Excitation-Contraction Coupling and Cross Bridge Cycling p8

Flashcards covering key vocabulary and concepts related to excitation-contraction coupling and cross bridge cycling in muscle physiology.

Excitation-Contraction Coupling

The process of transmitting an action potential along the sarcolemma and the sliding of myofilaments during muscle contraction.

Action Potential (AP)

A brief electrical impulse that propagates along the sarcolemma, leading to muscle excitation.

Axon Terminal

The end part of a motor neuron where neurotransmitters are released into the synaptic cleft.

Acetylcholine (ACh)

A neurotransmitter released at the neuromuscular junction that binds to receptors on the sarcolemma, initiating muscle contraction.

Troponin

A protein that binds calcium ions and, upon activation, causes tropomyosin to move away from myosin-binding sites on actin.

Cross Bridge Cycle

The series of events that occur when myosin heads bind to actin, propel the thin filament, detach, and reset for the next contraction.

Sarcoplasmic Reticulum (SR)

The specialized endoplasmic reticulum in muscle cells that stores and releases calcium ions.

Calcium Ion (Ca2+)

An essential ion that binds to troponin, leading to changes in muscle filaments and enabling contraction.

T tubules

Extensions of the sarcolemma that penetrate into the muscle fiber and conduct the action potential to deeper structures.

Rigor Mortis

The stiffening of muscles postmortem due to high intracellular calcium and lack of ATP, preventing cross bridge detachment.

End Plate Potential

A local depolarization of the sarcolemma due to the influx of Na+ ions, initiated by ACh binding.

Latent Period

The time delay between the arrival of an action potential at a muscle fiber and the start of contraction.

Myofilaments

The filaments of myofibrils, composed of actin (thin) and myosin (thick), responsible for muscle contraction.

Power Stroke

The phase of the cross bridge cycle where the myosin head pivots and pulls the thin filament towards the M line.

Cocking of Myosin Head

The resetting of the myosin head into a high-energy conformation after ATP hydrolysis, preparing for another cycle.

Muscle Fiber

A single muscle cell that is capable of contraction, formed by the fusion of many myoblasts.

Neuromuscular Junction (NMJ)

The synapse between a motor neuron and a skeletal muscle fiber.

ATP

Adenosine triphosphate, the energy currency of the cell that provides energy for muscle contraction mechanisms.

Sliding Filament Model

Describes how thin and thick filaments slide past each other during muscle contraction without changing length.

Sarcomere

The basic contractile unit of muscle tissue, defined by the area between two Z discs.

Z Disc

The boundary structure of a sarcomere, to which thin filaments are anchored.