Muscle Structure and Function

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What is the primary purpose of muscles?

to support the skeleton

to produce hormones

to contract for purposeful movement, manipulation of external objects, propulsion of contents through hollow internal organs, and emptying contents of certain organs to external environment (correct)

to regulate body temperature

What type of muscle is found only in the heart?

Skeletal muscle

Striated muscle

Smooth muscle

Cardiac muscle (correct)

Which type of muscle is characterized by dark and light bands?

Involuntary muscle

Unstriated muscle

Striated muscle (correct)

Voluntary muscle

What type of muscle is innervated by neurons in the autonomic nervous system?

Both cardiac and smooth muscle (C) Signup and view all the answers

Which type of muscle is connected to the bones?

Skeletal muscle (A) Signup and view all the answers

What is the main difference between skeletal muscle and cardiac muscle in terms of control?

Skeletal muscle is voluntary, while cardiac muscle is involuntary (C) Signup and view all the answers

What is the primary function of myofibrils in a muscle cell?

To contract and produce muscle force (C) Signup and view all the answers

What is the name of the functional unit of a myofibril, found between Z-lines?

Sarcomere (C) Signup and view all the answers

What is the role of the myosin subunit that binds actin?

Binding to actin (C) Signup and view all the answers

How do muscles grow?

By adding sarcomeres to the end of myofibrils (C) Signup and view all the answers

What is the composition of thin filaments?

Actin, troponin, and tropomyosin (B) Signup and view all the answers

What is the role of the myosin heads during muscle contraction?

To form cross bridges with actin (D) Signup and view all the answers

What is the structure of the backbone of an actin filament?

Two strands of actin twisted together (D) Signup and view all the answers

What is the role of tropomyosin in muscle contraction?

To cover actin binding sites when muscles are at rest (C) Signup and view all the answers

What is the function of troponin in muscle contraction?

To hold tropomyosin in place and block actin binding sites (A) Signup and view all the answers

What is the result of calcium binding to troponin?

The tropomyosin is shifted out of the way, exposing the actin binding sites (C) Signup and view all the answers

What is the function of the cross bridges in muscle contraction?

To form the connection between myosin and actin, bringing about contraction (C) Signup and view all the answers

What is the composition of the A band in a sarcomere?

All the thick filaments and some areas of the thin filaments (A) Signup and view all the answers

What is the main component of the H zone within the A band?

Myosin filaments (C) Signup and view all the answers

What happens to the length of the thick filaments during muscle contraction?

It remains the same (B) Signup and view all the answers

What happens to the actin binding sites when calcium is present?

They are uncovered by tropomyosin (B) Signup and view all the answers

What is the role of troponin in the absence of calcium?

It holds tropomyosin in place (B) Signup and view all the answers

What is the composition of the I band?

Only thin filaments (C) Signup and view all the answers

What is the role of the supporting protein that extends from the M lines to the Z lines?

It provides support to the sarcomeres (D) Signup and view all the answers

What surrounds individual muscle fibers?

Endomysium (D) Signup and view all the answers

What is the result of multiple myoblasts fusing together during development?

Formation of a muscle fiber with multiple nuclei (D) Signup and view all the answers

What is the function of satellite cells?

To differentiate into new muscle cells (C) Signup and view all the answers