ch. 9 Muscle Contraction Mechanism

These flashcards cover key vocabulary and concepts related to the mechanism of muscle contraction as discussed in the lecture.

Cross bridge attachment

The point where myosin heads attach to binding sites on actin filaments during muscle contraction.

Power stroke

The action of the myosin head pulling the thin filament inward during muscle contraction.

Sarcoplasmic reticulum

The organelle that stores and releases calcium ions to trigger muscle contraction.

T tubules

Invaginations of the sarcolemma that help transmit action potentials into the muscle fiber.

Neuromuscular junction

The synapse formed between a somatic motor neuron and a muscle fiber.

Acetylcholine (ACh)

A neurotransmitter released at the neuromuscular junction that stimulates muscle contraction.

Chemically gated ion channel

An ion channel that opens when a neurotransmitter binds to its receptor.

Voltage gated ion channel

An ion channel that opens in response to changes in membrane potential.

Calcium ions (Ca²⁺)

Ions released from the sarcoplasmic reticulum that bind to troponin to facilitate muscle contraction.

Troponin

A regulatory protein that binds calcium and causes tropomyosin to shift, exposing binding sites on actin.

Tropomyosin

A protein that blocks myosin binding sites on actin, preventing contraction in a relaxed state.

Skeletal muscle contraction

A process that involves the sliding of thick and thin filaments over each other, leading to muscle shortening.

Rigor mortis

A post-mortem state where muscles stiffen due to a lack of ATP preventing detachment of myosin heads from actin.

Acetylcholinesterase

An enzyme that breaks down acetylcholine in the synaptic cleft, stopping muscle contraction.

Motor unit

A single motor neuron and all the muscle fibers it innervates.

Isotonic contraction

A type of muscle contraction where the muscle changes in length while contracting.

Isometric contraction

A type of muscle contraction where the muscle exerts force without changing length.

Complete tetanus

A state of continuous contraction without any relaxation, caused by rapid stimuli.

Incomplete tetanus

A state of contraction where there is partial relaxation between stimuli.

Electrical signal

A change in membrane potential that propagates along the muscle cell membrane, triggering contraction.