MUSCLE PHYSIOLOGY

What are the three types of muscles in the human body?

Skeletal muscle, Cardiac muscle, Smooth muscle.

What is a key feature of skeletal muscle cells?

They have multiple nuclei in a single cell.

What surrounds the entire skeletal muscle?

Epimysium.

What type of muscle is responsible for involuntary contractions?

Cardiac muscle.

How are skeletal muscles attached to bones?

Most skeletal muscles are linked to bones by tendons.

What is the main contractile unit of a myofibril?

Sarcomere.

Which connective tissue surrounds individual muscle fibers?

Endomysium.

What is the role of tropomyosin in muscle contraction?

It prevents binding of myosin heads to actin when the muscle is at rest.

What causes a muscle to contract?

A rise in intracellular Ca2+ levels.

What is the term for a single, brief contraction of a muscle?

Twitch.

What are the two main types of muscle contractions?

Isotonic and Isometric.

What happens in fused tetanus?

There is no evidence of relaxation before the following contractions, resulting in sustained muscle contraction.

What type of exercise increases muscle size and strength?

Resistance (isometric) exercises.

What is the function of myosin heads during muscle contraction?

They bind to actin and pull filaments toward the center of the sarcomere.

What are the two main types of muscle fibers?

Type 1 (Slow oxidative) and Type 2 (Fast twitch).

What is the role of calcium in muscle contraction?

Calcium binds to the troponin complex, exposing binding sites on actin.

How do smooth muscles contract differently than skeletal muscles?

Smooth muscles do not have striations, myofibrils, or T-tubules and use calmodulin instead of troponin.

What is the primary energy source during sustained muscle activities?

ATP (adenosine triphosphate).

What happens during anaerobic glycolysis?

It generates lactic acid and uses glucose to produce energy without oxygen.

What muscle type is self-excitable and can contract without nervous stimulation?

Single-unit smooth muscle.

What mechanism initiates smooth muscle contraction?

Ca2+-regulated phosphorylation of myosin.

What is the 'all or none' principle in muscle contraction?

A minimal stimulus is needed to cause contraction, and once reached, all muscle fibers contract maximally.

What is a characteristic feature of cardiac muscle cells?

They have intercalated discs.

What type of muscle is generally more efficient in terms of energy consumption?

Smooth muscle.

What neurotransmitter stimulates skeletal muscle cells?

Acetylcholine.

What is the role of the neuromuscular junction?

It is the region where the motor neuron stimulates the muscle.

What does the length-tension relationship refer to in muscle physiology?

It refers to the extent to which muscle fibers can contract based on their initial length.

What can be a consequence of muscle fatigue?

Inability to contract even with a stimulus due to lack of oxygen.

What do graded muscle responses depend on?

The number of muscle fibers stimulated.

How does exercise influence muscle performance?

Exercise increases muscle size, strength, and endurance.

Which type of smooth muscle contracts as a single unit?

Single-unit smooth muscle.

What effect does nitroglycerine have on blood vessels?

It relaxes blood vessels by being converted to nitric oxide (NO).