Sensory physiology

Question 1

what two schemes are peripheral nerves classified by

Answer 1

contribution to compound AP

fiber diameter, myelin thickness, conduction velocity

Question 2

what is receptor adaptation

Answer 2

when a stimulus persists without change in position or amplitude, neural response diminishes => sensation is lost

Question 3

what receptors respond to prolonged and constant stimulation

Answer 3

slowly adapting receptors

Question 4

what receptors respond only at the beginning/end of a stimulus

Answer 4

rapidly adapting receptors

Question 5

what are mechanoreceptors responsible for

Answer 5

sense of touch

Question 6

what does meissner’s corpuscle sense

Answer 6

tap, flutter

Question 7

are meissner’s corpuscles rapidly or slowly adapting

Answer 7

rapidly adapting

Question 8

what do hair follicle receptors sense

Answer 8

motion, direction

Question 9

are hair follicle receptors rapidly or slowly adapting

Answer 9

either slow or rapidly adapting

Question 10

what do pacinian corpuscles sense

Answer 10

vibration

Question 11

are pacinian corpuscles rapidly or slowly adapting

Answer 11

rapidly adapting

Question 12

what do Merkel discs sense

Answer 12

touch, pressure

Question 13

are merkel discs rapidly or slowly adapting

Answer 13

slowly adapting

Question 14

What do ruffini corpuscles sense

Answer 14

skin stretch

Question 15

are ruffini corpuscles rapidly or slowly adapting

Answer 15

slow adapting

Question 16

where are receptive fields largest

Answer 16

calf, back and thigh

Question 17

what stimuli initiates pre-synaptic inhibition?

Answer 17

GABA => influx of Cl-

Question 18

what improves the brain’s ability to localize signals?

Answer 18

reduced NT release secondary to presynaptic inhibition

Question 19

what are the three steps of cortical processing

Answer 19

initial processing
integration
emotional response

Question 20

how does an amputation affect the homonculus?

Answer 20

because input to the leg is restricted, the portion of cortex devoted to that region decreases

Question 21

what are the main output neurons of the cortex

Answer 21

pyramidal cells

Question 22

what layers of the cortex are enlarged in the primary sensory cortex and why

Answer 22

layer III (medium sized pyramidal cell layer)
layer IV (granular layer)
because axons from the thalamus terminate in these layers

Question 23

through what layers of the cortex do the neuronal columns extend

Answer 23

all of them, 1-6

Question 24

how are neuronal columns organized functionally?

Answer 24

neighboring columns receive sensory information from the same part of the body, but a different modality

Question 25

what are the three parts of the somatosensory cortex

Answer 25

``` primary area (SI) secondary area (SII) association area ```

Question 26

what brodmann areas make up the primary somatosensory cortex

Answer 26

1,2,3

Question 27

which part of the somatosensory cortex is responsible for proprioception and size/shape discrimination

Answer 27

SI

Question 28

which part of the somatosensory cortex is responsible for comparison btwn objects and tactile sensations and determining whether a memory is stored

Answer 28

SII

Question 29

where is S2

Answer 29

in the wall of the sylvian fissure

Question 30

which part of the somatosensory cortex names objects and helps w proprioception

Answer 30

parieto-temporal-occipital (PTO) association cortex

Question 31

what characteristic of SI allows focusing activities

Answer 31

projections sent back to the thalamus and other subcortical structures

Question 32

how are primary and association areas of the sensory cortex linked?

Answer 32

via cortico-cortical projections

Question 33

are cortico-cortical projections on the same between the same or opposite hemispheres

Answer 33

either!

Question 34

what are corticofugal signals

Answer 34

signals transmitted cortex => postcortical structures to inhibit and suppress sensory input

Question 35

what is the difference between nociception and pain

Answer 35

pain is the SENSATION of tissue damage | nociception is the autonomic or behavioral conseqences of tissue damage

Question 36

what fibers carry slow pain

Answer 36

C

Question 37

what fibers carry fast pain

Answer 37

Adelta

Question 38

are axons of nociceptors typically myelinated?

Answer 38

no, usually unmyelinated or thinly myelinated

Question 39

what are free nerve endings

Answer 39

nerve endings which lack specialized receptor cells or encapsulations

Question 40

what kind of free nerve endings express substance P and cGRP

Answer 40

peptidergic

Question 41

what stimulus do peptidergic nerve endings respond to

Answer 41

NGF (nerve growth factor)

Question 42

what stimulus do non-peptidergic nerve endings respond to

Answer 42

GDNF (glial-derived neurotrophic factor)

Question 43

what kind of nerve endings are implicated in diabetic neuropathy

Answer 43

non-peptidergic

Question 44

what receptors sense noxious stimuli?

Answer 44

TRP receptors

Question 45

what is the MOA of TRP receptors

Answer 45

ligand-gated non-selective cation channels permeable to Ca, Na and K

Question 46

describe the gate control theory of pain

Answer 46

in the absence of pain signalling, tonically active inhibitory neurons suppress the pain pathway

Question 47

what function does the insular cortex have in the pain pathway

Answer 47

it integrates all signals related to pain

Question 48

what structure is important to the emotional component of pain

Answer 48

amygdala

Question 49

what is the underlying premise to referred pain

Answer 49

afferents from the injured site and site of referred pain converge in the dorsal horn

Question 50

what part of the cortex is most important for interpretation of nociception

Answer 50

insular cortex

Question 51

what ligand do we need to know that propagates neurogenic pain

Answer 51

BRADYKININ (increases nociceptor density in area of inflammation)

Question 52

what is the path of descending inhibition

Answer 52

periaqueductal grey matter => locus coerulus and raphe nucleus release NE/serotonin => activate local inhibitory interneurons

Question 53

what fibers are activated by rubbing an area of pain, and how does it reduce sensation of pain

Answer 53

Abeta fibers activate inhibitory interneurons

Question 54

do Adelta fibers react to substance P and CGRP?

Answer 54

no, only C fibers do

Question 55

does EAA bind to NMDA or non-NMDA receptors

Answer 55

non-NMDA

Question 56

what TRP receptor is activated by physical heat and capsacin

Answer 56

TRPV1

Question 57

what TRP receptors is activated by menthol and cold

Answer 57

TRM8

Question 58

what neuropeptides are expressed by peptidergic nerve endings

Answer 58

substance p | CGRP