sensory systems

Question 1

where does the DRG lie and what are its targets?

Answer 1

it lies on the spinal nerve

its targets are skin and skeletal muscle.

Question 2

what part of the SC is the brachial plexus and what does it do?

Answer 2

it’s between C3-T2.

it supplies the arm.

Question 3

what part of the SC is the lumbosacral plexus and what does it do?

Answer 3

L3-S4

it supplies the leg.

Question 4

what are the 3 subclasses of DRG neurons?

Answer 4

1. proprioceptive neurons.
2. low threshold mechanoreceptors.
3. nociceptive neurons

Question 5

what are proprioceptive neurons like?

Answer 5

• large diameter soma.
• myelinated neurons.
• terminate centrally in intermediate zone of ventral horn.

Question 6

what info do proprioceptive neurons provide us with?

Answer 6

info on spatial awareness of limbs.

Question 7

what are low threshold mechanoreceptors like?

Answer 7

• medium to large diameter soma
• moderately myelinated axons.
• terminate centrally in deep dorsal horn and project rostrally in dorsal columns.

Question 8

what do proprioceptive neurons innervate?

Answer 8

muscle spindles and golgi tendons.

Question 9

who do low threshold mechanoreceptors innervate?

Answer 9

sensory structures in skin.

Question 10

what do Low threshold mechanoreceptors detect?

Answer 10

light touch, vibration, surface texture.

Question 11

what are nociceptive neurons like?

Answer 11

• have a small soma.
• non-myelinated.
• terminate centrally in the superficial dorsal horn.

Question 12

what do nociceptive neurons detect?

Answer 12

painful stimuli, temp, itch

Question 13

Ascending fibre tracts carrying nociceptive info are found in what region of the SC?

Answer 13

the anterolateral region.

Question 14

the spinothalamic tract is a … neuron relay?

Answer 14

3

Question 15

spinothalamic tract has what neurons?

Answer 15

DRG - sensory

Question 16

Spinoreticular tract detects what?

Answer 16

Dull, persistent, poorly localised pain and arousal response to nociceptive input.

Question 18

Spinomesencephalic tract provides what?

Answer 18

an autonomic and emotional response to painful stimuli.

Question 19

pain sensation is a … mechanism to minimise …

Answer 19

Pain sensation is a protective mechanism to minimise tissue damage.

Question 20

what is hyperalgesia?

Answer 20

increased sensitivity of nociceptive neurons to pain stimuli

Question 21

what does hyperalgesia cause?

Answer 21

guarding of damaged area and improved likelihood of healing.

Question 22

what happens in a reflex response to painful stimuli?

Answer 22

1. nociceptors detect painful stimuli.
2. nociceptor sends action p to dorsal horn.
3. nociceptor terminal in DH synapses with dendrites of an excitatory interneuron whose some in in DH.
4. axon of interneuron projects to motor neurons in VH.
5. motor neurons innervate muscles.

Question 23

what are endogenous opioids?

Answer 23

small peptides that are produced by the body in response to physical exertion, pain, excitement and sexual pleasure.