Neurology Flashcards
What is the vestibular system
a system in control of posture and balance.
in the inner ear, is a series of fluid-filled membraneous tubes (labyrinths), embedded in the temporal bone
What are the otolith organs?
utricle and saccule
they detect linear acceleration and encode info about the position of head in space
What does the utricle and saccule detect individually?
utricle= back/front tilt
saccule=vertical movement
What does the semi-circular canals detect?
rotational acceleration
What is found within the ampulla?
sensory receptors called cristae,
the cristae consists of a flexible gelatinous structure called capula,
the capula stretches across the entire width of the ampulla and responds to movement of the endolymph fluid within the canals
What is found embedded within the gelatinous cupula?
the cilia of hair cells,
these cilia synapse directly with the sensory neurons of the vestibular nerve
what do the hair cells in the gelatinous material detect?
rotational acceleration
How do the hair cells in the gelatinous material detect rotational acceleration?
if skull is rotated, the ampulla moves as it is embedded in the skull, the endolymph doesn’t movedue to it’s inertia.
the inertia of the endolymph produces drag which bends the cupula and the cilia embedded in it, in the opposite direction to movement.
What are the 2 types of hair cells found in the ampulla?
Large kinocilium and smaller stereocilia
What happens if there is distortion of cilia in the direction of the kinocilium?
There is depolarisation and icnreased discharge of APs in the vestibular nerve
What happens if there is distortion of the cilia away from the kinocilium?
There is hyperpolarisation and decreased discharge of APs in the vestibular nerve
What is the collective name of the sensory apparatus of the utricle and saccule?
maculae
How are the macula in the utricle orientated?
horizontally
How are the macula in the saccule orientated?
vertically
what are the sets of the cilia in the maculae?
kinocilium and a series of stereocilium
What do the cilia of the maculae protrude into?
protrude into the otolith membrane, embedded in the otolith membrane are CaCO3 crystals called otoliths
What happens if you tilt your head backwards?
the otolith is moved in the
direction of the kinocilium causing depolarisation and increased discharge of APs
What is the tonic labyrinthine reflex?
keeps the axis of the head in a constant relationship with the rest of the body, using information from the maculae and neck proprioceptors
What is the dynamic righting reflexes?
rapid postural adjustments that are made to stop you falling when you trip.
Long reflexes, involving extension of all limbs
What links are there between the visual and balance centres?
afferents from the semi-circular canals project and connect to afferent fibres travelling to extraocular nuclei and thus have strong input to influencing eye movement.
Visual system also sneds powerful descending projections which control posture
What is the static reflex (vestibulo-ocular reflex)
when you tilt your head your eyes intort/ extort to compensate, so for a certain range the image stays the right way up
What is the dynamic vestibular nystagmus?
a series of saccadic eye movements that rotate the eye against the direction of rotation of the head and body so that the original direction of gaze is preserved despite head rotating
What is caloric stimulation?
outer ear is washed with either cold or warm fluid, temperature gets through bone and sets up convention currents which affect the endolymph.
Warm fluid causes nytagmus towards affected side, cold causes nystagmus away from affected side (COWS cold opposite, warm same)
What does kinestosis mean?
motion sickness
What can result in nystagmus at rest?
lesions of the brain stem
What are the vertebral arteris a branch of?
subclavian arteries
What does the internal carotid artery give branch to?
anterior, middle cerebral and posterior communicating arteries
What do the 2 vertebral arteries join to form?
basilary artery
What does the vertebro-basilar system supply
brainstem and cerebellum
What does the basilar artery divide into at the level of the midbrain?
posterior cerebral arteries
Where do dural venous sinuses drain into?
internal jugular vein
Label the circle of willis
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Label the vesicle formation embryology diagram
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Label medulla section
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Label pons section
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What cranial nerves originate from the pons surface
V, VI, VII, VIII
Label midbrain section
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what cranial nerves originate from midbrain
CN III, IV
What are the 3 lobes of the cerebellum
anterior, posterior and flocculonodular
What does the surface of the cerebellum have on it
sulci and folia
What is abnormality of the cerebellum called?
ataxia
What are the groups of the nucleii contained in the thalamus?
anterior, medial and lateral
the thalamus is a sensory relay station
What separates the hypothalamus from the thalamus?
the hypothalamic sulcus
Name of fissure between cerebral hemispheres?
