Muscle Physiology

These flashcards cover key concepts related to the contraction of skeletal, cardiac, and smooth muscles, including structure, function, and mechanisms involved in muscle contraction.

What are the three types of muscle?

Skeletal, Cardiac, and Smooth.

What is one main function of skeletal muscle?

Locomotion.

What is the contractile unit of skeletal muscle?

Sarcomere.

What does the term 'A band' refer to in muscle structure?

Area where myosin and actin overlap, appearing dark.

What protein anchors actin filaments in the sarcomere?

Z line.

What are myofibrils composed of?

Myofilaments.

What is the role of tropomyosin in muscle contraction?

It stabilizes actin and covers myosin-binding sites.

Which proteins regulate the interaction between actin and myosin?

Tropomyosin and Troponin.

What is the function of the sarcoplasmic reticulum in muscle cells?

Stores calcium ions.

What causes a 'power stroke' during muscle contraction?

Release of ADP and Pi from the myosin head.

What is the role of calcium ions in muscle contraction?

Calcium binds to troponin, causing tropomyosin to move and uncover binding sites on actin.

Explain the 'walk-along' theory of muscle contraction.

The myosin head binds to actin, pulls it, releases, and re-cocks to continue the cycle.

What is the function of vehicle formation in neuromuscular transmission?

Transporting acetylcholine (ACh) to the presynaptic terminal.

What triggers the release of ACh at the neuromuscular junction?

Increased cytosolic calcium.

How does curare affect muscle contraction?

Blocks nicotinic ACh receptors, reducing EPP and preventing AP.

What is the effect of botulinum toxin on muscle contraction?

Decreases ACh release from nerve terminals.

What occurs when calcium binds to troponin?

Troponin undergoes a conformational change allowing muscle contraction.

What is the role of accessory proteins in muscle structure?

They help stabilize myosin and actin filaments.

What happens during excitation-contraction coupling?

Depolarization leads to calcium release from the sarcoplasmic reticulum.

What causes the relaxation of skeletal muscle after contraction?

Calcium is pumped back into the sarcoplasmic reticulum.

Where is the end plate potential generated?

At the neuromuscular junction.

What is Myasthenia Gravis?

An autoimmune disease causing muscle weakness due to ACh receptor antibodies.

What are the differences between skeletal and cardiac muscle structure?

Cardiac muscle is branched and has intercalated discs; skeletal muscle is long and cylindrical.

How does smooth muscle differ from skeletal muscle in terms of control?

Smooth muscle is involuntary; skeletal muscle is voluntary.

What is the primary characteristic of unitary smooth muscle?

Cells are electrically coupled and function as a single unit.

What role does calsequestrin play in muscle contraction?

Binds calcium in the sarcoplasmic reticulum to facilitate storage.

How does nitric oxide affect smooth muscle?

Causes relaxation of blood vessels.

What defines the refractory period in cardiac muscle compared to skeletal muscle?

It is longer in cardiac muscle, preventing tetany.

What structure serves as the voltage sensor in cardiac muscle cells?

Dihydropyridine (DHP) receptor.

Explain the role of myosin light chain kinase (MLCK) in smooth muscle contraction.

Phosphorylates myosin light chains to enable actin binding.

How do slow waves affect smooth muscle activity?

They create a rhythmical contraction pattern that is not action potentials.

What is the resting membrane potential of smooth muscle cells?

Approximately -50 to -60 mV.

What occurs during a muscle contraction at the molecular level?

Actin and myosin slide over each other, shortening the muscle.

What type of muscle has a high ratio of actin to myosin?

Smooth muscle.

In skeletal muscle, how is calcium released during contraction?

Through voltage-gated calcium channels in response to action potentials.