Neuro Flashcards
What does a lesion in the cerebellum cause
A lesion in the cerebellum can cause scanning dysarthria presenting as jerky, loud speech with pauses between words and syllables. Other features that can occur include dysdiadochokinesia, nystagmus and an intention tremor.
What does a lesion in the superior temporal gyrus cause
A lesion in the superior temporal gyrus can cause Wernicke’s (receptive) aphasia leading to sentences that do not make sense with word substitution and neologisms. It can also cause comprehension to become impaired which is not seen in this patient.
What does a lesion in the substantia nigra cause
A lesion in the substantia nigra can cause Parkinson’s disease which can cause speech to become monotonous. Other features that can occur are bradykinesia, rigidity and a resting tremor which are not seen in this patient.
What does an articulate fasciculus cause
The arcuate fasciculus is an area that connects Wernicke’s and Broca’s area with a lesion causing poor speech repetition which is not seen in this patient.
What groove separates the left and right hemispheres of the brain
-the longitudinal fissure
What structure connects the left and right hemispheres
-the corpus callosum
Where is the lateral fissure located
- the lateral fissure also sometimes called the sylvian fissure
- between the temporal and parietal lobe
What is the significance of the opercula
- opercula means lips in latin
- it lies over the insurer cortex (also called insula) which is deep to the sylvian fissure
Which structure runs from the longitudinal fissure to the lateral fissure and why is it important
- the central sulcus
- it separates the frontal cortex from the parietal cortex
- just anterior to it is the motor cortex
- just posterior to it is the somatosensory cortex
What joins the two lobes of the cerebellum
-the vermis
Which structures form the brainstem
- midbrain
- pons
- medulla
Give a brief summary of how we get information from the optic nerve
- half of the information from one eye is taken to the thalamus and then to he occipital cortex in the same side of the brain
- half crosses over in decussating tracts at the optic chasm into the thalamus and then the occipital cortex at the other side of the brain
What is meningitis
-inflammation of the meninges
Give the 3 layers of the meninges
- Dura mater (endosteal/periosteal layer and the inner meningeal layer)
- arachnoid mater
- pia mata
Where are the venous sinuses found
-between the endosteal layer and the meningeal layer of dura mater
What is the falx cerebri
-where the dura meter goes in between the left and right hemisphere
What is the tentorium cerebelli
- a piece of dura mater between the cerebellum and the occipital pole
What is the falx cerebelli
- a piece of dura that sits between the two lobes of the cerebellum
What is lies in the subarachnoid cisterns
-cerebral spinal fluid
What would a bleed actually penetrating into brain tissue be called
-an intracerebral hemorrhage
What are the two roles of the dura mater
- stops the brain moving around in the skull
- forms the venous sinuses
Give the venous sinuses and where they are found
- superior sagittal sinus - found running along the superior surface of the falx cerebri
- inferior sagittal sinus - found along the inferior edge of the falx cerebri
- straight sinus -running along the middle of the tentorium cerebelli
- transverse sinus -runs between the edge of the tentorium cerebelli and the occipital bone
- sigmoid sinus - runs along the mastoid portion of the temporal bone and drains into the jugular vein
- cavernous sinus - lies lateral to the optic chasm
What is the role of the diaphragm sellae
-it is a ring of dura that forms the roof over the pituitary gland
Which structures are within the cavernous sinus and why is it a site of clinical significance
- cranial nerve 3,4,6 (oculamotor, trochlear and abducens nerve)
- branch 1 and 2 of cranial nerve 5 (opthalmic and maxillary branch of the trigeminal nerve)
- internal carotid artery
-can be a root of infection into the brain
Which blood vessel supply the anterior part of the brain
Specify which branches supply the medial and lateral territories of the anterior aspect of the brain
-the internal carotid arteries
- the anterior cerebral artery supplies the medial aspect of the brain
- the middle cerebral artery supplies the lateral aspect of the brain
Which blood vessels supply the posterior part of the brain
Specify which branch supplies the temporal and occipital lobe
- the vertebral and basilar arteries
- the posterior cerebral artery from the basilar artery supplies the inferior and medial surfaces of the temporal lobes and the occipital lobes
Which arteries supply the cerebellum
- the superior cerebellar arteries
- the posterior inferior cerebellar arteries
- the anterior inferior cerebellar arteries
Where do the external cerebral veins (e.g superficial middle cerebral vein) drain into
-dural venous sinuses
Describe the passage of the internal carotid artery into the skull
Tbc use picture of insta
Where do the vertebral arteries pass into the cranium (skull)
-through the foramen magnum
Which vessels pass in through the foramen magnum and back out again and what do they do
-the anterior and posterior spinal arteries branch off the vertebral arteries as it enters through the foramen magnum and pass back out to supply the spinal cord
Which structure in the skull does the sigmoid sinus exit the skull to become the internal jugular vein
-the jugular foramen
Which structures pass through the optic canal in the sphenoid bone
- optic nerve
- ophthalmic artery
Which structures pass through the ethmoidal formina and what do they do
- the ethmoidal artery and vein
- they supply the anterior part of the nasal cavity and the nose
Where does the superior opthalmic vein pass through in the skull
-the superior orbital fissure
Where does the middle meningeal arteries pass through in the skull and what does it do
- the foramen spinosum
- supplies the skull, the dura, the skin and muscles on the superficial tissues of the skull
Which blood vessel travels through the internal acoustic meatus and what does it do
What is its clinical significance
- the labyrinthine artery
- supplies the labyrinth of the inner ear
- it travels through a small canal that transmits the facial, and vestibulocochlear nerve, diseases within the internal acoustic meatus will cause pulsatile tinnitus
- where the patient can hear their own heartbeat because the pulsating artery is pressing on the cochlear part of the vestibulocochlear nerve
Give a clinical significance of the internal acoustic meatus
- the labyrinthine artery travels through a small canal that transmits the facial, and vestibulocochlear nerve, diseases within the internal acoustic meatus will cause pulsatile tinnitus
- where the patient can hear their own heartbeat because the pulsating artery is pressing on the cochlear part of the vestibulocochlear nerve
What did Thomas Willis discover and when
-he described the circle of Willis in Cerebri Anatome of 1664
Give the difference between motor and sensory aphasia
motor aphasia - the inability to speak or to organize the muscular movements of speech, it is also called also aphemia, Broca’s aphasia. (Brodmann’s area 43, 44)
Sensory aphasia - a type of aphasia in which individuals have difficulty understanding written and spoken language, also known as Wernicke’s aphasia, receptive aphasia, or posterior aphasia (Brodmann’s area 22, 39, 40)
What is the left hemisphere of the brain more dominant in
- verbal
- linguistic description
- mathematics
- sequential
- analytical
- direct link to consciousness
What is the right hemisphere of the brain more dominant in
- non-verbal
- musical
- geometrical
- spatial comprehension
- temporal synthesis
What Brodmann’s area is the motor cortex
-area 4 and 6
Give the Homunculus organisation of the motor cortex from medial to lateral
Medial
- toes
- ankle
- knee
- hip
Superior
- trunk (chest)
- upper limb
- hand
- fingers
Lateral
- thumb
- neck
- face
- tongue
- voice
Where does the corticospinal (motor) tract decussate
- after the medulla
- into the anterior corticospinal tract
- into the lateral corticospinal tract
Describe the journey of the ventricles
- the two lateral ventricles
- through the interventricular foramen (foramen of Monro)
- the the third ventricle
- through the cerebral aqueduct (of Sylvian)
- the fourth ventricle
- through the foramen of Luschka
- through the foramen of Magendie
- into the subarachnoid spaces which surround the brain
Which blood vessel travels through the optic canal
-the opthalmic artery
How much of the brain made of water
-80%
How many nerve cell are in the brain
-100 billion nerve cells
Give the layers of neurones and their associated structures in the cortex of the brain from the pia to white matter
Pia
Level 1 - molecular - dendrites of deeper cells
Level 2 - external granular - other information
Level 3 - external pyramidal - association cortices
Level 4 - internal granular - sensory information
Level 5 -internal pyramidal -brainstem, spinal cord
Level 6 - multiform - thalamus
White matter
What makes up the central nervous system (CNS) and the peripheral nervous system (PNS)
CNS
- brain
- spinal cord
PNS
- cranial nerves
- spinal nerves
Describe the 3 main sections of the brain and what they contain
Prosencephalon (Telencephalon and Diencephalon)
Mesencephalon
Rhombocephalon (Metencephalon and Myelencephalon)
Telencephalon (Cerebral cortex, basal ganglia and the limbic cortex) Diencephalon (thalamus and hypothalamus) Mesencepahalon (tegmentum and tectum) Metencephalon (pons and cerebellum) Myelencephalon (medulla)
What does the medulla
- contains tracts carrying signals from between the rest of the body and the brain
- balance
- sleep and wakefulness
- movement
- maintenance of muscle tone
- cardiac, respiratory, circulatory and excretory reflexes
What do the pons do
- relays from the cortex and midbrain to the cerebellum
- pontine reticular formation (involved in pattern formation, coordination of eye movements like horizontal gaze and saccades)
What does the cerebellum do
- corrects ‘motor errors’ between intended movement and actual movements
- motor coordination and motor learning
What does the tectum do
- also called the colliculi (and corpora quadrigemina)
- creates visual/spatial and auditory frequency maps
The superior colliculi - sensitive to visual, orienting/ defensive movements
The inferior colliculi - sensitive to audio events
What is the tegmentum made up of
-made up of the periaquaductal grey,red nucleus and the substantia nigra
What does the periaquaductal grey do
- role in defensive behaviour
- role in analgesia
- role in reproduction
What does the red nucleus do
-role in pre-cortical motor control (especially in the arms and legs)
What does the substantia nigra do
- part of the basal ganglia
- has two parts, the pars reticulata and the pars compacta
- the pars compacta - receives basal ganglia input (dopamine cells and involved in Parkinson’s)
- the pars reticulata - give basal ganglia output
What does the thalamus do
- has 2 parts, the specific nuclei and the non specific nuclei
- relays signals from the basal ganglia and cerebellum back to the cortex
- specific nuclei - relay all sensation except smell to the cortex/limbic system
- non-specific nuclei - role in regulating the state of sleep, wakefulness and levels of arousal
What does the hypothalamus do
- regulates the pituitary gland which regulates hormonal secretion
- role in hormonal control of motivated behaviour including hunger, thirst, temperature, pain, pleasure and sex
What makes up the cerebral cortex
- cortical lobes
- subcortical portion
Cortical lobes - frontal, parietal, temporal and occipital lobe
Subcortical portions - the basal ganglia and limbic cortex
What does the basal ganglia do
-made up of the caudate nucleus, putamen and globus pallidus
- motor function
- role in action selection and reinforcement learning
What does the limbic system generally do
-made up of the amygdala, hippocampus, fornix, septum, mammillary bodies, cingulate gyrus
- emotion
- motivation
- emotional association with memory
- influences the formation of memory by integrating emotional states with stored memories of physical sensations
What does the amygdala do
-involved in associating sensory stimuli with emotional impact
What does the hippocampus do
- involved in long term memory
- involved in spatial memory
What does the fornix do
-carries signals from the hippocampus to the mammillary bodies and septal nucleus
What does the cingulate gyrus do
- links behaviour outcomes to motivation and autonomic control
- atrophies in schizoprenia
What does the septum do
-involved in defence and aggression
What do the mammillary bodies do
-important for formation of recollective memory (amnesia)
What part of the brain is the biggest in primates
-the cortical lobes
What does the frontal lobe do
- generates models of the consequences of actions (executive planning)
- working memory (short term information)
- control of behaviour that depends on context and setting
- judgement roles
- emotional modulation
- contains
- the precentral gyrus which sends motor instructions for fine motor movements controlling the hands and feet
- the primary motor cortex - initiation of voluntary movement contains cells that originate the descending motor pathways
- prefrontal cortex which generates sophisticated behavioural options that are mindful of consequences
- the premotor and supplementary motor areas - higher level motor planes and initiation of voluntary movement
Damage to which part of the brain might result in the inability to recognise faces and objects
-the infero-temporal cortex of the temporal lobe
What does the parietal lobe do
-contains the postcentral gyrus which receives sensation from the body
- maintains awareness of body and head position in space
- allows complicated spatio-temporal predictions e.g catching something when you are moving
What does the temporal lobe do
- contains the primary auditory cortex
- contains the infero-temporal lobe which allows recognition of faces and objects
- plays role in integrating sensory information from various parts of the body
- acts as an interface between the cortex and limbic system
What does the occipital lobe do
-vision
- the Dorsal stream is for Movement (the Where) think DUMB
- the Ventral stream is for Identification (the What) think VIP
What is the interthalamic adhesion and where is it
- the hole just below the foramen of Monroe
- a stalk that connect the thalamus in around 90% of brains
Which structure separates the two lateral ventricles in the brain
- septum pallucidum
- double membrane structure
What is the roof of the fourth ventricle
-medullary velum
How does the cerebral aqueduct separate the tectum and cerebral peduncle
- dorsal to the cerebral aqueduct is the tectum
- ventral to the cerebral aqueduct is the cerebral peduncle
In the cerebral peduncle
- dorsal to the substantia nigra is the tegmentum
- ventral to the substantia nigra is the crus cerebri
What are zonula occludentes?
