Muscular System Part 1

Questions and Answers

What is the primary component of tendons in skeletal muscle?

Muscle fibers

Collagen fibers (correct)

Reticular fibers

Elastin fibers

Which type of muscle is characterized by no striations and is under involuntary control?

Striated muscle

Smooth muscle (correct)

Skeletal muscle

Cardiac muscle

What unique feature connects cardiac muscle cells together?

Intercalated discs (correct)

Aponeuroses

Tendons

Nervous junctions

Which function is NOT associated with skeletal muscle?

Contract rhythmically Signup and view all the answers

What structural feature gives skeletal muscle its striated appearance?

Myofibrils Signup and view all the answers

In which part of the body would you primarily find smooth muscle?

Walls of hollow organs Signup and view all the answers

What is a primary function of the epimysium in skeletal muscle?

Blend into connective tissue attachments Signup and view all the answers

What shape do the fibers of smooth muscle cells typically take?

Spindle-shaped Signup and view all the answers

What is the structural and functional unit of a skeletal muscle fiber called?

Sarcomere Signup and view all the answers

Which band contains only thin filaments and is lighter in appearance?

I band Signup and view all the answers

What type of protein primarily composes thick filaments?

Myosin Signup and view all the answers

How do the myosin heads interact during muscle contraction?

They become cross bridges with actin. Signup and view all the answers

What is stored and released by the sarcoplasmic reticulum to initiate muscle contraction?

Calcium Signup and view all the answers

What is the central area within the A band that lacks actin filaments called?

H zone Signup and view all the answers

Which component of muscle tissue is responsible for banding patterns produced by myofilaments?

Myofibrils Signup and view all the answers

What is the role of ATPase enzymes within thick filaments?

To split ATP and release energy for contractions. Signup and view all the answers

What does the term 'graded responses' refer to in skeletal muscle contraction?

Different degrees of skeletal muscle shortening. Signup and view all the answers

How can graded responses be produced in skeletal muscles?

By changing the frequency of muscle stimulation. Signup and view all the answers

What characterizes a 'muscle twitch'?

A single, brief, jerky contraction. Signup and view all the answers

What happens when muscle stimulations become more frequent?

Muscle contractions get stronger and smoother. Signup and view all the answers

What is meant by unfused (incomplete) tetanus in muscle contraction?

Sustained but oscillating contractions resulting in partial relaxation. Signup and view all the answers

Which statement is true about muscle fiber contraction?

Muscle fibers will contract fully when stimulated adequately. Signup and view all the answers

In a whole muscle, what may happen during a contraction?

Not all fibers may be stimulated during the same interval. Signup and view all the answers

What results from the summation of muscle contractions?

Smoother and stronger muscle contractions. Signup and view all the answers

What is achieved when the muscle is stimulated at a rapid rate without evidence of relaxation?

Fused tetanus Signup and view all the answers

Which of the following accurately describes how muscle force is generated?

Dependent on the number of fibers stimulated Signup and view all the answers

What is the primary energy source that directly powers muscle contraction?

ATP Signup and view all the answers

Which pathway provides ATP the fastest after initial depletion?

Direct phosphorylation by creatine phosphate Signup and view all the answers

How long can creatine phosphate supplies last during muscle contraction?

Less than 15 seconds Signup and view all the answers

What type of exercise primarily relies on anaerobic glycolysis?

Weight lifting Signup and view all the answers

What happens to ADP after ATP depletion during muscle contraction?

It receives a phosphate group to regenerate ATP Signup and view all the answers

Which metabolic pathway is responsible for supplying ATP during rest and light to moderate exercise?

Oxidative phosphorylation Signup and view all the answers

Which mechanism is NOT a method for regenerating ATP in muscle cells?

Electrolysis of muscular tissue Signup and view all the answers

What is produced from glucose during anaerobic glycolysis?

Lactic acid Signup and view all the answers

What factor is NOT suspected to contribute to muscle fatigue?

Increased ATP supply Signup and view all the answers

Isometric contractions are characterized by which of the following?

Tension increases while the muscle does not shorten Signup and view all the answers

During which type of muscle contraction do myofilaments slide past each other?

