Week 9 ELM 18: Muscle I

Vocabulary flashcards for reviewing muscle structure and function.

Skeletal Muscle

A type of muscle classified along with cardiac and smooth muscle.

Striated Muscle

Muscle tissue characterized by repeating sarcomeres, which create a striped appearance.

Tendon

Connects skeletal muscle to bone.

Epimysium

The fibrous elastic tissue surrounding a muscle.

Perimysium

The sheath of connective tissue surrounding a bundle of muscle fibers.

Muscle Fiber

An individual muscle cell.

Fascicle

A bundle of muscle fibers.

Endomysium

A layer of connective tissue that surrounds individual muscle fibers within a fascicle.

Sarcolemma

The cell membrane of a muscle fiber.

Myofibrils

Basic rod-like unit of a muscle cell

T Tubule

Transverse tubules that conduct action potentials into the muscle fiber.

Terminal Cisterna

Enlarged areas of the sarcoplasmic reticulum surrounding the transverse tubules.

Triad

A T tubule and two terminal cisternae.

Sarcoplasmic Reticulum

The endoplasmic reticulum of a muscle cell, storing calcium ions.

Sarcomere

The basic contractile unit of a muscle fiber.

H-Zone

The region at the center of an A band of a sarcomere that is made up of myosin only.

A-band

The dark band of the sarcomere that corresponds to the presence of myosin filaments.

I-band

The light band of the sarcomere made up of actin filaments only.

Z-line

The border of the sarcomere.

M-line

The line in the middle of the A band.

Myosin

A motor protein that interacts with actin to cause muscle contraction. Highly diverse family of MOTOR proteins. Muscle myosin is class II. Head has ATPase activity. Motor powered by hydrolysis of ATP

Actin

The protein that forms (together with myosin) the contractile filaments of muscle cells and is involved in motion in other types of cells.

G-Actin

A globular multi-functional protein that assembles into filaments.

F-Actin

A filamentous polymer of globular (G) actin monomers.

Tropomyosin

A protein involved in muscle contraction. It is related to myosin and occurs together with troponin in the thin filaments of muscle tissue.

Troponin

A complex of three regulatory proteins (troponin C, troponin I, and troponin T) that is integral to muscle contraction in skeletal and cardiac muscle tissue.

TnT

Binds to tropomyosin, interlocking them together.

TnC

Binds to Calcium ions to produce a conformational change in troponin.

Tnl

Binds to actin in the thin myofilaments to hold the troponin-tropomyosin complex in place.

NMJ (Neuromuscular Junction)

The synapse between a motor neuron and a muscle fiber.

ACh (Acetylcholine)

A neurotransmitter released by motor neurons at the neuromuscular junction.

AChE (Acetylcholinesterase)

An enzyme that breaks down acetylcholine in the synaptic cleft.

nAChR (Nicotinic Acetylcholine Receptor)

Ion channel receptor that acetylcholine binds to at the NMJ.

VSCC (Voltage-Sensitive Calcium Channel)

A calcium channel that is activated by membrane depolarization.

DHP (Dihydropyridine Receptor)

A voltage-dependent calcium channel located on the T-tubule membrane of muscle cells.

Ryanodine Receptor

A calcium channel located on the sarcoplasmic reticulum membrane that releases calcium into the cytoplasm during muscle contraction.

SERCA (Sarco/Endoplasmic Reticulum Ca2+-ATPase)

A calcium pump that transports calcium from the cytoplasm back into the sarcoplasmic reticulum, causing muscle relaxation.

Myasthenia Gravis

Autoimmune disease where receptors are internalized, destruction and simplification of the end plate, and block of the acetylcholine binding sites.

Summary of nerve to muscle

Acetylcholine is released by motor neuron. Activates nACh receptors. Sarcolemma depolarized, action potential triggered and spread to T tubules. DHP receptor activated, triggers ryanodine receptor. Calcium ions released from sarcoplasmic reticulum. Troponin C bind Ca 2+ and is activate . Muscle contraction imitated. Calcium ions pumped back into SR

Pathology of myasthenia gravis

1. receptors become internalized

2. destruction and simplification of the end plate

3. block of the acetylcholine binding sites