Muscle Contraction and Structure Quiz
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Questions and Answers

What plays a critical role in muscle contraction by connecting to actin?

  • Acetylcholine
  • Calcium ions
  • Myosin (correct)
  • Tropomyosin

The strength of a muscle contraction relies solely on the size of the muscle fibers involved.

False (B)

What neurotransmitter is responsible for stimulating muscle contraction?

Acetylcholine

The process of myofilaments sliding past each other during muscle contraction is explained by the _______.

<p>Sliding Filament Theory</p> Signup and view all the answers

Match the structures with their functions in muscle contraction:

<p>Myosin = Attaches to actin and pulls Actin = Forms the thin filament Calcium ions = Stimulates muscle contraction by binding to troponin Acetylcholine = Neurotransmitter that initiates muscle contraction</p> Signup and view all the answers

Which type of muscle forms the structure of the heart?

<p>Cardiac Muscle (A)</p> Signup and view all the answers

Skeletal muscle is primarily responsible for involuntary movements.

<p>False (B)</p> Signup and view all the answers

What is the function of epimysium in skeletal muscle?

<p>Covers the whole muscle.</p> Signup and view all the answers

The thin layer of connective tissue surrounding each muscle fiber is called the ______.

<p>endomysium</p> Signup and view all the answers

Match the following muscle types with their characteristics:

<p>Skeletal Muscle = Attaches to bones for movement Smooth Muscle = Forms hollow organs Cardiac Muscle = Involuntary muscle that makes up the heart Fascia = Connective tissue separating muscle layers</p> Signup and view all the answers

What is the main role of myofibrils in skeletal muscle?

<p>Facilitating muscle contractions (A)</p> Signup and view all the answers

What differentiates myosin and actin in muscle tissue?

<p>Myosin is a thick myofilament, while actin is a thin myofilament.</p> Signup and view all the answers

The sarcoplasmic reticulum is responsible for the storage of sodium ions.

<p>False (B)</p> Signup and view all the answers

What is the role of calcium ions in muscle contraction?

<p>They initiate the contraction process. (A)</p> Signup and view all the answers

The H-zone contains both actin and myosin filaments.

<p>False (B)</p> Signup and view all the answers

What connects a nerve fiber to a muscle fiber?

<p>Neuromuscular Junction</p> Signup and view all the answers

The __________ is the light band composed of thin actin filaments.

<p>T-band</p> Signup and view all the answers

Match the components with their functions:

<p>Sarcoplasmic Reticulum = Stores calcium ions T-tubules = Transmits signals from the sarcolemma M-line = Anchors myosin filaments Synaptic Cleft = Releases neurotransmitters</p> Signup and view all the answers

Which of the following describes the A-band?

<p>It contains thick myosin filaments overlapping with thin actin filaments. (A)</p> Signup and view all the answers

Every muscle fiber has multiple motor end plates.

<p>False (B)</p> Signup and view all the answers

The __________ provides a gap between the motor end plate and neuron.

<p>Synaptic cleft</p> Signup and view all the answers

What is the role of acetylcholine (ACh) in muscle contraction?

<p>It is released when a nerve impulse reaches the presynaptic terminal. (A)</p> Signup and view all the answers

Muscle relaxation occurs when calcium ions are actively transported back to the sarcoplasmic reticulum.

<p>True (A)</p> Signup and view all the answers

What phenomenon describes a muscle fiber contracting completely when a threshold stimulus is applied?

<p>All-or-None Response</p> Signup and view all the answers

The enzyme that decomposes acetylcholine is called __________.

<p>acetylcholinesterase</p> Signup and view all the answers

Match the following components involved in muscle contraction with their functions:

<p>Acetylcholine = Chemical that signals muscle contraction Calcium Ions = Facilitates sliding filament movement ATP = Primary energy source for muscle contractions Creatine Phosphate = Transfers energy in active muscles</p> Signup and view all the answers

What happens to muscle fibers when the nerve impulse stops?

<p>Cross-bridges between actin and myosin are broken. (D)</p> Signup and view all the answers

Less than half of the energy produced during muscle activity is utilized for muscle contraction.

