Sensation

Question 1

what are the modalities sensed by the spinothalamic system

Answer 1

pain, temperature and crude touch

Question 2

what are the modalities sensed by the dorsal column

Answer 2

fine touch, 2 point discrimination, proprioception and vibration

Question 3

where are the cell bodies for primary sensory neurones found

Answer 3

in the dorsal root ganglion

Question 4

which sensory neurones decussate

Answer 4

secondary

Question 5

where do sensory neurones decussate

Answer 5

spinothalamic = ventral white commissure

dorsal column = medulla

Question 6

where are the cell bodies for the secondary sensory neurones

Answer 6

spinothalamic = dorsal horn

dorsal column = medulla

Question 7

where are the cell bodies for the tertiary sensory neurones

Answer 7

thalamus

Question 8

in the spinothalamic tract are fibres from higher regions added medially or laterally

Answer 8

medially

Question 9

in the spinothalamic tract are the lower fibres more medial or lateral

Answer 9

lateral

Question 10

in the dorsal column tract are fibres from higher regions added more medially or laterally

Answer 10

laterally

Question 11

in the dorsal column tract are the lower fibres more medial or lateral

Answer 11

medial

Question 12

where do the primary neurones of lower fibres in the dorsal column synapse

Answer 12

gracile nucleus

Question 13

where do the primary neurones of the upper fibres in the dorsal column synapse

Answer 13

cungate nucleus

Question 14

what is the name of the pathway of the secondary neurone in the dorsal column tract

Answer 14

medial lemniscus pathway

Question 15

what are rapidly adapting receptors

Answer 15

receptors which initially give a higher frequency of action potentials but then slows down the rate of frequency

Question 16

give an example of a rapidly adapting receptor

Answer 16

mechanoreceptors

Question 17

what are slowly adapting receptors

Answer 17

where the frequency of action potentials given off by the receptor remains the same

Question 18

give an example of a slowly adapting receptor

Answer 18

pain receptor

Question 19

what happens to the acuity with a large receptive field

Answer 19

it decreases - therefore, there a less distinct outlines of dermatomes as theres no overlap

Question 20

what is the receptive field

Answer 20

the regions containing receptors feeding back to one primary neurone

Question 21

describe the homunculus

Answer 21

lower regions of the body are projected medially on the cortex but the upper regions are projected laterally onto the cortex

Question 22

what happens if there is a lesion to the dorsal roots

Answer 22

you will lose all modalities at that level

Question 23

when does brown-sequard syndrome occur

Answer 23

when there is damage to one half of the spinal cord only

Question 24

describe the effect of brown-sequard syndrome

Answer 24

• anaesthesia across the single dermatome
• ipsilateral loss of dorsal column modalities at that level and below
• contralateral loss of spinothalamic modalities at that level and below

Question 25

what are the name of the primary neurones involved in the sensation of pain

Answer 25

C fibres

Question 26

how can the sensation of pain be inhibited

Answer 26

• mechanoreceptors
• heat
• opiates
• descending projections from the brain

Question 27

describe how mechanoreceptors inhibit pain

Answer 27

activating the mechanoreceptors by rubbing them excites inhibitory enkephalinergic interneurones which inhibit pain through activating A fibres