Muscle Physiology Quiz

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Questions and Answers

Which type of muscle is responsible for voluntary control?

Intercalated Muscle

Smooth Muscle

Cardiac Muscle

Skeletal Muscle (correct)

What is the primary location of cardiac muscle tissue?

Walls of the heart (correct)

Digestive tract

Skin

Attached to bones

How is the contraction of smooth muscle typically controlled?

By the nervous system and hormones (correct)

By direct stimulation from skeletal muscle

Automatically with no control mechanisms

Voluntarily with conscious thought

Which of the following is NOT a function of skeletal muscle?

Regulating blood pressure Signup and view all the answers

Which muscle type contains intercalated discs?

Cardiac Muscle Signup and view all the answers

What characterizes isotonic contractions?

Muscle shortens and movement occurs Signup and view all the answers

Which of the following is an example of an isometric contraction?

Pushing your palms together Signup and view all the answers

What is the primary purpose of muscle tone?

To provide a state of continuous partial contraction Signup and view all the answers

During which type of contraction do muscle filaments attempt to slide but cannot due to an immovable object?

Isometric contractions Signup and view all the answers

Muscle tone results from the systematic stimulation of which of the following?

Motor neurons in a synchronized manner Signup and view all the answers

What is the primary role of an antagonist muscle in movement?

It produces a reversing effect. Signup and view all the answers

Which type of muscle is responsible for reducing unwanted or excess motion in a joint?

Synergist Signup and view all the answers

What is the function of a fixator muscle during movement?

To stabilize the origin of a prime mover or hold a bone still. Signup and view all the answers

Which muscle type primarily leads the movement in a given action?

Prime mover Signup and view all the answers

Which of the following statements is true about synergist muscles?

They facilitate the movement by helping the prime mover. Signup and view all the answers

What is one of the primary functions of skeletal muscle, aside from producing movement?

Generate heat Signup and view all the answers

Which property of skeletal muscle refers to its ability to respond to stimuli?

Irritability Signup and view all the answers

What is the role of myofibrils within muscle cells?

Organelles that enable contraction Signup and view all the answers

What does the term 'extensibility' refer to in the context of skeletal muscle?

The ability to be stretched Signup and view all the answers

Which component of skeletal muscle gives it a striated appearance?

Light (I) and dark (A) bands Signup and view all the answers

What does 'contractility' refer to in skeletal muscles?

The ability to forcibly shorten Signup and view all the answers

In the case of a dislocated shoulder, which role of skeletal muscles is primarily compromised?

Stabilize joints Signup and view all the answers

Which property of skeletal muscle allows it to return to its resting length after being stretched?

Elasticity Signup and view all the answers

What initiates the attachment of myosin heads to actin in muscle contraction?

The binding of calcium ions to regulatory proteins Signup and view all the answers

Which of the following describes the 'all-or-none' principle of muscle fiber contraction?

Once stimulated adequately, all fibers contract to their maximum. Signup and view all the answers

How is energy provided for the sliding process during muscle contraction?

From the hydrolysis of ATP Signup and view all the answers

What occurs during the pivoting of the cross bridge in muscle contraction?

Thin filaments slide toward the center of the sarcomere. Signup and view all the answers

What is one way that graded responses in skeletal muscle contraction can be achieved?

By altering the frequency of stimulation Signup and view all the answers

What happens to muscle fibers in a skeletal muscle during different intervals of stimulation?

Not all fibers may be stimulated at the same time. Signup and view all the answers

What is the result of multiple cross bridges attaching and detaching during muscle contraction?

Sustained muscle contraction and shortening Signup and view all the answers

What is the significance of calcium ions in muscle contraction?

They enable the exposure of myosin-binding sites. Signup and view all the answers

What is the main role of a fixator muscle?

To anchor the origin of the prime mover Signup and view all the answers

Which muscle group primarily produces extension at a joint?

Muscles that cross the posterior side of the joint Signup and view all the answers

What action do muscles crossing on the medial side of a joint produce?

Adduction Signup and view all the answers

An example of a muscle that produces flexion is?

Pectoralis major Signup and view all the answers

Which of the following muscles is an antagonist to the pectoralis major?

Latissimus dorsi Signup and view all the answers

Which muscle action is produced by muscles that cross the lateral side of a joint?

Abduction Signup and view all the answers

In the context of muscle actions, what does a muscle crossing on the anterior side generally produce?

Flexion Signup and view all the answers

What is true about muscles crossing the knee and ankle joints in terms of their actions?

They do not conform to typical muscle action rules Signup and view all the answers

Study Notes

Introduction

Skeletal muscles require stimulation from motor neurons (nerve cells) to contract.
A motor unit is one motor neuron and all the skeletal muscle cells it stimulates.