median longitudinal fissure
What is the function of the corpus callosum
holds cerebral hemispheres together
Label sulcus
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label gyrus
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When can the insula be seen?
in supero-lateral view after part of the frontal and parietal lobe have been cut away
Which parts of the brain are motor, sensory or limbic?
posterior=sensory
anterior=motor
medial=limbic
What is area 4 of the brain?
primary motor complex
somatotopic representation of contralateral half of body
What is inferior frontal gyrus control and what area of the brain
area 44,45 and controls motor speech
know as Broca’s area of motor speech
What is the prefrontal cortex’s job?
cognitive, functions of higher order- intellect, judgment, prediction, planning
What is the job of the frontal lobe?
motor
What is the job of the parietal lobe?
somatosensory
What is the name and job of area of the brain 3,1,2?
primary sensory area
receives general sensations from contralateral half of body.
somatotopic representation
Job of superior parietal lobule
interpretation of general sensory information and conscious awarness of contralateral half of body
Job of inferior parietal lobule?
interface between somatosensory cortex and visual and auditory association areas
Signs of parietal lobe lesion?
hemisensory neglect, right-left agnosia, acalculia, agraphia
Job of superior temporal gyrus, areas 41, 42?
primary auditory cortex
What is the name of the auditory association area and where is it found?
Wernicke’s area, posterior to 41, 42 and found in the dominant hemisphere
What is Wernicke’s area important for?
for understanding the spokem word
What does the inferior surface of the temporal lobe receive?
fibres from the olfactory tract for concious appreciation of smell
What is the overall function of the temporal lobe?
hearing and smell
What is the overall function of the occipital lobe?
vision
Where can you find the visual cortex?
on the medial surface of the occipital lobe, on either side of the calcarine sulcus
What are areas 18 and 19 of the brain?
visual association cortex, used for interpreting visual images
What is the function of the limbic lobe?
functional area, responisble for memory and emotional aspects of behaviour
What does the limbic lobe include?
cingulate gyrus, hippocampus, parahippocampal gyrus and the amygdala
Label the areas of the cerebrum
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Label the limbic lobe
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What two areas of the brain are responsible for speech?
Broca’s area for motor speech and Wernicke’s area for auditory association
What is Broca’s aphasia?
Understands speech, misses small words and is aware of difficulties in speech.
Damage to frontal lobe so there i also weakness and paralysis of one side
What is Wernicke’s aphasia?
Fluent speech but with new and meaningless words, can’t understand speech and doesn’t realise mistakes.
there is damage to temporal lobe and no paralysis
What are the 3 types of myelinated axon fibres bundled into tracts?
Commisural fibres
Association fibres
Projection fibres
What are commisural fibres?
Mylinated axon fibres that connect corresoponding areas of 2 hemispheres eg corpus callosum
What are association fibres?
Mylinated axon fibres that connect one part of the cortex with the other, can be short or long
What are projection fibres?
Mylinated fibres that run between the cerebral cortex and various subcortical centres, they pass through the corona radiata and the internal capsule
What are the 3 basal ganglia?
Caudate nucleus, putamen and globus pallidus
and substanca nigra but this is found in the midbrain
What is the basal ganglia?
subcortical nuclei (collection of neuronal cell bodies) deep within each cerebral hemisphere
What is the name of the basal ganglia when you add the caudate to the putamen
lentiform nucleus
Label the basal ganglia
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Which basal ganglia receive input from the motor cortex, pre-motor cortex and thalamus?
Caudate nucleus and putamen
Which basal ganglia are the output regions?
Globus pallidus and substantia nigra
these basal ganglia then project to the thalamus
What is the major function of the basal ganglia?
initiation and termination of movements
they are often referred to as extrapyramidal system
What are the 3 columns that white matter is arranged into?
posterior, lateral and anterior
What are the 3 important tracts of the spinal cord?
corticospinal/ pyramidaltract, posterior/dorsal column, lateral spinothalmic tract
What does the corticospinal tract carry?
motor impulses from motor cortex to skeletal muscles
What does the posterior/ dorsal column carry?
carries touch, tactile localisation, vibration sense, proprioception
What does the lateral spinothalamic tract carry?
pain and temperature
Describe the pathway or corticospinal/pyramidal tract
Starts at area 4, projection fibres radiate to internal capsule, to the medulla where they cross at the decussation of pyramids, now in the lateral corticospinal tract, they synapse in the ventral horn and out to appropriate level
What are the 2 neurons in the descending motor tract?
