Neuro Flashcards
What divides the pre and post central gyrus
The central sulcus
What is the gap that divides the two hemispheres called? What runs down it?
Longitudinal fissure
Falx cerebri
What divides the temporal lobe from the frontal and parietal?
Lateral cerebral sulcus
What divides the cerebellum from the cerebrum?
The transverse fissure
What connects the lateral ventricles to the third ventricle?
Intraventricular foramen
What connects the third and fourth ventricle?
Cerebral aqueduct
How do the white and grey matter change in the spinal cord in c,t,l and s?
C - big white, small grey
T - smaller white, small grey, lat grey horns
L - big white, big grey
S - small white, big grey
What is at the end of the spinal cord
What are they made of?
Conus medularis
Flium terminale - extension of the pia blended with arachnoid and dura)
Where do the periosteal and meningeal dura mater separate?
Falx cerebri
Falx cerebelli
Tentorum cerebeli
Diaphragm sellae
What covers the pituitary gland?
Diaphragm sellae
What are the three ways the brain can herniate with increased icp?
Uncal - the uncus of the temporal lobe is pushed round the tentorum cerebeli
Subfacal - the cingulate gyrus is pushed between the falx cerebri and the corpus callosum
Tonsillar - cerebellar tonsils and brainstem pushed through foramen magnum
Which layer of dura persists in around the spinal cord?
Meningeal
What is the difference between the epidural and extradural space?
Extradural is around the brain. It is potential as the dura is adhered to the bone
Epidural is around the spine. It is real consisting of fat and connective tissue
Why is a basal skull fracture more likely to cause csf leakage?
The dura is not surgically seperable from the bone
At what point do the neuropores fuse?
25 and 28 days cranial and caudal respectivly
What occurs if the neuropores fail to fuse?
Spina bifida
Anencephaly
What might be suggestive of a neuropore deficit whilst the fetus is in utero? What else could cause this?
A raised alpha fetoprotein level
Omphalocele, gastroschisis
When should folic acid be taken to reduce chance of neuropore deformity?
3 months before and during 1st trimester
What are the cranial regions of the neural tube - how do they divide?
Procencephalon - telencephalon, diencephalon
Mesencephalon - mesencephalon
Rhomboencephalon - metencephalon, mylencephalon
Why is the axis of the brain different to the axis of the brainstem?
As the tube grows it runs out of space so folds. This creates a cervical flexure and a cephalic flexure
In which regions of the embryonic brain are the ventricles?
Telencephalon (lateral)
Diencephalon (third)
Metencephalon (fourth)
What is the derviative of the metencephalon?
Pons and cerebellum
What are the types of spina bifida?
Occulta
Meningocele
Mylomeningocele
How is the neural tube organised?
Dorsal alar plate (sensory)
Ventral basal plate (motor)
How are the alar and basal plates of the neural tube regualted?
Signalling from (dorsal) roof and (ventral) floor plates
What do neural crest cells contribute to?
Adrenal glands Sympathetic ganglion Enteric ganglion Schwann cells Melanocytes
What disrupts neural crest cell migration?
Alcohol
What are the functions of astrocytes?
Formationof bbb by foot processes (glia limitans) Structural support Nutrition (glucose lactate shuttle) Removal of neurotransmitters Maintain ionic environment
What is the glucose lactate shuttle?
Neurones cant store glycogen so astrocytes break theirs down to lactate, transport it to neurones where it is used to create pyruvate.
What would happen if K+ rose around the brains neurones? What stops this?
Decreased k gradient so decreased efflux so cell moves closer to membrane potential so increased excitability of neurones
Astrocytes
When does mylination of cns begin? When does it end?
4 months gestation until 1 - though not complete until maturity
How can the brain respond to damage?
Plasticity (forming new pathways)
Oligodendrocyte precursors to replace myelin lost in disease
How is the bbb formed around penetrating capillaries?
Foot processes of astrocytes inducing tight junctions between endothelial cells using occludins
Where is the bbb missing?
Choroid plexuses
Vomiting centre
Pituitary
Pineal gland
What does the bbb stop?
What does the bbb slow?
What does the bbb allow?
Stops proteins
Slows creatine, urea, ions
Allows glucose, lipid soluble substances
Why is it that csf glucose can be controlled?
They are actively transported
Why is the cns immunprivilaged?
Enclosed therefore inflammation would increase icp
What is the major excitatory and inhibitory neurotransmitters of the brain and spine?
Brain - ex = glutamate, in = gaba
Spine - ex = glutamate, in = glycine
What sorts of glutamate receptors are there?
