-laterally in the spinal cord.
474
What information does the spinothalamic tract carry?
Sensory information about crude touch, pain and temperature.
475
Describe the journey of neurons in the spinothalamic tract.
- First order enter spinal cord via dorsal root, synapse with dorsal horn. - After synapse, second order neurones decussate, usually after travelling upwards one/two vertebral levels. - Tract continues to the thalamus on the contralateral side. - Another synapse in thalamus, third order neurones continue via the internal capsule -> primary somatosensory cortex (in the parietal lobe).
476
Where is the lateral corticospinal tract located?
Laterally to the spinal cord.
477
What information does the lateral corticospinal tract carry?
Motor impulses.
478
Describe the journey of neurones of the lateral corticospinal tract.
- First order neurones (UMNs) leave the motor cortex and pass through the internal capsule. - They decussate within the medulla at the level of the medullary pyramids, continuing contralaterally in the spinal cord. - Once at their desired level, they synapse with the ventral horn. - After the synapse, second order neurones (LMNs) leave the cord via the ventral root towards the target muscle.
479
Where are the anterior and posterior spinocerebellar tracts located?
Most laterally in the cord.
480
What information do the anterior and posterior spinocerebellar tracts carry?
Unconscious proprioceptive information to the cerebellum.
481
Describe the decussation of the anterior/ventral spinocerebellar tract.
- Decussates twice. - Once at the level of entry to the cord. - Again as it enters the cerebellum though the superior peduncle.
482
Describe the decussation of the posterior/dorsal spinocerebellar tract.
- Does not decussate at all.
483
Which side of the cerebellum do the anterior and posterior spinocerebellar tracts terminate on?
Anterior - ipsilaterally to the side it entered he cord. Posterior - also ipsilaterally to entry of the cord.
484
Give 1 clinical relevancy of the spinal cord/tracts/.
Brown-Sequard syndrome.
485
What causes Brown-Sequard syndrome?
Damage to one side of the cord only (hemisection of the cord).
486
What happens if a patient suffers damage to the left-hand side of their spinal cord in terms of the tracts affected?
- 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.
487
What happens if a patient suffers damage to the left-hand side of their spinal cord in terms of the symptoms this would produce?
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.

Anatomy JD (6 decks)

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