Muscle Anatomy, Physiology, and Types: Nerve Innervation, Contraction, and Aging

What is the role of a motor neuron in muscle contraction?

It attaches to the epimysium and sarcolemma of multiple myofibers.

What is a motor unit?

A motor neuron and all myofibers stimulated by the same neuron.

How do all myofibers in the same motor unit behave during contraction?

They contract together.

What determines the precision of movements in muscle control?

The number of myofibers stimulated by the same motor neuron.

What is the relationship between motor unit size and control?

Fewer myofibers per neuron (smaller motor units) leads to greater control.

What is the function of neural transmitters in muscle contraction?

They stimulate muscle contraction by transmitting signals from neurons to skeletal muscle.

How does the signal travel through the muscle after reaching the sarcolemma?

It travels throughout the muscle via transverse-tubules (T-tubules).

What triggers the release of Ca2+ during muscle contraction?

The signal from the neuron causes Ca2+ to be released from the sarcoplasmic reticulum.

What is the role of motor unit recruitment in muscle contraction strength?

Strength of contraction is controlled by the recruitment of more or fewer motor units.

Which motor units are recruited first during contraction?

Smaller motor units are recruited prior to larger ones.

What happens to muscle fibers as a person ages?

There is a loss of muscle mass, thinner muscle fibers, and fewer muscle fibers.

What is rigor mortis?

Stiffness of muscles that occurs 4-18 hours after death due to Ca2+ leaking into the sarcoplasm.

What is myology?

The study of muscles.

What are the three types of muscle tissue?

Skeletal, cardiac, and smooth muscle.

What is the primary function of skeletal muscle?

Movement of bones and voluntary movements.

What characterizes cardiac muscle?

It has tubular cells with faint striations and is responsible for pumping blood through the heart.

What is a distinguishing feature of smooth muscle?

It is involuntary and controls the movement through hollow organs.

What is the length-tension relationship in muscles?

It refers to the optimal length of muscle fibers for maximum force generation.

What are slow-twitch fibers (Type I)?

Muscle fibers that take a long time to develop force, have greater endurance, and are found in muscles that maintain posture.

What are fast fibers (Types IIa and IIb)?

Muscle fibers that are more easily fatigued and capable of fast, powerful contractions.

What is the role of ATP in muscle contraction?

ATP is required for the release of cross-bridges during muscle contraction.

What happens to muscle fibers during contraction according to the sliding filament model?

Actin and myosin slide along each other, shortening the sarcomere.

What is the significance of intercalated discs in cardiac muscle?

They connect adjacent muscle cells and facilitate the spread of contraction.

What is the function of tendons?

They connect muscle to the periosteum of bone.

What is the sarcoplasmic reticulum's role in muscle fibers?

It stores and releases calcium needed for muscle contraction.

What is the appearance of smooth muscle cells?

They are spindle-shaped with a central nucleus and no visible striations.

What is the smallest contractile unit of muscle tissue?

The sarcomere.

What is the function of the epimysium?

It surrounds the entire muscle and binds together multiple fascicles.