Muscle Types

Skeletal muscles are surrounded and bundled by connective tissues—Endomysium surrounds individual muscle fibers Perimysium surrounds fascicles (bundles) of muscle fibers. Epimysium surrounds the entire skeletal muscle. Fascia is on the outside of the epimysium that blends with deep fascia.
Skeletal, Cardiac, and Smooth muscles have different characteristics, structures, and functions; they are also grouped within the body by CT coverings,
The epimysium of skeletal muscle blends with connective tissue attachment.
Tendons are cordlike structures mostly made of collagen fibers.
Aponeuroses are sheetlike structures of fibrous tissue.

Muscle Tissue Characteristics

Irritability/Responsiveness: the ability to receive and respond to a stimulus.
Contractility: the ability to forcibly shorten when stimulated.
Extensibility: the ability to be stretched.
Elasticity: the ability to recoil and resume resting length.

Microscopic Anatomy of Skeletal Muscle

Sarcolemma: specialized plasma membrane.
Myofibrils: long organelles inside muscle cells.
Light (I) Bands and Dark (A) bands give the muscle its striated (banded) appearance and are important parts of the Sarcomere.
Sarcoplasmic Reticulum (SR): specialized smooth endoplasmic reticulum that surrounds the myofibrils and stores and releases calcium.

Sarcomeres

Contractile unit of skeletal muscle cells.
Composed of thick (myosin) and thin (actin) filaments, organized in repeating units
Thick filaments: composed of the protein myosin, ATPase enzymes to split ATP to release energy, and possess projections (myosin heads).
Thin filaments: composed of the contractile protein actin, are anchored to the Z disc. At rest, the band lacks actin filaments called the H zone.

Muscle Contraction

Sliding Filament Theory describes myosin heads pulling on actin filaments causing the muscle cell to shorten, requiring Ca2+ and ATP; with AP stopping Ca supply for the final step.
Action potentials travel deep into the muscle fiber along membranous tubules (T-tubules), stimulating the SR to release Ca2+, triggering binding of myosin to actin, and initiating filament sliding. Contraction occurs and continues as long as calcium ions are available
Cells return to their resting state; regulatory proteins returning to their resting shape, blocking myosin-binding sites.

Muscle Functions

Skeletal muscle has three roles beyond movement: maintaining posture and body position, stabilizing joints, and generating heat.

Neuromuscular Junction

Synapse: association site of the axon terminal, of the motor neuron and the sarcolemma of a muscle.
Neurotransmitter: chemical released by nerves upon arrival of nerve impulses in the axon terminal.
Acetylcholine (ACh): neurotransmitter that stimulates skeletal muscle.
Synaptic cleft: gap between nerve and muscle filled with interstitial fluid.

Contraction of a Skeletal Muscle as a Whole

Graded responses: different degrees of skeletal muscle shortening in response to different stimuli, by changing the frequency and number of muscle cells stimulated in one moment.
Summation of contractions: as more action potentials occur and the muscle doesn't have time to completely relax between, the muscle will begin to have stronger force with each new contraction.
Tetanus: if stimulation is very rapid, the muscle contractions will fuse into a smooth, sustained contraction.
Muscle force depends on the number of fibers stimulated. When all motor units are active and stimulated, the muscle contraction is as strong as it can get.

Providing Energy for Muscle Contraction

ATP is the primary source of energy for muscle contraction.
Three pathways regenerate ATP: direct phosphorylation of ADP by creatine phosphate, aerobic respiration, and anaerobic glycolysis and lactic acid formation.

Muscle Fatigue and Oxygen Deficit

If muscle activity is strenuous and prolonged, muscle fatigue occurs.
Factors contributing to fatigue: ion imbalances, oxygen deficit, and lack of energy (ATP) supply, lactic acid accumulation.
After exercise, the oxygen deficit is repaid by rapid, deep breathing to restore oxygen and ATP levels.

Types of Muscle Contractions

Isotonic contractions: muscle shortens and movement occurs.
Isometric contractions: muscle filaments try to slide, but the muscle is pitted against an immovable object, and tension increases but muscles do not shorten.

Muscle Tone

State of continuous partial contractions of a muscle.
Result of systematic stimulation of different motor units at different intervals

Effect of Exercise on Muscles

Aerobic exercise results in stronger, more flexible muscles with greater resistance to fatigue, improved metabolism, and better functioning of the nervous system.
Resistance exercise, like weightlifting, increases muscle size and strength. Individual muscle fibers enlarge.

Naming Skeletal Muscles

Direction of muscle fibers (e.g., rectus).
Relative size of muscle (e.g., maximus).
Location of muscle (e.g., temporalis).
Number of origins (e.g., triceps).
Location of origin and insertion (e.g., sterno-cleido-mastoid).
Shape of muscle (e.g., deltoid).
Action of muscle (e.g., flexor, extensor).

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Description

Test your knowledge on muscle physiology, including types of muscles, their functions, and contractions. This quiz covers key concepts related to skeletal, cardiac, and smooth muscles, as well as their roles in movement. Prepare to challenge your understanding of muscle tone, isotonic and isometric contractions, and more.