Metabotrophic - Gaq or Gai
Ionotrophic - Kainate, AMPA and NMDA
What is required for NMDA receptor activation?
Binding of glutamate
Degree of depolarisation to move Mg ion
What process is involved in the long term potentiation of glutamate receptors?
Activation of AMPA Depolarisation Activation of NMDA Calcium influx Upregulation of AMPA
What is the mechanism for glutamate excitotoxicity?
Ischemia - decreased atp therefore decreased na/k ATPase therefore decreased ecf sodium ions, therefore decreased or reversed na glutamate synporting increasing extracellular glutamate
Trauma or injury resulting in glutamate release
Increased glutamate causes increased intercellular calcium and cell death
What are the different sorts of gaba receptors?
GABAa = ionotrophic cl- channels GABAb = metabotrophic GPCRs decreasing GABA and glutamate release
What is the term for one sided weakness?
Hemiparesis
What is the term for one sided paralysis?
Hemiplegia
What is ataxia?
Uncoordianted movement
What is dysarthria?
Slurred speech due to lack of coordination of vocal muscles
What is dysphasia?
Difficulty in using language
- expressive
- receptive
What is agnosia?
No object perception
What is apraxia?
Unable to execute purposeful movement that is already learnt in spite of good power, sensation and coordination
Where is ACh released from in the brain? What are its effects?
Nucleus basalis and brainstem
Generally excitatory
What are the dopaminergic pathways in the cns? What do they do?
Negrostriatal (control of movement) Mesocortical (arousal and mood) Mesolimbic (emotion) Tuberohypophesal (inhibition of prolactin secretion) D1 = GalphaS D2 = GalphaI
What are the na pathways of the cns? What do they do?
Pons and medulla right through the cns
Effects arousal and mood
Where do 5ht neurones originate, what do they do?
Raphe nucleus in the brainstem
Widely distributed
Effects mood and wakefulness
What cell type covers choroid plexuses? What makes them special?
Ependymal - tight junctions with occludins allowing specific filtering
What is the rate of csf turnover.
20ml/hour
Describe the root of csf circulation
Lateral ventricles Interventricular foramen Third ventricle Cerebral aqueduct Fourth ventricle Central canal / medial/lateral apatures Subarachnoid space
Where is csf reabsorbed? How?
arachnoid granulations at the venous sinuses that have arachnoid matter that protrudes through the meningeal dura
What are the functions of csf?
Mechanical protection - shock absorber Maintains icp Reduces weight of brain preventing crushing of own blood vessels Chemical protection Circulation of nutrients
What is the pathogen, glucose and cellular composition of csf?
Sterile
Glucose 2/3rds of blood
Low numbers of WBC (no polymorphs)
No erythrocytes
What (grossly) can cause hydrocephalus?
Overproduction of csf
Blockage of csf flow
Under reabsorption of csf
Differentiate communicating and non communicating hydrocephalus
Communicating - free flowing csf but inadequate reabsorption
Non communicating - blockage to csf flow
What is the most common site of csf flow blockage?
Cerebral aqueduct
Give 2 examples of communicating hydrocephalus
Congenital absence of arachnoid granulations
Blockage of arachnoid granulations due to RBCs in SAH
Give two examples of non communicating hydrocephalus
Tumour compressing cerebral aqueduct Spina bifida (aquaductal stenosis, open myleomeningoceal)
What is the main arterial supply to the meningies?
Middle meningeal artery as a branch of the maxillary artery
Where does the middle meningeal artery enter the cranium?
What happens then?
Foramen spinosum
Branches to anterior and posterior
Where do the meningies drain?
Through paired middle meningeal veins through the foramen spinosum into the pterygoid venous plexus
Where do the vertebral arteries pass?
Up the transverse foramen of the top 6 cervical vertebra then through the foramen magnum
What are the branches of the vertebral and basilar artery from posterior to anterior?
Posterior inferior cerebellar arteries Anterior inferior cerebellar arteries Pontine arteries Superior cerebellar arteries Posterior cerebral arteries
What are the branches of the internal carotid artery?
The anterior cerebral, middle cerebral and the posterior communicating
Where does the posterior cerebral artery span?
Ica to posterior cerebral
Where does the anterior cerebral artery supply?
Medial and anterior surface of the hemisphere
Where does the middle cerebral artery supply?
The lateral surface of the hemispheres
Where does the posterior cerebral artery supply?
Inferior hemisphere and occipital lobe
How does blood drain from the brain?
Small veins pass through arachnoid and meningeal dura into dural venous sinus
Emissary veins into extracranial veins
Through the dural venous sinuses into then ijv
What is the order of drainage through the sagittal dural venous sinuses?