- these are tight junctions that link the cells of the arachnoid mater together
- the arachnoid mater is made of collagen, elastin and reticulin fibres
Explain the Cartesian Dualism by Rene Descartes 1641
-there are two kinds of ‘foundation’, mental and body
Give 4 alternative explanations to dualism of brain and behaviour
- reductive physicalism (Neurath)
- interactionism (Mead/ Blumer)
- epiphenomenalism (Huxley)
- mysterterism (Berkeley)
Explain reductive physicalism by Neurath
- states that everything can be explained by the physical
- e.g the serotonin theory to explain the biological view of depression
Explain interactionism by Mead/Blumer
- states that entities can have an effect on one another
- mental distress causes physical symptoms e.g cancer survival rates depending on increased or decreased depression, tension headaches causing distress stress
Explain epiphenomenalism by Huxley
- physical affects the mental but the mental cannot affect the physical
- a hierarchical
- conscious experience is an epiphenomenon of neuronal processes in the brain
Explain the mystertersim
- states that the mind can only be understood from reflection
- deeply personal and subjective
- consciousness cannot be resolved by humans
Give a brief summary of what the
- frontal lobe
- neocortex cortex
- limbic brain
- brain stem and cerebellum do
Frontal lobe
- problem solving
- creativity
- planning/organisation
- language (expressive)
Neocortex cortex
- sensory perception
- language
- conscious thought
Limbic brain
- emotions
- nurturing
- habits
- memory
Brain stem and cerebellum
- survival
- homeostasis/regulation
- arousal
- reflexive behaviours
Give 4 functions of the dopamine pathway of the brain
- compulsion
- reward (motivation)
- pleasure, euphoria
- motor function (fine tuning)
- perservation
Give 4 functions of the serotonin pathway of the brain
- mood
- memory processing
- sleep
- cognition
Give 4 executive tests for frontal lobe function
- wisconsin card-sorting test
- verbal fluency test e.g 4 legged animals in 1 min
- proverb interpretation e.g those in glass houses shouldnt throw stones
- similarities test e.g chair/table, apple/banana
- cognitive estimates e.g give the height of the average woman
- primitive reflexes/ luria test
Give 3 positive symptoms of schizoprenia
- delusions
- hallucinations
- disordered thoughts
Give 2 negative symptoms of schizoprenia
- distant, withdrawn and appear unemotional, lose interest, stop washing and spend a lot of time alone
- not able to carry on with normal activities, difficult to concentrate on work or study
What is the epidemiology of schizoprenia
1 in 100 - general population
1 in 10 - parents with schizoprenia
1 in 8 - non identical twin
1 in 2 - identical twin
Define delusions and give an example
-strongly held beliefs that are untrue and can seem quite bizzare e.g the police are after me because of my special powers
Define hallucinations
-the person sees, hears, smells or feels something that isnt there
Define thought disorder
-when someone is not thinking straight and it is hard to make sense of what they are saying
In Schizoprenia, are brain changes present after or prior to symptom presentation
-prior to symptom presentation
What is the difference between neurology and psychiatry
Psychiatry is treating brain symptoms cause abnormal voluntary actions
Neurology is treating brain symptoms that cause abnormal involuntary actions
Give the methods of studying the nervous system
- visualising and stimulating the brain
- recording psychophysiological activity
- invasive research methods
- pharmacological research methods
- genetic manipulations
Give the difference between magnetic resonance imaging (MRI) and functional magnetic resonance imaging (fMRI)
- MRI is using a magnet to see the position of hydrogen atoms in water molecules in the body
- fMRI is essentially the same, but the scanner is made sensitive to iron in haemoglobin in blood, when oxygenated the haemoglobin hides the iron so the fMRI examines the oxygenation of blood in tissue
What are the 3 guiding principles for all research involving animals in the UK
- replacement (can another method be used)
- refinement (is it done in the best way to maximise cost;benefit equation)
- reduction (can it be done with smallest number of) animals
Give the difference between the types of muscle fibres
Slow twitch (red fibres)
- type 1
- oxidative
- fatigue resistant
Fast twitch
2A - glycolytic and oxidative (intermediate)
2B - glycolytic (white)
Why is the release of creatine kinase clinically important
- creatine kinase is released on muscle fibre damage
- serum creatine kinase can be measured
What does creatine kinase do
Creatine kinase replenishes creatine phosphate
What is creatine phosphate used for
-creatine phosphate is a short term energy store for muscle fibres
What splits the cranium into 3 cranial fossa
The lesser wing of the sphenoid bone divides the anterior cranial fossa and middle cranial fossa
The petrous part of the temporal bone divides the middle cranial fossa and the posterior cranial fossa
What bone marks the edge of the anterior cranial fossa
-the lesser wing of the sphenoid bone
What are the two parts of the temporal bone
- ridge on the petrous part of the temporal bone (bony hard)
- squamous part of the temporal bone (flat sheet)
What structures pass through the cribriform plate which forms the roof of the sphenoethmoidal recess
-1st order neurons of the olfactory system lie in the nasal cavity and their axons pass through the cribriform plate to synapse on the olfactory bulb in the cranium
What is the crista galli and what does it mean
- the central ridge on the cribriform plate
- means the roosters comb
- the falx cerebri attaches to the apex of the crista galli
What is the hole on the body of the sphenoid bone called an what does it do
- the sphenoid air sinus
- communicates with the nasal cavity
What forms the pituitary fossa
- the sella turcica (means Turkish saddle) forms the pituitary fossa
- the pituitary gland sits in it
What structures lie in Meckel’s cave
-the 3 ganglia that make up the trigeminal nerve, it is just underneath the cavernous sinus
What structures does the optic canal transmit
- optic nerve
- opthalmic artery
What structures does the superior orbital fissure
- occulomotor, trochlear and abducens nerve
- opthalmic branch of the trigeminal nerve
What does the inferior orbital fissure communicate with
-the maxillary sinus (fossa)
What does the foramen rotundum transmit
-the maxillary branch of the trigeminal nerve
What structure does the foramen ovale transmit
- the mandibular branch of the trigeminal nerve
- the motor and sensory divisions of the mandibular branch lie side by side in the foramen ovale
What structure does the foramen spinosum transmit
- the middle meningeal artery
- supplies the skull and the dura
What is attached to the ridge of the petrous part of the temporal bone
-the tentorium cerebelli
Which part of the parietal lobe is concerned with language and mathematical operations
-the supramarginal and angular gyrus
What are the supramarginal and angular gyrus of the parietal lobe concerned with
-language and mathematical operations
What is the non-dominant lobe of the parietal lobe of the parietal lobe important for
-visuospatial functions
What is the prefrontal cortex important for
-higher cognitions functions and determination of personality
Where is Broca’s area found and why is it important
- inferior frontal gyrus of the frontal lobe
- important for language production and comprehension
Where is olfaction perceived in the brain
-the frontal lobe
Where is Wernicke’s area located and why is it important
-the superior temporal gyrus of the temporal lobe in the left hemisphere
Where is the brain’s pleasure center
-the nucleus accumbens
What does the nucleus accumbens do
- the brains’s pleasure center
- sexual arousal
- the high experienced with recreational drugs
Where is the cerebrospinal fluid found
-in the subarachnoid cisterns between the arachnoid mater and the pia mater
Where do the tracts of the corticospinal (motor) tract cross over
-the caudal medulla
What are the symptoms of an upper motor neurone lesion
- increased tone (spasticity)
- pyramidal weakness
- increased reflexes
- no muscle atrophy
What are the symptoms of a lower motor neurone lesion
- muscle atrophy
- deceased tone
- focal weakness
- decreased reflexes
On the surface of the brain, where do arteries lie
-the subarachnoid space
What features limit molecules crossing the brain-blood barrier
- the basement membrane of the CNS blood vessels lack fenestrations
- pericytes wrap around endothelial cells and regulate capillary blood flow, immunity and vascular permeability
- astrocytes end foot processes envelop CNS capillaries and restrict the flow of molecules into the CNS parenchyma
- the adjacent endothelial cells of the blood vessels are bonded by tight junctions which prevent molecules crossing through them
What event and vessels usually cause an extradural haemorrhage
- head injury
- middle meningeal artery
What event and vessels usually cause an subdural haemorrhage
- high impact injury like a road traffic accident
- bridging veins
- appears as a crescent on CT head
What event and vessels usually cause a subarachnoid haemorrhage
- head injury
- berry aneurysm
- sudden severe headache and high mortality rate
Where do intracerebral haemorrhages usually occur and what cause
- internal capsule
- rupture of the lenticulostraite artery due to high blood pressure
What is meningism
-a triad of headache, neck stiffness and photophobia
What is amaurosis fugax
-temporary loss of vision to one eye (like a veil across one eye)
What causes amaurosis fugax
-part of the carotid plague breaking off and occluding the central retinal artery - a warning of thrombus of the internal carotid artery
What makes up the blood brain barrier
- the endothelial cells of the capillaries
- the basement membrane (made of basement membrane and pia mater)
- astrocytic end-feet
How much of the total brain blood supply is by the vertebral arteries
-20%
How much of the total brain blood supply is by the carotid artery
-80%
Where can the basilar artery be found
-the anterior median fissure of the pons
Which artery is a common site for berry aneurysm
-the anterior communicating artery of the circle of Willis which lies in the subarachnoid space
Give a summary of the venous drainage of the brain
- internal cerebral veins to the external cerebral veins
- external cerebral veins to the dural venous sinses
- dural venous sinuses (sigmoid sinus really) to the internal jugular vein
Where does the Great cerebral vein of Galen drain into
-the straight sinus
How do intracranial venous sinuses and the veins outside of the skull communicate and why is that clinically important
- emissary veins
- they are a possible route of infection or inflammation to spread into the cranial cavity from the outside
Where is the majority of CSF produced
-the choroid plexus in the lateral ventricle
Where is the choroid plexus formed
-the lining of the ventricles
What allows tight control over the volume and composition of the CSF
-tight junctions prevent passage of fluid from the extracellular space of the choroid plexus into the ventricles except through the choroidal cells themselves
How is CSF reabsorbed into the venous drainage of the brain
