Peripheral Nervous System: Autonomic Nervous System ‘NMJ Ion Flow’ by Casey Henley is licensed under a Creative Commons Attribution Non-Commercial Share-Alike (CC BY-NC-SA) 4.0 International License. The depolarization of the cell by the sodium influx will activate nearby voltage-gated ion channels. ![]() The ionotropic nicotinic acetylcholine receptors in the postjunctional folds of the muscle fiber are non-selective cation channels that allow the influx of sodium and the efflux of potassium. The action potential leads to contraction of the muscle fiber. In a healthy system, an action potential in the motor neurons always causes an action potential in the muscle cell. The depolarization will cause nearby voltage-gated channels to open and fire an action potential in the muscle fiber. Nicotinic acetylcholine receptors allow for the influx of sodium ions into the muscle cell. ‘Neuromuscular Junction’ by Casey Henley is licensed under a Creative Commons Attribution Non-Commercial Share-Alike (CC BY-NC-SA) 4.0 International License. Neurotransmitter action is terminated through breakdown by acetylcholinesterase. Acetylcholine is released at the NMJ and acts on nicotinic acetylcholine receptors located in the postjunctional folds of the muscle fiber. The neuromuscular junction (NMJ) is the synapse between a motor neuron and a muscle fiber. Acetylcholinesterase, an enzyme that breaks down acetylcholine and terminates its action, is present in the synaptic cleft of the neuromuscular junction. Acetylcholine is the neurotransmitter released at the NMJ and it acts upon ligand-gated, non-selective cation channels called nicotinic acetylcholine receptors that are present in postjunctional folds of the muscle fiber. The NMJ is one of the largest synapses in the body and one of the most well-studied because of its peripheral location. Synapse: Neuromuscular JunctionĪll somatic motor neurons release the same neurotransmitter, acetylcholine, onto the skeletal muscle target/effector organ at the neuromuscular junction (NMJ). ‘Somatic Nervous System’ by Valerie Hedges is licensed under a Creative Commons Attribution Non-Commercial Share-Alike (CC-BY-NC-SA) 4.0 International License. The neurotransmitter released onto the skeletal muscle is acetylcholine. ![]() The somatic nervous system efferent path consists of a neuron that has a cell body within the central nervous system that extends all the way to the target tissue: skeletal muscles. This somatic motor neuron has its cell body in the central nervous system and has an axon that extends all the way to the target/effector organ, which-for the somatic nervous system-will be a skeletal muscle. The axon of this neuron is heavily myelinated, which allows for fast delivery of messages. The somatic nervous system has an efferent path from the central nervous system to the target / effector organ that is made up of one neuron. The somatic nervous system is also called the “voluntary nervous system” since it is used to cause muscle movement related to intentional actions. The nerves that innervate the muscles of the legs as we run are part of the efferent somatic nervous system. We also think of the somatic nervous system as the branch that sends signals to our skeletal muscles. ![]() For example, the nerves that detect pressure or pain on the foot are part of the afferent somatic nervous system. The somatic nervous system represents all the parts of the PNS that are involved with the outside environment, either in sensing the environment or acting on it.
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