The Muscular System

Which type of muscle tissue is under voluntary control?

Skeletal muscle

Which of the following muscle types has striations (striped appearance)?

Both skeletal and cardiac muscle

Which of the following muscle types is involuntary?

Both B and C

Which type of muscle is responsible for propelling blood throughout the body?

Cardiac muscle

Which type of muscle is found in the walls of hollow organs like the stomach, intestines, and blood vessels?

Smooth muscle

Which type of muscle tissue has intercalated discs for communication between cells?

Cardiac muscle

Which of the following muscle types is multinucleated?

Skeletal muscle

Which of the following muscle types is responsible for movement of the limbs and body?

Skeletal muscle

Which muscle type has the ability to contract without nervous stimulation?

Both B and C

What is the name of the connective tissue layer that surrounds individual muscle fibers?

Endomysium

Which connective tissue layer surrounds groups of muscle fibers, forming fascicles?

Perimysium

What is the function of the epimysium in skeletal muscles?

To surround and protect the entire muscle

Which of the following connective tissues is responsible for connecting skeletal muscles to bones?

Tendon

The connective tissue layers in skeletal muscles contribute to which of the following functions?

Transmitting force from muscle contraction to bone

Which connective tissue structure within skeletal muscle contains blood vessels and nerves that supply muscle fibers?

Perimysium

Which connective tissue layer is responsible for separating muscles from each other and forming the outer boundary of the muscle?

Epimysium

What type of connective tissue fibers are primarily found in the endomysium?

Both collagen and reticular fibers

Which connective tissue component of skeletal muscles helps to resist overstretching and provides structural support?

Epimysium

The fusion of the connective tissue layers (endomysium, perimysium, epimysium) forms what structure that attaches the muscle to the bone?

Tendon

Which connective tissue layer contains the smallest blood vessels (capillaries) and nerve fibers that directly supply muscle fibers?

Endomysium

An aponeurosis is best described as:

A broad, flat sheet of connective tissue that connects muscles to other muscles or bones

Which of the following is a key structural difference between tendons and ligaments?

Tendons connect muscles to bones, while ligaments connect bones to bones

What is the primary function of fascia in the body?

To separate and surround muscles and other internal structures

What is the primary function of the sarcolemma in muscle cells?

To transmit electrical impulses to muscle fibers

What structure inside the muscle fibers is responsible for the striated appearance and contraction of muscles?

Myofibrils

What is the characteristic feature of the I band in a sarcomere?

It contains only actin filaments

The A band in a sarcomere is characterized by:

A region that includes both actin and myosin

Myosin is best described as

A thick filament protein that interacts with actin to produce muscle contraction

What is the primary role of actin in muscle contraction?

To form cross-bridges with myosin for muscle contraction

What is a cross-bridge in the context of muscle contraction?

The attachment point between actin and myosin filaments

The sarcoplasmic reticulum (SR) in muscle cells is responsible for:

Storing and releasing calcium ions to regulate muscle contraction

A sarcomere is best described as:

A single muscle contraction unit from one Z-line to the next

Which of the following statements about the sarcomere is TRUE?

The sarcomere is the part of the muscle that contracts when calcium is released

During muscle contraction, the I band:

Shortens in length

What happens to the A band during muscle contraction?

It remains unchanged

The release of calcium from the sarcoplasmic reticulum results in:

Binding of myosin heads to actin to form cross-bridges

In a sarcomere, which structure is responsible for holding the actin filaments in place?

Z-line

Which of the following occurs when a muscle contracts?

The I band shortens, and the A band remains the same length

What is the primary function of the neuromuscular junction?

To transmit electrical impulses from the nerve to the muscle, leading to contraction

What neurotransmitter is released at the neuromuscular junction to initiate muscle contraction?

Acetylcholine

Which of the following happens first when an action potential reaches the neuromuscular junction?

Acetylcholine is released from synaptic vesicles

What occurs after acetylcholine binds to receptors on the muscle cell membrane?

The muscle cell becomes depolarized, and an action potential is generated in the muscle fiber

The action potential in the muscle fiber is propagated along the:

T-tubules

Which ion is primarily involved in the depolarization of the muscle membrane during an action potential?

Sodium

What is the role of calcium ions in muscle contraction?

Calcium ions bind to troponin, causing a conformational change that allows actin and myosin to interact

What happens during repolarization of the muscle membrane after an action potential?

Potassium ions leave the muscle cell, restoring the resting membrane potential

What is the function of the sarcoplasmic reticulum in muscle contraction?

It stores and releases calcium ions, which are critical for muscle contraction

What is the role of the T-tubules during muscle contraction?

They conduct the action potential deep into the muscle fiber

Which of the following is true about the motor end plate at the neuromuscular junction?

It is where the acetylcholine receptors are located on the muscle fiber

What is the resting membrane potential of a muscle fiber, and how is it maintained?

It is negative, maintained by the active transport of sodium and potassium ions

What does the term "action potential" refer to in the context of muscle cells?

The electrical signal that travels along the nerve and initiates muscle contraction

What is the function of acetylcholinesterase at the neuromuscular junction?

To break down acetylcholine and stop the signal for muscle contraction

Which of the following is NOT a function of the synaptic cleft?

To transmit electrical impulses between neurons

What is the synaptic cleft?

The space between the presynaptic neuron and the postsynaptic cell

What is the role of the presynaptic terminal in neurotransmitter release?

It stores neurotransmitters in synaptic vesicles

What is a muscle twitch?

A single, rapid contraction and relaxation of a muscle fiber in response to a single stimulus

What is meant by "summation of contractions" in muscle response?

The increase in force generated by a muscle as a result of repeated stimuli before the muscle can fully relax

What characterizes unfused incomplete tetanus?

Muscle fibers contract with partial relaxation between stimuli, resulting in a sustained but wavering contraction

What is complete tetanus in muscle contraction?

A sustained contraction where muscle fibers do not relax at all, resulting in maximal tension

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

Lifting a dumbbell during a bicep curl

What is an isotonic contraction?

type of muscle contraction where the muscle changes length but maintains constant tension

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

Lifting a dumbbell during a bicep curl

Which of the following is true about isometric contractions?

The muscle generates force but does not change length

During an isotonic concentric contraction, what happens to the muscle?

The muscle shortens while generating tension