- arachnoid villi (arachnoid granulations)
- along nerves to the lymphatics (the nasal mucosa lymphatics which drain into the deep cervical lymph nodes) (minor route)
Where does the vertebral arteries travel through into the skull
- though the foramina of the transverse processes of the C1 to C6 vertebra
- the foramen magnum
Where is the hypoglossal canal found and what does it do
- inside the foramen magnum
- transmits the hypoglossal nerve from the medulla to the tongue
What structures pass through the jugular foramina
- the 9th, 10th and 11th cranial nerve (glossopharyngeal, accessory and hypoglossal nerve)
- jugular vein
Where does the facial nerve exit the skull
-the stylomastoid foramina
Where does the cavernous sinus drain blood
-through the inferior pertrosal sinus and out through the jugular foramina
Where is the superior tracespetrosal sinus found
-along the ridge of the petrous part of the temporal bone
What is a diploic vessel and why is it clinically important
- an abnormal hole near the jugular foramina where there has been an anastomosis between the venous drainage from the brain (internal jugular vein) and the veins from the outside of the skull (external jugular vein)
- if an area on the outside of the skull becomes infected, it can spread intracranially
What forms the triangle of danger in the head and why is it clinically important
- the upper teeth
- the maxilla
- extending up to the frontal sinus on each side
- blood from the part of the face can drain backwards through the orbit into the cavernous sinus
- so infection from that area can spread through the blood stream intracranially
Where does the spinal root of the accessory nerve pass into the skull
Through the foramen magnum
Where does the spinal root of the accessory nerve pass out of the skull
-through the jugular foramina
What are the 2 branches the ophthalmic nerve from the trigeminal nerve divides into in the orbit and the subdivisions
- the frontal nerve
- the lacrimal nerve
- the lacrimal nerve gives off the nasociliary nerve which carries parasympathetic fibres to the ciliary body
- the frontal nerve gives off the supraorbital nerve and the supratrochlear nerve
What does the trochlear nerve innervate
-the superior oblique muscle
Where does the tendon of the superior oblique muscle insert into
-the posterior superior aspect of the globe
What is the action of the superior oblique muscle of the eye
-pulls the eye up and in so it is looking down and out
What muscle does the abducens cranial nerve supply
-the lateral rectus muscle
What action does the lateral rectus muscle have on the eye
-pulls the eye laterally so it is looking out (abduction of the eye)
What muscles does the oculomotor nerve supply
- levator palpabrae superioris (raises the eyelid)
- superior rectus (makes eye look up and out) extorsion
- inferior rectus (makes eye look down and out) extorsion
- medial rectus (makes the eye look in)
- inferior oblique (makes the eye look up and in, counteracts superior rectus movements), intorsion
What nerve supplies levator paalpebrae superioris and what does this muscle do
- occulomotor nerve
- raises the eyelid (opens the eyes)
Which eye muscles causes intorsion and what is it trying to counteract
- the superior oblique muscle causes intorsion
- it counteract the extortion caused by the inferior rectus muscle
What nucleus does the occulomotor nerve carry parasympathetic fibres from and why
From the Edinger-Westphal nucleus to give control of the ciliary body which controls the focusing of the lens and the pupillary diameter
-reflex that controls light entry and focusing
What nerves runs along the top of the orbit and where does it come from
- the frontal nerve
- a branch of the ophthalmic nerve
What is attached to the eyeball anteriorly
-a ring of conjunctiva
Where are the cell bodies of the vestibular and cochlear components of the vestibulocochlear nerve
- the nucleus (cell bodies) of the vestibular part is in the pons and the medulla
- the nucleus (cell bodies) of the cochlear part is in the inferior cerebellar peduncle
How do the both components of the vestibulocochlear nerve travel from their nucleus to the internal acoustic meatus
- they both exit the brain through the cerebellopontine angle
- travels through subarachnoid space and enters internal acoustic meatus
What do the parts of the vestibulocochlear nerve supply
- the cochlear part supplies the cochlear
- the vestibular part supplies the semicircular canals and the otolith organs
Where does the cochlear part of the vestibulocochlear nerve sit in the cochlear
- it forms a spiral ganglia and sits within the spiraled cochlear
- travels into the cells bodies and makes the cochlear nerve ganglia, these are central to the Organ of corti with the endolymph channels
Is the vestibulocochlear nerve sensory, motor or both
Entirely sensory
Describe the semicircular canals
- they are all at 90 degrees to each other
- they act as accelerometers
What connects the cochlear and semicircular canals and what does it contain
- the utricle
- contains calcified deposits (otoliths) attached to the wall with otoliths modified cilia
- when the head is in different positions, the otoliths will pull on the cilia and send that information to the brain that tells the brain the orientation of the skull
Give some causes, symptoms and signs of raised intracranial pressure
Causes
- space occupying lesions (tumour, haematoma, abscess)
- idiopathic intracranial hypertension
Symptoms
- headache
- nausea
- visual disturbances
- later altered consciousness levels
Signs
- papilloedema
- increased blind spot on visual field testing
Give the origin, insertion, innervation and function of the levator palpebrae superioris
Origin = common tendinous ring at the posterior of the orbit Insertion = upper eyelid Innervation = occulomotor nerve Function = raises the eyelid
Give the origin, insertion, innervation and function of the superior rectus muscle
Origin = common tendinous ring Insertion = inserts into anterior of eyeball Innervation = occulomotor nerve Function = makes eye look up and out (medial rotation)
Give the origin, insertion, innervation and function of the superior oblique muscle
Origin = body of the sphenoid bone Insertion = posterior part of the eyeball Innervation = trochlear nerve Function = intorsion, makes the eye look down and out (medial rotation)
Give the origin, insertion, innervation and function of the lateral rectus muscle
Origin = common tedinous ring Insertion = eyeball Innervation = abducent nerve Function = makes the eye look out (abduction)
Give the origin, insertion, innervation and function of the medial rectus muscle
Origin = common tendinous ring Insertion = eyeball Innervation = occulomotor nerve Function = makes the eye look in (adduction)
Give the origin, insertion, innervation and function of the inferior rectus nerve
Origin = common tendinous ring Insertion = eyeball Innervation = occulomotor nerve Function = makes the eye look down (lateral rotation)
Give the origin, insertion, innervation and function of the inferior oblique muscle
Origin = floor of the orbit Insertion = eyeball Innervation = occulomotor nerve Function = extorsion, makes the eye look up and out (lateral rotation)
What are the lacrimal puncti
-small medial holes in the upper and lower eyelids
What are the parasympathetic nerves from the CNS
- 1973 so nerves occulomotor, facial, glossopharyngeal and vagus nerve
- sacral nerves 2, 3 and 4
Which of the parasympathetic fibres have branches that travel to the orbit
Cranial nerves 3 and 7, occulomotor and facial
Where do the parasympathetic branches of the CNS that travel to the orbit originate and what do they do
Cranial nerve 3 originates in the Edinger-Westphal nucleus in the midbrain
- the nerves travel into the branch to the inferior oblique muscle but branch off and enter the ciliary ganglion
- the ciliary ganglion give fibres that innervates the ciliary muscle (accommodation) and the sphincter pupillae
Cranial nerve 7 leave the middle ear and synapse in a ganglion in the pterygopalatine fossa
-it supplies the lacrimal gland
What are the sympathetic nerve fibres from the CNS
T1 to L2
Where do the sympathetic fibres to the orbit arise from and what do they supply
T1 through the stellate ganglion (which is T1 + lower cervical ganglion)
- pass up through superior cervical ganglion
- supplies the dilator pupillae muscle and blood vessels of the orbit
What is jugular foramen syndrome
-compression of the cranial nerves 9, 10 and 11 can lead to dysphonia, loss of gag reflex and unilateral wasting of sternocleidomastoid and trapezius muscle
What is foramen magnum syndrome and give the associated signs and symptoms
-compression of the spinal cord, lower brain stem or part of the cerebellum
Symptoms
- pain in head
- neck
- limbs
- trunk made worse by straining
- cerebellar symptoms include vertigo, gait disturbance
Signs
- decerebrate posture
- cardiorespiratory failure
- death
- pyramidal signs
What is arnold-chiari malformation and give some associated symptoms
- congetinal malformation where the cerebellar tonsils go through the foramen magnum
- can block CSF and cause hydrocephalus
Symptoms include
- headcahes
- fatigue
- muscle weakness in the head and face
- difficulty swallowing
- dizziness
- nausea
- impaired coordination
- maybe syringomyelia
What is macula sparing
- visual field loss that preserves vision in the center of the visual field so the macula is spared basically
- often occurs as the occipital pole has a blood supply from middle and posterior cerebral arteries
What tests all the extraocular muscles of the eye individually and how
The H test
On the outside of the H
SR - elevation
LR - abduction
IR - depression
On the inside of the H
IO - adduction and elevation
MR - adduction
SO - adduction and depression
List the 3 ear ossicles in order
- malleus
- incus
- stapes
What is an acoustic neuroma, give symptoms
- a benign tumour of myelin sheath of cranial nerves 8 (vestibulocochlear)
Symptoms
- unilateral deafness
- dizziness
- tinnitus
- fullness in ear
What is cerebellopontine angle syndrome
- when acoustic neuroma progress undected
- can include ataxia and paralysis of cranial nerves 7 and 5
- around 5-10% is caused by rare genetic condition neurofibromatosis type 2
Give the two muscles that control eyelid position and the cranial nerve that innervates them
the orbicularis oculi muscle
- it closes the eyelid
- innervated by the facial nerve
the levator palpebrae superioris muscle
- elevates the upper eyelid
- innervated by the occulomotor nerve
What kind of membrane is the conjunctiva and is it vascular
- a mucous membrane
- highly vascular
What are the 3 layers of a tear film
- anterior lipid layer (meibomian glands)
- aqueous layer (lacrimal and accessory glands) which contains antibodies, enzymes and vitamin C
- mucin layer (conjunctival goblet cells)
What does a tear film do
- provide nutrients and oxygen for the cornea
- protection from infection, contamination and foreign bodies
- allows a smooth clear refracting surface
Is the corneal vascular
No
What is the function of the cornea
-refraction and transmission of light
What are the 3 layers of the cornea
- epithelium (cell turnover, stratified non-keratinising, limbal ste cells)
- stroma (regular lamina of collagen fibres)
- endothelium (single layer)
