Session 3

Question 1

What are the different modalities of the somatosensory system?

Answer 1

Pain, temperature, pressure, vibration, 2 point discrimination, proprioception

Question 2

What is the physiological basis for different modalities and qualities of the somatosensory system?

Answer 2

Modalities - different receptors

Qualities (e.g.hot/cold) - different subtypes, how the receptor is activated

Question 3

Describe the difference between phasic and tonic receptors

Answer 3

Phasic (or rapidly adapting) - level of firing reduces. E.g. feeling clothes on body
Tonic - constant level of firing

Question 4

Describe the different functions of the dorsal column medial lemniscus pathway

Answer 4

Light touch, proprioception, vibration, 2 point discrimination

Question 5

Where do fibres from the lower half of the body travel in the dorsal column in relation to fibres from the upper part of the body?

Answer 5

Closer to the midline

Question 6

Where do fibres in the dorsal column decussate?

Answer 6

Midbrain (medial lemniscus)

Question 7

Describe the different functions of the spinothalamic pathway

Answer 7

Pain, temperature, crude touch

Question 8

Where do fibres from the lower half of the body travel in the spinothalamic tract in relation to fibres from the upper part of the body?

Answer 8

Lateral

Question 9

Describe the route of the secondary order neurone entering the spinalthalamic tract

Answer 9

Synapses with the first order neurone in the dorsal HORN on the ipsilateral side. Decussates to enter the spinothalamic tract on the contralateral side

Question 10

How does the activation of mechanoreceptors alleviate pain?

Answer 10

By exciting inhibitory enkephalinergic interneurones in the cord

Question 11

What effect does vitamin B12 deficiency have on the nervous system?

Answer 11

Causes demyelination of large nerve fibres in the spinal cord