Sensory Physiology

Question 1

What do Aalpha afferent neurons do?

Answer 1

large and fast

supply primary muscle spindles, golgi tendon organs

Question 2

What do Abeta afferent fibers do?

Answer 2

secondary muscle spindles

skin mechanoreceptors

Question 3

What do Aa motor fibers supply?

Answer 3

extrafusal sk m fibers

Question 4

What do Agamma fibers supply?

Answer 4

intrafusal fibers

Question 5

What do B motor fibers supply?

Answer 5

preganglionic autonomic fibers

Question 6

What do c motor fibers supply?

Answer 6

postganglionic autonomic fibers

Question 7

What is a generator potential and how does it vary?

Answer 7

somatosensory’s response to a stimulus

small with weak stim

strong stim –> large generator potential –> action potential

Question 8

What is the significance of the thalamus in sensory systems?

Answer 8

info from all sensory systems except olfactory are relayed through the thalamus on way to cerebral cortex

Question 9

What is convergence?

Answer 9

branches of 2 different primary afferents synapse on one secondary

Question 10

What is divergence?

Answer 10

one primary neuron has 2 branches that synapse on 2 different secondaries

Question 11

What are the 2 ways to get a strong stimulus?

Answer 11

all branches of one afferent or branches from multiple afferents converging

Question 12

How do the number of active receptors change with intensity of stimulus?

Answer 12

increase in number w/ intensity

Question 13

What is receptor adaptation?

Answer 13

when a stimulus persists unchanged for several min w/out change in position or amplitude –> neural response diminishes and sensation is lost

Question 14

What are slow adapting and rapidly adapting receptors?

Answer 14

slow adapting: responde to prolonged and constant stim

rapidly adapting: only active at beginning or end of stimulus - when intensity increases or decreases

Question 15

What are the rapidly adapting receptors and what they sense?

Answer 15

meissner corpuslce - tap, flutter

hair follicle receptor (can also be SA) - motion, direction

pacinian corpuscle - vibration

Question 16

What are the slowly adapting receptors and what they sense?

Answer 16

hair follicle (can also be RA) - motion, direction

merkel disk - touch, pressure

ruffini corpuscle - skin stretch

Question 17

What is the relationship btw tactile and acuity and receptive fields

Answer 17

acuity highest in smallest fields (lips)

acuity lowest in largest fields (back)

Question 18

What is the relationship btw convergence and tactile acuity?

Answer 18

more convergence –> less acuity

Question 19

What is pre-synaptic inhibition?

Answer 19

powerful form of inhibitory control

diminished excitatory signal: GABA –> Cl influx –> hyperpolarization –> less NT release

Question 20

How does presynaptic inhibition help you?

Answer 20

helps the brain not get overwhelmed –> can localize signal betters

Question 21

Are somatotopic maps fixed?

Answer 21

no

continual imput can magnify its map

restricted input decreases part of cortex devoted to that region

Question 22

What layers of the cortex are enlarged in sensory cortexes?

Answer 22

3 and 4 –> main site of axons from the thalamus

Question 23

How are neurons arranged in regard to depth?

Answer 23

neurons stacked above and below are very similar

columns side by side are different (explains homunculus) - usually same part of body, but different sensory modality

Question 24

Where is the primary somatosensory cortex

Answer 24

post-central gyrus

first stop for most cutaneous senses

Question 25

Where is the secondary somatosensory cortex?

Answer 25

in wal of sylvian fissure receives input from S1 --\> compares btw objects, diff tactile sensations and det whether something becomes a memory

Question 26

What is the PTO?

Answer 26

parieto-temporal-occipital association cortex input from multiple places --\> high level interpretation of sensory inputs

Question 27

What does S1 send projections to?

Answer 27

back to subcortical structures usually thalamus descending axons \> ascending permits focusing activities

Question 28

What do cortico-cortico projections do?

Answer 28

est parallel paths of sensation allows for simultaneous processing can be ipsi or contra

Question 29

What are corticofugal signals?

Answer 29

cortex --\> lower relay controls intensity of sensory sensitivity typically inhibitory

Question 30

What is the doctrine of specific nerve energies?

Answer 30

no matter where along the afferent path is stim, sensation will occur and will arise from origin of sensation

Question 31

What type of pain does Adelta encode?

Answer 31

quick pain

Question 32

What type of pain do C fibers encode?

Answer 32

slow pain

Question 33

What are the different modes of nociception?

Answer 33

thermal mechanical chemical receptors can be polymodal can be silent and then turned on

Question 34

What are the 2 types of free nerve endings?

Answer 34

peptidergic: express substance P, CGRP, responsive to NGF most visceral afferents, 1/2 of cutaneous afferents non-peptidergic: no neuropeptides, responsive to GDNF, 1/2 of cutaneous afferents

Question 35

What are TRP receptors?

Answer 35

sense noxious stimuli ligand-gated non-selective cation channels activated in response to temp (menthol, capsaicin)

Question 36

What do C and Adelta use as NTs?

Answer 36

C = EAA and SP/CGRP Adelta = EAA

Question 37

What is descending inhibition?

Answer 37

signals from higher brain that dampens pain input PAG stim by opiates, EAA, and cannabinoids --\> locus coeruleus and raphe nucleus --\> 5HT and NE --\> dorsal horn --\> activate inh interneurons --\> opiates --\> reduction of SP from C fiber --\> reduces nociception

Question 38

What is the gate control theory of pain?

Answer 38

C fiber to 2ndary neuron and also to interneuron that inhibits 2ndary neuron to reduce pain signals w/ strong pain - C fiber releases glycine --\> inhibits interneuron --\> EAA to secondary nerve --\> pain Abeta fiber can also stimulate the interneuron at the same time --\> inhibits secondary neuron (like when you rub your finger when you smash it)

Question 39

What is sub-threshold inflammation?

Answer 39

not apparent on histology but still causes pain bradykinin involved

Question 40

What parts of the cortex are important in processing pain?

Answer 40

S1 and S2 - localization insular cortex - integrates all signals, damage causes asymbolia

Question 41

What does the amygdala do in pain?

Answer 41

emotional component

Question 42

What do the hypothalamus and medulla do in pain?

Answer 42

visceral input w/ autonomic nerves --\> hypothalamus and medulla --\> physio changes