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Flashcards in Sensory receptors Deck (56):
1

what are sensory receptors

are nerve endings, often with specialized non-neural structures

2

What do sensory receptors induce

convert different forms of energy into frequency of Action Potentials (APs)

3

what is a sensory modality

a type of stimulus activating a particular receptor

4

what is the type of energy a receptor normally responds to called

an adequate stimulus

5

What are Mechanoreceptors

stimulated by mechanical stimuli

6

what are the mechanoreceptors in joints and muscles that signal information related to body or limb position called

Proprioceptors

7

What are the receptors that respond to pain

Nociceptors

8

Damage to the nerve by stimuli activates a generator potential which in turn opens

ion channels causing ion flow across the membrane

9

an adequate stimulus causes a graded membrane potential change called

receptor potential

10

For action potential to be fired what needs to happen

receptor potential reaches threshold

11

frequency coding of stimulus intensity means

the larger the receptor potential the higher the frequency of APs in sensory neurone

12

Merkel receptors senses

pressure and texture

13

Pacinanan corpuscle sense

vibration

14

meissners corpuscle senses

flutter and stroking movement

15

ruffini corpuscle senses

skin stretching

16

Adaption of sensory nerves is

stimulus is enough to trigger an AP, but as stimulus continues generator potential decreases so mechanoreceptor only responds to onset of stimulus
ie stimulus there but you are no longer consciously aware

17

Rapidly/Moderately-adapting receptors are

Pacinian corpuscles and Meissner’s corpuscles

18

Slowly-adapting receptors are

Merkel’s discs and Ruffini endings

19

Why don't Nociceptors adapt

important not to ignore painful stimuli

20

Whats is the structure of Pacinian corpuscles

a myelinated nerve with a naked nerve ending,
naked nerve ending enclosed by a connective tissue capsule of layered lamella

21

Describe how Pacinian corpuscles respond to stimuli

mechanical stimulus deforms capsule
nerve ending is stretched
ion channels open
Na+ enters local depolarisation
generator potential reaches threshold
APs fire at myelinated nerve
detect stimulus ON

22

How does the Pacinian corpuscles show rapid adaptation

Due to fluid redistribution in the capsule, removes mechanical stretch of nerve ending, causing stimulus to disappear and AP stop firing

23

What can cause an AP to fire again in a Pacinian corpuscles after stimulus is applied

withdrawal of stimulus causes capsule to bring back and AP fired again

24

What is necessary for quick adaptation in Pacinian corpuscles and enhance sensory function

the lamella

25

what is the receptive field

a somatic sensory neuron is activated by stimuli in a specific area

26

What are the two things that tell parts of the skin apart

receptive field size
neuronal convergence

27

Neuronal convergence occurs when there is

sensory neutrons with neighbouring receptive fields

28

what can neuronal convergence stimulate

large secondary receptive field

29

relatively insensitive area indicated by
and example

So convergence and a large secondary receptive field
eg. fingers and lips

30

What is acuity

The ability to locate a stimulus on the skin and differentiate it from another close by

31

Example of low acuity is

two different points are stimulated but one signal is sent to the brain

32

What is lateral inhibition

Central neurone inhibits surrounding neighbour pathways this pinpoints where stimulus is

33

Inhibition of lateral neutrons enhances what

perception stimuli, awareness of where exactly stimuli is coming from

34

All sensory information goes to the brain then is relayed through what to what

relayed through thalamus to somatosensory cortex

35

What are the three things present and needed in proprioceptors

Muscle spindles
golgi tendon organs
joint receptors

36

What monitors muscle length and rate of change, controlling reflects and voluntary movement

Muscle spindes

37

Where are muscle spindles located

in the intrafusal of muscle fibres

38

What do golgi tendons do

tension on tendons

39

What is tension produced by

muscle contraction

40

What is the 3 functions of proprioceptors

Provide sensory information for:
Voluntary movement
spinal chord reflexes
kinaesthesia

41

What lies in parallel with muscle fibres

muscle spindles

42

What innervates end of intrafusal muscle spindle

gamma motor neurons

43

what innervates end of extrafusal muscle spindle

alpha motor neurons

44

How do afferent neurones position themselves around the muscle spindle

they spiral around

45

What motor neurone is smaller in diameter

gamma

46

How are golgi tendons arranged

in series with muscle fibres

47

When muscle contraction increases tension in golgi tendon sensory axon fires but why doesn't sensory axon fire from muscle spindle

as activated muscle stays the same length therefore doesn't activate muscle spindle

48

Gamma motor invasion of the muscle spindles allows

brain to be informed about muscle length
prevents spindle fibres flopping, allows them to contract

49

What happens to muscle spindles when muscles contracts and shortens

gamma motor neurons contract poles of muscle spindle, shortening to match the muscle fibre.

50

Why does the muscle spindle need to contract

to allow information to be transmitted to the brain

51

spindle sensitivity to stretch is maintained by

gamma motorneurons

52

the work of alpha and gamma is called

co-activation

53

What does co-activation allow

this restores tension and resets sensitivity of the central sensory part of intrafusal fibres, at a new muscle length

54

What are the two kinds of intrafusal fibre

nuclear bag fibres
nuclear chain fibres

55

Reflex contraction inhibited by

muscle spindles

56

Muscle contraction stretches golgi tendon organ but if excess load is applied what happens

Goligi tendon reflex causes relaxation due to motor neurone being inhibited, thus protecting muscle