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Flashcards in Somatosensory Systems & Pain Deck (30)
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1

4 attributes of a stimulus

1. modality
2. intensity
3. location
4. duration

2

What is rate coding ?

the more intense the stimulus --> more action potentials

3

rapidly adapting mechanoreceptors

respond only at the beginning and end of a stimulus, signalling the rate at which the stimulus is applied or removed

4

slow adapting mechanoreceptors

respond throughout a continuous stimulus. As the pressure increases, the total number of APs discharged rises, leading to higher firing rates

5

What is proprioception?

awareness of position of your body in space

6

Do intrafusal muscle fibers detect signals during muscla contraction?

No, because it only responds to stretch or tension. They do respond to contraction but by a different mechanism

7

Explain intrafusal and extrafusal muscles

intrafusal is the sensory muscles fibers that are parallel with the extrafusal but they have specializations.

8

What type of nerves mediate fine touch and proprioception?

large diameter, myelinated sensory fibers

9

touch and proprioception ascend through the brain ipsilaterally or contralaterally? What is the path called?

ipsilaterally; dorsal column/medial lemniscal system

10

What is the pathway of the dorsal column/medial lemniscal system?

sensory receptor --> peripheral nerve --> dorsal root --> axon collateral projects to ipsilateral dorsal column --> ascend in dorsal column to nuclei in medulla --> synapse 2nd order neuron crosses --> becomes medial lemniscus --> projects to thalamus and synapses --> thalamic neuron projects to primary sensory cortex (post central gyrus)

11

homunculi

representation of the body parts of the surface of the primary sensory cortex

12

What gyrus is in the parietal lobe immediately behind the central sulcus?

primary sensory cortex

13

what does the parietal association cortex do?

combines sensory information; awareness of our body and environment

14

What is neglect syndrome? How does it occur?

not recognizing a side of the body as belonging to them. Can result from a lesion of the right parietal cortex

15

how is pain produced?

produced by tissue injury but may also be produced by disturbed central sensory transmission

16

paraesthesia

altered or abnormal sensation

17

phantom limb

sensation that an amputated limb is still present, often with painful paraesthesia

18

causalgia

burning pain following nerve damage that persists long after tissue healing has occurred

19

plasticity

CNS may reorganize and not in a good way

20

anesthesia

loss of sensation

21

analgesia

lack of perception of pain from a normally nociceptive stimuli

22

thermal anesthesia

loss of temperature appreciation

23

referred pain

pain from deep structures perceived as arising from another area from the body

24

allodynia

pain arising from what is normally a non painful stimulus

25

what kind of nerve fibbers mediated nociception?

unmyelinated or small diameter myelinated sensory fibers

26

gate theory of pain transmission

activity in non-nociceptive afferents activates inhibitory interneurons that inhibit ascending spinothalamic tract neurons and decrease transmission through the nociceptive pathway

eg. acupuncture activates large diameter sensory fibers which activates inhibitory neurone decreases pain

27

allodynia

perception of pain from what would normally be non-nociceptive stimulus

28

what is a consequence of dysfunctional gate control?

because inhibitory interneuron is not activated, the second order (ascending) spinothalamic tract neuron becomes more active

29

the endogenous opioid system

stimulation around the cerebral aqueduct (midbrain-periaqueductal grey area) produces long lasting pain reduction

30

referred pain

nociceptive afferents from viscera enter the spinal cord at the same spinal segment as nociceptive afferents from skin/muscle/joints --> convergences onto common neurons --> perception of pain other than the site of origin