NS: Peripheral Somatosensation

Question 1

What is peripheral somatosensation?

Answer 1

Information from skin and musculoskeletal system conveyed to the spinal cord

Question 2

What is the general purpose of Somatosensation?

Answer 2

• Investigate the world
• Move accurately
• Avoid/minimize injuries

Question 3

Explain tonic vs phasic receptors and provide examples of both

Classification of sensory receptors

Answer 3

Tonic - respond the entire time a stimulus is present
E.g., pain

Phasic – adapt; stop responding while stimulus is still present
E.g., putting on a watch, and you aren’t aware of it anymore unless you direct attention towards it

Question 4

What type of neuron is the 1st order neuron?

Answer 4

Pseudounipolar - has 2 axons, central (goes into spinal cord from the T junction) & peripheral (goes to the T junction from the free nerve endings)

free nerve ending (peripheral axon) –> T junction (soma) –> spinal cord (central axon)

Question 5

True or false: The soma is located inside the spinal cord in the dorsal root ganglion

Answer 5

False: soma is locaed doutside the spinal cord in the dorsal root ganglion

Question 6

True or False: a type III fiber is larger in diameter and therefore has faster conduction velocities than a type Ib fiber

Answer 6

False: it is smaller in diameter and slower compared to type Ib

Ia - Ib - II - III - IV

(largest to smallest)
larger diameter = faster conduction velocities

Question 7

When Karen accidentally hit her hip on the edge of a counter, she immediately rubbed the painful area. Explain why rubbing the area helps with the pain.

Answer 7

Nociceptive receptors are being activated when hitting her hip, by providing mechanical stimulus (fibers with larger conduction velocity) will travel faster than the pain receptors

Gate control theory – has been disputed, both signals are reaching brain and being integrated and ALTERS the experience of pain (other signal still getting through!! Its NOT blocking the pain)

Question 8

Why would sensation be more accurate in the finger tip than at the calf?

Answer 8

Discriminative touch:
More innervation in the hand compared to calf -> smaller receptive fields in hand

Much more likely to land on 2 different receptive fields on the finger than on the calf it might feel like the same receptive field

Question 9

What does a muscle spindle detect? Function?

Answer 9

absolute muscle length, changes in muscle length

function:
- spinal level = stretch reflex
- ascending = regulates muscle length during mov’t; constributes to sense of effort

Question 10

What do the golgi tenon organ detect? Function?

Answer 10

detects muscle tension

function:
- spinal level = inverse stretch reflex autogenic
Inhibition (protective response)
- Ascending = modulate muscle output in response to fatigue

Question 11

What do the joint receptors detect? Function?

Answer 11

Detects deformation of the structures in which they are embedded

Function: minor influence on perceived joint angle (especially durinig rapid mov’ts)

function is still debated

Question 12

What do the cutaneous receptors detect?

Answer 12

Detects: Pressure, vibration, temperature, tissue damage

Function:
* Spinal level = placing reaction and
withdrawal reflex movements
* Ascending = info. about body position
for orientation within environment

Question 13

Describe the somatosensory pathway

Answer 13

• The 1st order neuron/primary afferent enters through the dorsal root into the dorsal horn of the spinal cord –> brainstem
• 2nd order neuron travels from the brainstem to the thalamus
• 3rd order neuron travels from the thalamus to the cerebral cortex

slides has a better table/diagram