Upper motor neuron originating from the primary motor cortex and the lower motor neuron from spinal cord
Describe the posterior/ dorsal column tract?
1st order neurons synapse in 2nd neuron at lower part of medulla.
2nd order neuron decussates in the medulla, this tract is now the medial lemniscus and passes through the brainstem to the thalamus.
3rd order neuron starts at thalamus and axons pass through the internal capsule and radiate to post-central gyrus (area 3,1,2)
Describe the lateral spinothalamic tract?
1st order neuron enters the grey mater and ends at this level.
2nd neuron crosses over to reach the lateral column and is now known as the lateral spinothalamic tract.
the 2nd order neuron ends in the thalamus and 3rd order passes through the internal capsule and radiates to the post-central gyrus
What is a reflex?
An involuntary stereotyped pattern of response brought about by a sensory stimulus
What type of reflex is monosynpatic?
Stretch reflex
What type of reflex is polysynaptic?
Flexor reflex
Why is stretch reflex important?
It is important in control of muscles tone and posture
What type of neuron mediates reflexes?
Lower motor neurones
What is the difference between upper and lower motor neurone lesions?
UMN= increased tone, causing spasticity
LMN= decreased tone and flaccidity
What would happen if you had a Left UMN lesion at the internal capsule and how would this differ from a l UMN at the upper cervical spinal cord level?
You would have right sided paralysis, hyper-reflexia and increased tone.
If it was at the cervical spinal cord level you would have left sided paralysis, hyper-reflexia and increased tone
What would happen if you have left lmn lesion?
left sided paralysis, arreflexia and flaccidity
what are motor neuron diseases?
group of diseases affecting the lower motor neuron in the ventral horn of the spinal cord
What affect would lesions have in the posterior/ dorsal column tract
lesion above decussation= contralateral sensory loss
lesion below decussation= ipsilateral sensory loss
What would happen if there was a lesion on the lateral spinothalamic tract of the right side?
pain and temperature from left side of body
Where does activity for sleep originate?
in the reticular formation of the brain stem, sends projections to the thalamus and higher cortical areas
How is the suprachiasmatic nuclei involved in the sleep wake cycle?
electrical stimulation of the SCN stimulates the release of melatonin from the pineal gland- creating the feeling of sleepiness.
The hypothalamus also releases an excitatort neurotransmitter orexin which is required fot wakefullness
Where is the suprachiasmatic nuclei found?
in the hypothalamus
What is the name of the system in the reticular formation responsible for the sleep-wakefullness cycle?
the Ascending Reticular Activating System
What system is used to assess level of a conscious person?
an ElectroEncepheloGram (EEG)
Describe an alpha wave on an EEG
When in a relaxed, awake state, is characterised by high frequency, high amplitude waves
Describe a beta wave on an EEG
when in an alert, awake state, it has a high frequency and a low amplitude with asynchronous waves
describe theta waves?
seen when asleep or in times of emotional stress and frustration, characterised by low frequency waves which vary in amplitude
Describe delta waves seen on an EEG
occur in deep sleep and are characterised by low frequency and high amplitude
Describe stage 1 of the sleep cycle
slow wave, light sleep with theta wavesn(high amplitude, low frequency)
Describe stage 2 of the sleep cycle
slower frequency with bursts of rapid waves called sleep spindles (clusters of rhythmic waves, 12-14Hz)
Describe stage 3 of the sleep cycle
Delta waves (high amplitude, low frequency), with short episodes of faster waves
Describe stage 4 of the sleep cycle
Delta waves- know as deep sleep
Sleepwalking and talking occurs at this stage, more restful and associated with decreased vascular tone, respiratory and basal metabolic rate
Describe REM sleep of the sleep cycle
Rapid eye movements, 25% of sleep, profound inhibition of other skeletal muscls due to inhibitory projections from pons to spinal cord.
HH/RR become irregular and brain metabolism increases, EEG patter mimics beta waves
Roles of sleep?
Neuronal plasticity, learning and memory, cognition, clearance of waste products from CNS, conservation of while body energy, immune function
Describe insomnia
chronic inability to obtain the necessary amount or quality of sleep to maintain adequate daytime behaviour
What is the fancy name for sleep walking
somnambulism
Type of receptors in the skin?
