Muscular System Quiz

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Questions and Answers

What type of muscle tissue is primarily responsible for producing body movements and is under voluntary control?

Connective muscle tissue

Skeletal muscle tissue (correct)

Smooth muscle tissue

Cardiac muscle tissue

Which muscle tissue is found only in the heart and is not under voluntary control?

Cardiac muscle tissue (correct)

Striated muscle tissue

Skeletal muscle tissue

Smooth muscle tissue

Which characteristic distinguishes smooth muscle tissue from the other types of muscle tissues?

It has multiple nuclei.

It is voluntary.

It is non-striated. (correct)

It is striated.

Which of the following statements accurately describes skeletal muscle fibers?

They are long cylindrical cells with multiple nuclei. Signup and view all the answers

What is the primary function of the muscular system related to internal body activities?

To stabilize body positions Signup and view all the answers

Identify a function of smooth muscle tissue.

Moving substances within the body Signup and view all the answers

Which component is NOT found in skeletal muscle tissue?

Cardiocytes Signup and view all the answers

What characteristic of cardiac muscle cells contributes to their involuntary function?

Centrally located single nucleus Signup and view all the answers

What initiates the muscle action potential at the motor end plate?

Acetylcholine binding to its receptors Signup and view all the answers

What role does acetylcholinesterase play in muscle contraction?

It destroys excess acetylcholine in the synaptic cleft Signup and view all the answers

What happens after calcium ions enter the sarcoplasm?

Binding sites on actin are exposed Signup and view all the answers

What is the final result of calcium release and muscle contraction?

Power strokes that pull thin filaments toward the center of the sarcomere occur Signup and view all the answers

Which process occurs to ensure calcium levels return to a resting state after contraction?

ATP is used by active transport pumps Signup and view all the answers

What is the role of the transverse tubule in muscle contraction?

It conducts the muscle action potential into the muscle fiber Signup and view all the answers

Which ion is crucial for exposing the binding sites on actin during muscle contraction?

Calcium (Ca2+) Signup and view all the answers

What prevents muscle contraction from continuing indefinitely?

The activity of acetylcholinesterase Signup and view all the answers

What primarily determines the amount of tension produced by muscle fibers?

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

Which phase is NOT part of a muscle twitch?

Recovery phase Signup and view all the answers

What is the result of incomplete tetanus?

Muscle fibers never completely relax Signup and view all the answers

How does the size of motor units affect muscle contraction?

The total strength depends on motor unit size and activation Signup and view all the answers

What primarily causes muscle fatigue during intense activity?

Depletion of ATP resources Signup and view all the answers

Which type of muscle contraction results in the muscle length remaining constant?

Isometric contraction Signup and view all the answers

What speeds up the contraction time of muscle fibers?

Presence of fast fibers Signup and view all the answers

What is one characteristic of slow fibers compared to fast fibers?

They resist fatigue better Signup and view all the answers

Which type of muscle is characterized as 'white muscle'?

Muscles mainly composed of fast fibers Signup and view all the answers

What physiological change does training induce in muscle fibers?

Hypertrophy of stimulated muscle fibers Signup and view all the answers

What initiates the series of steps for muscle contraction?

Nerve impulse arrival at the axon terminal Signup and view all the answers

What happens after calcium binds to troponin during muscle contraction?

Tropomyosin is moved to expose the active sites Signup and view all the answers

Which component is essential for the recovery stroke in muscle contraction?

ATP Signup and view all the answers

What is the primary role of acetylcholinesterase in muscle contraction?

To break down acetylcholine and limit contraction duration Signup and view all the answers

Which sequence correctly represents the steps in muscle contraction after an action potential?

Action potential, Calcium release, Recovery stroke Signup and view all the answers

What happens during the power stroke of muscle contraction?

Myosin heads rotate towards the center of the sarcomere Signup and view all the answers

How does ATP relate to the muscle contraction cycle?

ATP is necessary for the detachment of myosin heads from actin Signup and view all the answers

Which part of the muscle fiber contains the thick and thin filaments involved in contraction?

Myofibril Signup and view all the answers

What is the role of calcium in the sliding filament theory?

It exposes binding sites on actin for myosin to attach Signup and view all the answers

What is the primary function of the T-tubule in muscle contraction?

To transmit the action potential into the muscle fiber Signup and view all the answers

What is the primary function of pacemaker cells in the heart?

They send electrical signals causing the heart to contract. Signup and view all the answers

Which type of muscle tissue is under involuntary control?

Both smooth and cardiac muscle Signup and view all the answers

What surrounds individual muscle fibers in skeletal muscle?

Endomysium Signup and view all the answers

The thick and thin filaments in muscle fibers are primarily made up of which proteins?

Actin and myosin Signup and view all the answers

What initiates the muscle fiber contraction process?

The action potential at the neuromuscular junction Signup and view all the answers

What is the role of calcium ions in muscle contraction?

They activate tropomyosin to expose binding sites. Signup and view all the answers

Which structure serves as the attachment point for muscles to bones?

Tendons Signup and view all the answers

What is the main role of skeletal muscle in the body?

Producing skeletal movement Signup and view all the answers

What is the sarcolemma identified as?

The muscle cell membrane Signup and view all the answers

Which structure is responsible for the storage of calcium in muscle cells?

Sarcoplasmic reticulum Signup and view all the answers

What happens to acetylcholine after it has stimulated a muscle action potential?

It is broken down by enzymes. Signup and view all the answers

Which muscle tissue type is not striated?

