Sensory Receptors

Question 1

In cutaneous sensory receptors, the nerve endings

Answer 1

are protected by a capsule

Question 2

In many cases, the stimulus required to trigger an AP depends on

Answer 2

causing a membrane deformation which activates stretch sensitive ion channels

Question 3

Stretch sensitive ion channels may be present

Answer 3

in the distal tip of the affront axon or in specialised sensory cells that then release neurotransmitter to create a generator potential in the axon’s dendrites

Question 4

Explain sensory transduction in the skin

Answer 4

The transduction process in all sensory endings involves opening or closing of ion channels

Question 5

Explain frequency coding

Answer 5

• the bigger the stimulus, the greater the receptor potential and therefore the higher the frequency of APs
• this is the frequency coding of APs
• high frequency = high stimulus intensity

Question 6

What do muscle spindles monitor?

What is this important for?

Answer 6

Muscle length and the rate at which it changes

Important for reflexes as well as voluntary movement

Question 7

What fibres is skeletal muscle made up of?

Answer 7

Extrafusal and intrafusal fibres

Question 8

Extrafusal fibres are

Answer 8

regular muscle fibres

Question 9

Intrafusal fibres have

Answer 9

specialised motor and sensory innervation from muscle spindles

Question 10

The end of intrafusal fibres contains

Answer 10

sarcomeres and are contractile

Question 11

Intrafusal fibres are controlled by

Answer 11

gamma motoneurones

Question 12

Muscle stretch is the

Answer 12

adequate stimulus for these receptors

Question 13

As the muscle lengthens,

Answer 13

ion channels open and so length is monitored

Question 14

Describe the efferent control of spindle function

Answer 14

• agonist muscle contracts, spindle contracts and output is decreased
• this causes antagonistic muscle to lengthen and those spindles increase their outflow of APs
• this allows you to know exactly what is happening around the joint position

Question 15

Describe the role and mechanism of action of the Golgi tendon organs

Answer 15

• monitor muscle tension
• nerve endings are intermingled with the tendons at the ends of muscles
• act as stretch receptors and monitor the stretch in tendons
• since tendons are inelastic, the muscles must develop tension to stretch them and so measure muscle tension