Muscle Physiology Quiz

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Questions and Answers

Which method is NOT a way in which a muscle fiber can acutely increase force output?

Decreasing firing rate of motor neurons (correct)

Recruiting more motor units

Preloading the muscle

Increasing speed of contraction

What is an example of an isometric muscle action?

Bicep curls

Lifting a weight

Doing a plank (correct)

Lowering a weight

As contraction speed increases, the force generated by a muscle fiber generally:

Increases

Becomes unpredictable

Decreases (correct)

Remains the same

Which type of contraction involves the muscle lengthening while producing force?

Eccentric contraction Signup and view all the answers

When aiming to generate maximum force during concentric contractions, what speed should you focus on?

Slow speeds Signup and view all the answers

Which term best defines contractions where muscle length changes and force is produced simultaneously?

Dynamic Signup and view all the answers

What is true about the relationship between force generation and eccentric muscle actions?

Force can be generated quickly without loss Signup and view all the answers

What defines isotonic contractions?

Force remains constant while length changes Signup and view all the answers

What is the primary function of muscle spindles?

To sense changes in muscle length and initiate the stretch reflex. Signup and view all the answers

How can more force be generated in a muscle without increasing the strength of the signal?

By recruiting more motor units. Signup and view all the answers

What occurs during summation in muscle contractions?

Increased frequency of stimuli prevents relaxation of muscle fibers. Signup and view all the answers

Where is isometric muscle action represented on the force velocity curve?

At a velocity of zero. Signup and view all the answers

What role do Golgi tendon organs (GTOs) play in muscle contraction?

They prevent excessive tension by signaling muscle relaxation. Signup and view all the answers

Power differs from force primarily because it includes which factor?

The time component of the action. Signup and view all the answers

What sequence is involved in the neurophysiological model of the stretch reflex?

Muscle spindle activation triggers signal to the spinal cord. Signup and view all the answers

What type of muscle contraction is considered the weakest?

Concentric contraction. Signup and view all the answers

What is the role of the amortization phase in the stretch-shortening cycle (SSC)?

To conduct a brief pause for optimal force production Signup and view all the answers

How does the Golgi tendon organ (GTO) activation benefit muscle stretching?

Promotes muscle relaxation for better range of motion Signup and view all the answers

In what order does the General Adaptation Syndrome (GAS) process occur?

Alarm, Resistance, Adaptation Signup and view all the answers

Which of the following best describes the eccentric phase of the SSC?

Muscle lengthening under tension Signup and view all the answers

Which of the following is NOT a neural adaptation to strength training?

Increased muscle fiber cross-sectional area Signup and view all the answers

Which type of training is primarily aimed at achieving hypertrophy?

Performing 6 to 12 repetitions with 67-85% load Signup and view all the answers

What occurs during the concentric phase of the stretch-shortening cycle?

Elastic energy from tendons is converted into kinetic energy Signup and view all the answers

Which of the following factors is NOT crucial for muscle adaptation in resistance training?

Regular consumption of protein supplements Signup and view all the answers

What is the primary role of beta receptors in the bronchi?

Relax bronchi to improve airflow Signup and view all the answers

Why do steroid hormones utilize intracellular receptors while peptide hormones do not?

Steroid hormones can pass through cell membranes Signup and view all the answers

What pathway does epinephrine use to stimulate fat metabolism?

Cyclic AMP pathway Signup and view all the answers

What is the main function of IGF-1 stimulated by growth hormone?

Stimulate fat metabolism Signup and view all the answers

What differentiates the mechanism of action between steroid and peptide hormones?

Peptide hormones bind to receptors on cell membranes Signup and view all the answers

During a graded exercise test (GXT), why do levels of epinephrine and norepinephrine increase?

As a response to physical stress and activation of the sympathetic nervous system Signup and view all the answers

Which hormone is produced by the adrenal cortex that aids in protein metabolism?

Cortisol Signup and view all the answers

What is the role of glucagon in glycogenolysis?

Activates cyclic AMP pathway to initiate glycogen breakdown Signup and view all the answers

What is the effect of increasing the firing rate of motor neurons in muscle contraction?

It can lead to a supramaximal force output. Signup and view all the answers

Which type of muscle fibers are primarily recruited for greater power outputs?

Type 2b fibers Signup and view all the answers

What does hypertrophy refer to in muscle development?

Increase in the size of muscle cells. Signup and view all the answers

Which adaptation occurs primarily in endurance athletes to improve VO2max?

Increase in a-vo2 difference. Signup and view all the answers

During acute responses to exercise, what typically happens to heart rate (HR) and stroke volume (SV)?

Both HR and SV increase. Signup and view all the answers

What is the role of RNA polymerase in transcription?

