B.33 Somatosensation

Question 1

Receptive Field

Answer 1

-part of receptor surface that elicits response in particular neuron in response to stimulus

Visual:
- retina which activates visual Neuron when stimulated

Somatosensory:
- skin portion that activates somatosensory neuron

Question 2

Body Schema

Answer 2

• subconscious
• representation of body parts in space
• „updated“ during movement
• used for spatial organisation of actions -> postural
• considered Bottom -Up*

Question 3

Body Image

Answer 3

• feeling what body is like
• personal perception
• can be altered-> for example thumb feels bigger when hurt or anaesthetics used
• considered Top-Down”
• conscious

Question 4

Cortical magnification

Answer 4

• proportion of cortex dedicated to body parts
• > related to sensitivity not to size of body part - I.e fingertips, lips big representation , trunk and legs small

Low magnification In cortex = larger receptor fields for that body part = fewer Neurons involved and vice versa

Question 5

Somatotopy

Answer 5

• means spatial topography in brain is preserved, I.e. adjacent parts represented by adjacent cortex position

Question 6

Wilder Penfield

Answer 6

• Canadian neurosurgeon
• mapped functions of various brain regions (cortical homunculus)
• stimulation studies, helped define primary somatosensory cortex -> patients with epilepsy, local anaesthetic, electrically stimulates area to find problem while patient conscious

Question 7

Afferent vs Efferent

Answer 7

Nervefibres!

Afferent :
Incoming signal, peripheral to brain and cns

Efferent:
Outgoing signal

in the CNS, afferent and efferent projections can be from the perspective of any given brain region. That is, each brain region has its own unique set of afferent and efferent projections. In the context of a given brain region, afferents are arriving fibers while efferents are exiting fibers.

Different in PNS:
The efferent fiber is a long process projecting far from the neuron’s body that carries nerve impulses away from the central nervous system toward the peripheral effector organs (mainly muscles and glands). A bundle of these fibers is called a motor nerve or an efferent nerve. The opposite direction of neural activity is afferent conduction,[1][2][3] which carries impulses by way of the afferent nerve fibers of sensory neurons.

Question 8

Cortical plasticity

Answer 8

• monkeys fingers sewn together, had clear boundaries in cortical representation but after few weeks boundary blurred -> from cortical perspective it is one finger
  ! Shows that map is not static
  !temptoal and environmental factors contribute to cortical change