What does depolarization of the sarcolemma mean?
The electrochemical gradient across the muscle plasma membrane (more sodium moves in than potassium out) causes a local depolarization of the motor end-plate. This depolarization initiates an action potential on the muscle fiber cell membrane (sarcolemma) that travels across the surface of the muscle fiber.
What happens during depolarization of the sarcolemma?
The binding Ach causes depolarization of the sarcolemma by opening ion channels and allowing Na+ ions into the muscle cell. Na+ ions diffuse into the muscle fiber and depolarization occurs. As Ca+ levels rise, Ca+ ions bind with Troponin which removes the blocking action of Tropomyosin from the Actin binding sites.
What is the name of a prolonged muscle contraction?
A tetanic contraction (also called tetanized state, tetanus, or physiologic tetanus, the latter to differentiate from the disease called tetanus) is a sustained muscle contraction evoked when the motor nerve that innervates a skeletal muscle emits action potentials at a very high rate.
What causes the sarcolemma to depolarize?
The neurotransmitter acetylcholine diffuses across the synaptic cleft, causing the depolarization of the sarcolemma. The depolarization of the sarcolemma stimulates the sarcoplasmic reticulum to release Ca2+, which causes the muscle to contract.
What enzyme degrades acetylcholine?
Acetylcholinesterase (AChE) is a cholinergic enzyme primarily found at postsynaptic neuromuscular junctions, especially in muscles and nerves. It immediately breaks down or hydrolyzes acetylcholine (ACh), a naturally occurring neurotransmitter, into acetic acid and choline.
What kind of stimulus electrical or chemical travels from the axon terminal to the sarcolemma?
At the NMJ, the axon terminal releases a chemical messenger, or neurotransmitter, called acetylcholine (ACh). The ACh molecules diffuse across a minute space called the synaptic cleft and bind to ACh receptors located within the motor end-plate of the sarcolemma on the other side of the synapse.
What part of the sarcolemma contains acetylcholine receptors?
what part of the sarcolemma contains acetylcholine receptors? The part of the sarcolemma that contains acetylcholine receptors is the motor end plate. *Acetylcholine released at the neuromuscular junction triggers a muscle action potential, which leads to muscle contraction.
What is the role of sarcolemma in muscle contraction?
The plasma membrane of a skeletal muscle fiber is called the sarcolemma. The sarcolemma is the site of action potential conduction, which triggers muscle contraction. Within each muscle fiber are myofibrils—long cylindrical structures that lie parallel to the muscle fiber.
Which term best describes a prolonged painful muscle contraction?
Muscle cramp denotes an episodic, involuntary, painful contraction of a muscle. Muscle spasm is a more encompassing term referring to any involuntary muscle contraction.
What promotes depolarization stage?
The depolarization is brought about by the entry of sodium and calcium ions that results from the opening of membrane channels.
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