motor units, muscle spindles, golgi tendon organs and joint receptors

Question 1

What motor neurons make up LMN and what do they do?

Answer 1

Alpha motor neurones

Innervate bulk of fibres within a muscl that generate force

Question 2

What is the function of gamma motor neurones

Answer 2

Innervate a sensory organ called the muscle spindle

Question 3

Triceps brachii and anconeus msucle work together to produce a force, what name is given to these muscles?

Answer 3

Synergistic muscle

Question 4

Biceps brachii and brachialis oppose triceps and anconeus, what name is given to these muscles?

Answer 4

Antagonistic muscles

Question 5

How many spinal nerves are there?

Answer 5

31 pairs

Question 6

What is a motor unit?

Answer 6

An alpha motor neuron and all the muscle fibres it innervates

Question 7

What is a motor neuron pool?

Answer 7

All the alpha motor neurones that innervate a single muscle

Question 8

How is force of muscle contraction graded?

Answer 8

Frequency of action potential discharge of alpha MN

Recruitment of synergistic motor units

Question 9

How is a muscle twitch sustained into a contraction?

Answer 9

Summation of twitches causes a sustained contraction

Question 10

Benefit of a smaller motor unit?

Answer 10

Allows for finer movements e.g. extraocular eye muscles

Question 11

How do fast and slow fibres differ?

Answer 11

How fast myosin ATPase splits ATP to make energy for cross bridge cycling

Question 12

Features of slow fibres

Answer 12

Type 1
ATP from oxidative phosphorylation
Red (High myoglobin)
Slow contract and relax
Fatigue resistant

Question 13

Features of fast (IIa) fibres?

Answer 13

fast contract and relax
Oxidative phosphorylation
Fatigue resistant

Question 14

Features of fast (IIb) fibres?

Answer 14

ATP from glycolysis
Fast contraction
not fatigue resistant
White

Question 15

What are the 3 types of motor units?

Answer 15

Slow
Fast fatiguing
Fatigue resistant

Question 16

Relationship between speed of twitch and size of alpha MN?

Answer 16

Fast- large or intermediate

Slow- Small

Question 17

What is the Henneman size principle?

Answer 17

Smaller alpha MNs have a lower threshold than larger ones hence slow are more easily activated

Question 18

What is the myotatic reflex?

Answer 18

When a skeletal muscle is pulled, it pulls back

Question 19

What does the muscle spindle consist of?

Answer 19

Capsule
Intrafusal fibres
Sensory afferents
Gamma MN efferents

Question 20

Describe the myotatic reflex arc

Answer 20

Stretch spindle
Activate 1a Afferent
Excitatory synaptic transmission in spinal cord
Activation of alpha MN
Contraction

Question 21

Three types of intrafusal fibres?

Answer 21

Bag 1 (dynamic)- sensitive to rate of change of muscle length
Dynamic MN

Bag 2 (Static)- more sensitive to absolute length
Static MN

Chain fibres- absolute length
Static MN

Question 22

Two types of afferent fibres?

Answer 22

1a

II, more slowly conducting

Question 23

What are golgi tendon organs?

Answer 23

Located at tendon muscle junction

Monitor changes in muscle tension

Question 24

What is the function of golgi tendon organs?

Answer 24

Act to regulate muscle tension to protect muscle from overload and regulate at an optimal range

Question 25

What type of fibres innervate golgi tendon organs?

Answer 25

1b

Question 26

What are paciniform endings?

Answer 26

Found in periosteum near articular attachments and fibrous part of joing capsule
Acceleration detectors

Question 27

What are Ruffini endings?

Answer 27

Found mainly in joint capsule

Static postion and speed of movement