Superior sagittal sinus joins straight sinus (from inferior sagittal sinus and great cerebral vein) at the confluence of sinuses
Confluence of sinuses splits bilaterally into the transverse sinuses into the sigmoid sinus then the ijv
What is the drainage into and out of the cavernous sinus?
Superior opthalmic veins and spenoparietal sinus drain in anteriorly
Drains out posteriorly via the superior and inferior petrosal sinus into the transverse and sigmoid sinus respectively
How can blood move through the emissary veins?
In both directions - though usually out away from the brain
What is sensation?
A conscious or unconscious awareness of an internal or external stimuli
What are the neurones of general sensation?
1st order - contain or link to sensory receptor
2nd order - link 1st to thalamus
3rd order - link thalamus to cerebral cortex
Where do third order sensory neurones travel?
Through the internal capsule
What is the advantage of having multiple neurones in the sensory pathways?
Allow for divergence, convergence and modification from external neurones
What are the three general types of sensory receptors? Give an example of what each detects
Free nerve endings - e.g. Cold
Encapsulated nerve endings - e.g. Pressure
Synapse with specialised cell - e.g. Vision
Are sensory receptors totally specific for one stimuli type?
No - large input from another modality can cause stimulation e.g. Seeing stars when hit in the eye
What is the term for different types of one sensation (e.g. Sweet and sour taste)?
Qualities
What sensory receptors are present in muscles? What do they do?
Spindle fibres - detect change in muscle length
Golgi tendon organs - detect change in muscle tension
What do we need to know about a sensory stimuli?
What type
Where
How long
How strong
How can we determine stimuli strength?
Rate of firing of action potentials (frequency coding)
Activation of neighbouring cells
How can neurones encode a time frame for a stimuli?
Phasic response - rapidly adapting, only fire for a short time when stimuli changes - i.e. an on and off signal
Tonic response - slowly adapting, fires for the entire time the stimulus is active
What methods does the ns use to localise a sensory stimuli?
Lateral inhibition
Two point discrimination
Convergence and divergence
What is the process of lateral inhibition?
Each first order neurone sends inhibitory interneurones to neighbouring second order neurones localising a stimulus.
What is two point discrimination?
What does it depend on?
The distance at which you can distinguish two stimuli as distinct
Depends on receptive field of the neurones and the degree of convergence of 1st orders on 2nd orders and 2nd orders on 3rd orders.
What does neurone divergence cause in sensory pathways?
Amplification of signal
Where in the cns do we convert afferent sensory impulses into the feeling of sensation?
Thalamus - crude localisation and modality
Post central gyrus (somatosensory cortex) - sharp localisation
After reaching the somatosensory cortex where are sensory inputs relayed too?
Cortical association areas (combining multiple modalities into a general picture) Subcortical areas (movement alteration) Limbic system (emotion)
How does then limbic system associate with sensation?
Pain is unpleasant and upsetting
Same touch can be nice from a partner but nasty from a stranger
What are the ascending tracts of the spinal cord?
What modalities do they convey?
Posterior column medial leminiscal - fine touch (light touch, vibration, hair movement), conscious proprioception
Anteriolateral system - pain, crude touch, temperature
Spinocerebellar - unconscious proprioception
Cuneocerebellar - unconscious proprioception from upper c-spine
Where does the posterior column medial leminiscus tract run?
First order enters spinal cord, passes into gracile or cuneate nucleus, ascends to medulla and synapses in cuneate or gracile nucleus.
Second order decussate and ascend the medial leminiscus pathway to the ventral posterior lateral nucleus of the thalamus
Third order ascend through the internal capsule to the somatosensory cortex
What is the route of the anteriolateral system?
1st order enter spinal cord and ascend or descend up to 3 segments in the dorsolateral tract of lissauer. They then synapse in lamina I, II, or V
2nd order neurones decussate immediately crossing in the anterior grey commiseur before ascending in the anteriolateral system to the ventral posteriolateral nucleus of the thalamus
3rd order neurones pass through the internal capsule to the somatosensory cortex
What is the route of the spinocerebellar tract?
First order enter the spine. These are the same neurones as the dorsal column medial leminiscal. They branch giving two synapses in the dorsal horn.
Second order neurones ascend in two different ways. The anterior set decussate ascending contralaterally before decussating again syanpsing at the ipsolateral cerebellum. The posterior set ascend ipsolaterally and do not decussate at all
Where do lower motor neurones have their cell bodies?
Lamina IX of the ventral horn
What is a motor unit?
A combination of a lower motor neurone and the muscle fibres it supplys
What are the classifications of nerve fibres based on speed of conduction? What is an example of each?
