Tendon

Dense connective tissue that connects muscle to bone

Fascicles

Compartments that contain bundles of skeletal muscle fibers

Sarcomeres

• Segment of the myofibril between two successive Z lines
• Causes the muscle fiber to appear striated
• Basic units of contraction

Sarcolemma

• Plasma membrane of the muscle cell
• Highly invaginated by transverse tubules (T tubules)

Transverse Tubules

Run across the muscle fiber and contains extra fluid

Sarcoplasma

Cytoplasm of the muscle cell

Sarcoplasmic Reticulum

Stores calcium and is in the sarcoplasma

Myofibrils

Threadlike structures bundled together in parallel

2 Types of Myofibrils

1. Actin
2. Myosin

Actin

• Thin filament
• Two strands of globular proteins
• Light portion (I band)

Myosin

• Thick Filaments
• Protein strands with globular parts called  cross bridges
• Dark portions (A bands)

Z Line

actin are attached to

Cross Bridge

Part of the myosin that will attach to the actin

The 1st step of a muscle contraction...

ATP binds to a myosin head

After the ATP binds to the myosin head in a muscle contraction then...

Ca binds to actin (troponin) causing tropomyosin to move and expose attachment sites

After the Ca binds to the actin and exposed the attachment sites in a muscle contraction then...

The myosin head will attach to the actin forming a cross bridge

After the cross bridge is formed between the actin and myosin in a muscle contraction then...

This causes the sliding movement of the actin toward the center of the sarcomere.  Pulls the Z lines together

The final step in a muscle contraction is...

The Ca is released and goes back to the sarcoplasmic reticulum and the muscle relaxes.

Motor Neuron

A nerve cell that is connected to muscle fiber

Neuromuscular Junction

Connection between the nerve fiber and muscle fiber

Motor End Plate

Junction between the nerve fiber and muscle fiber

Neurotransmitter

Stores chemicals in tiny vesicles at the ends of the nerve fibers and carries the action potential across the synapse

Motor Unit

A motor neuron and several muscle fibers

The neurotransmitter between a neuron and a muscle is...

Acetylcholine

Myoglobin

Allows muscel cells to store oxygen temporarily and reduces the muscles need for a continuous blood supply during muscular contraction

Hemoglobin

Oxygen binds to this molecule and travels through the blood

Oxygen Debt

When lactic acid accumulates in the muscle

Muscle Fatigue

Accumulation of lactic acid and may lose ability to contract muscle

Muscle Cramps

Muscle contracts spasmodically and does not completely relax due to a lack of ATP, which is needed to move the Ca back into the sarcoplasmic reticulum

Rigor Mortis

• A few hours after death the joints become fixed and may continue for up to 72 hours
• Due to an increase in Ca and a drcrease in ATP
• Prevents muscle relaxation