What nerve innervates the cornea
- the ophthalmic branch of the trigeminal nerve
- very sensitive to touch and pain
What fills the anterior chamber of the eye and what produces this substance
- aqueous humour
- produced by ciliary body
What is the function of the iris and how does it do this
-controls light entry into the eye
- dilator muscles with alpha receptors are innervated by the sympathetic nerves
- sphincter muscles with M3 muscarinic receptors are innervated by the parasympathetic nerves
What is the function of the lens and what is it attached to
- changes shape to control the refracting power of the eye
- attached to ciliary body (muscle) by zonule
What is the function of the ciliary body
- contains ciliary muscles that control the focussing power of the lens
- innervated by parasympathetic fibres of the oculomotor nerve and has M3 muscarinic receptors
- accomodation is the change in shape of the lens
- caused by contraction of the ciliary muscle in the ciliary body
- causes relaxation of zonular fibres which are attached to the elastic capsule of the lens
What does the retina do
-contains photoreceptors that convert light energy into nervous impulses
Layers of the retina (from outside to inside)
- photoreceptors (rods and cones)
- 1st and 2nd order neurones (bipolar and ganglion cells)
- interneurones (amacrine and horizontal cells)
- neuroglial cells (Muller cells)
- pigment cells
- supporting membranes
What is significant about the macula (lutea)
-has the highest concentration of cones
What is significant about the fovea (centralis)
- it is in the center of the macula
- just consist of cone photoreceptors
- best visual acuity at the fovea
What does the choroid do
- it is highly vascular and provides bloods supply to the outer retina
- it is heavily pigmented with melanin which absorbs stray light
- it also removes heat from the retina
What is the optic disc
- exit for 1.2 million ganglion cell axons
- it has a lot of capillaries so pink in colour
- no photoreceptors (so has a blind spot)
Give 3 things the diameter of the pupil will change in response to
- change in light intensity
- proximity of object
- state of arousal (sympathetic nervous system)
Explain the path of the pupil reflex
Stimulus
Afferent limb
- retina (photoreceptor cells)
- optic nerve
- decussation at the chiasm (so stimulation of one eye will cause a pupil response in both eyes)
- optic tracts
Central neurone
-pretectal nucleus
Efferent limb
- Endinger-Westphal nucleus in the midbrain
- parasympathetic fibres from the occulomotor nerve
- synapse in ciliary ganglion in the orbit
- short ciliary nerves innervates the sphincter muscle
What is the pupil response to shining light in the left eye
-constriction of both right and left pupil
What is the pupil response to removing light
-both pupils dilate
What is the pupil response to shining light in the right eye
-constriction of both the right and left pupil
Describe the intraocular pressure of the eye
- the eye has an intraocular pressure that is 15-20 mmHg higher than atmospheric pressure
- so eye can move around without being deformed
Where does the aqueous humour leave the anterior chamber
Through the anterior chamber angle (trabecular meshwork)
Give the blood supply to the eye and its branches
The ophthalmic artery
- the central retina artery (supplies inner retina)
- ciliary arteries (supplies outer retina, ciliary body and iris)
What do the retinal arteries of the eye contribute to and how
- the blood retinal barrier which protects the retina and limits drug entry
- the retinal capillaries have tight junctions so do not leak fluid
- no lymphatics in the retina
Explain the two visual systems (scotopic and photopic)
Scotopic
- rod photoreceptors (in peripheral retina)
- monochromatic and suited to low light conditions
Photopic
- cone photoreceptors (in the macula)
- chromatic and suited to bright light conditions
Give the 3 types of cones photoreceptors
Red, green and blue
Where is the blindspot of the eye
The optic disc (in the temporal field of the eye)
What is emmetropia
- when the length of the eye matches the resting focal length of the refracting surfaces (cornea and eye ball)
What is refractive error
-when the refracting power does not match the length of the eye
Give the 2 forms of refractive error
- myopia - when the eyeball is too long (or the lens system too strong) so image falls short of the retina and the image is blurred
- hyperopia or hypermetropia - when the eyeball is too short (or the lens system not strong enough) so image goes further than retina
What is astigmatism
The refracting power of the cornea is not uniform eg light in the vertical plane focuses on the retina while light from the horizontal plane focuses in front (short) of the retina
Describe the near reflex of the eye (accomodation)
As images are brought closer to the eye
- the lens increases its refracting power
- the eyes converge (to maintain single vision)
- the pupils constrict
What is presbyopia
-losing the accommodation reflex as we get older due to stiffness of the lens
What is visual acuity
- the ability to see detail (resolution)
What is the normal visual acuity on a snellen chart
6/6 also known as 20/20
Is steropsis (seeing the world in 3D) prsent at birth
No, it develops later
Describe the visual pathway from retina onwards
- light hits photoreceptors in the retina
- 1st order bipolar neurone pass message to second order ganglion cell neurone still in retina
- the ganglion cell axon runs in the nerve fibre layer through the optic disc and into the optic nerve
- the optic nerve runs through the optic canal to the optic chaism
- the optic chiasm is just above the pituitary gland
- ganglion cells axons lieing medially at the optic chiasm cross over to the other side
- these ganglion axons then travel to the thalamus
- ganglion cell fibres synapse with cells in the lateral geniculate nucleus (3rd order neurone)
- axons from the lateral geniculate nucleus enter the optic radiations
- information from the lower visual field is carried in superior fibres that enter the white matter of the parietal lobe
- information from the superior visual field is carried in the inferior fibres which enter the white matter of the temporal lobes
- fibres from the optic radiations synapse with cortical cells in the visual cortex of the occipital lobe
- the visual cortex lies on the medial surface of the occipital lobe and is either side of the calcarine sulcus
- fibres carrying information from the central retina (macula) lie at the posterior pole of the macula
- the macula receives its blood supply from both the middle and posterior cerebral artery
The image projected on the retina is upside down and laterally inverted true or false
True
Nerve fibres from the superior retina stay superior along the entire visual pathway True or False
True
Nerve fibres from the inferior retina stay inferior along the entire visual pathway True or False
True
Nerve fibres from the retina nasal to a vertical line through the fovea cross at the chiasm True or False
True
Nerve fibres from the retina temporal to a vertical line through the fovea do not cross at the chiasm True or False
True
The optic tracts contain fibres from the temporal retina (nasal visual field) from the same side and the nasal fibres (temporal visual field) from the opposite side True or False
True
What could cause loss of centre of vision (central scotoma) in the eye
- Macular degeneration
- Optic neuritis
What could cause tunnel vision in the eye
- Retinitis pigmentosa
- glaucoma
What could cause loss of vision in an ‘arc’ shape in the eye
-glaucoma
What could cause an enlarged blind spot in the eye
-swollen optic disc
What could cause loss of temporal field of vision in both eyes (bitemporal hemianopia)
A pituitary tumour pressing down on the optic chiasm
What would occur in an optic tract lesion
Loss of field of vision on both eyes
- qcontralateral (on the opposite side to the site of the problem)
- homonymous (temporal in one eye and nasal in the other)
- heminopia (affecting up to 1/2 the visual field)
- incongruous (greater in one eye than the other)
What would occur in an optic radiation lesion
- either affect the inferior visual field (parietal lobe lesion) or superior visual field alone (temporal lobe lesion)
- contralateral (on the opposite side to the site of the problem)
- homonymous (temporal in one eye and nasal in the other)
- congruous (similar in both eyes)
- quadrantinopia (quarter of the visual field)
What would occur in lesions or disorders of the primary visual cortex
- contralateral (on the opposite side to the site of the problem)
- homonymous (temporal in one eye and nasal in the other)
- heminopia (affecting up to 1/2 the visual field)
- congruous (similar in both eyes)
Types of strokes
- ischemic stroke (thrombotic and embolic) (blockage of artery)
- hemorrhagic stroke (subarachnoid and intracerebral) (rupture of artery that later clots)
- Transient ischemic attack (TIA) (temporary cerebrovascular event that leaves no permanent damage)
Risk factors for cerebrovascular disease
Modifiable
- smoking
- high blood pressure
- carotid or aterial diseases
- history of transcient ischemic attacks
- diabetes
- high blood cholesterol
- obesity or physical inactivity
Non modifiable
- age (more common in older people)
- gender (more common in men)
- heredity and race
- prior stroke or heart attack
In terms of cerebrovascular disease, what would be the appropriate primary and secondary intervention
Primary prevention
-used QRISK 3 calculator to assess cardiovascular risk as 10 year risk of fatal or non-fatal stroke
Then give lifestyle advice for cardiovascular disease
E.g at least 30 mins of moderate-intensity exercise a day at least 5 days a week
-prescribe aspirin
-prescribe statin therapy if above 20% or greater in 10 year risk of CVD
Secondary prevention (after a cardiovascular event has occured e.g MI or stroke)
- offer 300mg aspirin a day
- offer clopidogrel if they have peripheral arterial disease or multivascular disease
- offer statins
- carotid endarterectomy - (surgical removal of buildup in the carotid artery)
Public health campaigns and impact on morbidity/mortality
FACE
Face - the face may have dropped on 1 side, they may not be able to smile and their mouth or eye may have dropped
Arms - the person with suspected stroke may not be able to lift both arms and keep them there because of weakness or numbness
Speech - their speech may be slurred or garbled, they may have trouble speaking an might not understand what you say
Time - dial 999
Deaths related to stroke has reduced by 49% in the past 15 years
Give the definition and examples of primary and secondary prevention
Primary prevention
This is aimed at healthy individuals, to prevent disease from occurring. Examples include:
Vaccinations. Adopting a healthy lifestyle - for example: Diet. Weight. Exercise. Avoidance of smoking. Avoidance of excess alcohol. Practising safe sex. Avoidance of drug abuse.
Secondary prevention
This is aimed at patients with an existing pathology, to reduce the risk of recurrence or progression - for example:
Aspirin in arterial disease.
Beta-blockers and angiotensin-converting enzyme (ACE) inhibitors after myocardial infarction.
Smoking cessation in chronic obstructive pulmonary disease (COPD) and established arterial disease.
