Peripheral Sensory Mechanisms Flashcards Preview

MD1 Neuroscience > Peripheral Sensory Mechanisms > Flashcards

Flashcards in Peripheral Sensory Mechanisms Deck (43):
1

What does the somatosensory system do?

Mediate sensations from whole body surface, including skin and deeper tissues
Extrareceptor sense - tells us about outside world

2

What is the structure of the skin?

Most of body covered by hair skin
Palmar surface of hands and soles of feet covered by glabrous skin - skin ridges prominent

3

Why is the skin different on the hands and lips?

Specialised to obtain perceptual information from these body parts

4

How many mechanoreceptor types, in terms of sense of touch, are there in glabrous skin?

4

5

Which receptors are close to the surface?

Meissner corpuscles
Merkel complexes

6

Which receptors are deeper in the skin?

Ruffini organs
Pacinian corpuscles

7

What type of axons are these receptors innervated by?

Large myelinated axons
Cell bodies in dorsal root ganglia

8

Can you tell the receptor type by the axon?

No, all the axons look the same

9

Where are Meissner corpuscles?

Tips of dermal-epidermal folds

10

Where are Merkel cells?

In valleys of dermal-epidermal folds

11

Where are Ruffini corpuscles?

In upper dermis

12

Where are Pacinian corpuscles?

In deep dermis and hypodermis

13

What is the structure of touch receptor?

Cells of non-neural origin form capsules around nerve endings
Tethered into structure of skin
Each detects slightly different aspect of force

14

How is mechanical force detected by touch receptors?

Mechanical force applied
Radiates minute force through skin
Deforms receptors

15

What happens when the force gets too high; ie: is damaging?

Touch receptors don't give any information - they've plateaued out

16

What happens to the ion channels in the touch receptors when a force is applied?

Membrane stretches
Na ion channels physically open
If Na depolarises membrane enough, action potential initiated

17

What determines receptor size?

Location of receptor

18

Why do deeper receptors have larger receptor fields?

Detect radiating forces over larger areas

19

Why do more superficial receptors have smaller receptor fields?

Detect forces over smaller areas

20

Define a slowly adapting receptor

Give off action potentials that are constant with stimulus applied
Have slight increase in receptor firing when stimulus first applied

21

Define a rapidly adapting receptor

Detects changes in stimulus only
Don't signal if stimulus is continued to be applied, but doesn't change over time

22

What are tactile responses related to?

A stimulus activating it

23

When do rapidly adapting receptors firer?

When stimulus is applied and then removed

24

How do nociceptors respond to a stimulus?

Increase in firing rate when stimulus is removed

25

Are nociceptors extrareceptors or intrareceptors?

Intrareceptors - respond when tissue itself has changed its status

26

What are the two slowly adapting touch receptors?

Merkel complexes
Ruffini endings

27

What do Merkel complexes respond to?

Indentation

28

What do Ruffini endings respond to?

Sustained skin movement

29

What are the two rapidly adapting touch receptors?

Meissner receptors
Pacinian receptors

30

What do Meissner receptors respond to?

Transient response to skin movement

31

What do Pacinian receptors respond to?

Transient response to vibration

32

Which touch receptor has the smallest receptor field?

Merkel complex

33

Out of the two, which is more sensitive: Merkel complex or Meissner corpuscle?

Meissner corpuscle

34

Which touch receptor can be classified as "proprioceptive", and what does this really mean?

Ruffini organ
Tells a lot about shape of hand
- Bigger receptor field
- Responds best to stretch of skin or something moving across skin

35

Which touch receptor is the most sensitive?

Pacinian corpuscle

36

What are the proportions of touch receptors?

Pacinian corpuscles = 15%
Ruffini organs = 20%
Merkel complexes = 25%
Meossner corpuscles = 40%

37

When doing a simple manipulation task, what information does each touch receptor relay?

Meissner encodes rate of force
Merkel encodes grip force
Pacinian encodes vibrations
Ruffini encodes hand posture

38

Where else are different types of mechanoreceptors used?

In muscles detecting force and stretch
Transduction in auditory system

39

Which region is more sensitive to two point discrimination: fingertips, or wrist?

Fingertips

40

Are dermatomes discrete?

No, all dermatomes overlap extensively

41

If sensitivity loss follows a dermatome pattern, where is the damage likely to be?

At spinal segment level

42

Is dermatomal pattern of loss the same as the pattern of loss that occurs when there's damage beyond a nerve plexus?

No, and it's important to distinguish the two patterns

43

What nerve innervates the somatosensory structures in the face?

Trigeminal nerve

Decks in MD1 Neuroscience Class (55):