17. The Motor Unit

Question 1

What is a motor Unit?

Answer 1

A motor unit is made up of a single motor neuron & all of the skeletal muscle fibers innervated by that motor neuron’s axonal terminals

Groups of motor units often work together to coordinate the contractions of a single muscle

Question 2

Alpha Motor Neuron

Answer 2

Slide 4

Question 3

What is The fundamental unit of the neuromuscular system?

Answer 3

The fundamental unit of the neuromuscular system is the motor unit

Question 4

The number of muscle cells innervated ranges from < 20 to 1000 < The Ratio of muscle fibers to motor neuron indicates the degree of control.

What happens when the innervation ratio is small?

Answer 4

The smaller the innervation ratio the more precise control of the muscle

• Small motor units are not very strong but provide dexterity

Question 5

The number of muscle cells innervated ranges from < 20 to 1000 < The Ratio of muscle fibers to motor neuron indicates the degree of control.

What happens when the innervation ratio is large?

Answer 5

The larger the innervation ratio the coarser the control of the muscle

• Larger motor units aren’t as precise but generate more force

Question 6

What muscle types usually have a smaller innervation ratio?

Answer 6

• Slow Twitch
• smaller nerve call
• fine movements
• low force
• high precision

Question 7

What muscle types usually have a larger innervation ratio?

Answer 7

• Fast Twitch
• large nerve cell
• motor movements
• Higher force
• less precision