Lecture 6: Golgi Tendon Organ

Question 1

Spindles lie in ____:

Answer 1

Parallel

Question 2

GTOs lie in ____:

Answer 2

Series

Question 3

GTOs lie in between:

Answer 3

Muscle fibres and tendons

Question 4

What type of afferent fibre innervates the GTO?

Answer 4

Ib

Question 5

____ pound Ib afferent per GTO:

Answer 5

1

Question 6

How many muscle fibres are within a GTO, and which different MUs are they from?

Answer 6

10-20, from many different MUs, not just one or two

Question 7

Ib activation mechanism:

Answer 7

Free ending

Question 8

Ib activation in GTOs:

Answer 8

• Mechanical deformation of the Ib afferent branches between the collagen fibres
• Opens mechanically gated channels, change in membrane potential and generation of AP

Question 9

Non linear characteristics of GTOs:

Answer 9

• Not all muscle fibres go through a GTO
• Not all muscle fibres in a GTO are association with the Ib ending
• Increase in force does not always increase Ib firing

Question 10

Level of force necessary to excite a GTO depends on ____:

Answer 10

Mode of activation

Question 11

What kind of stretch activates GTO? Where does this kind of force go?

Answer 11

Passive stretch, about 2 Newtons
Passively applied force goes through connective tissue

Question 12

Is the GTO designed to monitor force actively or passively?

Answer 12

Actively

Question 13

Passively stretched muscles stimulate _____ in muscle spindles:

Answer 13

Extrafusal and intrafusal muscle fibres

Question 14

Actively contracted muscles stimulate ____ in muscle spindles:

Answer 14

Alpha motor neurons

Question 15

What effect does passive stretching have on muscle length in both GTOs and muscle spindles?

Answer 15

Stretches

Question 16

What effect does active contraction have on muscle length in both GTOs and muscle spindles?

Answer 16

Shortens

Question 17

Negative feedback of GTOs:

Answer 17

• Ib synapses on an inhibitory interneuron
• Ib interneurons inhibit the motor neuron pool of homonymous muscle

Question 18

Reciprocal excitation of GTOs:

Answer 18

• Ib inhibits agonist motor neuron pool and synergist motorneuron pool
• Ib feedback facilitates the antagonist motor neuron pool. Balances excitability around the joint