Muscle Control and Contraction Types

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Questions and Answers

What effect does frequency of stimulation have on muscle tension?

It can increase muscle tension through twitch summation. (correct)

It makes the muscle fibers relax more quickly.

It does not affect muscle tension.

It decreases muscle tension.

What distinguishes isometric contraction from isotonic contraction?

Isometric contraction maintains constant muscle length while generating tension. (correct)

Isometric contraction can only be sustained for short durations.

Isometric contraction involves muscle shortening while isotonic does not.

Isometric contraction is responsible for body movements.

What is the primary outcome of tetanus in muscle fibers?

Continuous contraction without relaxation occurs. (correct)

Muscle fibers relax completely.

Muscle fibers exhibit less stiffness.

Muscle fibers can generate only one twitch.

Which factor does NOT influence the extent of muscle tension that can be developed?

Color of the muscle fiber. Signup and view all the answers

Which type of contraction involves changing muscle length while the load remains constant?

Isotonic contraction. Signup and view all the answers

What is the role of the sensory receptors in muscle tension monitoring?

They monitor muscle tension and length. Signup and view all the answers

What primarily causes muscular fatigue?

Depletion of energy sources and accumulation of lactic acid. Signup and view all the answers

Which statement accurately describes twitch summation?

It occurs when repetitive stimulation allows higher tensions. Signup and view all the answers

What occurs during concentric contraction?

Muscle fibers shorten while contracting. Signup and view all the answers

What role does muscle tone play in the body?

It maintains postural stability. Signup and view all the answers

Which of the following is NOT a type of muscle proprioceptor?

Alpha motor neuron Signup and view all the answers

What primarily regulates muscle tone?

Postural reflexes and motor system output Signup and view all the answers

Which pathway is NOT involved in supplying ATP during muscle contraction?

Lactic acid fermentation Signup and view all the answers

What is the purpose of the Golgi tendon organ?

Detect changes in muscle tension. Signup and view all the answers

How does muscle contraction continue in a muscle fiber?

By constantly supplying ATP. Signup and view all the answers

What distinguishes internal muscles from external muscles?

Internal muscles contain muscle spindles. Signup and view all the answers

What is the initial source of ATP during the onset of exercise?

Creatine phosphate Signup and view all the answers

What enzyme catalyzes the reaction of creatine phosphate donating a phosphate group to ADP?

Creatine kinase Signup and view all the answers

How many ATP molecules are generated through oxidative phosphorylation from one glucose molecule?

32 Signup and view all the answers

Which of the following factors increases oxygen availability to muscles during exercise?

Increased myoglobin in some muscle types Signup and view all the answers

What happens when oxygen delivery cannot meet the ATP demand during intense exercise?

Glycolysis increases to generate ATP anaerobically Signup and view all the answers

Which statement correctly compares glycolysis with oxidative phosphorylation?

Glycolysis can occur without oxygen, while oxidative phosphorylation cannot. Signup and view all the answers

What is a disadvantage of using glycolysis for ATP production during high-intensity exercise?

Cannot sustain energy for long periods Signup and view all the answers

What is the primary end product of anaerobic glycolysis when oxygen is not available?

Lactate Signup and view all the answers

What primarily causes muscle fatigue during intense exercise?

Increase in inorganic phosphate Signup and view all the answers

Which type of muscle fibers is best suited for endurance activities?

Slow-oxidative (type I) fibers Signup and view all the answers

What term describes the oxygen deficit that occurs during high-intensity exercise?

Oxygen debt Signup and view all the answers

How does aerobic exercise affect muscle fibers?

Increases capillary supply to oxidative fibers Signup and view all the answers

What must happen to lactate for its conversion back into a usable form for energy production?

It requires conversion back to pyruvate, which needs oxygen Signup and view all the answers

Which factor does NOT influence the speed of muscle contraction?

Duration of exercise Signup and view all the answers

What physiological change is indicative of central fatigue?

Inadequate activation of motor neurons Signup and view all the answers

What is the main energy source for fast-glycolytic (type IIx) muscle fibers?

Glycolytic metabolism Signup and view all the answers

Study Notes

Control of Muscle Tension

Muscle tension depends on the number of muscle fibers contracting and the tension developed by each contracting fiber.
Factors influencing tension development:
- Frequency of stimulation
- Length of the fiber at the onset of contraction
- Extent of fatigue
- Thickness of the fiber

Twitch Summation and Tetanus

A single action potential produces only one muscle twitch.
Repeated fiber stimulation produces longer and greater tension.
Stimulation of the muscle fiber by a second stimuli before it has completely relaxed causes a second contractile response that adds on top of the first twitch, known as twitch summation.
Tetanus is a continuous contraction without relaxation due to rapid stimulation, which is 3-4 times stronger than a single twitch.
Twitch summation is possible because the action potential duration is much shorter than the twitch duration.

Types of Contraction

Isotonic Contraction: The load remains constant as the muscle changes length. Used for body movements and moving objects.
Isometric Contraction: The muscle is prevented from shortening so tension develops at constant muscle length.

Concentric and Eccentric Contraction

Concentric Contraction: Muscle shortening while contracting.
Eccentric Contraction: Muscle fiber lengthening while still actively contracted in opposition to being passively stretched by the load.

Muscle Tone

Ongoing, involuntary, low-level state of tension in a muscle even at rest.
Important in maintaining postural stability.
Results from elastic properties of the muscle and continuous minimal stimulation by motor neurons.
Regulated by postural reflexes and output from the multineuronal motor system.

Muscle Sensory Receptors

Proprioceptors are found in joints and muscles providing information about body part location and movement.
Two types:
- Golgi Tendon Organ: Detects changes in muscle tension.
- Muscle Spindle: Monitors muscle length.

Muscle Spindles

External muscle (skeletal muscle) is innervated by alpha motor neurons.
Internal muscle (skeletal muscle with muscle spindles) is innervated by sensory neurons and other motor neurons.

Production of ATP in Muscle Fibers

Three pathways supply additional ATP during muscle contraction:
- Creatine Phosphate: Provides ATP rapidly, especially at the start of exercise.
- Oxidative Phosphorylation: Takes place in the mitochondria with the presence of oxygen. Provides a rich yield of ATP but is relatively slow.
- Glycolysis: Used when oxygen delivery or oxidative phosphorylation cannot keep up with ATP demand. Can occur anaerobically, but has a lower ATP yield and leads to lactate production.

Fatigue

Muscle fatigue occurs when the muscle can no longer respond to stimulation with the same degree of contractile activity.
Central fatigue occurs when the central nervous system no longer adequately activates motor neurons.

Types of Muscle Fibers

Slow-Oxidative (Type I) Fibers: Slow contraction speed, primarily use oxidative phosphorylation for ATP.
Fast-Oxidative (Type IIa) Fibers: Fast contraction speed, use a mix of oxidative phosphorylation and glycolysis for ATP.
Fast-Glycolytic (Type IIx) Fibers: Fastest contraction speed, primarily use glycolysis for ATP.

Effects of Exercise on the Muscle

Aerobic Exercise: Promotes metabolic changes within oxidative muscle fibers by increasing mitochondria and capillaries.
Resistance Exercise: Promotes hypertrophy of muscle fibers, increasing the number of myofibrils and sarcomeres.

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Description

This quiz explores the control of muscle tension, focusing on factors that influence tension development. It covers concepts such as twitch summation and tetanus, along with the different types of muscle contractions. Test your understanding of how muscles respond to stimulation and the mechanics behind muscle contractions.