7.3 Somatosensory System

Question 1

What is the direction information passes thought a neuron?

Answer 1

Dendrite - cell body - axon

Question 2

What kinds of neurons are primary sensory, interneurons and motor neurons?

Answer 2

Primary sensory: unipolar or pseudounipolar
Interneurons: bipolar
Motor neurons: multipolar

Question 3

How is the unipolar sensory neuron distributed?

Answer 3

the nerve endings with specalised sensory receptors, cell bodies in the peripheral ganglia and the central processes enter the CNS and synapse

Question 4

How do we discriminate different information?

Answer 4

Receptor type, fibre type and pathways

Question 5

What are the nerve endings in Glabrous skin?

Answer 5

Meissner (FA1/RA)
Pacinian (FA2/PC)
Merkel (SA1)
Ruffini (SA2)
Free nerve endings

Question 6

What are the nerve endings in hairy skin?

Answer 6

Hair follicle afferents
Merkel (SA1)
Ruffini (SA2)
Free nerve endings

Question 7

Where are the nerve endings located ?

Answer 7

Meissner, Merkel superficial

Pacinian and Rufini deep

Question 8

Which receptors transmit fine touch information?

Answer 8

Meissner and Merkel

Question 9

What type of receptor, where, what do they respond to and function - Meissner

Answer 9

FA1, glaborous skin and upper dermis, change in pressure, fine touch (texture and motion)

Question 10

What type of receptor, where, what do they respond to and function - Pacinian

Answer 10

FA2, glaborous skin , deep dermis, changes in pressure, event detection, high frequency vibrations

Question 11

What type of receptor, where, what do they respond to and function - Merkel

Answer 11

SA1, glaborous and hairy skin, upper dermis, pressure status, fine touch (shape/form of edges and points/dots)

2nd derivative discrimination

Question 12

What type of receptor, where, what do they respond to and function - Ruffini

Answer 12

SA2, glaborous and hairy skin, lower dermis, skin stretch, proprioception

Question 13

What type of receptor, where, what do they respond to and function - free nerve endings

Answer 13

galborous and hairy skin, upper dermis, mechanical, temperature, tissue damage, sensitisation

Function: noxious hot/cold, mechanical trauma, itch and chemical irritants

Question 14

What influences the sensitivity of the skin?

Answer 14

type of receptor, numerical density and distribution

Question 15

What are the proprioceptors and what is their respective function?

Answer 15

Golgi tendon organs (1b): sense tension (force of contraction or stretch); inhibits alpha motor neuron activity to reduce muscle tone

Muscle spindles (1a and IIa): sense stretch in the muscle length, results in activation of alpha motor neurons to initiate the jerk/myotatic reflexes

Question 16

Where do sensory fibres have their cells bodies and where do they enter the spinal cord?

Answer 16

DRG

A central process that enters the spinal cord ini the dorsal horn

Question 17

Where do large diameter fast conducting nerves send their information?

Answer 17

DORSAL COLUMNS

Question 18

Where do small diameter, slow conducting fibres send their information?

Answer 18

Spinothalamic

Question 19

Where does all sensory information pass through?

Answer 19

Thalamus

Question 20

What information does the Ventral posterolateal thalamus receive?

Answer 20

Afferents from the entire body

Question 21

What information does the VPM region of the thalamus recurve

Answer 21

Information from the face via the trigeminal

Question 22

What does the anterior group of the thalamus do?

Answer 22

Attention and learning

Question 23

What does the medial thalamus do?

Answer 23

Planning and active memory

Question 24

What are the inputs and outputs to the VPL

Answer 24

In - medial lemniscus and spinothalamic tract (spinal nerves from limbs and trunk)
Out - somatosensory cortex

Question 25

What are the inputs and outputs for the VPM

Answer 25

In - medial lemniscus and trigeminal system (face, ocular surface, tongue, oral cavity and masa, cavity)
Out - somatosensory

Question 26

What information travels where in the dorsal column system?

Answer 26

Gracile from lower body

Cuneate from upper

Question 27

Where does information from the dorsal column system go?

Answer 27

Comes in the medulla, form and accurate course to the medial lemniscus on contra lateral side, ascend through brainstem and end up on the VPL before projecting to the primary somatosensory cortex

Question 28

What are broad and areas of the primary somatosensory cortex?

Answer 28

1: cutaneous (FA1 and 2)
2: deep receptors from muscles/joints/some cutaneous
3a: mainly muscle spindles
3b: mainly cutaneous (RA1 and SA1)