Where is the interpeduncular fossa
-between the crus cerebri
Where is the bulbopontine sulcus
-the junction between the pons and the medulaa
Where is the basilar sulcus
-groove running down the front of the pons where the basilar artery normally sits
Where is the anterior median fissure usually found
-on the front (ventral aspect) of the medulla dividing it into two halves
Where is the ventral lateral sulcus
-groove that divides the pyramids and olives of the medulla
What are the olives important for
- carry fibres between the spinal cord and cerebellum
- important for motor coordination
- the inferior olivary nucleus lie just underneath
What do the inferior cerebellar peduncles do
- carry fibres between the medulla into the cerebellum
- carry afferent and efferent fibres so are bidirectional
What do the superior cerebellar peduncles do
- carry fibres between the midbrain and cerebellum
- carry afferent and efferent fibres so are bidirectional
What do the middle cerebellar peduncles do
- carry fibres between the pons and the cerebellum
- it is the largest of the 3 cerebellar peduncles
- carry afferent and efferent fibres so are bidirectional
What are the superior coliculi important for
-visual reflexes e.g looking towards a flash
What are the inferior colliculi important for
-audio reflexes e.g turning the head towards a sound
What does the substantia nigra contain
-dopaminergic neurones which project to the striatum in the basal ganglia
Why is the substantia nigra black
-the dopaminergic neurones produces neuromelanine (a black pigment)
Which neurones are most affected in Parkinson’s disease
-the dopaminergic neurones of the substantia nigra
Where does the red nucleus receive input from? And where does it give output to
- receives input from the cerebellum and motor cortex
- gives output to the rubro-spinal tract
What is the rubrospinal tract thought to be important for in humans
- for infants to learn crawling
- for arm swinging when adults are walking
What does the infundibulum stalk do
-connects the pituitary gland to the brain
Which is the trochlear nerve unusual in terms of where it arises form
-it is the only nerve that arises from the dorsal aspect of the brain stem and wraps around and comes out either side of the pons
Which cranial nerves emerge at the ponto-medullary-cerebellar angle
- the facial and vestibulocochlear nerve
- and sometimes the glossopharyngeal and vagus nerve
Where do the 1st order neurones of the olfactory system lie
-in the spheno-ethmoidal recess of the nasal cavity
Where do the 2nd order neurones of the olfactory system lie
-within the olfactory bulb
Where do 85% of the fibres from the olfactory tract pass to
- stay on the same side and pass into the cortex
- into the uncus of the temporal lobe of the forebrain
Where do 15% of the fibres from the olfactory tract pass into
-deccusate and pass into cortex on opposite side
Where do the 1st order neurones of the optic nerve lie
-within the retina
Which side of the brain will fibres arising from the nasal retina pass to
-across the optic chiasm to the opposite side of the brain
Which side of the brain will fibres arising from the temporal retina pass to
-will arrive at the optic chiasm and stay on the same side of the brain
After the optic chiasm what path do the optic fibres take
- the optic fibres continue to the lateral geniculate body which lies on the inferior part of the thalamus (they synapse unto a 3rd order neurone)
- 3rd order neurone passes through the temporal and parietal lobe to reach the calcurine sulcus in the occipital lobe
Do the axons concerned with pupillary reflexes synapse in lateral geniculate body as they travel to the pretectal and Edinger-Westphal nucleui
No they synapse in the nuclei deep to the superior colliculus
Which lobe would the fibres of the superior visual quadrants travel through
-the parietal lobe
Which lobe would the fibres of the inferior visual quadrants travel through
-the temporal lobe
Explain how lesions along different points on the optic tract can lead to the different types of visual loss
Lesion between the retina and optic chiasm - total visual loss in one eye
Lesion at the optic chiasm - bitemporal heminopia (so the nasal fibres from both eyes that collect information from the temporal visual fields are damaged)
Lesion between the optic chiasm and lateral geniculate body of the thalamus - left or right contralateral homonymous hemianopsia
Lesion along Meyer’s loop (lateral through temporal lobe) - contralateral upper quadrantic anopsia
Lesion along Baum’s loop (through parietal lobe) - contralateral lower quadrantic anopsia
Lesion of both optic radiations just before the calcarine sulcus - left or right contralateral homonymous hemianopia with macular sparing
What is the significance of Meckel’s cave
-it is where the trigeminal divides into the opthalmic, maxillary and mandibular branch
Describe the size of the motor and sensory nucleus of the trigeminal nerve
Motor nucleus in the pons - small
Sensory nucleus in the pons - large and extends from the cerebral peduncles through the midbrain, pons, medulla and down into the upper part of the spinal cord
Where is the nucleus of the 6th cranial nerve
- immediately underneath the facial colliculus on the floor of the fourth ventricle
- termed facial colliculi because facial nerve fibres pass over the top of the 6th nerve nucleus to make up the floor of the 4th ventricle
What is the nervous intermedius a branch of and what does it do
- a branch of the facial nerve that arises separately from the main facial nerve branch
- it joins the facial nerve in the internal acoustic meatus and travels with it to the middle ear where it leaves the facial nerve and joins the lingual branch of the trigeminal nerve to supply special taste to the anterior 2/3rd of the tongue
Where do the nerve nuclei of the facial nerve lie
-in the floor of the fourth ventricle
Which glands does the facial nerve give parasympathetic innervation to
- the lacrimal glands
- the submandibular glands
- the sublingual glands
Where do the nucleus for the vestibular and cochlear component of the vestibulocochlear nerve lie
- the vestibular aspect lies in the lateral part of the medulla and pons
- the cochlear aspect lies in the inferior cerebellar peduncle
Where does the 2 components of the accessory nerve arises from
-the spinal accessory nerve arises from the nerve rootlets from C1 to C5
Where does rootlet from the medulla that later joins the vagus nerve to become the superior laryngeal and recurrent laryngeal nerve arise from
-the nucleus ambiguous
What does the spinal component of the accessory nerve innervated
-sternocleidomastoid and trapezius muscle
Describe the journey of the hypoglossal nerve to the tongue muscles
- travels through the hypoglossal canal
- down the carotid artery
- at the level of the posterior belly of the muscle of diagastric travels at 90 degrees to lie under the tongue
Where do the nuclei of the 9th, 10th, 11th and 12the cranial nerve lie and what is the exception
- in the floor of the 4th ventricle
- all except some motor neurones that supply sternocleidomastoid and trapezius muscle within the cervical spinal cord
What is bulbar palsy, give symptoms and signs
-this where motor neurones of the 9th, 10th, 11th and 12th are affected by a form of motor neurone disease
Symptoms
- dysphagia (difficulty swallowing)
- slurring of speech
- dysphonia (difficulty forming sounds)
- excess saliva - dribbling
Signs
- wasting and fasciculating tongue
- absent gag reflex
Causes
- motor neurone disease
- guillain-barre syndrome
Pseudobulbar palsy presents with similar symptoms but the lesion is in the upper motor neurones e.g caused by stroke or multiple sclerosis
Describe the distribution of fibres from the corticospinal tract at the pyramids
- 80% deccusate at the medullary pyramids and form the lateral corticospinal tract
- 10% join the ipsilateral (uncrossed) lateral corticospinal tract
- 10% travel in the (uncrossed) anterior corticospinal tract
What does the pineal gland do
-an endocrine gland that synthesises melatonin
What does the inferior brachium do
-convey auditory information from the medial geniculate body to the inferior colliculi
What does the superior brachium do
-conveys visual information from the lateral geniculate body to the superior colliculi
Why are the gracile and cuneate tubercle important
- they are usually called the dorsal column nuclei
- major relay site for the dorsal column sensory pathway
What is Bell’s Palsy, give symptoms and signs
-acute unilateral inflammation of the facial nerve (lower motor neurone)
Symptoms (unilateral)
- pain behind ear
- paralysis of facial muscles and failure to close eye
Signs (unilateral)
- absent corneal reflex
- hyperacusis (certain sounds heard unpleasantly loud)
- loss of taste on anterior 2/3 of the tongue
- if caused by Herpes Zoster virus (virus causing shingles), a vesicular rash will be seen in the external auditory canal and on the oropharynx
What can occur when sodium levels are correctly too quickly
- central pontine myelinolysis
- this is destruction of the myelin in the pons
- causes confusion, balance problems, dysphagia, hallucinations, reduced consciousness, slurred speech, tremor and weakness in the face or limbs
Describe the journey of the optic tracts from the retina
- retina to optic nerve to optic chiasm
- most to synapse at the lateral geniculate body
- few to synapse at the pretectal nucleus and superior colliculi (midbrain for visual reflexes)
- from the lateral geniculate body through internal capsule to the visual cortex
What sort of vision loss can a pituitary tumour lead to
-bitemporal heminopia because the tumour would be pressing down on the fibres crossing over at the optic chiasm
Another name for Meyer’s loop is
Loop of Archambault
Acoustic neuromas grow on the 8th cranial nerve causing nerve compression. Which adjacent crania nerve could also be compressed by the growing tumour and what symptoms may this cause
- can compress the facial nerve causing paralysis of the facial muscles
- loss of the taste sensation to the anterior 2/3 of the tongue
- loss of innervation to the stapedius so an intolerance to loud noises
Give the different in length of the pre and post ganglion efferent nerves for the sympathetic and parasympathetic system
Parasympathetic nerves - long preganglion nerves and short post ganglion nerves so they synapse close to their target organ
Sympathetic nerves - short preganglion nerves and long postganglion nerves so they synapse far from their target organ
Give an an easy way to test the superior and inferior recti muscles of the eye in isolation of the oblique muscles
- getting the patient to 23 degress to the side
- sit in front of patient and place finger at eye level at arms length from their face and out to the rigth
- then move finger up and down
Which eye muscles can never be tested in isolation
-the superior and inferior oblique muscles
Does the vestibulo-ocular reflex still work even if unconscious
-yes it is a brain stem test
What does the cupula of the ear do
-a gelatinous vane that bends when fluid within the semicircular ducts moves because of angular rotation
What does the cristae of the ear do
- found at the base of the ampulla of the semicircular canals
- contains hair cells with stereocilia on top respond to angular acceleration (rotation of the head, includes turning the head side to side)
What does the maculae of the ear do
- they are hair cells so receptors with otoconia on top (small calcium, carbonate crystals)
- they respond to linear acceleration (so tilted the head up and down)
What is the utricle of the ear sensitive to
- most sensitive to gravity
- changes in the head position from an upright position
What is the saccule of the ear most sensitive to
- most sensitive to gravity
- changes in the head from a laid down position
What does the organ of corti do
-senses sound
The vestibular nuclei is connected to the 3rd, 4th and 6th cranial nerve nuclei by the medial longitudinal fasciculus True or False
True
What is Meiniere’s disease
-swelling of the membranous labyrinth so excess endolymph
How is angular acceleration of the head (rotation of the head) detected
- when the head turns in a direction, the endolymph in the horizontal semicircular canal moves in the opposite direction
- at the ampulla which contains the cristae, the stereocilia of the hair cells move towards kinocilium (longest stereocilia)
- this causes the hair cells to depolarise increasing impulses to the afferent nerve of the vestibulocochlear nerve
- this is the ear of the direction being turned to
- in the other ear
- the endolymph moves the hair cells away from the kinocilium which causes the hair cells to hyperpolarise
- this reduces the impulses to the afferent vestibulocochlear nerve
How is linear acceleration of the head detected (tilting head upwards) from standing
- the utricle of the ear is one of the otolith organs and is most sensitive to changes from standing
- the kinocilia in the utricle point towards the striola (middle line) in the maculae (patches of hair cells topped by otoconia)
- this will activate impulses in the afferent vestibulocochlear nerve
How is linear acceleration of the head detected (tilting head forwards) from laying down