Isotonic contractions Signup and view all the answers

What is the primary byproduct of glucose breakdown during aerobic respiration?

Carbon dioxide Signup and view all the answers

What mechanism is used to repay the oxygen deficit after strenuous exercise?

Rapid, deep breathing Signup and view all the answers

How many ATP molecules are produced from anaerobic glycolysis?

2 ATP Signup and view all the answers

Study Notes

Connective Tissue and Muscle Attachments

Epimysium of skeletal muscle integrates with connective tissue to form attachments.
Tendons are cordlike structures primarily made of collagen fibers, designed for strength and small size to cross joints.
Aponeuroses are sheetlike structures that connect muscles to bones or connective tissues indirectly.

Types of Muscle Tissue

Smooth Muscle: Lacks striations, involuntary control, found in walls of hollow visceral organs (e.g., stomach, urinary bladder). Fibers are spindle-shaped and uninucleate with slow, sustained contractions.
Cardiac Muscle: Contains striations, also involuntary and found only in the heart. Composed of uninucleate, branching cells connected by intercalated discs via gap junctions, with contractions regulated by a pacemaker.

Functions of Muscle Tissue

All muscle types facilitate movement. Additionally, skeletal muscle plays vital roles in:
- Maintaining posture and body position.
- Stabilizing joints.
- Generating body heat.

Microscopic Anatomy of Skeletal Muscle

Sarcolemma: Specialized plasma membrane around muscle fibers.
Myofibrils: Long organelles with a striated appearance due to alternating light (I bands) and dark (A bands).
Sarcomere: The contractile unit of muscle fiber, the basic structural and functional element of skeletal muscle composed of thick (myosin) and thin (actin) filaments.

Myofilaments and Contraction Mechanism

Thick Filaments (Myosin): Mainly comprised of myosin proteins with ATPase enzymes to release energy for muscle contractions, featuring myosin heads that form cross bridges with thin filaments.
Thin Filaments (Actin): Primarily composed of actin, anchored to the Z disc. The zone devoid of actin within the A band is termed the H zone; this area diminishes during contraction as actin and myosin overlap.

Muscle Contraction and Graded Responses

Graded responses in muscle contraction reflect varying degrees of skeletal muscle shortening.
Muscle fibers exhibit an all-or-none response; a fiber either contracts completely or not at all when adequately stimulated.
Variations in fiber stimulation frequency and the number of fibers activated contribute to graded responses.

Types of Muscle Response to Stimulation

Muscle Twitch: A single, brief contraction; not typical during exercise.
Increased stimulation frequency leads to more robust and smoother contractions, known as unfused tetanus.
Fused Tetanus: Occurs with rapid stimulation, generating continuous contraction without relaxation.

Energy Sources for Muscle Contraction

ATP: The only direct energy source for muscle contraction, stored in small quantities.
After initial energy depletion, several pathways regenerate ATP:
- Creatine Phosphate (CP): Transfers a phosphate to ADP, rapidly regenerating ATP without oxygen and depleted in less than 15 seconds.
- Aerobic Respiration: Efficiently produces ATP using oxygen, breaking glucose into carbon dioxide and water, yielding approximately 32 ATP.
- Anaerobic Glycolysis: Generates about 2 ATP by breaking down glucose without oxygen, producing lactic acid.

Muscle Fatigue and Oxygen Debt

Strenuous and prolonged activity causes muscle fatigue due to:
- Ion imbalances (Ca²⁺, K⁺).
- Oxygen deficit and lactic acid build-up.
- Diminished ATP supply.
Oxygen debt is compensated post-exercise through rapid, deep breathing.

Muscle Contraction Types

Isotonic Contractions: Myofilaments slide past each other, causing muscle shortening and movement (e.g., bending knees, lifting weights).
Isometric Contractions: Muscle tensions increase without shortening, as seen when pushing against an immovable object.

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Description

Explore the intricate connective tissue structures associated with skeletal muscles, including epimysium, tendons, and aponeuroses. This quiz will help you understand the various muscle types and their attachments to bones and cartilage. Test your knowledge of muscle anatomy and connective tissues.