Muscle Tissue Quiz for Biology Class 11

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Questions and Answers

Which type of muscle tissue is categorized as involuntary?

Smooth muscle

Skeletal muscle

Both B and C (correct)

Cardiac muscle

What is the ability of muscle to respond to stimuli called?

Extensibility

Excitability (correct)

Contractility

Elasticity

Which connective tissue sheath directly surrounds individual muscle fibers?

Epimysium

Perimysium

Fascia

Endomysium (correct)

Which of the following is NOT a function of muscles?

Produce exchange of gases Signup and view all the answers

What role do nerves play in skeletal muscle function?

They control activity of muscle fibers. Signup and view all the answers

Which characteristic of muscle refers to its ability to return to its resting length after being stretched?

Elasticity Signup and view all the answers

Which of the following muscle types is under conscious control?

Skeletal muscle Signup and view all the answers

What is the dense irregular connective tissue that surrounds an entire skeletal muscle called?

Epimysium Signup and view all the answers

What primarily affects the force of muscle contractions?

The number of cross bridges attached Signup and view all the answers

Which factor does NOT influence force of muscle contraction?

Type of exercise performed Signup and view all the answers

Which statement regarding muscle fiber recruitment is true?

It involves activating more motor units. Signup and view all the answers

How does the relative size of muscle fibers affect muscle contraction?

Bulkier muscles can develop more tension. Signup and view all the answers

At what degree of muscle stretch do sarcomeres generate maximum force?

Between 80% and 120% of resting length Signup and view all the answers

Which factor does NOT influence the speed of muscle contraction?

Hydration levels in the muscle Signup and view all the answers

What role does the frequency of stimulation play in muscle contraction?

Higher frequencies increase the contraction force. Signup and view all the answers

What happens when a sarcomere is stretched beyond 120% of its resting length?

Force of contraction decreases. Signup and view all the answers

What is the primary attachment point of a muscle that is less movable?

Origin Signup and view all the answers

What type of attachment is considered the most common for muscles?

Indirect attachment Signup and view all the answers

Which structural feature of skeletal muscle accounts for approximately 80% of the muscle cell volume?

Myofibrils Signup and view all the answers

What is the smallest contractile unit of a skeletal muscle fiber?

Sarcomere Signup and view all the answers

What feature is characteristic of the A band in myofibrils?

Dark region Signup and view all the answers

Which of the following is NOT a component of the myofilament structure within a sarcomere?

Collagen Signup and view all the answers

What provides the resistance against abrasion from rough bony projections in muscles?

Collagen fibers Signup and view all the answers

What structure serves as the muscle fiber plasma membrane?

Sarcolemma Signup and view all the answers

What initiates the process of cross bridge formation in muscle contraction?

Attachment of the myosin head to actin Signup and view all the answers

What distinguishes smooth muscle from skeletal muscle regarding connective tissue?

Smooth muscle contains only endomysium. Signup and view all the answers

During the working stroke of the cross bridge cycle, what movement occurs?

Myosin head pivots and pulls the thin filament toward the M line Signup and view all the answers

In smooth muscle, how is calcium primarily sourced for contraction?

From extracellular sources predominately. Signup and view all the answers

What causes the detachment of the myosin head from the actin filament?

Attachment of ATP to the myosin head Signup and view all the answers

What is the arrangement of thick and thin filaments in smooth muscle?

They have a diagonal arrangement. Signup and view all the answers

What role does Ca2+ play in muscle contraction?

Ca2+ binds to troponin, exposing myosin-binding sites on actin Signup and view all the answers

What is the role of calmodulin in smooth muscle?

It binds to calcium to regulate contraction. Signup and view all the answers

What is the primary mechanism for the cessation of contraction in muscle fibers?

Pumping of Ca2+ back into the sarcoplasmic reticulum Signup and view all the answers

Which statement accurately describes the electrical connections between smooth muscle fibers?

Smooth muscle fibers are connected via gap junctions. Signup and view all the answers

Which of the following correctly describes the cocking of the myosin head?