It synthesizes mRNA from DNA. Signup and view all the answers

What is primarily responsible for the release of growth hormone (GH) from the pituitary gland?

Growth releasing hormone from the hypothalamus. Signup and view all the answers

Which of the following statements about hyperplasia is correct?

It refers to an increase in the number of muscle cells. Signup and view all the answers

What happens to blood glucose levels during exercise?

They increase due to glycogen breakdown in the liver. Signup and view all the answers

What is a common chronic response to regular endurance training?

Increased muscular density. Signup and view all the answers

What is the primary role of glucagon in the body?

To promote the breakdown of glycogen to glucose Signup and view all the answers

Which hormone is primarily produced by adipose tissue and regulates body fat?

Leptin Signup and view all the answers

Which of the following statements about the JAK/STAT pathway is true?

STAT dimer regulates gene transcription after entering the nucleus. Signup and view all the answers

What adaptation occurs in response to aerobic training that contributes to improved cardiovascular efficiency?

Enhanced capillary density Signup and view all the answers

How does activating the AMPK pathway during exercise benefit individuals with Type 2 diabetes?

It enhances insulin sensitivity. Signup and view all the answers

What is the correct sequence of events in protein synthesis after a steroid hormone binds to its receptor?

Steroid binds to receptor, initiates gene transcription, mRNA is translated. Signup and view all the answers

Which factor is NOT associated with an increased VO2max?

Decreased capillary density Signup and view all the answers

Which of the following muscle adaptations occurs at rest after aerobic training?

Lower excess post-exercise oxygen consumption (EPOC) Signup and view all the answers

Study Notes

Muscle Fiber Force Output

Muscle fibers acutely increase force output through five ways:
- Recruiting more motor units. This depends on the load.
- Increasing the firing rate of motor neurons. Repeated activation without relaxation allows tension summation.
- Recruiting specific motor unit types. Type 1 (slow-twitch) fibers are used for strength, while Type 2 (fast-twitch) fibers are used for power.
- Activating the stretch reflex using preloading. The muscle is activated as it's stretched.
- Increasing the speed of contraction.

Muscle Actions

Static (isometric): The muscle produces force, but its length doesn't change. Examples include planks and wall sits.
Dynamic: The muscle produces force, and its length changes.
- Concentric: The muscle shortens while producing force. An example is lifting weights (reps).
- Eccentric: The muscle lengthens while producing force. An example is lowering weights (reps).
Isotonic: The force stays the same during the movement. Examples often include bicep curls.
Isokinetic: The speed of the movement stays the same, meaning it can be concentric or eccentric. Examples include weight machines or hydro-exercise.

Force and Velocity Relationship

Force and velocity of contraction are inversely related. As velocity increases, force decreases (and vice versa). Faster contractions generate less force. This is primarily seen in concentric isotonic contractions (shortening/speed).

Muscle Spindles and GTOs

Muscle spindles are located within muscles. They sense changes in muscle length and trigger the stretch reflex to prevent excessive stretching and maintain stability.
Golgi tendon organs (GTOs) are located within the tendons. They detect tension in the tendon and trigger relaxation to prevent muscle damage during forceful contractions.

General Adaptation Syndrome (GAS)

This is a physiological response to stress, including resistance training.
The process includes alarm, resistance, and an adaptation or exhaustion period.
Proper recovery leads to adaptation, while improper recovery leads to exhaustion.

Neural Adaptations in Strength

Neural adaptations are important in early strength gains.
Greater recruitment of motor units and improved stimulation of motor units allow for increased force production. Proprioceptors also play a role.

Muscle Hypertrophy

Hypertrophy is an increase in muscle size.
Sarcoplasmic hypertrophy involves an increase in the amount of sarcoplasm (fluid portion of muscle cells).
Myofibrillar hypertrophy involves an increase in the size of the myofibrils, increasing the number of myofilaments (actin and myosin).

Bioenergetic Adaptations

Bioenergetics is a component of endurance training that enhances the processes of producing and delivering energy.

VO2 (Oxygen Consumption)

VO2 is the measurement of oxygen consumption.
VO2 max is the maximal amount of oxygen that can be consumed during exercise.

Hormonal Responses

During exercise, various hormones play critical roles and are regulated by the hypothalamus and the pituitary gland.
Hormones like GH, epinephrine, and norepinephrine play a part in acute responses to exercise.
Long-term adaptations can include changes in muscle's ability to produce energy and the cardiovascular system's capacity.

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Description

Test your knowledge on muscle physiology with this quiz covering various aspects of muscle contractions, force generation, and the roles of different muscle receptors. Answer questions about isometric, eccentric, and isotonic contractions, as well as how muscles adapt to generate force. Perfect for students studying kinesiology or exercise science.