Smooth Signup and view all the answers

Which of the following best describes the primary function of smooth muscle?

Regulate blood flow and digestive processes Signup and view all the answers

Study Notes

Musculoskeletal System (Part 2)

Learning Outcomes: Students will be able to list muscle types and characteristics, understand action potential mechanisms, identify components of neuromuscular junctions, and learn about muscle contraction/relaxation.
Functions of the Muscular System:
- Produce body movements.
- Stabilize body positions.
- Move substances within the body.
- Produce heat.
- Support soft tissue.
- Guard body entrances and exits.
- Provide nutrient reserves.
Types of Muscle Tissues:
- Skeletal muscle tissue: Primarily attached to bones, striated, and voluntary.
- Cardiac muscle tissue: Forms the heart walls, striated, and involuntary.
- Smooth muscle tissue: Located primarily in internal organs, non-striated (smooth), and involuntary.
Skeletal Muscle Tissue Details:
- The most abundant tissue in the human body.
- Under voluntary control.
- Contains skeletal muscle cells, connective tissues, blood vessels, and nerves.
- Each skeletal muscle cell is called a skeletal muscle fiber.
- Each skeletal muscle fiber is long, cylindrical, contains many nuclei, and is striated (alternating light and dark bands).
- Skeletal muscle fibers bind together with connective tissue, nerves, and blood vessels to form bundles.
- These bundles form muscles.
Cardiac Muscle Tissue Details:
- Only found in the heart.
- Composed of cardiac muscle cells (cardiocytes).
- Striated.
- Usually contains a single, centrally located nucleus.
- Not under voluntary control.
- A bundle of specialized cells (pacemaker cells) in the upper heart sends electrical signals, causing rhythmic contraction and blood pumping.
Smooth Muscle Tissue Details:
- Found in many internal organs (abdomen, intestines) and blood vessel walls
- Spindle-shaped with a single nucleus.
- Not striated.
- Not under voluntary control.
- Its contractions move food through the digestive tract, control blood flow, and change pupil size in response to light.

Skeletal Muscle Tissue Organization

Epimysium: Surrounds the entire muscle.
Perimysium: Sheathes bundles of muscle fibers (fascicles).
Perimysium and epimysium contain blood vessels and nerves.
Endomysium: Covers individual muscle fibers.
Tendons: Attach muscles to bones or other muscles.

Skeletal Muscle Fiber Structure

Sarcolemma (cell membrane).
Sarcoplasm (muscle cell cytoplasm).
Sarcoplasmic Reticulum (modified ER) with high calcium concentration.
T-tubules and myofibrils aid in contraction.
Sarcomeres: Regular arrangement of myofibrils.

Muscle Fiber Components

Myofibrils: Bundles of protein filaments (actin and myosin).
Actin: Thin filaments.
Tropomyosin: Covers active sites on actin.
Troponin: Binds to G-actin and holds tropomyosin in place.
Myosin: Thick filaments.
Myosin heads form cross-bridges during contraction.
Interactions between actin and myosin prevented by tropomyosin when not contracting.

Muscle Contraction Mechanics

Created when muscles contract.
Series of steps starting with excitation at the neuromuscular junction..
Action potential triggers calcium release from the sarcoplasmic reticulum.
Thick/thin filament interaction causing muscle fiber contraction.

Sliding Filament Theory

Thick and thin filaments slide past each other during contraction.
Cyclic process begins with calcium release from the sarcoplasmic reticulum.
Calcium binds to troponin.
Troponin moves, exposing actin active site.
Myosin head forms cross-bridge and bends toward H zone.
ATP allows release of cross-bridge.

Muscle Relaxation

Acetylcholinesterase breaks down acetylcholine (ACh).
Limits the duration of contraction.

Tension Production by Muscle Fibers

Amount of tension depends on the number of cross-bridges formed.
Skeletal muscle contracts most forcefully over a narrow range of resting lengths.
Twitch: Contraction and relaxation of muscle in response to a stimulus (lag, contraction, relaxation phases).

Summation

Repeated stimulation before the relaxation phase has been completed results in wave summation (one twitch added to another.)
Incomplete tetanus = muscle never relaxes completely.
Complete tetanus = relaxation phase entirely eliminated.

Motor Units and Recruitment

Motor units consist of a motor neuron and the muscle fibres it stimulates.
A motor neuron usually makes contact with about 150 muscle fibers.
Control of precise movements consists of many small motor units.
Muscles that control voice production have few muscle fibers per motor unit, while those for eye movements have more, and limbs have the largest (2000-3000).

Muscle Fatigue

Muscle fibers use ATP faster than they produce it, resulting in weaker contractions.
New ATP binding is needed to break the cross-bridge.
Examples: Muscle cramps, Rigor mortis (muscle stiffness after death).

Types of Muscle Contractions

Isometric: Tension rises, length remains constant.
Isotonic: Tension rises, length changes (concentric & eccentric).

Muscle Performance

Fast fibers (II myosin): large, powerful, fast contractions, fatigue quickly, abundant myofibrils & glycogen (white muscle)
Slow fibers (I myosin): endurance, half the diameter of fast fibers, take longer to contract but resist fatigue, greater capillary & mitochondrial density (red muscle)

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Description

Test your knowledge of the muscular system with this quiz covering muscle types, functions, and characteristics. From skeletal to smooth and cardiac muscle, assess your understanding of how these tissues contribute to body movements and internal functions.