It results from the hydrolysis of ATP, positioning myosin in a high-energy state Signup and view all the answers

What must occur before cross bridge cycling begins?

Release of ACh at the neuromuscular junction Signup and view all the answers

Why does smooth muscle have a greater power despite having fewer thick filaments?

Thick filaments have myosin heads along their entire length. Signup and view all the answers

What defines the bulging appearance of smooth muscle during contraction?

The location of dense bodies. Signup and view all the answers

What is the sequence of events at the neuromuscular junction that leads to muscle contraction?

Action potential, ACh release, Ca2+ influx, myosin binding Signup and view all the answers

Which feature is absent in smooth muscle that is typically found in skeletal muscle?

Striations and sarcomeres. Signup and view all the answers

What is the role of calmodulin in smooth muscle contraction?

It binds to calcium and activates myosin kinase. Signup and view all the answers

How does smooth muscle contraction differ from skeletal muscle contraction?

Smooth muscle contraction is triggered by increased intracellular calcium levels. Signup and view all the answers

Which statement is true about the mechanism of relaxation in smooth muscle?

Dephosphorylation of myosin allows relaxation. Signup and view all the answers

What characterizes unitary smooth muscle?

It contains many gap junctions facilitating synchronous contraction. Signup and view all the answers

What is a key function of the stress-relaxation response in smooth muscle?

It allows temporary storage of contents in organs. Signup and view all the answers

Which component is primarily responsible for initiating contraction in smooth muscle?

Calcium ions from extracellular space. Signup and view all the answers

What distinguishes multiunit smooth muscle from unitary smooth muscle?

Independent contraction of muscle fibers. Signup and view all the answers

What mechanism stops contraction in smooth muscle?

Calcium detachment from calmodulin. Signup and view all the answers

What role does ATP play during smooth muscle contraction?

It energizes the sliding process of actin and myosin. Signup and view all the answers

How do neural stimuli affect smooth muscle contraction?

They can modify the rate and intensity of contraction. Signup and view all the answers

Study Notes

Muscle Tissue Overview

Muscle tissue is responsible for movement, posture maintenance, and heat production.
Three types of muscle tissue exist: skeletal, cardiac, and smooth.

Types of Muscle Tissue

Skeletal muscle: Voluntary muscle attached to bones, responsible for locomotion and manipulation.
- Cells (fibers) are long, cylindrical, multinucleated, and striated.
- Controlled consciously.
Cardiac muscle: Involuntary muscle found only in the heart.
- Cells are branching, uni- or binucleate, and striated.
- Controlled involuntarily.
Smooth muscle: Involuntary muscle found in the walls of hollow organs (except the heart).
- Cells are spindle-shaped, uninucleate, and non-striated.
- Controlled involuntarily

Muscle Characteristics

Excitability (responsiveness): Ability to receive and respond to stimuli.
Contractility: Ability to shorten forcibly when adequately stimulated.
Extensibility: Ability to be stretched.
Elasticity: Ability to recoil and resume resting length after stretching.

Skeletal Muscle Anatomy

Nerve and blood supply: Skeletal muscle requires substantial oxygen and nutrients, and waste removal during contraction. Nerves control each fiber separately, enabling precise control.
Connective tissue sheaths: Sheaths of connective tissue (epimysium, perimysium, and endomysium) surround and support individual muscle fibers and groups of fibers (fascicles).
- Epimysium: Dense irregular connective tissue surrounding the entire muscle.
- Perimysium: Fibrous connective tissue surrounding fascicles (bundles of muscle fibers).
- Endomysium: Fine areolar connective tissue wrapping each muscle fiber.
Attachments: Muscles attach to bones in at least two points:
- Origin: Attachment to the less movable bone.
- Insertion: Attachment to the movable bone. -Direct (fleshy): Epimysium fused to periosteum. -Indirect: Connective tissue wrappings extend beyond the muscle as a tendon or aponeurosis.

