Sensory physiology Flashcards
How are peripheral ns. classified
action potential and fiber properties
What is the largest sensory afferent fiber type
Ia
What is the fastest sensory afferent fiber type
Ia
What is the slowest and smallest afferent fiber type
C
What kind of receptors respond to prolonged and constant stimulation
SA Receptors
What kind of receptors respond only at the beginning or end of a stimulus
RA receptors
What kind of receptor is a Meissner corpuscle
RA
What sensation is sensed by a Meissner corpuscle
tap/flutter
What type of receptor is a hair follicle
RA/SA
What type of sensation is felt by a hair follicel
motion/direction
What type of receptor is a pacinian corpuscle
RA
What is felt by a pacinian corpuscle
vibration
What type of receptor is a merkel disc
SA
What is felt by a merkel disc
touch/pressure
What type of receptor is a ruffini corpuscle
SA
What is felt by a ruffini corpuscle
skin stretch
What receptor types have large field sizes
Ruffini corpuscle
Pacini corpuscle
What receptor types have small field sizes
Merkel disc
Meissner corpuscle
What is presynaptic inhibition
neurotransmission controlled by pre and post synaptic inhibitory mechanisms, most powerful form. GABAergic associated of Cl, results in hyperpolarization and less NT release.
What is the function of a presynaptic inhibition
Reduces NT release, improves brains ability to localize signal
How many layers are in the cortex
6
What layers are enlarged in primary sensory cortex
3 and 4
What are the main sites of termination of axons from thalamus in the cortex
III and IV
What are the main type of output neurons
pyramidal cells
What type of neurons are stacked above and below each other
are fundamentally similar
What type of neurosn are stacked side by side
significantly different
Where is S1 located
postcentral gyrus
What is the function of S2
Cognitive touch, comparisons between objects, different tactile sensations and determining whether something becomes a memory
Function of S1
Integration of info for position sense as well as size and shape discrimination
Function of parieto-occipital-temporal association cortex
analyzes spatial coordinates of self, so names of objects, etc.
Function of corticofugal signals
from cortex to relay stations in thalamus/medulla/SC
Control intensity of sensory sensitivity, and typically inhibit/suppress sensory input.
What is the law of projection
no matter where on afferent pathway is stimulated, perceived sensation is from origin of sensation (like thumb or something)
What is the law of specific nerve energies
no matter where along afferent pathway is stimulated, sensation that will occur is determined by nature of sensory receptor in periphery connected to it
What is pain
unpleasant sensory and emotional experience associated with actual /potential tissue damage
What is nociception
neural process of encoding noxious stimuli. May be autonomic/behavioral. Pain not be a factor.
Pain fibers tend to have what types of afferent fibers
C and Adelta
What neuropeptides are expressed in peptidergic free nerve endings
substance p
CGRP
What are peptidergic neurons responsive to
NGF
Where are peptidergic free nerve endings typically found
most of visceral
half of cutaneous afferents (chronic infl. and visceral pain)
What is non-peptidergic free endings responsive to
GDNF
Where are non-peptidergic free endings found
few visceral
half of cutaneous afferents (diabetic neuropathy)
What does TRPV1 respond to
capsaicin
What does TRPA1 respond to
mustard stuff
What does TRPM8 respond ot
menthol
What is the purpose of the TRP receptors
ligand-gated nonselective cation channel that is permeable to Ca, Na or K
What are some other signaling modalities that sense pain
SP *CGRP
Histamine
Kinins
What do C fibers respond to
EAA and SP/CGRP
What do Adelta fibers respond to
EAA
What is the gate control theory
absence of input from C fibers, tonically active inhibitory interneuron suppresses pain pathway (turns interneuron on that has inhibitory function) Known as Abeta fibers
What is descending inhibition
activated by opoiates/ eaa/cannabinoids
Descends to LE or Raphe nucleus
serotonin and NE release into dorsal horn and activate inhibitory interneurons
release opiates, that activate mu receptors on C fiber, reduces SP from C fiber and reduces nociception
What is another chemical that can cause pain because of molecular inflammation
bradykinin, which increases excitability and facilitates activation of dorsal horn neurons
What is the function of the insular cortex
interpret nociception, integrates all signals related to pain
What is asymbolia
damage to insular cortex that means you can feel pain, but don’t care about it
What is the function of the amygdala regarding pain
emotions associated with it
Where does visceral input go for pain
hypothalamus and medulla, integrates physiological changes
What type of pain is cutaneous
fast pain and slow pain
What type of pain is deep pain (periosteum, etc.)
usually dull and achy, muscle spasms
What type of pain is muscle (injury/ischemia)
fast pain and slow pain
What type of pain is visceral
poor localization, sensitive to stretch, referred pain.