A alpha - LMN, proprioception A beta - touch A delta - sharp pain, temperature B - preganglionic autonomic C - dull pain
How can lmn be activated?
Input from higher centres
Reflex
What is a reflex?
An involuntary, unlearned, automatic repeatable response to a specific stimuli that does not require the brain
What must a reflex involve?
A receptor Afferent neurone Integration centre Efferent neurone Effector
Describe the process of a stretch reflex
Tendon hammer stretches tendon
Spindle fibre stretched
Afferent impulse to spinal cord
Afferent impulse up spinocerbellar and DCML (proprioception to brain)
Synapse in cord lamina IX with LMN - excitatory to muscle to contract and inhibits antagonistic muscle causing relaxation
What muscles maintain tone during sleep?
Respiratory
Extraoccular
Urinary and anal sphincters
What are typical signs of LMN lesion? How are they distributed?
Weakness Muscle wasting Loss of tone Decreased or absent weakness Initial fasiculations
Tend to be localised to a specific peripheral nerve
What two broad groups can UMNs be classified into?
Pyramidal tracts from cortex to effector (CN and spine)
Extrapyramidal tracts from brainstem to effector
What are the pyramidal tracts motor tracts? What do they supply?
Corticospial - cortex to spinal lmns
Corticobulbar - cortex to CN lmns
Where do the corticospinal and corticobulbar tracts origionate
30% in the precentral gyrus (motor cortex)
30% in the premotor cortex and supplementary motor area
40% in the somatosensory cortex
After origination where do the UMNs of the corticospinal tract travel?
Internal capsule
Brainstem
Decussation of pyramids in medulla
85% decussate into the contralateral lateral corticospinal tract
15% remain ipsolateral in the anterior corticospinal tract
All synapse in lamina IX (most via an interneurone)
How many of the fibres of the corticospinal tract decussate? Which part of it do they entre?
85%
The lateral section
Where do the fibres of the corticobulbar UMN travel?
Through the internal capsule, most decussating and not decussating giving bilateral innervation synapsing with the CN nuclei. The exception to this is the UMN to the facial nerve supplying the muscles of facial expression
What is the function of the motor cortex and premotor cortex with supplimentary motor area?
Motor cortex - coordinates action
PMC and SMA - formulating a plan and organising supplementary muscle activation
What is the process of altering the state of the other muscles around the body prior to a movement called? What coordinates this?
Body set
PMC and SMA
What are the extrapyramidal motor pathways?
Tectospinal
Rubrospinal
Reticulospinal
Vestibulospinal
Which extrapyramidal pathways decussate? What do they do?
Tectospinal - decussates, controls head and eye movement to visual and audible stimuli. Stops in upper thoracic spine.
Rubrospinal - decussates, controls upper limb flexor tone. Stops in upper thoracic spine
Which extrapyramidal tracts do not decussate? What do they do?
Reticulospinal - posture and rhythmic movements by facilitation and inhibition of LMNs
Vestibulospinal - balance and antigravity msulces
What are signs of upper motor neurone lesions? Where are they found?
Hypertonia Hyperreflexia Clonus Babinskis sign Movement weakness Clasp knife reflex
Tend to be widespread
What are the three regions of the cerebellum? What do they do?
Vestibulocerebellum - coordination of balance via vestibulospinal and reticulospinal tracts. Occular reflex allowing eyes to tract object as head turns
Spinocerebellum - receives proprioceptive info and a copy of the motor plan in order to predict errors in movement and correct them before they occur
Cerebrocerebellum - hand eye coordination, motor learning and memory, predicts sensory consequence of actions
Signs of cerebellar dysfunction?
Dysdidochokinesia Ataxia Nystagmus Intenetion tremor Speech problems Hypotonia Past pointing
What are the functions of the basal ganglia?
Decision to move
Direction of movement
Amplitude of movement
Motor expression of emotion
What makes up the basal ganglia?
The caudate nucleus The putamen The globus pallidus The substantia nigra The subthalmic nucleus
What comprises the striatum?
The caudate nucleus
The putamen
What comprises the lenticular nucleus?
The putamen and globus pallidus
What are the pathways of the basal ganglia? What do they achieve?
Direct pathway - increase movement
Indirect pathway - decreased movement
When the cortex wants to move what is the effect on the direct pathway of the basal ganglia?
Stimulation of the striatum
Inhibits the GPi/SNr
Reduced inhibition of the thalamus
Increased positive feedback to the cerebral cortex affirming the movement
When the cortex signals for movement what is the effect on the indirect pathway?
