2 - Somatosensory system 1

Question 1

What are the somatic senses?

Answer 1

• Pain
• Temperature
• Pressure
• Stretch
• 2-point discrimination
• Vibration

Question 2

Which receptors detect pain?

Answer 2

Nociceptors

Question 3

Which receptors detect temperature?

Answer 3

Thermoreceptors

Question 4

Which receptors detect pressure on skin?

Answer 4

Pacinian corpuscles

Question 5

Which receptors detect stretch?

Answer 5

Ruffini nerve endings

Question 6

What is meant by a tonic receptor? Give an example:

Answer 6

Slow adapting, continue to fire APs as long as stimulus continues

• Nociceptors
• Muscle spindle
• Golgi tendon

Question 7

What is meant by a phasic receptor? Give an example:

Answer 7

Fast adapting, freq of APs decrease over time even if stimulus is unchanged
All mechanoreceptors:
- Pacinian corpuscle
- Baroreceptors

Question 8

What type of receptors are fast adapting? What does this mean?

Answer 8

Phasic receptors
Freq. of APs decrease over time even if stimulus is unchanged = we can adapt to certain sensory stimuli
ie Pacinian corpuscles

Question 9

What type of receptors are slow adapting? What does this mean?

Answer 9

Tonic receptors
Freq. of APs continues as long as stimulus continues = we cannot adapt to certain stimuli ie pain
ie Nociceptors

Question 10

What is the 1st law of the somatosensory system?

Answer 10

1st order neurone is receptor, and has cell body in dorsal root ganglion of spinal cord

Question 11

What is the 2nd law of the somatosensory system?

Answer 11

2nd order neurone crosses the midline and passes up to thalamus

Question 12

What is the 3rd Law of the somatosensory system?

Answer 12

3rd order neurone passes from thalamus to sensory cortex via corona radiata

Question 13

Which order neurone in the somatosensory system is the receptor?

Answer 13

1st order neurone

Question 14

Which order neurone in the somatosensory system crosses the midline? Where does this neurone end-synapse?

Answer 14

2nd order neurone

Thalamus

Question 15

Which order neurone in the somatosensory system delivers sensory information to the cortex?

Answer 15

3rd order neurone

Question 16

Receptors of the somatosensory system have cell bodies…

Answer 16

in the dorsal root ganglion of spinal cord

Question 17

What factors affect the acuity of a somatic receptor?

Answer 17

• Receptive field
• Density of receptors
• Lateral inhibition

Question 18

In which parts of the body do somatic receptors have high acuity? (^density, low receptive field)

Answer 18

• Hands

- Face

Question 19

What is the relationship between acuity and receptive field?

Answer 19

Acuity is inversely proportional to the size of the receptive field
- ^ acuity if small receptive field

Question 20

What is meant by lateral inhibition?

Answer 20

The primary neurone which is MOST stimulated by the stimulus can inhibit lateral neurones, allowing localisation of the stimulus

Question 21

How do inhibitory neurones help us localise a stimulus?

Answer 21

Lateral inhibition
The primary neurone which is MOST stimulated by the stimulus can inhibit lateral neurones, allowing localisation of the stimulus

Question 22

Why is there a large representation of the face and hands on the cortical homunculus?

Answer 22

Representation of each body part is proportional to the density of receptors in that region
^density receptor on face/hands = ^representation

Question 23

Which areas of the body are represented on the medial aspect of the cortical homunculus?

Answer 23

Lower limb + genitals

Question 24

Which areas of the body are represented on the upper lateral aspect of the cortical homunculus?

Answer 24

Trunk + Upper limb

Question 25

Which areas of the body are represented on the lower lateral aspect of the cortical homunculus?

Answer 25

Face

Question 26

Describe the area of the brain responsible for the motor function of swallowing:

Answer 26

Lower lateral aspect of the pre-central gyrus (primary motor cortex)
- Frontal lobe

Question 27

Describe the area of the brain responsible for the motor function to bend the knee:

Answer 27

Medial aspect of pre-central gyrus (primary motor cortex)

- Frontal lobe

Question 28

Describe the area of the brain responsible for detecting a change in pressure on the feet:

Answer 28

Medial aspect of the post-central gyrus (primary somatosensory cortex)
- Parietal lobe

Question 29

Describe the area of the brain responsible for detecting a change in temperature in the hands:

Answer 29

Middle lateral aspect of the post-central gyrus (primary somatosensory cortex)
- Parietal lobe

Question 30

Describe the area of the primary motor cortex:

Answer 30

Pre-central gyrus, frontal lobe