- the saccule is one of the otolith organs and is most sensitive to change from laying down
- the kinocilia of the saccule points away from the striola (midline) of the maculae (patch of hair cells topped by otoconia)
What is the purpose of the vestibulo-occular reflex
- controls eye movements to stabilise images during head movements
- as the head moves in one direction, the eyes reflexively move in the other direction
- only effective up to a speed of 50 degrees per second
Give 3 neurones involved in the vestibulo-occular reflex circuit
- one neurone in the scarpa’s (vestibular) ganglion
- one neurone in the vestibular nucleus
- one neurone in the extraoccular motor nucleus
How can the vestibulo-occular reflex be tested in the unconscious
- using caloric nystagmus
- putting either cold or really warm water in the ear
Using cold water
- cold water cools the tympanic membrane which cools the middle ear and the endolymph (usually in the horizontal semicircular canal which is closest to the middle ear)
- the cooling creates convection currents that causes hyperpolarisation of the hair cells
- the causes the eyes to move slowly towards the ear that water has been added then quickly shift to reset to the other side and then back again to the original ear side
- if cold water was put into the right ear, it would be called left beating nystagmus
What do hair cells in the organ of corti respond to
-sound
What features help to maintain the ionic imbalance between the perilymph and endolymph
-tight junctions
What ions is endolymph rich in
-potassium ions
What connects the cilia at the tip of the hair cells in the vestibular system
-tip links
Which tube in the cochlear contains the organ of corti
-the scala media
Which tube in the cochlear contains is attached to the round window
-scala tympani
Which tube in the cochlear is connected to the oval window
-scala vestibuli
Where can the organ of corti be found
- sits on the basilar membrane which forms the division between the scalae media and tympani
- in the scalae media
What is sound
-the displacement of air particles following a sinusoidal pattern of compression and rarefacation
An increase in amplitude will cause an increase in (with sound)
-in volume of sound
An increase in number of waves per second will correspond with (with sound)
-an increase in pitch
What is our range of hearing
20Hz- 20KhZ
What fills the components of the auditory system - air or water
Outer ear (pinna to the tympanic membrane) - air Middle ear (tympanic membrane to the oval window) - air Inner ear (oval window to the internal acoustic meatus) - fluid
What is the pinna of the ear formed from
-the pharyngeal arches 1 and 2 (the 6 Hillocks of the HIS)
When does the pinna and the ear canal form in utero
Between the 10th and 18th week in utero
What is the ear canal made frome
- 1/3 cartilage
- 2/3 bone
Give the diameter of the tympanic membrane
8 x 10mm in diameter
Give the bones of the middle ear
- malleus (23mg)
- incus (27mg)
- stapes (2.5mg)
Give the muscles of the middle ear and their innervation
- tensor tympani
- stapedius
What is the smallest bone in the body and how much does it weigh
- the stapes
- 2.5mg
What role of the middle ear
- amplification of the airborne sound vibration
- 200 fold increase boost in pressure from tympanic membrane to inner ear
How does the middle ear amplify sound
- area of the stapes footplate to the tympanic membrane is 14:1
- lever action of the ossicles, the handle of the malleus is 1.3 times longer than the long process of incus
What are the parts of the vestibulocochlear apparatus responsible for
Cochlear - responsible for hearing
Labyrinth - responsible for balance
What is the perilymph fluid rich in
- sodium ion
- some chloride ion
- like ECF and CSF
How is the gradient of the cochlear fluids maintained
- sodium potassium ATPase pump
- NKCC1 CIC-K chlorine channels
Where is the basilar membrane stiffest
-at the base
Where is does the basilar membrane receive its lowest frequencies
-at the apex
How is sound information (frequency, intensity, sound transduction and amplification) encoded
Frequency (pitch) is encoded in nerve by location along the basilar membrane
Intensity (loudness) is encoded in nerves by numbers responding and by firing rate
Sound transduction is encoded inner hair cells and outer hair cells
Amplification is encoded by outer hair cells
How does the sound travel from the auditory fibres from the inner hair cells to the brain
- inner hair cells
- spiral ganglion
- cochlear nerve
Central auditory pathway (ECOLI)
- eight nerve (cochlear part of the vestibulocochlear nerve)
- cochlear nucleus
- olive (superior olivary nucleus)
- lateral leminiscus
- inferior colliculus
- medial geniculate body
- the auditory cortex in the superior temporal gyrus of the temporal lobe
Give the types of hearing loss
- conductive hearing loss (defective outer/middle ear)
- sensorineural hearing loss (defective inner ear)
What is psychological stress
-mental or emotional strain or tension resulting from adverse or demanding circumstances
What is physiological stress
-sensory, emotional and subjective experience associated with potential damage of body tissue and bodily threat
Types of stress
- Eustress (good stress) - positive stress which is beneficial and motivating e.g striving for a goal within reach
- Distress (bad stress) - negative stress which is damaging and harmful e.g when a challenge or threat is not resolved by coping or adaptation
What is acute stress and give examples
- short-lived response to a novel situation experienced by the body as a danger (usually without conscious processing)
- e.g brief illness, noise, short-term danger
What is chronic illness and give examples
-arises from repeated or continued exposure to threatening or dangerous situations especially those that cannot be controlled
E.g physical illness, disability and pain, unemployment, bullying and discrimination, caregiving
Explain the 3 phases of the stress response (Selye’s syndrome)
Alarm - Threat or stressor identified or realised and the body’s response is a state or alarm
Adaptation - body engages defensive countermeasures
Exhaustion - body runs out of defences and resources are depleted
Which two systems of the brain primarily mediated the stress response
- autonomic nervous system (sympathetic-adrenal-medullary system) (SAM)
- hypothalamo-pituitary (HPA) axis
What are the 5 elements of the human stress response
- biochemical
- physiological
- behavioural
- cognitive
- emotional
Explain the sympathomedullary pathway
- hypothalamus activates the adrenal medulla
- adrenal medulla (controlled by the autonomic nervous system) releases adrenaline and noradrenaline into the bloodstream
- body prepares for ‘fight or flight’
- adrenaline and noradrenaline reinforces the pattern of sympathetic activation e.g increased hear rate and blood pressure
- releases energy
Explain the pituitary-adrenal system
- higher brain centres activate hypothalamus
- hypothalamus releases corticotrophin (CRF)
- pituitary gland releases adrenocorticotrophic (ACTH)
- adrenal cortex releases corticosteroids
- corticosteroids causes changes, liver releases energy and the immune system is suppressed
What are the fight or flight chemicals released
- glucocorticoids (cortisol)
- catecholamines (adrenaline and noradrenaline)
Which areas of the brain mediate responses to different types of stressors
-the amygdala and the hippocampus
Give 4 factors that modify the perception of threat and stress response
- context
- appraisal
- vulnerability
- learning
What is allostasis
- how multiple and complex systems adapt collectively in changing environments through dynamic change
- (e.g via autonomic nervous system and the hypothalamo-pituitary axis)
- allostatic states are inherently fragile and decompensation can happen quickly
What is allostatic load
-cumulative exposure to stressors (and cost to the body of allostasis) which if unrelieved leads to systems wearing out
What is Dunbar’s number
-the cognitive limit to the number of people with whom one can maintain stable social relationships
Describe how the ascending tracts are divided
Conscious tracts
- dorsal column-medial lemniscal pathway
- anterolateral pathway (spinothalamic pathway)
Unconscious tracts
-spinocerebellar tracts
Describe the dorsal column-medial lemniscal pathway (DCML)
Carries sensory for fine touch (tactile), vibration and proprioception
1st order neurone travels form the fasciculus cuneate in the dorsal column of the spinal cord to the medulla oblongata and synapse with the nucleus cuneate
2nd order neurone travels form the medulla oblongata where they decussate to the contralateral side and travel through the medial leminiscus to the thalamus
3rd order neurone travels from the ventral posterolateral nucleus of the thalamus through the internal capsule to the primary sensory cortex
-it is the same for the fasciculus gracilis which just has a 1st order neurone synapse at the nucleus gracilis
- fasciculus cuneate (lateral) carries sensation for the upper limbs from T6 and above
- fasciculus gracilis (medial) carries sensation for the lower limbs from T6 and below
Describe the anterolateral system (the spinothalamic tract system)
- anterior spinothalamic tract - crude touch and pressure
- lateral spinothalamic tract - pain and temperature
1st order neurone enter the spinal cord and travel up 1 or 2 veterbra to synapse on the substantia gelatinosa on the dorsal horn of the spinal cord
2nd order neurone travel from the substantia gelatinosa and decussate then divide into the anterior and lateral spinothalamic tracts and both travel up the contralateral side to the thalamus
3rd order neurone travel from the ventral posterolateral nucleus of the thalamus through the internal capsule to the primary sensory cortex
Describe the spinocerebellar tract (unconscious sensation)
Carries unconscious information from muscle to the brain that help coordinate and refine motor movements
- posterior spinocerebellar tract - carries proprioceptive information from the lower limbs to the ipsilateral cerebellum
- anterior spinocerebellar tract - caries proprioceptive information form the lower limbs to the ipsilateral cerebellum (but decussates twice)
- cuneocerebellar tract - carries proprioceptive information form the upper limbs to the ipsilateral cerebellum
- rostral spinocerebellar tract - carries proprioceptive information form the upper limbs to the ipsilateral cerebellum
What are the folds of the cerebellum called
-folia
What separates the two lobes of each of the hemispheres of the cerebellum
-the primary fissure
What are the two lobes of each of the hemisphere of the cerebellum called
-the anterior, middle and posterior lobes
Name the two fissures within the cerebellum
- the primary fissure
- the horizontal fissure
Where do each of the cerebellar peduncles go to
- the superior cerebellar peduncle goes to the midbrain
- the middle cerebellar peduncle goes to the pons
- the inferior cerebellar peduncle goes to the medulla
Name the deep nuclei cerebellum nuclei
- dentate
- vestigial
- interpose
Which is the largest of the deep cerebellum nuclei
-dentate
Where does the output bundles of the dentate nuclei pass to
-the superior cerebellar peduncle
Why is the dentate nuclei important
-planning, initiation and control of movement
Which are the smallest of the deep cerebellar nuclei
-the interpose nuclei
Where are the flocculli and what are they connected to
- they are lateral to the peduncles
- they are connected by white matter tracts to the nodule
What do the floccullar-nodular node do
- receive vestibular input from the labyrinths of the ear and from the vestibular nuclei through the inferior cerebellar peduncle
- referred to as the vestibular cerebellum and important for eye movements and balance
What does the spinocerebellum do
-consists of the vermis and medial hemispheres
- receives sensory inputs for balance and position sense from the spino-cerebellar tracks
- send outputs via the deep cerebellum nuclei to the lateral and descending motor pathways
- important for voluntary movements and postural control (motor execution)
What does the cerebro cerebellum do
- receive corticopontine inputs
- inputs from the cortex via the pons through the middle cerebellar peduncle
- output is via the dentate nuclei to the motor cortex via the red nucleus and thalamus so the rubro-thalamic tract
- involved with motor planning
What is the fossa of the 4th ventricle called
-the rhomboid fossa
Where are the gracile and cuneate tubercles located in relation to the 4th ventricle
Just below the rhomboid fossa
-they are also called the dorsal column nuclei
What is the dorsal column medial leminiscus pathway important for
- fine touch
- vibration
- 2 point discrimination
- proprioception
What divided the rhomboid fossa into left and right
-the median sulcus
What are the medullary striae
-pontocerebellar fibres that divide the floor of the 4th ventricle into the rostral pontine portion and the caudal medullary portion
How is the locus coeruleus differentiated in the floor of the 4th ventricle
- a slightly blueish gray area
- contains pigmented noradrenergic neurones
what does the locus coeruleus contain and what are its functions