Increased stimulation of the striatum
Increased inhibition of the GPe
Decreased inhibition of the subthalmic nucleus
Increased inhibition of the thalamus
Decreased positive feedback to the cerebral cortex dampening movement
What does the nigostriatal pathway do to the direct and indirect pathways? Which receptors are involved?
Direct, D1 receptor - increased stimulation - increases excitation of thalamus
Indirect D2 receptor - decreased stimulation - decreases inhibition of thalamus
What are the effects of parkinsons disease?
Resting tremor
Increased tone
Bradykinesia
Mask facies
What is the effect of huntingdons disease?
Damage to the striatum removing inhibition on the GPe causing decreased inhbition of the thalamus
What is pain?
An unpleasant sensation and emotional experience associated with actual or potential tissue damage
What are the two parts to pain?
Nociception (detection of stimuli from actual or potential damage causing ascending unconscious neural traffic)
Conscious perception of pain - the sensation
What varies in people who deal with pain differently, what doesn’t?
Tollerance varies
Threshold does not!
What alters pain tolerance?
Environment (e.g. Better tolerance with adrenaline post accident)
Emotion (worse tolerance if upset, depressed)
Age (better tolerance in elderly)
Distracting injury
Where do pain fibres ascend?
Ascend in the lateral part of the anteriolateral system to the ventral posteriolateral nucleus of the thalamus
What are the contents of the anteriolateral system?
Spinothalmic - perception of pain Spinoreticular - arousal to pain Spinotectal - looking at source Spinohypothalmic - autonomic response Spinomesencephalic - descending inhibition and emotion
What are the four stages of pain?
Transduction - the activation of the receptor
Transmission - relay
Modulation
Perception
What is pain transduction?
Release of k, serotonin, bradykinin, h, prostaglandins from damaged tissue activating nociceptors
What fibres convey pain? What activates them?
A delta - mechanical
C - mechanical, thermal, chemical
What sort of pain do different nerve fibres produce?
A delta - sharp stabbing localised pain
C - dull throbbing poorly localised pain
Which lamina do primary pain fibres terminate?
I, II, V
Where does the anteriolateral system arise (lamina)
Lamina I and V
How can pain be modulated physiologically?
The gate control theory
Descending inhibition
What is the gate control theory of pain?
Stimulation of A beta fibres by rubbing causes stimulation of interneurones in lamina II which cause inhibition of lamina I and V
What effects do A delta and C fibres have on lamina II?
Inhibition of interneurones that inhibit lamina I and V thus decreasing own inhibition
What substances do A dela and C fibres relase in the 1 st and second lamina? What about the inhibitory synapses?
Substance P and glutamate
Glycine
What is the decending inhibition of pain?
Direct - spinothalmic tract to periaquiducal grey matter to raphae nucleus
Indirect - spinomesencephalic to raphae nucleus
Raphae nucleus releases 5HT, enkephalins and noradrenaline into lamina I and V inhibiting the spinothalmic tract
Where is pain percieved?
Third order neurones to primary sensory areas but also limbic system and hypothalamus for emotional and stress response
Differentiate hyperalgesia from allodynia
Hyperalgesia - increased pain at normal threshold stimulus due to peripheral and central sensitisation
Allodynia - pain from stimuli that are not normally painful or pain in an area not stimulated
What is peripheral sensitisation?
Painful stimuli (5HT, K, PGE etc) trigger c fibre. C fibre releases substance P that activates mast cells releasing histamine and other chemicals. These cause vasodilation and also reactivate the original fibre in a vicious cycle.
What is central sensitisation?
Glutamate released at first order synaptic bulbs activate AMPA receptors, depolarising second order neurones. Depolarisation allows for opening of NMDA receptors allowing calcium influx. Calcium influx up regulates expression of AMPA. This occurs with long term stimulation.
What is the general cut off for a pain to be chronic? What is the usual aetiology of chronic pain?
3 months
Often not known
What is the mechanism behind neuropathic pain?
Of neuronal origin, no nociception
Occurs due to increased excitability post injury (ectopic) and activation of neighbouring fibres (ephapatic)
What is phantom limb sensation caused by?
Not fully understood but may be cortical remodelling
What is complex regional pain syndrome? What are the two types?
No history of trauma - type 1 History of trauma (often minor) - type 2 1) initiation of pain 2) sympathetic and inflammatory response 3) increase pain 4) sympathetic and inflammatory response And so on
Causes pain, oedema, vasomotor disturbance, movement limitation, muscle waisting, skin thickening
What can cause pain in cancer?
The disease
The treatment!
Differentiate opiate and opioid
Opiate from a poppy
How does the inner ear form?
