muscular sytem

What are muscles composed of?

Muscles are composed of many cells.

What is a muscle?

A group of muscle cells with the same origin, insertion, and function.

What are fascicles?

Muscle cells wrapped with connective tissues (fascia).

What are muscle fibres?

Long muscle cells that are multinucleate and vary in length from mm to 30 cm.

What are myofibrils?

Long cylindrical structures packed within muscle fibres that contain actin and myosin.

What is the contractile unit of muscle?

The sarcomere.

What gives striated appearance to skeletal muscle?

The arrangement of filaments in the sarcomere.

What are Z lines?

Attachment points for sarcomeres.

What happens during muscle contraction?

Myosin heads pull on actin, powered by ATP, leading to the shortening of the sarcomere.

What are isotonic contractions?

Muscle shortens while maintaining a constant force; movement occurs.

What are isometric contractions?

Force is generated, but the muscle doesn’t shorten; no movement occurs.

What are slow twitch fibres?

Muscle fibres that contract slowly and make ATP as needed by aerobic metabolism, used for endurance activities.

What are fast twitch fibres?

Muscle fibres that contract quickly, used for brief high-intensity activities, and capable of anaerobic metabolism.

How does genetics influence muscle fibre ratios?

Your genetic makeup determines the primary ratio of slow twitch to fast twitch fibres.

What role do pacemaker cells play in cardiac muscle?

They dictate the rate of contractions of the whole heart.

What defines smooth muscle?

Filaments arranged in criss-crossed bundles without sarcomeres, and no striations.

What is muscular dystrophy?

A disease where modified dystrophin proteins enable calcium leakage into cells, causing muscle weakening and wasting.

What causes muscle cramps?

Often caused by dehydration and ion imbalance.

What results in pulled muscles?

Overstretching of a muscle, leading to fibre tears.