Somatosensory Systems

Question 1

What are the X5 somatosensations?

Answer 1

Touch
Pain
Non-painful visceral sensation
Itch
Proprioception

Question 2

What are the X4 mechanisms of sensation?

Answer 2

1) transduction= converting stimuli to electrical activity
2) transmission = moving the signal to the brain
3) perception = consciously being aware of the stimuli
4) modulation = an effector response to the stimuli

Question 3

What are the main categories (and subcategories) of sensory axon fibres?

Which of these is the fastest and slowest?

Which of these are myelinated?

Answer 3

A alpha = fastest
A beta
A delta
C = slowest

The A fibres are all myelinated

Question 4

What are the X4 properties of a stimulus that receptors respond to?

What do each of these mean?

Answer 4

1) modality = receptors only respond to their own type of adequate stimuli
2) intensity = this is encoded in the frequency of firing and number of receptors activated
3) duration = encoded for by how long receptors fire for
4) location = where the stimulus is

Question 5

Which receptor property is linked to the idea of receptor specificity?

Answer 5

Modality

Question 6

Which receptor property is linked to the idea of receptor sensivity?

Answer 6

Intensity

Question 7

Which receptor property is linked to the idea of receptor fields?

Answer 7

Location

Question 8

With respect to receptor intensity and duration, what are the X2 types receptor and how does each one react to changes in intensity?

Answer 8

Slowly adapting receptors
= start firing when stimuli starts
= fires more frequently as the intensity increases

Rapidly adapting receptors
= fire when a stimulus starts, stops or changes intensity

Question 9

What is meant by the receptive field of a sensory neuron?

Answer 9

The special domain within which stimulation will excite or inhibit the neuron.

Question 10

Which part of the body has the lowest threshold for a two-point perceptual test?

Answer 10

Fingertips and face

Question 11

How many mechanoreceptors are there for touch?

How are they named?

Answer 11

X4

They are named RA or SA for rapidly or slowly adapting:

RA1 = meissner corpuscle
SA1 = merkel disc
RA2 = pancinian corpuscle 
SA2 = ruffini ending

Question 12

What stimuli do the sensory neuron nocireceptors respond to?

Answer 12

Noxious, damaging stimuli

Question 13

How do the touch receptors change in receptive field sizes and location?

Answer 13

As you travel from RA1 to SA2 they:

1) increase in receptor field size
2) move deeper into the dermis layer

Question 14

What are the X2 types of proprioreceptors and where are they found?

Answer 14

1) joint

2) muscle

Question 15

What two types of muscle receptors are there and what orientation are they arranged in?

Answer 15

1) muscle spindles
= lie in parallel to the main muscle fibres
= respond to fibre length

2) Golgi tendon organs
= lie in series with main muscle fibres
= respond to tension of fibres

Question 16

Which fibres transmit signals for cold?

What is its size and myelination status?

Answer 16

A delta = a small myelinated fibre

Question 17

Which fibres transmit signals for hot?

What is its size and myelination status?

Answer 17

C fibres = small unmyelinated

Question 18

What effect is seen with very high temperatures?

Answer 18

A paradoxical response where heat is felt as cold

Question 19

What happens if temperatures reach damagingly high levels?

Answer 19

Nocireceptors fire as well as the normal thermoreceptors receptors

Question 20

How many modalities or nocireceptors are there?

What are they called and how are they named?

Answer 20

X4 = named after what triggers them:

1) thermal
2) mechanical
3) polymodal
4) silent = respond to changes in tissue such as inflammation

Question 21

What are the names of broadmanns areas of the primary somatosensory cortex?

Answer 21

3a, 3b, 1 and 2

Question 22

What is the term in somatosensory cortex processing where individual modalities are organised and kept separate?

Answer 22

Parallel processing

Question 23

Which of broadmanns areas does most information go to?

Answer 23

3b

Question 24

Which of broadmanns areas have information from the largest and which from the smallest receptive fields?

Answer 24

3a = smaller
3b
1
2 = largest