3.1.1 Somatosensory I

Question 1

How can sensation be divided?

Answer 1

General sensation
Special sensation e.g. vision, taste, hearing

Question 2

How can general sensation be divided?

Answer 2

Somatic sensation
Visceral sensation

Question 3

What is somatic sensation?

Answer 3

Conciously percieved, well-localised sensation

Question 4

What is visceral sensation?

Answer 4

Unconcious sensation, poorly localised

Visceral=Vague

Question 5

What are different varities of sensory experience called?

Answer 5

Modalities

Question 6

What is a modality?

Answer 6

Unit of sensation, each with a different receptor type

Question 7

What are the modalities of the spinothalamic system?

Answer 7

• Temperature (thermoreceptors)
• Pain (nociceptors)
• Pressure/ crude touch (mechanoreceptors)

Question 8

What are the modalities of the dorsal column-medial lemniscus system?

Answer 8

• Vibration (mechanoreceptors)
• Proprioception (ability to locate limbs in pitch black, golgi tendon organs)
• Fine touch (mechanoreceptors)
• Two point discrimination (mechanoreceptors)

Question 9

What is the first stage of encoding sensory information?

Answer 9

Primary sensory neurones (dorsal root ganglion neurones/first order sensory neurones) receive information from receptors

Each primary neurone receives information from a single receptor type

Question 10

Where do you find the cell body of first order sensory neurones?

Answer 10

Dorsal root ganglion

Question 11

Where do primary sensory neurones project to?

Answer 11

Projects to the ipsilateral side

Question 12

What is the difference between strong and weak receptor activation?

Answer 12

Strong stimulus, strong receptor activation, causes high frequency of action potentials

Weak stimulus, weak receptor activation, low frequency of action potentials

Question 13

What are the two types of receptors in relation to action potential frequency?

Answer 13

Rapidly adapting receptors
Slowly adapting receptors

Question 14

What do rapidly adapting receptors do?

Answer 14

Respond best to changes in strength of stimulation

Frequency of firing diminishes rapidly after initial stumulus.

These receptors allow us to be unaware of clothes on our skin

e.g. mechanoreceptors

Question 15

What do slowly adapting receptors do?

Answer 15

Change their frequency of firing very little after initial stimulus

Explains why pain can be so persistent

Stops you getting used to pain so you have to do something about it

e.g. Nociceptors

Question 16

What is a receptive field?

Answer 16

Single primary sensory neurone supplies a given area of skin

Question 17

What happens to sensory acuity if there is a large receptive field?

Answer 17

Sensory acuity will be low
e.g. skin of back

Question 18

What happens to sensory acuity if there is a small receptive field?

Answer 18

High sensory acuity, very good 2 point distinguishing ability

e.g. fingertips

Question 19

Why do we need to be aware of receptive field overlap?

Answer 19

Dermatomes have fuzzy boundaries, so when testing need to test in the middle of the dermatome to minimise any overlap