Muscle Contraction

Interactive Lecture

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​Muscle
Contraction

Fill in the Blanks

Contraction produces

, which is the force exerted on a load or object to be moved.

Multiple Choice

Which of the following best describes a concentric contraction?

• The muscle elongates while producing force

• The muscle contracts without changing length

• The muscle shortens while producing force

• The muscle remains relaxed and passive

Fill in the Blanks

In an isotonic contraction, muscle length changes to move a load. When the muscle shortens, it is called a concentric contraction, and when it lengthens, it is called a

contraction.

Open Ended

Explain the difference between isotonic and isometric contractions.

Multiple Choice

Which muscle acts as the prime mover (agonist) during the flexion of the elbow?

• Triceps brachii

• Brachioradialis

• Brachialis

• Biceps brachii

Fill in the Blanks

During the flexion of the elbow, the muscle that acts to stabilize the joint and assist the prime mover is called the

.

Multiple Choice

Which system controls the activities of skeletal muscles?

• Autonomic nervous system

• Somatic motor nervous system

• Central nervous system

• Endocrine system

Fill in the Blanks

Neural control regulates istonic and

contractions, as well as graded muscle responses and muscle tone.

Multiple Choice

What defines a motor unit?

• A single muscle fiber

• A motor neuron and all the muscle fibers it innervates

• A group of motor neurons

• A single axon terminal

Open Ended

Explain how the size of a motor unit affects muscle control and provide examples of activities that involve small and large motor units.

Multiple Choice

What are the three phases of a muscle twitch as

recorded on a myogram?

• Latent period, contraction phase, relaxation phase

• Initiation phase, action phase, recovery phase

• Stimulation phase, active phase, resting phase

• Onset period, peak phase, decline phase

Multiple Choice

Which of the following mechanisms is used to produce graded muscle responses?

• Increasing muscle fiber size

• Changing the frequency of stimulation and the number of motor units stimulated

• Decreasing the number of muscle fibers

• Altering the type of muscle fiber

Fill in the Blanks

A threshold stimulus is strong enough to produce an observable muscle contraction, but a

stimulus is not.

Match

Match the type of stimulus with its effect

• Subthreshold

• Threshold

• Maximal

No observable muscle contraction

Weak contraction produced

Strong contraction produced

• No observable muscle contraction

• Weak contraction produced

• Strong contraction produced

Multiple Choice

What is the primary function of muscle tone?

• To produce active movement

• To keep muscles firm, healthy, and ready to respond

• To increase muscle size

• To decrease muscle fatigue

Fill in the Blanks

Muscle tone is maintained by

and involves the alternating activation of groups of motor units in response to input from stretch receptors in muscles.

Poll

How do you feel right now?