Lecture 29: Transmission 2

Question 1

Whats of note about somatosensory organisation for mechanoreception;

Answer 1

Amount of input = size of dedication

Somatotopic mapping exists from neuron to brain and different types of information have different pathways

Question 2

Describe some cytoarchitecture of the dorsal horn;

Answer 2

Sensory neurons enter the dorsal horn and terminate around lamaelle 3-4 but there are interneurons between sensory types

Question 3

What are the types of first order neurons?

Answer 3

Psuedounipolar nuerons
Bifurcating fibres

Reflex pathways start here

Question 4

Write notes on pseudounipolar neurons;

Answer 4

◦Pseudounipolarneurons
Cell bodies located in dorsal root ganglia
Enters via medial dorsal roots of spinal nerve
Bifurcates at the posterior funiculus (sensory intergration, descending regulation)

Question 5

Write some short notes on bifurcating fibres;

Answer 5

Bifurcating fibers
Long ascending and short descending
Dorsal Column Pathway
Fasciculus Gracilis(below T6) or Cuneatus(above T6) (first segregation of info)
Gracilis medial DRG and Cuneatuslateral DRG
Connects to interneurons and motorneurons

Question 6

What are the gracalis and cutaneous nuclie?

Answer 6

The first relay stations! first order neurons terminate here and cell bodies of the second order neurons are located here.

Question 7

What are the internal arcuate fibres?

Answer 7

Decussation!!!

• Fibers of second order neurons
• Travel ventromedially through reticular formation
• Moves to contralateralside

Question 8

Whats the medial laminiscus pathway?

Answer 8

Medial Lemniscus

• On contralateralside second order fiber’s pathway
• Ascends through Caudal and Rostralmedulla, Pons and Midbrain
• Synapses with Third Order Neurons in Thalamus
• Topographic map reverses
• Trigeminal lemniscus

Question 9

Whats the function of second order nuerons?

Answer 9

The first relay station is able to modulate activity using interneurons to increase or decrease firing of second order neurons/relay stations adjacent to the main (highest rate of firing) receptors second order neuron / relay station

i.e precise sensation (sharpness of info) vs not

Question 10

What is the theory of feedback and feedforward circuitary;

Answer 10

Inhibitory interneurons sharpen contrast between stimuli

this occurs at the relay stations

Question 11

Whats the second order relay station / 2nd 3rd junction?

Answer 11

Ventral Posterior Lateral Nucleus

Second order neurons terminate in Nucleus
Cell Bodies of Third order neurons in Nucleus
Information from leg in lateral, arms in medial and face most medial

Topographic mapping still here (all nuclie are)

Question 12

Where do the third order neurons project through?

Answer 12

Posterior limb of the Internal Capsule
Fibers from Third order ascend
And the Corona Radiata

Question 13

Where do third order neurons terminate?

Answer 13

PostcentralGyrus

- Terminating in the somatosensory cortex

Question 14

What are the areas of the primary somatosensory cortex?

Answer 14

1,2,3a,3b

Question 15

Write notes on broadmans area 3b;

Answer 15

Most projections from VPLN
Initial processing of tactile discrimination
Projects to Brodmann’sarea 1 and 2 (major)
Two columns Rapid and slow adapting

Question 16

Write notes on broadmans area 1,2

Answer 16

Brodmann’sArea 1 & 2
Area 1 responsible for Texture; mainly rapid adapting
Area 2 responsible for size and shape of objects

Question 17

Write notes on the secondary somatosensory cortex;

Answer 17

Secondary Somatosensorycortex;
Superior border of lateral fissure
Primary cortex projects to secondary
Some third order neurons directly synapse

Question 18

Whats topographicly mapped?

Answer 18

Everything

Question 19

What does the secondary somatosensory cortex project to?

Answer 19

The hippocampus ad amagdyla (memory formation)

Question 20

What does the boadmans area 2 project to?

Answer 20

Parietals area 5,7

then to motor and premotor cortices