Sensory receptors

Question 1

What are the 3 types of sensory receptors

Answer 1

Mechanoreceptors- pressure, touch
Proprioreceptors- mechanoreceptors in joints and muscles- Signal info about body position
Nociceptors- respond to painful stimuli

Question 2

What is a receptor potential

Answer 2

Adequate stimulus causes graded membrane potential change
Adequate stimulus=membrane deformation
Occurs in skin mechano/proprioceptors

Question 3

What does High stimulus intensity mean for APs

Answer 3

Produces most APs

Question 4

What does the frequency coding of stimulus intensity involve

Answer 4

1. Larger stimulus
2. Larger receptor potential
3. Higher frequency of APs

Question 5

What happens to mechanoreceptors once there is a maintained stimulus

Answer 5

Adaptation
Mechanoreceptors adapt to maintained stimulus
Only signals when theres a change in stimulus

Question 6

What sensory receptors can’t adapt

Answer 6

Nociceptors

Question 7

What is a receptive field

Answer 7

Somatic sensory neuron activated by stimuli in specific area

Question 8

What is lateral inhibition

Answer 8

Receptors at edge of a stimulus more strongly inhibited than receptors near centre

Question 9

What are some different proprioceptors

Answer 9

Muscle spindles
Golgi tendon organs
Joint receptors

Question 10

What is the function of muscle spindles

Answer 10

Monitors Rate of change of muscle length

Question 11

What is the function of golgi tendon organs

Answer 11

Monitor tension on tendons

Question 12

What is the function of joint receptors

Answer 12

Monitors Rate of angular movement and Tension on joint

Question 13

What 3 things do these proprioceptors do

Answer 13

Control voluntary movements
Generate spinal reflex movements
Kinaesthesia- info on body position and function

Question 14

What are muscle spindles made up of

Answer 14

Intrafusal and extrafusal muscle fibres

Cross section of extrafusal and intrafusal fibres

Question 15

What are the two types of intrafusal fibre

Answer 15

Nuclear bag fibres- bag shaped with nuclei
Nuclear chain fibres- nuclei in a chain

Question 16

What are annulospiral endings

Answer 16

Primary endings from Ia afferent nerves wrapped around intrafusal fibres

Question 17

What do the ends of intrafusal fibres contain

Answer 17

Sarcomeres

Question 18

What is the function of gamma a motor neuron

Answer 18

Innervate extrafusal muscle

Question 19

What is the function of Gamma (y) motoneurones

Answer 19

Innervate
Cause contraction of contractile ends of intrafusal fibres

Question 20

When a muscle length changes from L0 to L1 what happens to APs

Answer 20

Increase in AP frequency proportional to velocity of stretch
Increase of AP frequency at new steady state

Question 21

What is the function of stretch receptors?

Answer 21

monitor stretch of tendon

Question 22

How do muscles develop tension

Answer 22

Contract to stretch the tendons

Question 23

How does GTO monitor muscle tension

Answer 23

Muscle contraction increases tension
This stretches nerve endings of GTO
Initiates APs in group 1b afferent fibre from GTO

Question 24

What would happen if a motor neuron fired without y

Answer 24

Extrafusal muscle contracts and shortens
Intrafusal stays same length (becomes slack)
1a sensory firing decreases

Question 25

What happens when a and y fire together

Answer 25

Muscle and spindle shorten together
No drop off in 1a firing

Question 26

In reality how do a and y motor neurons work togther

Answer 26

a-y coactivation
spindle 1a report muscle shortening
y motor nerves maintain stretch sensitivity of spindle