L12: Pain and Vestibular Control Flashcards
the translation of a noxious stimulus into neural activity
transduction
propogation of nerve impulses from receptors into the CNS
transmission
facilitation of inhibition of neurons and interneurons in the spinal cord
modulation
what is nociception
perception of pain
what is mechanical deformation
stretch or damage to the receptor membrane that opens ion channels
the application of chemicals opens ______ in chemoreceptors
ion channels
changes in _____ alters the permeability of the membrane thermoreceptors
temperature
pain is detected through
free nerve endings
what type of pain do A-delta fibers detect
immediate, sharp pain
what type of pain do C fibers detect
dull, burning pain
what does free nerve ending mean
non myelinated endings
does pain occur in the brain
no
where are nociceptors located
skin, joints, internal organs and bones
T/F: temperature extremes and pain can be perceived as pain
True
Transient Receptor Potential channels (TRP)
_____ receptors increase AP frequency with increase in temperature
Warm
_____ receptors increase AP frequency with decreases in temp
cold
in what nerve fibers are warm receptors located
C
in what nerve fibers are cold receptors located
Aẟ with non-mylenated endings
Aẟ fibers have what 2 types of nociceptors
mechanical & Noxoius thermal nociceptors
_____ nociceptors respond to mechanical damage: cutting, crushing, pinching
Mechanical
_______ nociceptors respond to extreme heat and cold
noxious thermal
C Fibers have what two types of nociceptors
Thermal & Polymodal
thermal nociceptors respond to …
thermal gradients
what do polymodal nociceptors respond to
various novious damaging stimuli : thermal, mechanical, chemical
____ nociceptors are peripheral and mostly found in _____
polymodal, skin
pathways that convey somatic sensation require how many neurons
3
1st, 2nd and 3rd order sensory neurons
what sensory neuron has a cell body in the dorsal root ganglion, is an afferent neuron, and has peripheral receptors that detect stimuli
First order sensory neuron
what sensory neuron has a soma in the spinal cord or brainstem and synapses with a 3rd order neuron
2nd
what sensory neuron is located in the thalamus and synapses in the cortex layers (2-6)
3rd order
what is the only sensory neuron in the pain pathway with receptors in the PNS
first order sensory neuron
the spinothalamic pathways transmit information on ______, ________ and light touch
pain, temp
where do first order pain neurons synapse
onto 2nd order neurons in the spinal cord
where do 2nd order pain neurons synapse
in the thalamus - perception of pain
where do 3rd order pain neurons synapse
somatosensory cortex - location of pain
what is a non-adpating receptor
nociceptors that are activated as long as a lesion is present
hyperalgesia
increases sensitivity to pain
what causes hyperalgesia
tissue damage
initial injury only stimulates _____ pain sensation through what fibers
acute
A-delta
over time, dull pain sensations increase in intensity, stimulating ___ fibers
C
what things are released by the inflammatory response to pain
- bradykinins
- prostaglandins
- substance P (causes mast cells to release histamine which activates nociceptor endings)
- K+, H+
_______ in the ECF stimulate polymodal nociceptors and contribute to tissue inflammation
Bradykinins
Substance __ stimulates mast cells to release histamine
P
repeated sitmulation of ___ fibers enhances pain
C
Substance P binds ______ receptors in neurons and initiates vasodilation and inflammation
neurokinin 1
repeated stimulation of dorsal horn neurons causes ___________
central sensitization —> recruitment of glutamate receptors to make C fibers more senstiive
what inhibits the release of substance P, therefore alleviating pain
Enkephalin which is released from activation of opiate receptors
what are the analgesia endogenous opioid substances
- endorphins
- enkephalins
- dynorphins
what drug blocks the action of opioids
Naloxone
has high affinity for the μ opioid receptor, where it acts as a competitive antagonist.
where are μ opioid receptors concentrated
dorsal horns of spinal cord
how are serotonin and NE involved in modulating pain
they stimulate enkephalin releasing interneurons or pain modulating nucli in the brainstem
NE and 5-HT can be manipulated by a variety of pharmacological agents
NSAIDS block ______, a critical enzyme in the synthesis of _______
COX2
prostaglandins
this decreases sensitization to pain
exogenous opioids are good at agonizing ______ receptors
endogenous opioid
endocannabinoids help modulate ______ and increase following sustained physcial acvitiy
pain
located in the inner ear, informs CNS about head position and movement
vestibular system
what does the vestibular system measure
- static tilt of head
- linear acceleration
- rotary acceleration
the vestibular system is composed of _____ and _____
3 semicircular canals and 2 ampullae
what are the sensory receptor cells of the vestibular system
hair cells
clinical signs of vestibular syndrome
- head tilt
- nystagmus
- ataxia
- loss of balance
why do middle ear infections cause head tilt
infections cause pressure on the round/oval window of the cochlea
the pressure difference causes unbalanced AP frequency bw the affected and normal ear
at the base of each semicircular canal sit 3 _______ that contain a ridge within hair cells called _________
ampulla
crista ampullaris
2 of the 3 ampulla in the semicircular canals are connected to a _____ and ______
utricle & saccule
inside the 3 ampulla, the saccule and utricle are hair cells bathed in _____
endolymph
what 5 things do hair cells consist of
- cilia at luminal membrane
- synapse with sensory neuron
- vestibulochochlear nerve
- other hair cells along the crista ampullaris
- cupula (gelatinous mass)
bending of hair cells towards the cilia causes ____ channels to open
K+ –> depolarization
moving of the head in one direction will cause the endolymph to move across hair cells in the _____ direction
opposite = deceleration
hair cells are on the _____
macula
the utricle has a ______ oriented macula and the saccule has a _______ oriented macula
horizontally
vertically
mass of calcium carbonate crystals that sit atop the cilia and gelatinous cupula
otoliths
otoliths and _________ cause cilia to bend in the opposite direction of head movement
endolymph
what are the 3 targets of CN VIII via vestibular nuclei
- vestibulospinal tracts
- medial longitudinal fasciculus
- flocculondular node of the cerebellum
what is the goal of the vestibuloocular reflex
move extraocular eye muscles to maintain contact with the target as the head/body is in motion
what is the goal of the vestibulospinal reflex (VSR)
stabilize the body
what is the vestibulo-collic reflex
head and neck muscles adjusting to maintain head position
what is affected in peripheral vestibular syndrome
labyrinth within the petrosal bone
associated w/ head tilt
in central disease type vestibular syndrome, the _____ is affected
brain stem
associated w/ paresis/hemiparesis, gait and posture