Otic placode on ectoderm
Sinks and pinches off forming ottic vesicle
What forms the middle ear and eustachian tube?
Expansion of the 1st pharangeal pouch
What forms the ossicles of the ear?
Merckels and reicherts cartilage
What forms the external aucoustic meatus?
1st pharangeal cleft
What forms the auricle?
Proliferation of the first and second arches
Where does the ear form?
The embryonic neck
Which part of the ear is most susceptible to teratogenesis?
Inner ear from the otic vesicle
What is the first stage of eye formation?
Formation of the optic placode and outpouching of the proencephalon towards it
How does the lens of the eye form?
Invagination of placode forming vesical
How is the embyonic lens of the eye supplies with blood?
The hyaloid artery that runs up the optic stalk (from the proencephalon)
How does the hyaloid artery fit in the optic stalk? What does persistance of this feature cause?
The stalk contains a fissure, the choroid fissure. Persistence causes a coloboma
How does the central artery of the retina form?
Degeneration of distal hyaloid artery (proximal remnants becoming the central artery)
How does the proencephalon outpouching go on to form the optic nerve and retina
Stalk becomes optic nerve
End envelopes the lens forming a double layered cup
Outer layer becomes the pigment layer and inner layer becomes the sensory layer of the retina
How does the retina detach in pathology?
Opening of the intraretinal space between the pigment layer and the neural layer of the retina
How does the iris of the eye form?
Lining of the optic cup buckles forming the ciliary body and iris.
Hw doe the extraoccular muscles form?
From preotic myotomes
Where do the eyes develop?
Side of the embryonic head
What is the structure of the retina from back to front?
Pigment cells - absorb scattering light
Photoreceptive cells - rods and cones
Bipolar neurones
Ganglion cells
What is special about the fova?
Concentrated cone cells
Overlying neurones displaced
Difference between rods and cones inc. neural wireing
Rods - high sensitivity, many rods into one bipolar neurone, low acuity
Cones - low sensitivity, high acuity, one rod to one bipolar neurone , colour
Where is the fova?
Lateral to the optic disk
Which regions of the retina (and vision) form the left optic tract?
Left temporal retina (left nasal vision) and right nasal retina (right temporal vision)
Where do fibres of the optic tract go?
90% to lgn
10 % superior colliculus - edinger westphal - CNIII
What are the optic radiations?
inferior half of each retina - meyers loop
superior half of each retina - baums loop
Which optic radiation is direct?
Baums loop - superior retina (inferior visual field)
Where do fibres of the lgn go?
Primary visual cortex
In the primary visual cortex what patterns are maintained from the retina?
Spacial
Magnocellular vs parvocellular
How do fibres leave the primary visual cortex?
Ventral stream - to temporal - object recognition
Dorsal stream - to parietal - object location and motion
What are the four types of strabismus?
Esotropia - defective eye looks in
Exotropia - defective eye looks out
Hypertropia - defective eye looks up
Hypotropia - defective eye looks down
Why dont kids with strabismus have double vision?
Plasticity in nerves allows supression of vision
Why do occipital lesions spare the macular?
Dual blood supply to the regions that detect macular vision
Pupil reflex pathway
Light - retina - optic nerve - optic tract - pretectal nuculus - superior colliculus - edinger westphal nucleus - cniii, cillary ganglion, constrictor pupillae
Why is the pupil reflex pathway bilateral?
Optic tract contains fibres from both retina
Neurones from superior colliculus innervate both edinger westphal nuclei
What two parameters of sound are detectable?
Frequency and volume
What is the decibel scale?
A measure of volume
dB = log10 (P2/P1)
How do louder sounds get detected as being louder?
More intense vibrations of sensory hairs and activation of neighbouring fibres
What are the three chambers of the cochlea?
Scala vestibuli
Scala media
Scala tympani
Where are the cells that detect sound located in the cochlea?
In the scala media
What is the membrane that sits above the hair cells in the ear?
Tectoral membrane
What are the membranes between the cavities of the cochlea?
Scala vestibuli VESTIBULAR MEMBRANE Scala media BASALAR MEMBRANE Scala tympani
What fluid is found in the cavities of the cochlea?
Scala vestibuli and scala tympani = perilymph
Scala media = endolymph
What windows border the cavities of the cochlea?
Scala vestibuli - oval window
Scala tympani - round window
What are the distribution of the hair cells in the cochlea? Which is more sensitive? What is the function of the others?
1x inner hair cell = most sensitive
3x outer hair cells = vibrate with the sound alternating the tension on the tectoral membrane
How is movement of the oval window translated into movement of the hair cells of the cochlea?