<p>True (A)</p> Signup and view all the answers

Threshold stimuli are the minimum strength of stimuli required to cause muscle __________.

<p>contraction</p> Signup and view all the answers

What is one consequence of muscle fatigue?

<p>Muscle fibers contract slowly and are more susceptible to fatigue. (B)</p> Signup and view all the answers

Fast muscle fibers are best suited for lengthy exercises.

<p>False (B)</p> Signup and view all the answers

What does lactic acid accumulation result in?

<p>Cramps and muscle soreness.</p> Signup and view all the answers

A sustained contraction without relaxation is called a ______ contraction.

<p>tetanic</p> Signup and view all the answers

Match the muscle fiber types with their primary function:

<p>Slow fibers = Aids in lengthy exercises Fast fibers = Aids in sudden bursts of activity</p> Signup and view all the answers

Which factor does NOT affect the degree of muscle fatigue?

<p>Duration of sleep (D)</p> Signup and view all the answers

Recruitment involves the activation of muscle fibers to respond smoothly to stimuli.

<p>True (A)</p> Signup and view all the answers

What is the latent period in a muscle twitch?

<p>The delay between the stimulus application and muscle response.</p> Signup and view all the answers

Which of the following statements about smooth muscle contraction is true?

<p>It uses energy primarily from ATP. (A)</p> Signup and view all the answers

Cardiac muscle fibers are connected end-to-end to form networks and contain intercalated disks.

<p>True (A)</p> Signup and view all the answers

What is the primary characteristic of cardiac muscle regarding its contraction?

<p>Self-exciting and rhythmic</p> Signup and view all the answers

Smooth muscle contraction can sustain forceful contractions longer with the same amount of ______.

<p>ATP</p> Signup and view all the answers

Match the following properties to their respective muscle types:

<p>Smooth Muscle = Can change length without changing tension Skeletal Muscle = Voluntary control Cardiac Muscle = Does not develop oxygen debt All Muscle Types = Contains actin and myosin</p> Signup and view all the answers

What is the role of a synergist muscle?

<p>To assist the prime movers (A)</p> Signup and view all the answers

Muscles require the stimulation of all motor units to contract effectively.

<p>False (B)</p> Signup and view all the answers

What type of muscle tissue is characterized by having no striations and is not organized into sarcomeres?

<p>Smooth muscle</p> Signup and view all the answers

The _______ is the stationary end of a muscle.

<p>origin</p> Signup and view all the answers

Match the following muscle types with their characteristics:

<p>Skeletal Muscle = Voluntary and striated Smooth Muscle = Involuntary and non-striated Cardiac Muscle = Involuntary and striated</p> Signup and view all the answers

Which of the following best describes muscle tone?

<p>Sustained contraction of a few muscle fibers (D)</p> Signup and view all the answers

Peristalsis is a wave-like motion found only in skeletal muscles.

<p>False (B)</p> Signup and view all the answers

What feature of visceral smooth muscle allows it to generate electrical impulses and stimulate neighboring fibers?

<p>Self-exciting fibers</p> Signup and view all the answers

Flashcards

Skeletal Muscle

Muscle tissue that attaches to bones and creates movement.

Smooth Muscle

Muscle tissue found in hollow organs.

Cardiac Muscle

Muscle tissue that forms the heart.

Fascia

Connective tissue that separates muscle layers.

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Tendons

Cord-like structures connecting muscle to bone.

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Muscle Fibers

Individual muscle cells that make up fascicles.

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Myofibrils

Structures within muscle fibers that contract.

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Striations

Alternating light and dark bands in muscle fibers.

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Sarcomere structure

The basic contractile unit of a muscle fiber, consisting of overlapping thin (actin) and thick (myosin) filaments arranged in a repeating pattern.

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Sarcoplasmic Reticulum

Network of channels surrounding myofibrils; stores calcium for muscle contraction.

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T-tubules

Inward extensions of the sarcolemma that act as a relay system, connecting the sarcolemma to the sarcoplasmic reticulum.

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Neuromuscular Junction

The point where a motor neuron connects to a muscle fiber, initiating muscle contraction.

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Synaptic Cleft

The gap between the neuron and muscle fiber across which neurotransmitters are released to stimulate contraction.