Meissner's corpuscle (light touch) Merkle's corpuscles (touch) Free nerve ending (pain) Pacinian corpuscle (deep pressure) Ruffini corpuscle (warmth)
What determines acuity?
density of innervation and size of receptive fields
What are the 3 types of primary afferent fibres that mediate cutaneous sensation?
A(beta)= large myelinated (30-70m/s) touch, pressure, vibration
A(gamma)= small myelinated (5-30m/s) cold, “fast” pain, pressure
C= unmyelinated fibres (0.5-2m/s) warmth, “slow” pain
what are the 2 types of primary afferent fibres that mediate proprioception?
Aalpha and Abeta
Where do the mechanoreceptors travel up and where to they cross over?
travel through ipsilateral dorsal column and decussate in the brainstem
Where do the thermoreceptive and nociceptive fibres travel up and where do they cross over?
they corss over in the spinal cord and project up through the contralateral spinothalamic tract
Where is sensory information transmitted?
somatosensory cortex of the postcentral gyrus
What activates signal transduction?
low pH, heat, local chemical mediators (bradykinin, histamine, prostaglandins)
What are the segmental controls of pain?
Activity in Aalphabeta fibres activates inhibitory interneurones, inhibitory internuerones releases opioid peptides(endorphins) that inhibit transmitter release from Agamma/C fibres.
What are the descending controls of pain?
the same inhibitory interneurones activate by descending pathways from peri-aqueductal grey matter and nucleus raphe magnus
How do NSAIDs work?
prostaglandins sensitise nociceptors to bradykinin, they inhibit cyclo-oxygenase which converts arachidonic acid to prostagalndins
How do local anaethetics work?
block Na+ action potentials and therefore axonal transmission
How do opiates work?
reduce sensitivity of nociceptors and block transmission release in dorsal horn, and thus activate descending inhibiotry pathways
What are the 3 key components of learning and memory?
Hippocampus- formation of memories
Cortex- storage of memories
Thalamus- searches and accesses memories
What are the 4 areas that make up the limbic system?
hypothalamus, hippocampus, cingulate gyrus and the amygdala
Reward and punishment of limbic system significance
deems certain things significant and storing them in memory
What symptoms would a patient with bilateral hippocampal damage experience?
immediate memory and intact long term memory but the inability to form new-long term memories, their reflexive memory would remain intact
What are the 4 types of memory?
immediate memory, short-term memory, intermediate long-term memory and long term memory
Describe immediate/sensory memory
The ability to hold experiences in mind for a few secs, based on different sensory modalities, visual memories decay faster than auditory ones
Describe short-term memory
secs-hours, brain’s post it note
used for short term tasks and is associated with reverberating circuits
Describe intermediate long-term memory
hours-weeks, what you did last weekend.
Associated with chemical adaptation at the presynaptic terminal
Describe long-term memory?
Can be lifelong, associated with structural changes in synaptic connections.
How is short-term memory maintained?
reverberating circuits
What are the 2 types of amnesia, and what is amnesia?
Amnesia is when reverberation fades and the 2 types are anterograde and retrograde
Describe anterograde amnesia?
cannot form new memories
Describe retrograde amnesia?
cannot access old memories, when thalamus is damaged
How does intermediate long-term memory work?
involves chemical changes in presynaptic neurons: increasing Ca entry to presynaptic terminals increases neurotransmitter release
What are the structural changes required at synapses in long-term memory?
increases in NT release sites on presynaptic membrane, increase in number of NT vesicles stored and releases, increase in number of presynaptic terminals
what is long term potentiation?
well rehearsed pattern of neuronal firing unique to particular memory
What are the 2 types of long term memory?
declarative/ explicit memory and procedural/reflexive/implicit memory
Describe declarative long term memory?
abstract memory for events (episodic memory) and for words, rules and language (semantic memory), relies heavily on the hippocampus
Describe procedural memory
Aquired slowly through repetition, includes motor memory
How is short term memory converted to long term memory?
consolidation
How does memory exist during the consolidation process?
memory exists as electrical activity and is vulnerable to being wiped out
What determines the significance of an event and wether it should be remembered?
frontal cortex and limbic system
What is “coding” of memories
New memories are stored in sensory and association area of the cortex, results in new memories being stored alongside other existing memories the brain deems similar
What is the Papez Circuit?
hippocampus-mammillary bodies- anterior thalamus- cingulate gyrus,
if an experience is considered useful the reverberating activity continues between the papez circuit, the frontal cortex, the sensory and association areas until consolidation proccess is complete
Why is memory impaired in Korsakoff’s syndrome?
chronic alcoholism causes a vitamin B1 deficiency which leads to damage of limbic system structures
Why is memory impaired in Alzheimer’s
there is severe loss of cholinergic neurones throughout the brain, including the hippocampus
Why is REM sleep important for memory?
dreaming may enable memory consolidation, it reinforce’s weak circuits.