Pressure wave in perilymph, deformation of vestibular membrane, pressure wave in endolymph, deformation of basilar membrane, hair cells move against tectoral membrane
What happens to the hair cells on movement?
Bending of steriocillia opens K+ channels, K+ diffuses into the cell due to high conc. in endolymph, cell depolarises, calcium flows. Through vgCa channels, neurotransmitter released
What are the ganglia of the cochlear nerve termed?
Spiral ganglia
How do the ears detect changes in frequency?
Activation of hair cells at specific points down scala media
Where in the scala media are high frequencies detected
Near the oval and round windows?
Where in the scala media are the low frequencies detected?
Near the heicotrema
What is the range of frequencies in normal human hearing?
20-20000 Hz
What is the nervous propergation of sound from the hair cells to the brain?
Hair cell Spiral ganglion cell CNVIII Cochlear nucleus (medulla) Superior olivary complex Inferior colliculus Medial geniculate nucleus Auditory cortex
What can cause hearing impairment?
Loud noise Congenital defect Infection Ototoxic compounds Trauma Age
What are the three types of hearing impairment?
Conductive (blockage, rupture of membrane)
Sensory (hair cell destruction, hair cell death)
Neural (spiral ganglion damage, tinnitus)
What test can be used to quantify a degree of hearing loss? How does it work?
Audiogram
Sensitivity vs frequency
How can the function of the outer hair cells be measured?
Otoacoustic emissions
Treatments for hearing loss
Hearing aids
Cochlear implant
What are primary and secondary haemorrhagic strokes?
Primary - no structural lesion
Secondary - following a lesion (tumour, aneurysm, malformations, thrombotic disease). These abnormalities may themselves be secondary to diseases such as htn or dm
What could be effected by a frontal stroke?
Expressive dysphasia - brocca’s area
Motor disturbance - motor cortex and premotor areas
Disinhibition - cortical association areas
Incontinence - micturition inhibition centre
What could be caused by a temporal stroke?
Receptive aphasia - wernicke’s area
Memory problems - hippocampus
Superior quadrantanopia - meyers loop
What could a parietal stroke cause?
Inferior quadrantanopia or hemianopia - baums loop
Somatosensory deficits - somatosensory cortex
Nominal aphasia - angular gyrus
What could an occipital stroke cause?
Visual disturbance
What are the different grades of stroke?
Total anterior circulation (TACS)
Partial anterior circulation (PACS)
Lacunar (LACS)
Posterior circulation (POCS)
What is a lacunar stroke?
A stroke effecting a single perforating artery
Usually asymptomatic - if symptomatic single system signs
Differentials of stroke
Hypoglycemia Seizure Migrain Space occupying lesion Demylination
Blood tests in a stroke
Bm, fbc, inr, u+e
Scanning in a stroke
Ct, mri, carotid us, cxr, echo, holter, ecg
What is the blood supply to the spine?
Single anterior artery, duel posterior arteries
What sort of arterial occlusion is most serious in the spine? How does it present?
Anterior as no anastamosis
Acute painful with sensory loss and progression to upper motor neurone signs.
First signs of raised icp
Behaviour changes Decreased gcs Localising signs Pupil reactions Cushings triad
What is the shape of a epidural haematoma on imaging
Lentiform
What is the shape of a subdural haemotoma on imaging
Follows skull contours
What does cat stand for?
Computer axial tomography
How does bone appear on CT.
White
What is seen in a T1 MRI?
Fatty tissues (cortex)
What is seen in a T2 MRI.
Watery tissues (oedema, lesions)
Indications for ct head?
Gcs 1 vomiting post trauma
>65 with LOC or amnesia
Dangerous MOI
Complications of a skull fracture
Neuronal damage
Blood vessel damage
Infection risk
Signs of a SAH on CT
Blood in ventricles
What are the components of a TACS
Hemiparesis / hemianaesthesia
Hemianopia
High cerebral dysfunction (dysphasia, dyspraxia, cortical signs)
What are the componenets of a PACS?
2 of TACS
Which sort of stroke is most likely fatal?
Which sort of stroke has a high reoccurance rate ?
TACS
PACS
Where does a TACS effect
ICA or proximal MCA
Where does a PACS effect
Distal MCA or branch of MCA
Why do we need sleep?
Cns resetting
Toxin clearance
Long term memory
What are the two types of sleep? Differentiate appearance / dreaming / obs
REM - active brain (dreaming), body still (inhibition of motor neurones), difficult to disturb, erection, irregular pulse and rr
NonREM - low brain activity, body mobile (rolling over, sleep walking), decreased bp, spo2, rr,
Differentiate rem/nonrem sleep in terms of bmr
Increase bmr in rem
Decrease bmr in non rem
Differentiate rem / nonrem in terms of eeg
Rem - eeg as awake (beta)
Non rem - eeg alpha to theta to delta
How does the pattern of sleep change through the night?