- contains pigmented noradrenergic neurones
- functions are stress responses and arousal
What is the inferior tip of the rhomboid fossa called
- the obex
- it is where the floor of the 4th ventricle narrows and enter the central canal of the spinal cord
What is inside the obex and why is it important
- the area postrema is just inside the opex
- it is important for nasuea
- the area postrema is a chemodetector zone important for the emetic response
What do the facial colliculi of the floor of the 4th ventricle show
-where the axons of the facial nerve pass over the underlying abducens nerve nucleus
What does the vestibular area (vestibular trigone) contain
- contains the nucleus of the vestibulocochlear nerve
What does the hypoglossal triangle contain
- contains the nucleus of the hypoglossal nerve
- it is medial to the vagal triangle
What does the vagal triangle contain
- contains the nucleus of the vagus nerve
- lateral to the hypoglossal triangle
Where does the anterior cerebral artery run on the medial aspect of the hemisphere
-over the cingulate gyrus
Give an example of a commissural fibre and where it would run
- the corpus collosum
- white matter tracts running between the 2 hemispheres
What is the largest part of the diencephalon
-the thalamus
What percentage of brains have an inter-thalamic adhesion
90%
Where is the hypothalamic sulcus
-the groove between the thalamus and the hypothalamus
Where is the epithalamus and what does it include
- the dorsal and posterior aspect of the diencephalon
- includes the hebenula, the pineal body (produces melatonin so important for circadian rhythms), striae medularis
Where are the subthalamic nuclei and what do they do
- lie ventral to thalamus and lateral to the hypothalamus
- receive inputs from the substantia nigra and are important in the control of movement
Name the parts of the corpus collosum
- genu
- body
- splenium
- rostrum
What does the fornix do
- connects the hippocampus to the diencephalon
- has fibres that run behind the hypothalamus and connect to the mammillary body
What does the lamina terminalis do
- thin sheet of ependyma and pia that extends from the rostrum and fornix and forms the anterior wall of the 3rd ventricle
- stops the 3rd ventricle draining into the subarachnoid space
- extends down to the optic chiasm
What does the anterior commisure do
-connects the temporal lobes and olfactory structures in each of the hemispheres
Where in the calcarine sulcus does the visual cortex lie
-in the walls of the calcarine sulcus
What is different about the grey matter of the calcarine sulcus
- contains the striae of Gennari
- the striae of Gennari are a grey band running within it that is a band of myelinated axons coming from the thalamus that project into layer 4 of the visual cortex
- also the reason why the visual cortex is sometimes referred to as the striate cortex
What is a difference between the grey matter of the motor cortex and the somatosensory cortex
-the motor cortex grey matter is 2x as thick as that of the somatosensory cortex
Describe the different tracts from the cerebellum and which peduncles they use
Ventral spinocerebellar (contralateral) tract - superior cerebellar peduncle -sensory input for balance and position sense
Corticopontocerebellar tract - middle cerebellar peduncle - information from the primary motor cortex of the motor plan, the same information goes to the spine
Vestibulocerebellar tract - inferior cerebellar peduncle - vestibular impulses from labyrinths directly and via the vestibular nucleus
Dorsal spinocerebellar (ipsilateral) tract - inferior cerebellar peduncle -sensory input for balance and position sense
What are the borders of the 3rd ventricle
Anteriorly - lamina terminalis
Superiorly - tela choroidea
Inferiorly - optic chiasma, pituitary stalk, mammillary bodies and tegmentum
What are the 3 main types of connecting white matter of the brain
Association fibres - link cortical regions within one cerebral hemisphere e.g cingulum bundle, the superior longitudinal fasciculus, uncinate fasciculus
Commissural fibres - link similar functional areas of the two hemispheres e.g corpus callosum
Projection fibres - link the cortex with subcortical structures such as the thalamus and spinal cord e.g corona radiata and the internal capsule
What are projection fibres do
- link cortex with subcortical structures such as the thalamus and spinal cord e.g corona radiata and internal capsule
- white matter
What are commissural fibres
- link similar functional areas across the two hemispheres e.g corpus callosum
- white matter
What are association fibres
-link cortical regions within one cerebral hemisphere
What would occur if an object was presented solely to the left visual field of an individual with a totally divided corpus callosum
- the two cerebral hemispheres would behave autonomously
- the individual would be unable to name or read the object because the information is being directed to the right non-dominant hemisphere which does not evoke a verbal response
What brain development occurs at 10weeks
-cerebral expansion and commissures
What brain development occurs at 3 weeks and 6 weeks of embryo growth
3 weeks = eye formation
6 weeks = more flexures and swellings
When does CNS myelination begin in an embryo
5 months (or 25 weeks)
When does the lobed cerebrum begin to develop in an embryo
7 months
When do gyri and sulci start developing in an embryo
9 months
Give some critical periods in embryo development and what can occur during them
At 6 weeks = eye malformation e.g cataract
At 9 weeks = deafness from the organ of corti
At 5 to 10 weeks = cardiac malformations
At what trimester is the risk of CNS disorder high
2nd trimester
Can alcohol cross the placenta
-yes and the fetus does not clear it well so higher levels build up in the fetus
Give an approximation of the speed of conduction of a myelinated axon in a developing fetus
From 1 to 6 months = 32 to 50m/s
From 6 to 12 months = 33 to 60m/s
From 12 to 24 months = 40 to 60m/s
When does innervation of the dermal skin occur in a developing fetus
28 weeks
When does a dorsal root ganglion connection to the spinal cord occur in a developing fetus
-from 8 weeks
Do fetus show a stress response and what is it
-they have a stress awareness where they releases catecholamine which increase fluid uptake in the lung
Give 4 postnatal reflexes
- moro (startle) reflex
- stepping
- palmar grasp
- babinski reflex
Give a significant co-ordinated response in a developing child
- reaching
- begins at around 5 months
- language
- 5 stages
- (1) 9 to 18 months with 1st word
- (2) 18 to 24 month with 2nd words
- (3) 2 to 3.5 years with simple conversations (why stage)
- (4) 3.5 to 8 years with complexity
- (5) 8 years and over with adult language
What is a short term energy store alternative to ATP
-creatine phosphate
What enzyme is used to replenish creatine phosphate
-creatine kinase
What high serum levels of creatine kinase indicative of
-some sort of muscle damage as creatine kinase is released during muscle fibre damage
What gene is dystrophin coded on
- a 2.4 million basepair gene on Xp21
What mutation causes duchenne muscular dytrophy
-out of frame deletion on the Xp21 gene
What mutation causes Becker’s muscular dystrophy
-in frame deletion on the Xp21 gene
Explain myastenia gravis symptoms
- a type of neuromuscular junction disease
- auto immune attack on the acetylcholine receptors in synaptic junction
- antibodies destroy these receptors so more weakness with sustained muscle movement
- eye lid drooping after a while, tired after chewing for a while
Damage to motor or sensory neurons is called
-neuronopathies
Damage to axons is called
-axonopathies
How much CSF do we usually
-about 120 mls
What does CSF contain
- protein
- urea
- glucose
- salts
What produces aqueous humour
-the ciliary epithelium in ciliary body
What are the different types of astrocytes and where are found
- fibrous astrocyte -found in white matter
- protoplasmic astrocytes -found in grey matter
What are the functions of astrocytes
- developmental e.g radial glia
- structural e.g define brain micro-architecture
- envelope synapse e.g create tripartite synapse
- homeostatic e.g buffering K+ ions and glutamate
- metabolic support e.g glutamate to glutamine shuttle, lactate shuttle
- disease e.g gliosis (astrocytosis)
- neurovascular coupling (forms basis of bold fMRI)
Where would Bergmann glia be found
- cerebellum
- type of specialised astrocyte
Where would Muller cells be
- the retina
- type of specialised astrocyte
What are the different terms used to address gathered axons in the CNS and the PNS
CNS = tracts PNS = nerves
What are the different terms used to address abundance of cell bodies in the CNS and the PNS
CNS = nuclei PNS = ganglia
What are the circumventricular organs of the brain and why are they significant
- subfornical organ
- organum vasculosum of the lamina terminalis
- posterior pituitary
- area postrema
- pineal body
-they lack a normal blood brain barrier
What does the subfornical organ do
-circulating angiotensin 2 acts here to increase water intake
What does the organum vasculosum of the lamina terminalis do
-osmoreceptor controlling vasopressin secretin and thirst
What does the posterior pituitary gland do
-secrete hormones into blood
What does the area postrema do
-a chemoreceptor trigger zone that initiates vomiting in response to chemical changes in the plasma
What does the pineal body do
-secretes melatonin hormone into blood
Give some symptoms of multiple sclerosis
-eye movements (uncontrolled, seeing double)
-speech (slurred)
-paralysis (partial or complete)
-tremor
-co-ordination (lost)
-weakness (tired)
Sensory (numbness, prickling, pain)
What action potential is the threshold of excitation
It is at -60mV
What is the difference between spatial and temporal summation
Temporal summation
- one neurons with repeated stimuli in a short space of time
- single synapse
Spatial summation
- many neurons that fire at once and give cumulative effect to trigger an impulse
- involved multiple synapses
At what voltage do sodium channels close and potassium channels open
At +30mV which is the peak voltage, the sodium channels close and the potassium channels open causing massive outflow of K+ ions causing cell to become negatively charge and be hyperpolarised till -90mV
What is the speed of propagation of an action potential in an unmyelinated axon
0.5 to 2 mils per second so about 1 to 5mph
What is the speed of propagation of an action potential in a myelinated axon
Up to 150millisecs so about 330 mph
What does novichok do
Novichok is inhibitor of the enzyme acetlycholinesterase (which breaks down acetlycholine)
What does atropine do
- it is an acetlycholine receptor blocker
- used as part of treatment for novichok attack
Describe the 5 fundamental processes of synaptic transmission
Manufacture - intracellular biochemical processes
Storage - vesicles
Release - by action potential
Interact with post synaptic receptors - diffusion across the synapse
Inactivation - break down or re-uptake
Give 3 examples of fast acting neurotransmitters (short lasting effects)
- acetylcholine (ACh)
- Glutamate (GLU)
- Gamma-aminobutyric acid (GABA)
Give 3 examples of neuromodulators (slower acting)
- dopamine (DA)
- serotonin (5HT) (5-hydroxytryptamine)
- noradrenalin (NA) norepenephrine
Give 2 examples of local anaesthetics and how they work
- procaine and lignocaine
- sodium channel blockers
Give 4 substances that affect acetylcholine
- cigarettes (nicotine is an agonist)
- poison arrows (curare is an antagonist)
- spider toxins (black widow affect release)
- nerve gas (novichok blocks breakdown)
Give 3 substances that affect dopamine
- antipsychotic drug (chlorpromazine acts as a receptor blocker)
- stimulants (amphetamine/cocaine increases release and blocks reuptake)
- anti-parkinson drugs (L-DOPA increase manufacture)
Give 3 substances that affect serotonin
- antidepressant drugs (serotonin reuptake inhibitor like prozac)
- hallucinogens mimic serotonin (LSD is a serotonin receptor agonist)
- ecstasy
Which specific serotonin receptor do hallucinogenic drugs target
-the serotonin 2a receptor (5-HT2a)
Give 3 substances that affect GABA
- anti-anxiety drugs (inhibitory effects at GABA receptors e.g valium and benzodiazepines)
- anticonvulsant drugs (inhibitory effects at GABA receptors e.g benzodiazepines)
- anaesthetics (potentiate the effect of GABA e.g barbiturates)
Give 2 problems for drug design with neurotransmitters
- a region of the brain engaged in a particular function that is being targeted can use lots of different neurotransmitters e.g basal ganglia
- different regions of the brain use the same neurotransmitters
What does the eustachian tube do
- ventilation of the middle ear space
- drainage of secretions
What is Dunbar’s number
- the cognitive limit to the number of people with whom one can maintain stable social relationships (150)
- basically amount of people you would feel randomly meeting and joining for a coffee
Give 2 measures of morbidity and how they are calculated
- prevalence (number of cases at one point in time/total population) - it is the proportion of a population with a disease at a point in time
- incidence (number of new cases/population at risk) - rate at which new cases occur in a population in a certain time period
