Motor Unit: Definition, Structure, Function, and Types

Question 1

What is the primary function of the motor unit?

Accepted Answer

To initiate and regulate muscle contractions

Answer

To store energy for future muscle contractions

Answer

To transmit sensory information to the spinal cord

Answer

To regulate blood flow to muscles

Question 2

Which structure connects the neuron to the muscle fiber?

Accepted Answer

Neuromuscular junction

Answer

Sarcomere

Answer

Myofibril

Answer

Synapse

Question 3

Which muscle fiber type is best suited for sustained, low-intensity activities?

Accepted Answer

Type I

Answer

Type IIx

Answer

Type IIb

Answer

Type IIa

Question 4

What principle governs the recruitment of motor units during muscle contraction?

Accepted Answer

Size principle

Answer

Fatigue resistance

Answer

Twitch potentiation

Answer

Rate coding

Question 5

Which of the following factors does NOT influence the force output of a muscle?

Accepted Answer

Age of the individual

Answer

Muscle length

Answer

Cross-sectional area of muscle fibers

Answer

Frequency of motor unit activation

Question 6

Where are calcium ions stored within the muscle fiber?

Accepted Answer

Sarcoplasmic reticulum

Answer

Endoplasmic reticulum

Answer

Mitochondria

Answer

Golgi apparatus

Question 7

Which neurotransmitter is released at the neuromuscular junction to initiate muscle contraction?

Accepted Answer

Acetylcholine

Answer

GABA

Answer

Serotonin

Answer

Dopamine

Question 8

What condition occurs when a motor unit is repeatedly activated and loses its ability to function effectively?

Accepted Answer

Neuromuscular fatigue

Answer

Spasm

Answer

Contracture

Question 9

Which technique is commonly used to assess the electrical activity of motor units?

Accepted Answer

Electromyography

Answer

Ultrasonography

Answer

Arthrography

Answer

Magnetic resonance imaging

Question 10

How does the motor unit contribute to the control of movement?

Accepted Answer

It serves as the basic unit for muscle force generation and coordination

Answer

It plays a role in pain perception

Answer

It assists in the regulation of blood pressure

Question 11

Which of the following is NOT a component of the motor unit?

Accepted Answer

Muscle spindle

Answer

Alpha motor neuron

Answer

Muscle fibers

Answer

Motor end plate

Question 12

What neurotransmitter is released at the motor end plate to trigger muscle contraction?

Accepted Answer

Acetylcholine

Answer

Dopamine

Answer

Norepinephrine

Answer

Glutamate

Question 13

State the size principle of motor unit recruitment.

Accepted Answer

Motor units are recruited in order of increasing size, with smaller units being activated before larger ones.

Answer

Larger motor units are always recruited before smaller ones.

Answer

All motor units are recruited simultaneously.

Question 14

What is the primary function of muscle spindles in relation to motor unit function?

Accepted Answer

Provide sensory feedback on muscle length

Answer

Control muscle contraction directly

Answer

Generate action potentials

Answer

Transmit sensory information to the spinal cord

Question 15

Which technique is commonly employed to assess motor unit function?

Accepted Answer

Electromyography (EMG)

Answer

Positron emission tomography (PET)

Answer

Magnetic resonance imaging (MRI)

Answer

Ultrasound

Question 16

How can aging impact motor unit function?

Accepted Answer

It may lead to a reduction in the number and size of motor units.

Answer

Aging generally has no significant effect on motor unit function

Answer

It enhances motor unit recruitment patterns

Question 17

Which component is NOT found within the structure of the motor unit?

Accepted Answer

Myelin sheath

Answer

Sarcolemma

Answer

Muscle fiber

Answer

Motor neuron

Question 18

Identify the primary neurotransmitter released by motor neurons at the neuromuscular junction:

Accepted Answer

Acetylcholine

Answer

Epinephrine

Answer

Dopamine

Question 19

Which type of motor unit exhibits the following characteristics: smallest muscle fibers, recruited first during muscle contraction?

Accepted Answer

Type I

Answer

Type IIb

Answer

Type IIa

Answer

Type IIx

Question 20

What is the term used to describe the progressive increase in motor unit recruitment as force requirements intensify?

Accepted Answer

Size principle

Answer

Asynchrony principle

Answer

Chronotropy principle

Answer

Tonicity principle

Question 21

Which factor plays a significant role in determining the size of a given motor unit?

Accepted Answer

Muscle fiber type

Answer

Joint angle

Answer

Age

Answer

Speed of contraction

Question 22

Describe the role of the Golgi tendon organ in the context of motor control:

Accepted Answer

Detects changes in muscle tension, inhibiting excessive muscle contraction

Answer

Initiates muscle contraction

Answer

Regulates blood supply to muscles

Question 23

How does aging primarily affect the motor unit?

Accepted Answer

Diminished size and number of motor units

Answer

Increased size and number of motor units

Answer

Enhanced recruitment patterns

Answer

Minimal impact on motor unit characteristics

Question 24

Which of the following represents a potential strategy to enhance motor unit function?

Accepted Answer

Exercise training

Answer

Dietary supplementation

Answer

Pharmacological therapy

Answer

Surgical intervention