Sequence of events in synaptic transmission
1- synthesis and packaging of neurotransmitter in presynaptic terminal
2- Na2+ AP invades terminal
3-activates voltage gated Ca2+ channels
4-triggers Ca2+ dependent exocytosis of pre-packaged vesicles of transmitter
5-Transmitter diffused across cleft and binds to inotropic and/or metabotropic receptors to evoke postsynaptic reponse
6- Presynaptic auto-receptors inhibit further transmitter release
7-Transmitter is inactivated by uptake into glia or neurones
8-Or transmitter is inactivated by extracellular breakdown
9- Transmitter is metabolised within cells
Pharmacological manipulation to reduce synaptic transmission
Block voltage-gated Na+ channels, inhibit synthesis and packaging of neurotransmitter, activated presynaptic inhibitory receptors, increase uptake of transmitter, block release machinery, increase breakdown of transmitter, block voltage-gated Ca2+ channels, activate presynaptic inhibitory receptors, block postsynaptic receptors
Pharmacological manipulation to increase synaptic transmission
Increase synthesis and packaging of neurotransmitter, activate postsynaptic receptors with an agonist, block uptake of transmitter, block breakdown of transmitter, potentiate effects of transmitter on receptor
Name types of neurotransmitters
Acetylcholine, monoamines, amino acids, purines, europeptides, NO
Name types of monoamines
Noradrenaline, dopamine, serotonin
Name types of amino acids
glutamate, GABA, glycine
Name types of purines
ATP, adenosine
Name types of neuropeptides
endorphins, CCK, substance P
What isthe anatomical distribution of dopamine in the brain?
brain stem, basal ganglia, limbic system and frontal cortex
What are the physiological functions affected by dopamine
voluntary movement, emotions/ reward, vomiting
What causes parkinson’s disease?
degeneration of dopamine cells in the substanca nigra and dopamine deficiency in the basal ganglia
Describe the steps of dopamine synthesis
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Describe the steps of dopamine breakdown
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What enzyme breaks down dopamine into dihydroxphenylacetic acid?
monoamine oxidase B (MAO-B)
What breaks down DOPAC into homovanillic acid?
Catechol-O-methyltransferase
What breaks down dopamine into 3-Methoxytryptamine (3-MT)
catechol-O-methytransferase (COMT)
What breaks down 3-MT into homovanillic acid?
monoamine oxidase B (MAO-B)
Dopaminergic drugs
DA precurosr- levodopa, DA agonists (ergots: bromocriptine, pergolide, cabergoline non-ergots: ropinerole, pramipexole, rotigotine), apomorphine
What enzyme inhibitors are used in parkinsons?
Peripheral AAAD inhibitors eg carbidopa, benserazide
MAOB inhibitors eg selegiline, rasagiline, safinamide
COMT inhibitors eg entacapone, tolcapone
What are the side effects of peripheral AAAD inhibitors?
decrease peripheral side effects of levodopa and allos a greater proportion of the oral dose to reach CNS
Side effects f dopaminergic drugs?
nauase, vomiting, psychosis, impulsivity/ abnormal behaviours
What symptoms of Parkinson’s do dopaminergic drugs not help?
dysarthria, balance, cognition
Were dies the area postrema function?
in the medulla outside the bbb
What DA antagonist doesn’t cross the BBB?
Domperidone, is an anti-emetic
What is dyskinesias?
abnormal involuntart movements, is often caused by dopimergic drugs
Noradrenaline function?
reuptake blockers eg tricyclic drugs are antidepressants, MAO inhibitors are antidepressants
Serotonin function
selective serotonin reuptake inhibitors are antidepressants, triptans are used for the treatment of migraine
GABA function
GABA agonists are anti-epilepsy drugs, also have anti-anxiety properties
