Sliding Filament Theory

Front

The contractile unit of a muscle:

Back

sarcomere

Answer explanation

The sarcomere is the basic contractile unit of muscle fibers, responsible for muscle contraction. It is composed of actin and myosin filaments, which slide past each other during contraction, making it the correct answer.

Front

Thick filaments within a myofibril are:

Back

Myosin

Answer explanation

Thick filaments in a myofibril are primarily composed of myosin. Myosin is a motor protein that interacts with actin to facilitate muscle contraction, making it the correct answer.

Front

Thin filaments in a myofibril are

Back

Actin

Answer explanation

Thin filaments in a myofibril are primarily composed of actin. Actin proteins form the structure of these filaments, which play a crucial role in muscle contraction, distinguishing them from myosin, which makes up thick filaments.

Front

The energy needed to perform a muscle contraction comes directly from

Back

ATP

Answer explanation

The energy required for muscle contraction is derived from ATP (adenosine triphosphate). ATP provides the necessary energy for the interaction between actin and myosin filaments during contraction.

Front

The plasma membrane of a skeletal muscle cell is called the:

Back

sarcolemma

Answer explanation

The plasma membrane of a skeletal muscle cell is called the sarcolemma. It surrounds the muscle fiber and plays a crucial role in muscle contraction and signaling.

Front

Do the lengths of the thick and thin filaments change during contraction?

Back

No

Answer explanation

No, the lengths of thick and thin filaments do not change during contraction. Instead, the filaments slide past each other, which shortens the overall muscle fiber without altering the filament lengths.

Front

Skeletal Muscle contraction is initiated when the ________ sends a message to the muscle cell.

Back

Motor Neuron

Answer explanation

Skeletal muscle contraction begins when the Motor Neuron sends a signal to the muscle cell, triggering the contraction process. The other options do not play a direct role in initiating muscle contraction.

Front

What state is the sarcomere in #1?

Back

Relaxed

Answer explanation

The sarcomere in #1 is in a relaxed state, meaning the muscle fibers are not actively contracting. This allows for optimal length and readiness for contraction when stimulated.

Front

What state is the sarcomere in #2?

Back

Contracting

Answer explanation

The sarcomere in #2 is in a contracting state, which means the muscle fibers are actively shortening and generating force. This is distinct from being relaxed or fully contracted.

Front

What two chemicals are necessary for muscle contraction to occur?

Back

Calcium and ATP

Answer explanation

Calcium and ATP are essential for muscle contraction. Calcium ions trigger the interaction between actin and myosin filaments, while ATP provides the energy needed for the contraction process.