Start into non rem
Duration and frequency of rem increases during the night
Tend to awake naturally from rem
What is the change in neurotransmitters during rem/nonrem sleep?
In rem ach increases and 5ht/na decrease
In non-rem all of ach, 5ht and na decrease
What are the different eeg wave types in order of decresing frequency?
When are they seen?
Beta - awake eyes open
Alpha - awake eyes shut
Theta - children, mediating adults
Delta - deep sleep, coma
Where in the brain would closing eyes cause a decrease in eeg wave frequency from beta to alpha with an increase in amplitude?
Occiput as its sending ‘im not seeing anything signals
Two types of parasomnia
Sleep paralysis
Acting out dreams
Two types of hypersomnia
Narcolepsy
Obstructive sleep apneoa
What activates RAS
Sensation - auditory, visual, nociception, viceral
What inhibits ras?
Alcohol,
Sedatives
Sleep centre
Where is the reticular formation? Why?
In the white matter of the pons where it can sense ascending tracts
Functions of the reticular formation?
Sleep regulation
Motor control
Motivation and reward
Cvs and rs control and autonomics
Functions of reticular activating system?
Raises conciousness (depresses hypothalmic sleep centre) Filters incoming signals (removing response to background stimulation)
What generates eeg loops ?
Thalmocoritcal loops - stimulation from thalamus to cortex is reinforced by positive feedback from cortex to thalamus - staying awake!
What happens in the different layers of the cortex?
1/2/3 - signals too and from other areas of cortex
4 - input from body
5/6 - output too body
What are the functional classifications of the areas of the cortex (generally)?
Primary sensory / primary motor areas
Secondary sensory / supplementary motor areas
Tertiary areas
Association cortex
Which areas of the brain deals with more than one modality of sense?
Association areas
What are the functions of the Frontal Parietal Temporal Occipital Association areas?
Frontal - interlect, personality, mood
Parietal - language, calculation, visiospacial
Temporal - memory, language
Occipital - vision
Lesions of the association areas of the parietal cause…
Attention deficites
Contralateral neglect
Lesions of the association areas of the temporal lobe cause
Agnosia
In a left handed person which hemisphere is more likely to be dominant?
Left!
What processes in the brain are effected by lateralisation?
Dominant - language, maths, logic, motor skill
Non dominant - visiospacial, music, art, emotion, body awareness
What connects the hemispheres?
Corpus callosum
Anterior and posterior commissure
What is the function of broccas area?
Dysfunction?
Formulation of language components
Expressive dysphasia - poorly constructed disjointed speech
What does wernicks area do?
Dysfunction?
Interpretation of written and spoken word
Receptive dysphasia - lack of comprehension and with fluid but nonsensical speech
Define the two categories of memories. What major brain areas are associated with each?
Declarative - things you can state - hippocampus
Procedural - motor memories - cerebellum, premotor cortex, basal ganglia
What is needed to transfer memories from short to long term memory?
Rehersal
Emotion
Association
Automatic (trivia!)
Where are memories ‘stored’?
Each modality in its appropriate cortical area - then combined by the hippocampus
What brain functions are vital in memory formation?
Neuronal plasticity
Long term potentiation
Why dont we remember everything
Long term depression
What pathology causes anterograde amnesia?
Hippocampal damage
What disease may cause reterograde amnesia”
Alzheimers
What is dementia?
Aquired loss of cognitive ability sufficiently severe to interfere with daily function and quality of life
Can be direct (neuronal damage) or indirect (vascular)
What is the cut off age for presenile demetia?
65
Causes of dementia and differentiating factors
Cjd - young Picks disease - personality change Vascular - stepwise progression Alzheimers - senile onset Lewis body - parkinsonism
What are the effects of sub cortical damage in dementia?
Slowness and forgetfulness
What are the effects of anterior cortical damage in dementia?
Decreased inhibition
Antisocial behaviour
Irresponsibility
Effects of posterior cortical damage in dementia?
Loss of memory
Disturbed language
What structural changes occur in dementia?
What happens to csf pressure?
Cortical atrophy with ventriculomegaly
Csf pressure normal (normal pressure hydrocephalus)
What are the types of the following nerve fibres: Light touch Proprioception Pain Temperature Muscle fibre motor Muscle spindle motor
Light touch - A alpha Proprioception - A alpha Pain - C Temperature - A delta Muscle fibre motor - A alpha Muscle spindle motor - A beta
