Motor Unit Structure & All-or-None Principle

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Questions and Answers

What does a motor unit consist of?

Only muscle fibers that contract independently
Sensory neurons and muscle fibers
The anterior motor neuron and specific muscle fibers it innervates (correct)
Multiple motor neurons and muscle fibers

How does the number of muscle fibers per motor neuron relate to a muscle's function?

It generally relates to how much strength is needed
The number is constant regardless of function
It generally relates to the muscle's particular movement function (correct)
It generally increases with greater precision of movement required

What is the All-or-None Principle in relation to motor units?

All muscle fibers in a motor unit contract or none do (correct)
Motor units can vary in their contraction strength
Some muscle fibers may contract while others do not
A stronger stimulus causes a stronger contraction

What is true about muscle fibers receiving input from a motor neuron?

<p>Generally, each muscle fiber receives input from only one motor neuron (D)</p> Signup and view all the answers

Which statement best describes motor neurons' ability to control muscle contractions?

<p>Motor neurons must either fully stimulate or not stimulate muscle fibers. (B)</p> Signup and view all the answers

Flashcards

Motor Unit

A motor neuron and the muscle fibers it controls.

All-or-None Principle

A motor neuron either fully activates or completely ignores its muscle fibers.

Motor Neuron

A nerve cell that sends signals to muscle fibers.

Muscle Fiber

An individual muscle cell.

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Precision Movement

A movement that requires fine control.

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Study Notes

Motor Unit Structure

Motor unit comprises the anterior motor neuron and the specific muscle fibers it innervates.
Each muscle fiber typically receives input from only one neuron.
However, a single motor neuron can innervate multiple muscle fibers.
The number of muscle fibers per motor neuron is related to the muscle's function.
Muscles demanding less precision have hundreds of fibers per motor neuron.
Muscles requiring fine control have one muscle fiber per motor neuron.

All-or-None Principle

Sufficient stimulus to trigger an action potential in the motor neuron causes all muscle fibers in the motor unit to contract simultaneously.
No partial activation of muscle fibers is possible.
A motor unit generates either full contraction or no contraction, no gradation of force.
Stronger action potentials do not produce stronger contractions within a single motor unit.

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Description

This quiz explores the structure of motor units and the all-or-none principle in muscle contraction. You will learn about the relationship between motor neurons and muscle fibers, as well as how action potentials lead to muscle contraction. Test your understanding of muscle physiology concepts!