Muscular System UPDATED

What is a primary function of the muscular system?

Enables voluntary and involuntary movements of the body.

What is a secondary function of the muscular system?

Provides support and stability to joints during movement.

How does the muscular system contribute to heat production?

Generates heat through muscle contractions to help maintain body temperature.

What are the three main connective tissue layers surrounding skeletal muscles?

Epimysium, Perimysium, Endomysium.

Epimysium

The outermost layer encasing the entire muscle and continuous with a tendon.

Perimysium

The intermediate layer that surrounds a fascicle, which is a bundle of muscle cells.

Endomysium

The innermost layer that surrounds the plasma membrane of a muscle cell.

What are muscle cells and muscle fibers?

Interchangeable terms referring to the same structure.

Myoblasts

Cells that fuse to create long, cylindrical, multinucleate muscle fibers.

Sacrolemma

The plasma membrane of muscle cells.

Sarcoplasm

The inner contents of muscle cells, akin to cytoplasm.

Transverse tubules

Extensions of the sarcolemma that interface with the sarcoplasmic reticulum.

Sarcomere

The functional, contractile unit of the muscle fiber composed of myofilaments: actin and myosin.

Smooth Endoplasmic Reticulum

Highly modified and stores calcium ions that are required for muscle contraction

Myofibril

A complex organelle composed bundles of myofilaments that are responsible for muscle contraction and are arranged in a repeating pattern of sarcomeres.

Actin

Proteins that attach to the ends of the sarcomere at Z-lines.

Myosin

Proteins located in the center of the sarcomere.

How are actin and myosin incorporated into the contractile units of the sacromere?  

Myosin heads attach to actin. Myosin pulls actin in, shortening the sarcomere. Myosin detaches when ATP binds. Myosin resets to repeat the process.

Z disc

An anchoring protein for thin filaments; delineates the boundaries of a sarcomere.

A Bands

Dark bands containing thick myosin filaments overlapping with thin actin filaments.

I Bands

Light bands composed solely of thin actin filaments.

H zone

A light band located at the center of an A band, lacking thin filaments.

M line

A dark band at the center of the H zone, composed of anchoring proteins.

Titin

An elastic protein that connects the thick filaments of neighboring sarcomeres.

How does the muscular system contribute to the overall maintenance of homeostasis?

Heat production: Muscle contractions generate heat, helping to regulate body temperature. Posture: Muscles help maintain posture, supporting the body and preventing falls. Circulation: The heart (a muscle) pumps blood, delivering oxygen and nutrients throughout the body.