physiology Flashcards
what is the role of oligodendrocytes
produce myelin to insulate axons in the CNS
what is the consequence of demyelination
slower conduction and reduced consistency of neuronal conduction
name an autoimmune cause of demyelination
MS
name a virus that causes demyelination and the disease it can cause
JC virus - progressive multifocal leukoencephalopathy
who usually presents with progressive multifocal leukoencephalopathy
immunocompromised patients
what causes central pontine myelinosis and what is the clinical consequence
rapid correction of hyponatraemia
SEVERE neurological deficit
where in the circle of willis is the most common area for a stroke to occur and why
middle cerebral artery
has direct pathway from the heart via the internal carotid artery
what lobe does the middle cerebral artery supply
temporal
what lobe does the posterior cerebral artery supply
occipital lobe
what is common presentation of carotid artery disease
contralateral weakness or sensory loss
in which vascular lesion would you expect weakness predominantly in the contralateral face and arm
middle cerebral artery stroke
What symptoms are characteristic of an anterior cerebral artery (ACA) stroke
Contralateral leg weakness and sensory loss
Which artery disease is associated with vertigo, ataxia, dysarthria, and dysphagia
vertibro-basilar artery disease
Why does an MCA stroke often cause more pronounced weakness in the face and arm than in the leg
MCA supplies the lateral aspect of the cerebral cortex, including the primary motor and sensory cortices responsible for the face and upper limbs
How can vertebro-basilar artery disease lead to visual disturbances?
supplies the occipital lobes, where the visual cortex is located
what do glial cells arise from
neuroectoderm
whar do microglia arise from
mesoderm
role of M1 microglia and M2
1 are proinflammatory
2 phagocytose
what does dysfunction of astrocytes cause
leaky blood brain barrier
what type of cells produce CSF
ependymal cells
what does the presence of red neurons on histology indicate
irreversible neuronal injury within the last 12-24 hours
what does neuronal atrophy on histology suggest
chronic injury e.g. neurodegenerative disease
name 3 conditions which cause reactive gliosis
alzheimers, MS, stroke
what is cytotoxic oedema and how does it occur
oedema due to cell death
dying cells take up water as ions move into cells
what causes ionic oedema
changes in blood e.g. excess water
what causes vasogenic oedema
partial breakdown in the blood brain barrier
what causes haemorrhagic conversion oedema
complete breakdown of the blood brain barrier
name some features of non-REM sleep
synchronised, rhythmic EEG
partial relaxation of muscles and reduced cerebral blood flow
reduced HR, blood pressure and tidal volumes
name some features of REM sleep
fast activity on EEG - similar to wakefulness
atonic muscles
increased cerebral blood flow, impaired thermal regulation
what are the 3 main types of pain
nociceptive, inflammatory and pathological
what causes nociceptive pain
immediate protective response to intense stimuli
what causes inflammatory pain
activation of the immune system in injury or infection
what are the 2 main types of pathological pain
neuropathic and dysfunctional
what 2 types of fibres are nociceptors made of
Aδ-fibres and C-fibres
what receptors mediate fast pain and how is this described
Aδ-fibres - stabbing, pricking sensation
what receptors mediate slow (secondary pain) and how is this described
C-fibres - burning, throbbing, cramping, aching
where do nociceptors synapse with the CNS
dorsal horn of the spinal cord
what kind of pain fibres are transmitted by the spinoreticular tract
C-fibre pain
what is the role of dendrites
receive inputs from other neurones and convey electrical signals to the soma
what is the role of axons
conducts output signals as action potentials to the presynaptic terminal
what causes depolarisation
increase in sodium into the cell causes a reduction in negative charge (increase in charge)
what causes repolarisation
increase in potassium out of the cells reduces the membrane potential
what are the 3 main types of neurotransmitters based on their function
excitatory, inhibitory, neuromodulators
what is the most abundant neurotransmitter in the brain
glutamate
what are the 2 main types of ACh receptors
nicotinic and muscarinic
what is transduction
conversion of a physical stimulus into a change in membrane potential
what is the role of first order neurones
transduction of a stimulus into electrical activity
name 2 factors that affect the speed of axon conduction
diameter of the axon and myelination
what causes shingles
infection of the dorsal root ganglion neurones by varicella zoster
where is the somatosensory cortex found
post central gyrus of the parietal cortex
immediately posterior to the central sulcus
what innervates skeletal muscles
alpha motor neurons
what is a motor unit
a motor neuron and all the fibres it innervates
what spinal level is being assessed with supinator (wrist) reflex
C5-6
what spinal level is being assessed with biceps reflex
C5-6
what spinal level is being assessed with triceps reflex
C7
what spinal level is being assessed with quadriceps reflex
L3-4
what spinal level is being assessed with the gastrocnemius (ankle) reflex
S1
what reflex protects a muscle from excessive contraction
the golgi tendon reflex
where does the rubrospinal tract originate
red nucleus of the midbrain
where does the vestibulospinal tract originate
vestibular nuclei
what is the role of the vestibulospinal tract
posture and supporting against the force of gravity
where do the tectospinal tracts originate
superior colliculi
what is the role of the tectospinal tracts
mediate orienting towards visual targets
where does the reticulospinal tract originate
reticular formation - collection of neurons in the pons and medulla
what is the role of the reticulospinal tract
involved in balance
what is the direct pathway for visual signal transmission
photoreceptors - bipolar cells - ganglion cells - merge to form the optic nerve
what are the 2 types of photoreceptors
rods and cones
what is the visual pigment molecule called
rhodopsin
what is visual aciuty
the ability to distinguish between 2 nearby points
where does transduction occur in the auditory pathway
organ of corti hair cells
what are the 2 main components of the vestibular system
semicircular canals
saccule and utricle
what is the role of the semicircular canals
sense head angular acceleration (head rotation)
what is the role of the saccule and utricle
sense linear head acceleration
what are the semicircular canals filled with
endolymph
what is the role of the vestibulo-ocular reflex and what does it cause
allows objects to remain in focus during head movements
causes eyes to move in the opposite direction to head movement
what is the role of the vestibulo-colic reflex
keeps the head still in space, or on a level plane when walking
what is the role of the vestibulo-spinal reflex
adjusts posture for rapid changes in position
how do the cerebellum and basal ganglia work in association with the motor cortex
cerebellum sends excitatory output
basal ganglia sends inhibitory output
what is the role of the cerebellum
important in coordination, precision and timing of movements as well as in motor learning
what are the 3 functional areas of the cerebellum
cerebrocerebellum
spinocerebellum
vestibulocerebellum
what is the role of the cerebrocerebellum
planning movements and motor learning
regulates the coordination of muscle activation
what is the role of the spinocerebellum
regulates body movements by allowing for error correction
what is the role of the vestibulocerebellum
involved in controlling balance and ocular reflexes - mainly fixation on a target
what is dysdiadochokinesia
difficulty in carrying out rapid, alternating movement
what is ataxia
impaired coordination, balance and speech
what is an intention tremor
involuntary tremor that increases as they approach the target, often resulting in past pointing
