Pain and Vestibular Control Flashcards
Map pain from stimulus to perception
transduction ->transmission ->modulation -> perception
what is transduction?
translation of noxious stimulus into neural activity
what is transmission?
propagation of nerve impulses from receptors into CNS
what is modulation?
facilitation of inhibition of neurons and interneurons in spinal cord
what is perception?
result of the integration of projection pathways with modulation to produce the final conscious, subjective and emotional response
what are the stimulus energies of nociception?
mechanical deformation
application of chemicals
change in temperature
how does mechanical deformation cause nociception?
stretches or damages the receptor membrane and open ion channels
how does application of chemicals cause nociception?
opens ion channels in chemoreceptors
how does changes in temperatures cause nociception?
alters permeability of membrane of thermoreceptors
what is pain detected through?
free nerve endings
what are the nerve fibers that detect pain?
Ad fibers
C fibers
what type of pain does Ad fibers detect?
immediate, sharp
what type of pain does C fibers detect?
dull, burning pain
does pain occur in the brain?
NO
what type of channels do warm and cold receptors have?
transient receptor potential (TRP) channels
what receptor increases AP frequency with an increase in temperature?
warm receptor
where are warm receptors located?
C nerve fibers
what receptor increases AP frequency with a decrease in temp?
Ad fibers
when are heat nociceptors activated?
> 45 degrees celsius
what type of nociceptors are in Ad fibers?
mechanical - mechanical damage (cutting, crushing, pinching)
noxious thermal - extreme heat and cold
what type of nociceptors are in C fibers?
thermal - thermal gradients
polymodal - various noxious damaging stimuli (thermal, mechanical, chemical)
how is pain transmitted to the brain?
3-neuron afferent pathway
what are the 3 neurons needed to convey pain?
first-order sensory neuron -> second-order sensory neuron -> third-order sensory neuron
which neurons are in the PNS and the CNS for pain afferent pathway?
PNS - first-order
CNS - second-order, third-order
what do first order neuron synapses onto?
2nd order neuron in spinal cord
what do second order neuron synapse onto?
thalamus - perception of pain
what do 3rd order neuron synapse onto?
somatosensory cortex - location of pain
what spinothalamic tract transmits pain?
lateral spinothalamic
what is a non-adapting receptor?
nociceptors are activated as long as lesion is present
what is hyperalgesia?
an increased insensitivity to pain
what type of fiber and pain does initial injury stimulate?
acute pain sensation
Ad fibers
what type of fibers and pain is present for pain over time?
dull pain sensation increases in intensity
C fibers
what does the inflammatory response release?
bradykinins, prostaglandins, substance P
what does bradykinins in ECF stimulate?
polymodoal nociceptors and contribute to tissue inflammation
what does substance P stimulate?
mast cells to release histamine
how does substance P enhance pain sensitivity?
bind neurokinin 1 receptors in neurons -> vasodilation and inflammation -> sensitizes afferent pain fibers to inc pain perception
what causes central sensitization?
repeated stimulation of dorsal horn neurons
what make C fibers more sensitive?
recruitment of additional glutamate receptors
what constitutes a memory of the state of c-fiber nociceptors?
repeated stimulation of dorsal horn neurons
recruitment of additional glutamate receptors
what mechanisms are the pain-relieving pathway?
endogenous opioid mechanisms
how do endogenous opioids relieve pain?
activate opiate receptors -> block release of substance P in spinal cord and preiaqueductal gray matter of midbrain
how does enkephalin relieve pain?
inhibit release of substance P
what are the analgesia endogenous opioid substances?
enkephalin, endorphins, dynorphins
what blocks opioid substances?
naloxone
u-opioid receptor competitive antagonist
what type of opiate receptors are concentrated in the dorsal horn of the spinal cord?
u-receptors
what locations in this pathway would morphine act?
dorsal horn
raphe nucleus
what are the methods of exogenous pain control?
serotonin & norepinephrine
NSAIDs
Endocannabinoids
Exogenous opioids
how does serotonin and norepinephrine modulate pain?
stimulate enkephalin release interneurons or pain modulating nuclei in brainstem
what does the vestibular system meaure?
static tilt of the head
linear acceleration
rotary acceleration
what movements are facilitated by the vestibular system?
correction of posture and balance
maintain focus of the eyes and head moves
what do the two ampulla connect to?
utricle and saccule
what do the sensory nerves in the hair cells lead into?
vestibulocochloear nerve
what does bending toward the large cilia in a hair cell lead to?
K+ channels open -> depolarization -> exocytosis of neurotransmitters glutamate and aspartate
what does bending the hair cells in the ampullae in the opposite direction lead to?
hyperpolarization
what direction of the hair cells in the ampullae excites and inhibits?
excites - toward largest
inhibit - away from largest
what can the semicircular canals detect?
rotational acceleration and deceleration
what does the utricle and saccule detect?
linear acceleration and deceleration
what orientation is the utricle macula?
horizontal
what orientation is the saccule macula?
vertical
what happens in the utricle and saccule when a head tilts?
otoliths will pull down causing firing rates to change
Fill in the blanks
1. utricle and saccule otolith organs project to the ________________ to facilitate ____________________
2. crista ampulla of semicircular canals feed ____________________ to provide compensatory eye movements in response to rotation
3. ____________________________________ receives and returns inputs to fine tune coordination of postural and oculomotor reflexes
- utricle and saccule otolith organs project to the vestibulospinal tracts to facilitate a-y coactivation
- crista ampulla of semicircular canals feed medial longitudinal fasciculus to provide compensatory eye movements in response to rotation
- Flocculonodular node of cerebellum recieves and returns inputs to fine tune coordination of postural and oculomotor reflexes
what is the goal of the vestibuloocular reflex?
move extraocular eye muscles to maintain visual contact with target
what is the goal of the vestibulospinal reflex?
stabilize body
what reflex is this testing?
vestibulospinal reflex
what is activated when the head is rotated and extensors are activated on the side where the head is rotated?
vestibular nerve and nucleus
lateral and medial vestibulospinal tracts
which reflex maintains eyes on visual target while head/body is in motion?
vestibulo-ocular
which reflex does the head and neck muscles adjust to maintain head position?
vestibulo-collic
what is the goal of the vestibulocollic reflex in birds?
maintain position of head
what are the two types of vestibular syndrome?
peripheral - labyrinth within petrosal bone affected
central disease. -brain stem affected
which vestibular syndrome is head tilt associated with?
peripheral condition
which vestibular syndrome is paresis/hemiparesis and gait and posture affects associated with?
central disease
what can a middle ear infection lead to?
head tilt, pressure difference -> unbalanced action potential frequency between affected and normal ear
