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
