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Flashcards in Somatosensory Deck (69)
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1

Why is somatosensory system important?

The somatosensory system provides a crucial line of communication between us & outside world

2

What conditions occur when you damage peripheral or central components of somatosensory system?

Damage to peripheral or central components results in conditions such as neuropathy, neuralgia, phantom pain

3

What are the 4 main classess of somatosensory receptors?

Tactile
Proprioception
Thermal sensations
Nociceptive (painful) sensations

4

What receptors are involved in Tactile sensation?

mediated by low threshold Mechanoreceptors, Merkel, Ruffini, Meissner & Pacinian types

5

What is Tactile sensation?

Not harm ful sensation to light touch

6

What mediates proprioception?

Mediated by muscle (spindle) & joint (Golgi tendon) receptors, some inputs from cutaneous mechanoreceptors

7

Thermal sensation is mediated by what?

Mediated by thermoreceptors localized to discrete zones that exhibit hot & cold sensitivity

8

What mediates Mociceptive (painful) sensation?

Mediated by mechanical, thermal & polymodal nociceptors

9

What are the different sensory receptors of the skin?

Free nerve endings
Meckels disks
Meissners corpuscle
Pacinian corpuscle
Ruffini's corpuscles

10

What are the 3 layers of the skin?

Epidermis
Dermis
Subcutis/hypodermis

11

Where are each of the sensory receptors of the skin found?

Meissners and Merkel are found just beneath the epidermis. Meissners sit between the dermal pupillae and Merkels are aligned with the pupillae.

Ruffini’s corpuscles located deep in dermis, long axis of the corpuscle is orientated parallel to the skin.

Pacinian corpuscles are large encapsulated endings located in the subcutaneous tissue.

12

What is the morphology of cutaneous skin receptors?

A. Meissners Corpuscles - looping axonal terminals that inter-twine supporting cells

B. Merkel’s - dome structure atop axon terminals

C. Pacinian Corpuscles - sensory axon surrounded by fluid filled capsule, onion-shaped appearance

D. Ruffini endings - nerve terminals intertwined with collagen fibrils

E. Nociceptors - free nerve endings that penetrate epithelial cells, no morphological specialization

13

What is the area, function and speed of adapatibility of merkel cells?

Dermo-epidermal boundary
Slow adapting
Pressure form, texture
Small receptive field size

14

What is the area, function and speed of adapatibility of meissner corpuscle?

Papillary dermis
Rapidly adapting
Flutter, motion
Small receptive field size

15

What is the area, function and speed of adapatibility of Pacinian corpuscle?

Deep in subcutis
Rapidly adapting
Vibration --> mechanical distortion
Large receptive field size

16

What is the area, function and speed of adapatibility of Ruffini corupuscle?

Dermis
Slow adapting
Stretching and shearing of skin
Large receptive field size

17

What is the fiber type of all the skin reecptors?

Ab

18

How do you test the receptive field of cutaneous sensory receptors?

Testing the receptive field of sensory receptors using a stimulus probe on the hand, and recording action potentials from a single median nerve axon.

Results for main types of cutaneous sensory receptors.

19

Is two point discrimiation same across the whole body?

Two point discrimination thresholds vary across body surface
Sensitivity is correlated with density of sensory innervation

20

What areas have high and low two point discrimination?

Areas of high sensitivity – fingertips , face

Areas of low sensitivity – torso, limbs

21

What is the range of temperatures sensory fibres can response to?

cold pain
cold
warm
hot pain

22

What family of receptors are activated by temperature?

Trp family of receptors

23

What is the methanol receptor?

Trpm8 and is a cold receptor

24

What is the Capsaicin receptor ?

TRPV1/VR1 --> heat receptor

25

Where is capsaicin found?

Extract of chilli peppers

26

What chemical group does capsaicin belong? to?

Vanilloids

27

What receptor does Capsaicin act on and what is the consequence?

Act on thermal receptor that produces an inward Ca current.

28

What is the function of muscle spindles?

Muscle spindles provide sensory feedback from muscle fibres on body position and movement.

29

What is the function of golgi tendons?

Golgi tendon organs regulate muscle tension or force of contraction, and prevent muscle overloading.

30

What is the general principle for large diameter receptors?

Rapidly conducting afferents (I/II) associated with low threshold mechanoreceptors.