Somatosensory system

Question 1

Which receptors have free nerve endings?

Answer 1

Thermoreceptors
Nociceptors

(they need to quickly transmit information about heat or pain, so they don’t need an extra layer)

Question 2

Which receptors have enclosed nerve endings?

Answer 2

Mechanoreceptors (to sense the mechanical stimulus through a ripple effect)

Question 3

What are the four types of sensory neurons?

Answer 3

A alpha
A beta
A delta
C

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Question 4

What group is type C sensory neurons?

Answer 4

Type 4

Question 5

What group is type A beta sensory neurons?

Answer 5

Group 2

Question 6

What group is type A delta sensory neurons?

Answer 6

Group 3

Question 7

Which is the largest and fastest type of sensory neuron and why?

Answer 7

A beta - myelinated

Question 8

Which information do type Abeta axons send?

Answer 8

Innocuous mechanical information

Question 9

Which two sensory neurons send pain formation?

Answer 9

A delta

C fibres

Question 10

Which of the nociceptive neurons are myelinated?

Answer 10

Alpha delta

Question 11

Which information do type A delta axons send?

Answer 11

Noxious mechanical

Noxious thermal

Question 12

Which information do type C axons send?

Answer 12

Noxious thermal, chemical and mechanical

Question 13

How many heat ion channels are there and what are these?

Answer 13

TRPV1-4

Question 14

How many cold ion channels are there and what are these?

Answer 14

TRPM8

TRPA1

Question 15

What are sensory receptors?

Answer 15

Ttransducers that convert energy from the environment into neuronal action potentials

Question 16

What do Meissner’s corpuscles sense?

Answer 16

Fine discriminative touch

Low frequency vibration

Question 17

What do Merkel cells sense?

Answer 17

Light touch and superficial pressure

Question 18

What do Pacinian corpuscles sense?

Answer 18

Deep pressure
Vibration
Tickling

Question 19

What do Ruffini endings sense?

Answer 19

Continuous pressure, touch

Stretch

Question 20

What is the fifth mechanoreceptor and what does it sense?

Answer 20

Hair follicle receptor - sense light touch

Question 21

Order the types of sensory receptors in descending order of speed

Answer 21

Mechanoreceptors>nociceptors=thermoreceptors

Question 22

Which is faster - detecting sharp pain and the cold, or detecting dull aching pain and heat?

Answer 22

Pin prick and cold is faster than dull aching pain and heat

Question 23

Specifically, which sensations do A delta fibres detect?

Answer 23

Noxious sharp pain (pin prick)

Noxious cold

Question 24

Specifically, which sensations do C fibres detect?

Answer 24

Dull aching pain

Warmth

Question 25

What do tonic receptors detect and what is their adaptation speed?

Answer 25

Tonics are SLOW adapting;

detect continuous stimulus strength i.e constantly informs the brain of the status of the body

Question 26

Give an example of a tonic receptor

Answer 26

Merkel cells - slowly adapting for superficial pressure and fine touch to be perceived

Question 27

What do phasic receptors detect and what is their adaptation speed?

Answer 27

Phasic are fast adapting; detects change by firing at the start and end of the stimulus

Question 28

Give an example of a phasic receptor

Answer 28

Pacinian receptor is a Phasic receptor; sudden pressure excites the receptor

Question 29

What is a receptive field?

Answer 29

The region on the skin which causes activation of a single sensory neuron when activated’

Question 30

Which ganglia do the cell bodies from sensory nerves of the face go to?

Answer 30

Trigeminal ganglia

Question 31

What mediates lateral inhibition?

Answer 31

Inhibitory interneurons within the dorsal horn of spinal cord

Question 32

Which fibres form the dorsal column?

Answer 32

A beta fibres

Question 33

Which information does the dorsal pathway relay?

Answer 33

Fine discriminative touch

Vibration

Question 34

Crude touch is mediated by which fibres and which pathway do these ascend in?

Answer 34

A delta fibres

Anterior spinothalamic pathway

Question 35

Which pathway transmits info about pain and temperature? ascend

Answer 35

Lateral spinothalamic tract

Question 36

What would an anterior spinal cord lesion cause?

Answer 36

Intact dorsal columns so retained light touch, vibration and 2 point discrimination.
Damage to spinothalamic tract therefore pain and temp loss below level of lesion

Question 37

What is the pattern of loss of sensation in Brown Sequard syndrome?

Answer 37

Ipsilateral loss of fine touch and vibration

Contralateral loss of pain, temperature and crude touch