What do the parvocellular retinal ganglion cell do
- low contrast
- are involved in high linear spatial resolution
What do the kinocellular retinal ganglion cell do
-involved in blue-yellow colour opponency
What do the magnocellular retinal ganglion cell do
- motion detection
- high contrast
- low resolution
- colour blind
How many layers are within the lateral geniculate nucleus and what kind of cells do they contain
6 layers
Layer 1 and 2 -magnocellular retinal ganglion cells
Layer 3 to 6 -parvocellular retinal ganglion cells
-koniocellular retinal ganglion cells are spread within all layers
What part of the dorsal occipito-parietal area is involved with motion detection
V5/MT
What part of the dorsal occipito-parietal area is involved with colour detection
V4
Which areas of vision of the brain are the face-selective regions
- fusiform face area
- occipital face area
- superior temporal sulcus
Explain the function of vestibular eye movement
-holds image of the seen world steady on the retina during head rotations or translations
Explain the function of visual fixation eye movement
-holds the image of a stationary object on the fovea by minimising ocular drifts
Explain the function of optokinetic eye movement
-holds images of the seen world steady on the retina during sustained head rotation
Explain the function of smooth pursuit eye movement
- hold the image of a small moving target on the fovea
- aids gaze stabilization during sustained head rotation
Explain the function of nystagmus quick phases eye movement
-resets the eye during period of prolonged rotation and direct gaze towards the oncoming visual scene
Explain the function of saccades eye movement
-brings images of interest onto the fovea
Explain the function of vergence eye movement
-moves the eyes in opposite directions so that images of single object are placed or held simultaneously on the fovea of each eye
How do the frontal and supplementary eye fields contribute to saccades
Frontal eye fields
- generating voluntary saccades
- suppression of saccades during steady fixation
- involved with triggering memory guided saccades
Supplementary eye fields
- guide saccades during complex tasks
- contribute to predictive smooth pursuit
Describe the pursuit system
- parieta cortex enhances attention to moving target
- front eye field contribute to initiation and maintenance of smooth pursuit
- vertical smooth pursuit mediated by the y group (near inferior cerebellar peduncle) and down through superior vestibular nucleus
- projects into brainstem then flocculus of the cerebellum and then ipsilateral medial vestibular nucleus and then abducens nucleus
Lesion between the retina and optic chiasm would cause
total visual loss in one eye
Lesion at the optic chiasm would cause
bitemporal heminopia (so the nasal fibres from both eyes that collect information from the temporal visual fields are damaged)
Lesion between the optic chiasm and lateral geniculate body of the thalamus would cause
left or right contralateral homonymous hemianopsia
Lesion along Meyer’s loop (lateral through temporal lobe) would cause
contralateral upper quadrantinopia
Lesion along Baum’s loop (through parietal lobe) would cause
contralateral lower quadrantinopia
Lesion of both optic radiations just before the calcarine sulcus would cause
left or right contralateral homonymous hemianopia with macular sparing
Damage to the occulomotor nerve will present as
- the eye abducted (lateral rectus)
- the eye looks down and rotated (superior oblique)
Damage to the trochlear nerve will present as
- double vision (rotated) when looking down the stairs
- a trochlear palsy can also cause a hypertropia so head will tilt in the opposite side
Damage to the abducens nerve will present as
-eye cannot look laterally
Name 3 muscles of mastication that the mandibular branch of the trigeminal nerve innervates
- temporalis
- masseter
- pterygoids
What are the 3 trigeminal sensory nuclei called and what are they involved in
Mesencephalic (jaw jerk)
Main (touch and position from the face)
Spinal (pain and temperature form the face)
Hoe does the facial nerve supply the muscles of facial expression
- contralateral innervation of the lower face
- bilateral innervation of the upper face
Explain the difference in symptoms between a facial nerve lesion (bell’s palsy) and a supranuclear lesion (corticobulbar tract)
Facial nerve lesion - paralysis of both top and bottom half of the face
Supranuclear lesion - paralysis only of the lower quadrant of the contralateral side)
What does unilateral lesions of the nucleus ambiguus (with vagus and glossopharyngeal nerve) cause
- hoarseness
- dysphagia
- tachycardia
- deviation of the uvula to the side opposite the lesion
Which of the cranial nerves is the only one that does not travel through the thalamus
-olfactory nerve
Where is the degree of pain judged in the brain
-the insular cortex
Where is the pretectal nucleus
-in the superior colliculi
How will an optic nerve lesion affect the pupil
-it will remain dilated relative to normal
How does chronic stress affect dendrites of the brain
- glucocorticoids reduce the release of neurotrophins like brain derived neurotrophic factor (BDNF)
- low levels of brain derived neurotrophic factor associated with depression
How do antidepressants work
- Antidepressants increase glucocorticoid resistance (GR) expression (regulating hypothalamus HPA activity)
- Antidepressants increase neurogenesis
- they increase brain derived neurotrophic factor (BDNF) synthesis
- improve connectivity and increase number of synapses
What is the function of the default mode network
- It is what comes on when there is nothing to do
- brains screen saver mode
- daydreaming and consciousness
What is entrophy
Entrophy is a measure of disorder/ chaos
Depression is a disease of
- reduced plasticity
- increased self referential thinking
Describe the hypothalamus-pituitary-adrenal (HPA) axis
- the hypothalamus releases corticotrophin releasing hormone (CRH)
- the corticotrophin releasing hormone stimulates the anterior pituitary gland
- the anterior pituitary gland releases adrenocorticotrophic hormone
- adrenocorticotrophic factor stimulates the adrenal cortex
- the adrenal cortex releases cortisol which inhibits the hypothalamus and anterior pituitary
What would a bilateral medial temporal lobectomy cause
- inability to lay down new memories (anterograde amnesia).
Where would the posterior pituitary gland empty into and what hormones would be released
-released into the neuroendocrine system
- oxytocin
- antidiuretic hormone (ADH)
Where would the anterior pituitary gland empty into and what hormones would be released
-into the portal vein system
-prolactin
-LT and FSH
-growth hormone
-thyroid stimulating hormone
-adrenocorticotrophic hormone (ACTH)
-
Damage to hypothalamus causes
disruption of homeostasis and drive-related behaviours e.g.
Lesions of anterior hypothalamus causes
inability to dissipate heat
Lesions of posterior hypothalamus causes
inability to retain heat
Lesions of lateral tuberal nucleus causes
loss of hunger
Lesions of ventromedial nucleus causes
loss of satiety
What are the functions of the amygdala
- receives highly processed information
- produces instinctive emotional output
- responsible for emotional memory
What is the function of the hypothalamus
- coordinates drive related behaviour
- through extensive connections to brain
- through endocrine system
What is the tuberomammillary involved with
circadian rhythms
What is the suprachiasmatic involved
“master clock”
Is the basal ganglia output mainly inhibitory or excitatory
-inhibitory (GABA)
What is the knife clasp reflex
Clasp-knife response refers to a Golgi tendon reflex with a rapid decrease in resistance when attempting to flex a joint
-it would start off stiff, slow and resistive when pulling the forearm towards the body but then would suddenly get fast
What does the olfactory tract divide into
- the medial olfactory striae
- the lateral olfactory sriae
Where does the lateral olfactory striae project into
- form majority of the projections and projects into the uncus
- also project into the hippocampus and the orbito-frontal cortex via the thalamus
Where is the uncus found
-anterior end of the parahippocampal gyrus and this is where the primary olfactory cortex is situated
What is the lateral olfactory striae responsible for
-the initial perception and recognition of smells
Where does the medial olfactory striae project into
- the septal nuclei in the hypothalamus
- olfactory centers connected via the anterior commissure
What is the papez circuit responsible for
-memory
Which structures are within the papez circuit
- hippocampus
- fornix
- mammillary bodies
- cingulate gyrus
- parahippocampal gyrus (contains cingulum bundle)
What is the most important part of the parahippocampal gyrus in terms of the papez circuit
- the entorhinal cortex
- contains fibres that connect to the hippocampus and complete the papez circuit
What is the amygdala associated with
-fear
What does the striae terminalis do
-connects amygdala to the septum and hypothalamus
What is the pes hippocampi
- foot of the hippocampus
- looks like a paw
What is the hippocampus responsible for
- processing long term memories
- emotional responses
Which area of the brain is usually most affected in Alzheimers disease
-the hippocampus
Describe structures of the basal ganglia deep to the insular cortex from out to in
- extreme capsule (white matter)
- claustrum (grey matter)
- external capsule (white matter)
- putamen (grey matter and part of lentiform nucleus)
- lateral medullary lamina (white matter)
- globus pallidus external (grey matter and part of lentiform nucleus)
- medial medullary lamina (white matter)
- globus pallidus medial (grey matter and part of lentiform nucleus)
The caudate nucleus and the putamen form the
-corpus striatum
The putamen and the globus pallidus forms the
-lentiform nucleus
Does the hippocampus sit medially or laterally to the inferior horn of the lateral ventricle
-medially
Where is the brains reward center
- the nucleus accumbens
- the dopamine released here is related to reward and addiction behaviours
Where is the nucleus accumbens
-where the caudate and putamen meet
Where does the nucleus accumbens receive dopaminergic input from
- the ventral tegmental area in the midbrain
- the dopamine released here is related to reward and addiction behaviours
On an axial plane, what white matter tracts run through the genu of the corpus collosum
-forceps minor
On an axial plane, what white matter tracts run through the splenium of the corpus collosum
-forceps major
What is the basal nucleus of Meynert and what disease is it important for
- rich in cholinergic neurons
- these cholinergic neurons degenerate in Alzheimer’s disease
- Alzheimers patient are given acetyl cholinerase inhibitors to try and preserve acetylcholine levels
What sulcus separates the insular cortex from the frontal, parietal and temporal lobe
-the circular sulcus
What is another name for the 1st transverse temporal gyrus and what is located within it
- Heschl’s gyrus and is part of the temporal lobe
- the primary auditory cortex
The lenticostriate arteries are a branch of which artery and what do they supply
- the middle cerebral arteries
- the internal capsule
- they are a common site for stroke to occur (especially lacuna strokes)
How is dopamine associated with Parkinson’s disease
- not enough dopamine is produced
- increased muscle tone
- reduced movements
- so corpus striatum releases GABA which inhibits the cortex and movements
How is dopamine associated with huntington’s disease
- too much dopamine
- decreased muscle tone
- overshooting movements
- the striatum is attacked and GABA is not produced so the substantia nigra and dopamine are always activated
How is dopamine synthesised and stored
-tyroxine to L-dopa to dopamine to norepinephrine to epinephrine
What structure is majorly affected in huntington’s disease
-caudate nucleus
What are the symptoms associated with parkinson’s disease
Brady/akinesia
- problems with doing up buttons
- writing smaller
- walking deteriorated
Tremor
- resting tremor
- may be on one side only
Rigidity
- pain
- problems with turning in bed
Give the difference between the lentiform nucleus, striatum (neostriatum) and the corpus striatum
Lentiform nucleus = putamen and globus pallidus
Striatum(neostriatum) = caudate nucleus and putamen
Corpus striatum = caudate nucleus and putamen and globus pallidus
What is the neurotransmitter predominantly associated with C fibres for pain
-substance P
What is the neurotransmitter predominantly associated with A delta fibres for pain
-glutamate
After tissue damage, which factors can lead to activation of the nociceptors
Arachidonic acid Potassium 5-HT Histamine Bradykinin Lactic acid ATP
What vertebra is the iliac crest in line with
between L3 - L4
When do the secondary curvatures of the vertebral column develop after birth
- when the child holds their head up in the cervical region
- when the legs start weight bearing in the lumbar region
Describe the degree of movement of the vertebral column
Forward flexion - 40 degrees
Extension - 15 degrees
Lateral extension - 30 degrees
Rotation - 40 degrees
