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
on sheet
Label the vesicle formation embryology diagram
on sheet
Label medulla section
on sheet
Label pons section
on sheet
What cranial nerves originate from the pons surface
V, VI, VII, VIII
Label midbrain section
on sheet
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
on sheet
label gyrus
on sheet
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
on sheet
Label the limbic lobe
on sheet
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