Exam 2: Neurophysiology Part 2 - Vestibular system, Cerebellum, ANS Flashcards
what is vestibular system and where is it located
A bilateral receptor located in the inner ear
What does the vestibular system inform brain of (5)
Position and motion of the head
Sense of equilibrium and balance
Static tilt of head
Linear acceleration of head (vertical and horizontal)
Rotary acceleration of head
What is the vestibular system composed of
3 semicircular ducts
Utricle and saccule
What are the receptor units (secondary receptor cells) in the vestibular system
Hair cells - functional unit of inner ear
Vestibular structures
Kinocilium
Stereocilia
Gelatinous mass at top
Difference between kinocilium and stereocilia
Kinocilium - largest cilium and rest are stereocilia
What is the gelatinous substance at top of vestibular strucutre
Makes cilia move and bend, causes channels (K channels) to open and determine which way the cilia bends
what joins cilia together
links of spiral proteins
Direction of bending determines response
Cilia bend toward kinocilium = depolarization (increased # AP)
Cilia bend away from kinocilium = hyperpolarization (decreased # AP)
What do the semicircular ducts and ampullae detect
Rotary acceleration and deceleration of the head
What enables detection of acceleration and deceleration
Inertia causes delay in endolymph acceleration
In deceleration, opposite occurs (inertia continues to move endolymph)
what causes bending of the hair cells in the vestibular system
the gelatinous cupula in the crista ampullaris displaces in a direction opposite to head’s rotation
what causes stimulation of crista ampullaris
starting and stopping acceleration
constant rotational velocity does not stimulate it
Depolarization and hyperpolarization of semicircular ducts
depolarization - increased AP frequency
hyperpolarization - decreased AP frequency
what do semicircular ducts provide brain with
info about direction and nature of head movement
What is the macula
receptor organ located in utricle and saccule
what are otholiths
“ear stones”
Heavy and dense layer above gelatinous layer that covers cilia
what does otoliths detect
linear acceleration and deceleration
Static head tilt
How otoliths behave in acceleration and head tilt
Head tilt - otoliths fall over and remain fallen over for as long as head is tilted
linear acceleration - otoliths lag behind producing bending of the hair cells
Orientation of utricle and saccule
Utricle macula - horizontally oriented
Saccule macula - vertically oriented
Parts of the vestibular nuclear complex (4)
Rostral vestibular nuclei
Medial vestibular nuclei
Lateral vestibular nuclei
Caudal vestibular nuclei
Vestibulo-occular reflexes (VOR)
Coordinate eye and head movements
When the head moves, the eyes remain fixed on original field of vision for as long as possible
Definitions: Ataxia Nystagmus Physiological nystagmus Postrotatory nystagmus Spontaneous nystagmus Acute vestibular disease
Ataxia - loss of voluntary motor coordination
Nystagmus - involuntary repetitive eye movements
Physiological nystagmus - normal, occurs during VOR
Postrotatory nystagmus - the converse eye movement
Spontaneous nystagmus - associated with pathologies in the vestibular system
Acute vestibular disease - characterized by persistent head tilt, falling, circling, rolling
Functions of cerebellum
Timing and coordination of movement
Adjusting and modulating the output of the motor cortices, corticospinal tract, brainstem motor pathways, and spinal cord
Where is cerebellum located
above brainstem
Various peduncles of cerebellum (3)
Rostral cerebellar peduncle - axons going out of cerebellum (output)
Middle cerebellar peduncle - axons going into cerebellum (input)
Caudal cerebellar peduncle - both input and output axons
Cells of the cerebellum and what layer they are in
Molecular layer:
Stellate cells
Basket cells
Axons of granule cells: parallel fibers
Purkinje cell layer (axons go to cerebellar nuclei):
Purkinje cells
Granule cell layer:
Golgi cells + granule cell bodies
what kind of neruons are purkinje cells
GABAergic neurons - induce IPSPs
GABA receptor is ionotropic receptor (Cl- channel)
GABA receptor is a ligated gated channel - channel for chlorine
Chlorine goes into cell and makes cell more negative
GABA synthesis
GABA synthesized from glutamate by enzyme glutamic acid decarboxylase
High affinity transporters terminate actions of these transmitters and return GABA to synaptic terminals for reuse
Regions of cerebral cortex that project to the cerebellum
Sensory association cortex of parietal lobe
Motor association areas of frontal lobe
Divisions of the cerebellum and their inputs
Vestibulocerebellum - vestibular sensory inputs
