Lecture 3

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What is the function of a motor unit?

Control involuntary muscle contraction

Generate sensory feedback

Control voluntary muscle contraction (correct)

Innervate multiple muscle fibers

Which term best describes the relationship between motoneurons and muscle fibers in a motor unit?

Many-to-many

One-to-one

Many-to-one

One-to-many (correct)

What is the final common pathway to create muscle contraction?

From sensory neurons to lower motor neurons

From cerebellum to spinal cord

From spinal motor neurons to muscles (correct)

From upper motor neurons to sensory receptors

Which Nobel laureate was involved in the concept of the motor unit?

C.S. Sherrington Signup and view all the answers

What is the primary role of neuromuscular electrical stimulation?

To improve voluntary force output Signup and view all the answers

How does electromyography contribute to understanding muscle function?

By recording electrical activity of muscles Signup and view all the answers

What is the primary mechanism for force gradation at the level of motor units?

Temporal summation Signup and view all the answers

How is temporal summation studied to understand force gradation?

Recording muscle force response from artificial electrical stimulation Signup and view all the answers

What effect does increased firing rates of motor units have on force production?

Increases force due to more Ca2+ release Signup and view all the answers

What happens during temporal summation of twitches?

Multiple action potentials sum up to increase force Signup and view all the answers

At what range of frequencies are recruited motor units typically found during voluntary control?

8-10Hz Signup and view all the answers

What does surface EMG measure in terms of muscle activity?

Electrical activity of many asynchronously activated motor units Signup and view all the answers

What type of muscle action involves muscle shortening while generating force?

Concentric Signup and view all the answers

Which type of muscle contraction is generally not experienced in day-to-day activities?

Isokinetic Signup and view all the answers

What is the functional measure for movement combining speed with force?

Power Signup and view all the answers

Which type of muscle contraction involves muscle lengthening while generating force?

Eccentric Signup and view all the answers

In which type of muscle contraction does the load remain fixed while velocity varies throughout the range of motion?

Isotonic Signup and view all the answers

Why are smaller motor units first recruited and last derecruited during muscle force gradation?

To simplify motor control schemes by limiting fatigue in tasks requiring low force levels. Signup and view all the answers

How is the recruitment of motor units related to the Henneman Size Principle explained?

By the size of motoneurons and synaptic density. Signup and view all the answers

What is the significance of the Henneman Size Principle in muscle control?

It simplifies motor control by recruiting smallest, fatigue-resistant units first. Signup and view all the answers

What does the Henneman Size Principle suggest about the recruitment of motor units during tasks requiring low force levels?

Smallest, fatigue-resistant units are recruited first to limit fatigue development. Signup and view all the answers

What is the method of selective recording of individual activated motor units using trains of action potentials known as?

Intramuscular EMG Signup and view all the answers

How does the CNS benefit from following the Henneman Size Principle in motor control?

By simplifying motor control schemes through orderly recruitment based on size. Signup and view all the answers

Which factor influences the shape of the force-frequency curve indicating the relationship between electrical stimulation frequency and force output?

Type II motor unit Signup and view all the answers

What is the main reason behind the orderly recruitment pattern of motor units according to the Henneman Size Principle?

To limit fatigue by recruiting smallest, fatigue-resistant units first. Signup and view all the answers

What is critical for force production in a muscle according to the content provided?

The contractile state of the muscle Signup and view all the answers

Which method involves electrical stimulation of muscle to produce a fused tetanus response?

Neuromuscular electrical stimulation Signup and view all the answers

What does the force/frequency curve describe in relation to electrical stimulation input and force output?

The relationship between electrical stimulation frequency and force output Signup and view all the answers

Can all motor units of a muscle be recruited and maximally activated during voluntary efforts according to the content?

Yes, most of the time, in most people and most muscles Signup and view all the answers