B7.004 Prework 1: Somatosensory Receptors

Question 1

3 main somatic modalities

Answer 1

discriminative touch
pain and temp
unconscious proprioception

Question 2

discriminative touch

Answer 2

touch
pressure
vibration
conscious proprioception

Question 3

unconscious proprioception

Answer 3

information about muscle stretch, joint position, and tendon tension

Question 4

cutaneous receptor types

Answer 4

mechanoreceptors
thermoreceptors
nociceptors

Question 5

proprioceptive receptors

Answer 5

muscle spindles

Golgi tendon organs

Question 6

variation among mechanoreceptors in skin

Answer 6

1. location of skin (body area and depth)
2. size of receptive field
3. duration of AP activity (slow/fast adaptability)

Question 7

types of cutaneous tactile receptors

Answer 7

Meissner corpuscle
Pacinian corpuscle
Ruffini corpuscle
Merkel's disks
free nerve endings
hair follicle endings
Krause corpuscle

Question 8

fiber type of discriminative touch receptors

Answer 8

A-beta

Question 9

hair follicle ending

Answer 9

function: hair displacement
location: hair follicle in hairy skin

Question 10

Ruffini endings

Answer 10

function: stretch/ pressure on skin
location: dermis of hairy/glabrous skin
medium sized fields, oriented to detect movement across skin

Question 11

Krause corpuscle

Answer 11

function: pressure
location: lips, tongue, genitals

Question 12

Pacinian corpuscle

Answer 12

function: vibration, deep pressures
location: deep dermis of hairy/glabrous skin
large, rapidly adapting fields

Question 13

Meissner corpuscle

Answer 13

function: vibration
location:dermis of glabrous skin
small, rapidly adaptive fields

Question 14

Merkel cells

Answer 14

function: pressure
location: epidermis of glabrous skin
small, slowly adapting fields

Question 15

variation in receptive fields of mechanoreceptors

Answer 15

different sizes
proportional to density / central map
(small central fields, dense innervation = large map)

Question 16

descriptions of nerve endings for pain and temperature

Answer 16

free endings
A-delta and C fibers
respond to mechanical, thermal, or noxious stimulation
located everywhere

Question 17

description of muscle spindle receptors

Answer 17

predominant stretch receptor in muscles
oriented in parallel with extrafusal fibers
typical limb muscle has 300-400 muscle spindles

Question 18

functional role of muscle spindle afferents

Answer 18

feedback to the cerebellum about muscle length and velocity
joint position sense
-extremes of joint position, not good sensors, low acuity
-tendon vibration
-pull on tendons in humans
servo-assistance of movement

Question 19

function of Golgi tendon organs (GTO)

Answer 19

monitor stresses and forces (tension) at the tendon

no motor component

Question 20

description of GTO

Answer 20

encapsulated structure containing elastic fibers that insert on 10-20 extrafusal muscle fibers
in series with extrafusal muscle fibers
bypassed by 99% of muscle fibers
innervated by group Ib afferents

Question 21

speed of electrical activity in primary afferent nerve axons

Answer 21

conduction velocity
depends on:
-fiber diameter
-myelination
fastest are largest and most myelinated

Question 22

list the fiber types from fastest to slowest

Answer 22

A- alpha : mechanoreceptor
A- beta: mechanoreceptor
A- gamma: mechanoreceptor
A- delta: nociceptors, thermal
C (unmyelinated): nociceptors, thermal

Question 23

give a general description of the 3 neuron pathways for perception

Answer 23

1st order - starts in periphery and terminated in dorsal roots
2nd order - starts in dorsal root, crosses spinal cord, terminates in thalamus
3rd order- starts in thalamus, terminates in somatosensory cortex

Question 24

dorsal column - medial lemniscus pathway

Answer 24

discriminative touch

proprioception

Question 25

anterolateral system

Answer 25

temperature
pain
very low acuity mechanosensation