Week 6 - Lecture 1 - Introduction to somatosensory nervous system

Question 1

in the brain, nerve impulses are required for

Answer 1

sensation (awareness of stimulus)

perception (interpretation of meaning of stimulus)

Question 2

Classifcation of somatosensory stimulus is based on

Answer 2

type of stimulus
location in body
structural complexity

Question 3

mechanoreceptors

Answer 3

activated by mechanical forces ( receptor stretching - membrane permeability change )

• stretch receptors of muscles
• skin receptors - respond to touch, pressure, vibration, and stretch

Question 4

Thermoreceptors

Answer 4

sensitive to changes in temperature

• cold receptors (10-40 degrees celsius) in superficial dermis
• heat receptors (32-40 degrees) ; in deeper dermis
• outside those temperature ranges - nociceptors activated - pain

Question 5

nociceptors

Answer 5

sensitive to pain-causing stimuli (eg. extreme heat or cold, excessive pressure, inflammatory chemicals )

Question 6

Exteroreceptors

Answer 6

respond to stimuli arising outside the body
receptors in skin for touch, pressure, pain and temperature
present in most special sense organs

Question 7

interoreceptors (visceroreceptors)

Answer 7

respond to stimuli arising in internal viscera and blood vessels

sensitive to chemical changes, tissue stretching and temperature changes of these organs

sometimes cause discomfort but usually we are unaware of their workings

Question 8

proprioceptors

Answer 8

respond to stretch in skeletal muscles, tendons, joints, ligament, and connective tissue coverings of bones and muscles
inform brain of one’s movements and position

Question 9

Nerve fibre types

Answer 9

Type A : largest, myelinated, rapid transmission

• Type A alpha and beta : may promote inhibitory effects to diminish pain sensation
• Type A delta : pressure, touch, cold, heat, pain

Type B : smaller than A, myelinated, slower conduction
- transmitted by cutaneous and subcutaneous mechanoreceptors

Type C : smallest, unmyelinated, slowest
- transmitted by warm -hot, mechanical, chemical, temperature induced pain

Question 10

Somatosensory processing

Answer 10

primary processing in the thalamus
processing refined in the PSC
interpretation in the somatosensory association areas

Question 11

five major somatosensory system modalities

Answer 11

discriminative touch 
proprioception (body position and motion) 
Nociception (pain and itch) 
temp
visceral function

Question 12

Acuity

Answer 12

ability to locate the site of initiation