Spinocerebellum - spinal and trigeminal sensory inputs, visual and auditory sensory inputs
Cerebrocerebellum - corticopontine inputs form motor cortices
Where each cerebellum division goes and what they do
Vestibulocerebellum - to vestibular nuclei –> coordinated balance and eye movement
Spinocerebellum - to descending brainstem and corticospinal pathways –> proper execution of coordinated movement
Cerebrocerebellum - to motor cortices –> planning coordinated, properly timed movement sequences
VOR and learned changes
Cerebellum helps reset VOR so eyes move appropriate distance in relation to head movement
Cerebellum plays role in motor learning and in fine-tuning of reflex behaviors such as in VOR
Common clinical signs associated with cerebellar disease (6)
Wide based gait
Ataxia - walk in uncoordinated manner
Dysmetria - inappropriate measure of muscular contraction
Asynergia - failure on components of a complex multi-joint movement to occur in a coordinated fashion
Intention tremor - oscillating movement disorder that worsens when animal is moving
Nystagmus (if Vestibulocerebellum is damaged)
Divisions of autonomic nervous system
Parasympathetic - rest and digest
Sympathetic - fight or flight
Where is the enteric nervous system located
Wall of the gut
What does ANS control
Visceral functions and glandular secretions in body maintaining homeostasis
Somatic nervous system vs autonomic nervous system:
Number of efferent neurons
SNS - one efferent neuron
ANS - 2 efferent neurons, in series: preganglionic neuron and postganglionic neuron
Somatic nervous system vs autonomic nervous system: Conduction speed
SNS - fast
ANS - slow
Somatic nervous system vs autonomic nervous system: Ganglia?
SNS - no ganglia
ANS - Lots of ganglia
Somatic nervous system vs autonomic nervous system: inhibitory or excitatory
SNS - EPSPs (aka EPP)
ANS - can induce EPSPs or IPSPs
Somatic nervous system vs autonomic nervous system: motor end plate or varcosicties
SNS - motor end plate
ANS - varacosities
Sympathetic nervous system characteristics (5)
Fight or flight
Perform vigorous physical activity
Increases HR, respiration, dilate pupils
Thoracolumbar origin
Short preganglionic neurons, long postganglionic neurons
Parasympathetic nervous system characteristics (5)
Rest and digest
Conserve and store energy
Controls breathing at rest, digestion, excretion
Craniosacral origin
Long preganglionic neurons, short postganglionic neurons
Cholinergic neurons: neurotransmitters and receptors
Neurotransmitters - acetylcholine
receptors - nicotinic, muscarinic
Adrenergic neurons: neurotransmitter and receptors
Neurotransmitter - norepinephrine
Receptors - alpha, beta
What type of neurons are preganglionic neurons in both divisions of ANS
Cholinergic neurons
What are the receptors of all postganglionic neurons in both divisions of ANS
nicotinic
Postganglionic parasympathetic neuron type and target tissue receptor
Cholinergic neuron
Muscarinic receptor
Postganglionic sympathetic neuron type and target tissue receptor
Adrenergic neurons
Adrenergic receptors
Adrenergic receptor a1
Sympathetic
Stimulatory G protein
2nd messenger - DAG, IP3 increased
increased calcium
Adrenergic receptor a2
Sympathetic
inhibitory G protein
2nd messenger: cAMP decreased
decreased calcium
Adrenergic receptor B1
Sympathetic
stimulatory G protein
2nd messenger cAMP increased
increased calcium
Adrenergic receptor B2
Sympathetic
stimulatory G protein
2nd messenger cAMP increased
decreased calcium
Cholinergic receptor: Muscarinergic receptor M1
Parasympathetic
stimulatory G protein
2nd messenger DAG, IP3 increased
increased calcium
Cholinergic receptor: Muscarinergic receptor M2
Parasympathetic
inhibitory G protein
2nd messenger cAMP decreased
Opens K channels
decreased calcium and K
Cholinergic receptor: Muscarinergic receptor M3
Parasympathetic
stimulatory G protein
2nd messenger DAG, IP3 increased
increased calcium
Cholinergic vs adrenergic effects: eye
Cholinergic - pupillary constriction
Adrenergic - pupillary dilation
Cholinergic vs adrenergic effects: heart
Cholinergic - decreased HR, conduction velocity, and contracting force
Adrenergic - increased HR, conduction velocity, and contraction force
Cholinergic vs adrenergic effects: arterioles
Cholinergic - dilation
Adrenergic - constriction
Cholinergic vs adrenergic effects: lungs
Cholinergic - bronchoconstriction
Adrenergic - bronchodilation
Cholinergic vs adrenergic effects: urinary bladder
Cholinergic - contraction of detrusor muscle
Adrenergic - relaxation of detrusor muscle
Cholinergic vs adrenergic effects: intestine
Cholinergic - increased motility and secretion
Adrenergic - decreased motility and secretion