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Motor Neuron

Nerve cell that stimulates the muscle fiber to contract.

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Motor End Plate

Specialized region of the muscle fiber membrane where the nerve fiber connects.

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Neurotransmitters

Chemicals released from the nerve to stimulate muscle contraction.

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Motor Unit

A motor neuron and all the muscle fibers it controls.

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Sliding Filament Theory

Muscle fibers shorten because myofilaments (actin and myosin) slide past each other.

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Myosin Cross-bridges

Parts of the myosin protein that bind to actin, pulling them together.

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Neurotransmitter for Muscle Contraction

Acetylcholine (ACh) is the chemical messenger that signals muscle contraction.

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Stimulus for Muscle Contraction

A neurotransmitter (ACh) is needed to begin a muscle contraction.

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Acetylcholine release

Nerve impulse triggers the release of acetylcholine into the synaptic cleft.

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Muscle impulse

Similar to a nerve impulse, traveling over the muscle fiber and sarcoplasmic reticulum.

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Calcium's role in contraction

Calcium ions bind to actin, initiating the sliding filament mechanism.

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Muscle relaxation

Nerve impulse stops; ACh is broken down, Calcium returns to SR.

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Threshold stimulus

Minimal stimulus needed to initiate muscle contraction.

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All-or-none response

Muscle fiber contracts completely or not at all after a threshold stimulus.

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ATP's role in muscle

Provides energy for muscle contraction; limited supply; replenished.

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Energy transfer in muscle

Energy from creatine phosphate transfers to active muscles to produce more ATP.

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Muscle Fatigue

The decrease in the ability of a muscle to generate force, typically during sustained or intense activity.

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Muscle Fatigue Cause: Blood Supply

Insufficient blood flow to the muscle can lead to muscle fatigue.

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Muscle Fatigue Cause: Acetylcholine

Lack of Acetylcholine (ACh) in the motor nerve fibers inhibits muscle contraction and leads to fatigue.

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Muscle Fatigue Cause: Lactic Acid

Build-up of lactic acid, a byproduct of anaerobic respiration, contributes to muscle fatigue.

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Myogram Twitch

A single muscle contraction followed by relaxation.

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Myogram Summation

Increasing the force of muscle contractions by rapidly repeating stimuli before the muscle completely relaxes.

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Muscle Recruitment

The process of activating more muscle fibers to increase the force of contraction.

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Tetanic Contraction

A sustained forceful muscle contraction with minimal or no relaxation.

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Muscle Tone

Sustained contraction in a muscle, even when seemingly at rest. A small amount of fibers are contracting to maintain posture

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Motor Unit Recruitment

Increasing the number of motor units contracting to increase muscle force.

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Muscle Origin

The stationary end of a muscle, situated at a place where movement is happening

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Muscle Insertion

The end of a muscle that moves when contracting.

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Prime Mover

The muscle responsible for the primary action of a movement.

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Smooth Muscle (Visceral)

Sheet of smooth muscle cells that contact, can stimulate contractions in neighbors, and creates a rhythmic pattern for repeated muscle contractions in organs

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Smooth Muscle (Multiunit)

Separate smooth muscle units and responds to neural stimulation and hormone stimulation, found in places like irises of eyes and blood vessels

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Peristalsis

Wave-like muscle contractions that move substances through tubular organs (like the intestines).

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Smooth muscle contraction similarities

Smooth muscle contraction, like skeletal muscle, involves actin and myosin interactions triggered by increased calcium levels.

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Smooth muscle differences from skeletal muscle

Smooth muscle uses ATP, but is slower to contract and relax, can sustain longer contractions, and its length can change without tension change. It can also be stimulated by hormones and various neurotransmitters.

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Cardiac muscle structure

Cardiac muscle cells are striated, branching and interconnected, forming a network. They contain actin and myosin, but not as uniformly arranged as in skeletal muscle. Intercalated discs join the cells.

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Cardiac muscle function

Cardiac muscle is self-exciting and rhythmic; its fibers contract as a coordinated unit.

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Cardiac muscle oxygen debt

Unlike some other muscle types, cardiac muscle does not accumulate an oxygen debt or fatigue.

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