Muscle Anatomy and Physiology: Connective Tissues, Contraction, and Levers

What type of connective tissue surrounds the entire muscle?

Dense regular connective tissue (Epimysium)

What type of connective tissue surrounds a muscle fascicle?

Dense irregular connective tissue (Perimysium)

What is a bundle of muscle fibers called?

A fascicle

What type of connective tissue surrounds each individual muscle fiber?

Areolar connective tissue (Endomysium)

What is a single muscle cell called?

A muscle fiber

What are the contractile structures found inside a muscle fiber?

Myofibrils

What protein makes up thick myofilaments?

Myosin

What protein makes up thin myofilaments?

Actin

What is the function of satellite cells in muscle tissue?

To help repair and regenerate muscle

How does parallel muscle arrangement affect force and range of motion?

It provides low force but a high range of motion

How does pennate muscle arrangement affect force and range of motion?

It provides high force but a low range of motion

What is a unipennate muscle arrangement?

Fibers located on only one side of the tendon

What is a bipennate muscle arrangement?

Fibers located on both sides of the tendon

Which pennate muscle arrangement is the strongest?

Multipennate

What characterizes a convergent muscle arrangement?

A fan-shaped structure with moderate force and range of motion

What is the function of a circular (sphincter) muscle?

To surround openings and control the passage of substances

What is the name of the muscle cell membrane?

Sarcolemma

What is the function of T-tubules?

To carry electrical signals deep into the muscle fiber

How many nuclei are typically found in a muscle cell?

Multiple nuclei

What is the primary function of mitochondria in muscle cells?

To produce ATP for muscle contraction

What is the function of the sarcoplasmic reticulum?

To store and release calcium ions (Ca²⁺)

What two proteins are contained within myofibrils for contraction?

Actin and myosin

Which filament is referred to as the thick filament?

Myosin

Which filament is referred to as the thin filament?

Actin

What are the primary characteristics of skeletal muscle?

Striated, voluntary, strong but fatigues easily.

What is the neuromuscular junction?

The site where a nerve communicates with a muscle.

What are the characteristics of smooth muscle?

Non-striated, involuntary, found in organs.

What factors control smooth muscle?

Nerves, hormones, and the environment.

What are the characteristics of cardiac muscle?

Striated, involuntary, found in the heart.

What is the function of intercalated discs in cardiac muscle?

They connect cardiac cells for coordinated contraction.

What controls the heart's rhythm?

The intrinsic conduction system.

What causes muscle atrophy?

A decrease in muscle size due to lack of use or nerve supply.

What causes muscle hypertrophy?

An increase in muscle size due to increased workload.

What is the basic mechanism of muscle contraction?

The sliding of actin over myosin using ATP.

How does muscle regeneration occur?

Through the repair of muscle using satellite cells.

What are the steps of muscle contraction?

Signal, Ca²⁺ release, myosin binds actin, power stroke, ATP resets.

What are the key connective tissue structures in a muscle cross-section?

Epimysium, perimysium, endomysium, fascicles, and fibers.

What is the functional tradeoff of fascicle arrangement?

The tradeoff between strength and range of motion.

What structures are visible in a longitudinal muscle fiber?

Sarcolemma, sarcoplasmic reticulum (SR), T-tubules, and myofibrils.

What is the lever formula for movement?

Output distance = (load distance ÷ effort distance) × input distance.

What is the lever formula for force?

Effort force × effort distance = load force × load distance.

How is a first-class lever defined?

The fulcrum is located between the effort and the load.

How is a second-class lever defined?

The load is located between the fulcrum and the effort.

How is a third-class lever defined?

The effort is located between the fulcrum and the load.

Which lever class is most common in the human body?

Third-class lever.

Which lever class is the strongest?

Second-class lever.

What type of lever is the triceps brachii?

First-class lever.

What is the advantage of the triceps brachii lever?

Large movement.

What is the disadvantage of the triceps brachii lever?

Requires high force.

What type of lever is the brachioradialis?

Second-class lever.

What is the advantage of the brachioradialis lever?

Requires less force.

What is the disadvantage of the brachioradialis lever?

Less movement.

What type of lever is the biceps brachii?

Third-class lever.

What is the advantage of the biceps brachii lever?

Fast, large movement.

What is the disadvantage of the biceps brachii lever?

Requires more force.

What type of lever is the brachialis?

Third-class lever.

What is the advantage of the brachialis lever?

Balanced movement and force.

What is the disadvantage of the brachialis lever?

Requires more force than the load.

What is the hierarchical organization of muscle?

Muscle → fascicle → fiber → myofibril → filaments.

What is the function of actin in contraction?

Provides the binding site for myosin.

What is the function of myosin in contraction?

Pulls actin during contraction.

What is the role of calcium in muscle contraction?

Allows myosin to bind to actin.

What is the role of ATP in muscle contraction?

Powers movement and resets myosin.