Muscular system physiology

Acetylcholine

• is responsible for producing lactic acid

• causes an action potential to begin in muscle fibers

• gives us good muscle tone

• causes cramps and spasms

Answer explanation

Acetylcholine is a neurotransmitter that triggers an action potential in muscle fibers, leading to muscle contraction. This is essential for muscle function, making the correct answer 'causes an action potential to begin in muscle fibers'.

Which chemicals must be present for muscles to contract?

• calcium

• ATP

• lactic acid

• ATP and Calcuim

Answer explanation

Muscle contraction requires ATP for energy and calcium ions to trigger the contraction process. Therefore, both ATP and calcium must be present for muscles to contract effectively.

Which structure contains large amounts of calcium used for muscle? 

• sarcomere

• mitochondria

• sarcoplasmic reticulum

• myofibril

Answer explanation

The sarcoplasmic reticulum is a specialized organelle in muscle cells that stores and releases calcium ions, which are crucial for muscle contraction. This makes it the correct answer for the structure containing large amounts of calcium used for muscle.

Contractile organelles within Skeletal Muscle Tissue which contains sarcomeres

• Myofibrils

• Muscle Fibers

• Fascicle

• Sarcolemma

Answer explanation

Myofibrils are the contractile organelles in skeletal muscle tissue that contain sarcomeres, the basic units of muscle contraction. Muscle fibers are made up of myofibrils, while fascicles are bundles of muscle fibers.

Connective tissue which surrounds individual muscle cells

• Endomysium

• Epimysium

• Perimysium

• Sarcolemma

Answer explanation

The endomysium is the connective tissue that surrounds individual muscle cells, providing support and insulation. In contrast, epimysium surrounds entire muscles, and perimysium surrounds bundles of muscle fibers.

Connective tissue which surrounds entire skeletal muscle organs

• Endomysium

• Epimysium

• Perimysium

• Sarcolemma

Answer explanation

The epimysium is the connective tissue that surrounds the entire skeletal muscle organ, providing support and protection. In contrast, endomysium surrounds individual muscle fibers, and perimysium surrounds bundles of fibers.

Type of connective tissue which surrounds fascicles

• Perimysium

• Epimysium

• Endomysium

• Sarcolemma

Answer explanation

Perimysium is the connective tissue that surrounds fascicles, which are bundles of muscle fibers. It provides support and protection, distinguishing it from epimysium (surrounds entire muscle) and endomysium (surrounds individual fibers).

A single contractile unit made up of thick myosin and thin actin filaments within a myofibril

• Sarcomere

• Myomere

• Sarcofibril

• Muscle Fiber

Answer explanation

The sarcomere is the basic contractile unit of muscle, consisting of thick myosin and thin actin filaments. It is essential for muscle contraction, making it the correct answer to the question.

The thick filaments within a sarcomere which contain protrusions with club-shaped heads.

• Actin

• Myosin

• Sarcosin

• Myotin

Answer explanation

The thick filaments in a sarcomere are made of myosin, which has club-shaped heads that interact with actin during muscle contraction. This distinguishes myosin from actin, sarcosin, and myotin.

The thin filaments within a sarcomere which are pulled on by the thick filaments.

• Actin

• Myosin

• Sarcosin

• Myotin

Answer explanation

The thin filaments in a sarcomere are primarily composed of actin. During muscle contraction, myosin thick filaments pull on these actin filaments, causing the muscle to shorten. Thus, the correct answer is actin.