Skeletal Muscle Microscopic Anatomy

Sarcolemma: Muscle fiber's plasma membrane.
Sarcoplasm: Muscle fiber's cytoplasm, containing glycogen for energy storage and myoglobin for oxygen storage.
Myofibrils: Densely packed, rod-like elements that run the length of the muscle fiber.
Sarcomeres: Smallest contractile unit of a muscle fiber, organized as repeating sections along myofibrils.
Myofilaments: Actin (thin) and myosin (thick) filaments within sarcomeres, responsible for the sliding filament mechanism of contraction.
- Actin filaments: Composed of actin, troponin, and tropomyosin.
- Myosin filaments: Composed of the myosin protein with heads that bind to actin.
Sarcoplasmic reticulum (SR): Smooth endoplasmic reticulum surrounding myofibrils, storing and releasing calcium ions (Ca2+).
T tubules: Infoldings of the sarcolemma, extending deep into the muscle fiber to conduct electrical impulses to the SR.

Excitation-Contraction Coupling

Sequence of events linking electrical stimulation to muscle contraction.
Action potentials travel along the sarcolemma and down the T tubules to stimulate Ca2+ release from the SR.
Ca2+ binding to troponin exposes myosin-binding sites on actin, leading to cross-bridge formation.

Sliding Filament Model of Muscle Contraction

Overlapping actin and myosin filaments slide past each other during contraction.
Actin filaments move towards the center of the sarcomere (M line).
Z discs move closer together, causing sarcomere shortening.

Cross-Bridge Cycling

Cycle of events during muscle contraction.

Cross-bridge formation: Myosin head binds to actin.
Power stroke: Myosin head pivots, pulling actin.
Cross-bridge detachment: ATP binds to myosin, causing detachment from actin.
Myosin reactivation: ATP hydrolysis "recocks" myosin head.

ATP Usage in Muscle Contraction

ATP required for cross-bridge cycling, Ca2+ pump, and other cellular activities.
ATP is regenerated quickly through three mechanisms:
- Creatine phosphate (CP) phosphorylation: Provides rapid ATP regeneration.
- Anaerobic pathway (glycolysis): Generates ATP without oxygen but produces lactic acid.
- Aerobic respiration: Provides most ATP during prolonged activity but requires oxygen.

Muscle Fatigue

Physiologic inability to contract despite continued stimulation.
Causes include: ionic imbalances, insufficient ATP, decreased glycogen, increased inorganic phosphate, and magnesium.

EPOC (Excess Postexercise Oxygen Consumption)

Extra oxygen needed to replenish ATP and CP, convert lactic acid, and resynthesis glycogen.

Types of Contractions

Isotonic contractions: Muscle changes length and moves a load.
- Concentric: Muscle shortens and does work (e.g., lifting a weight).
- Eccentric: Muscle lengthens while maintaining tension (e.g., lowering a weight).
Isometric contractions: Muscle develops tension but does not change length (e.g., pushing against a wall).

Other Important Factors

Motor units: A motor neuron and all the muscle fibers it innervates.
Muscle twitch: Simplest contraction resulting from a muscle fiber's response to a single action potential.
Graded muscle responses: Variations in the degree of muscle contraction, including temporal (wave) summation and recruitment, crucial for controlling skeletal movement.
Muscle fiber types: Skeletal muscle fibers are categorized by their speed of contraction (slow or fast) and primary metabolic pathways (oxidative or glycolytic); different types are specialized for different functions.
Smooth muscle: Differs from skeletal muscle in structure (e.g., no striations, less developed SR), mechanism of contraction (e.g., Ca2+ binding to calmodulin rather than troponin), and functional characteristics (e.g. stress-relaxation response).

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Description

Test your knowledge on muscle tissue with this engaging quiz designed for Biology Class 11 students. You'll explore topics like muscle types, functions, and characteristics, helping you reinforce your understanding of this fundamental subject. Perfect for exam preparation or self-assessment!