Conversely, the SNS creates alertness in the body. The PSNS maintains a calm state of arousal, with its function often simplified to “rest and digest”. A key role of the PSNS is stimulating saliva production in the mouth and stimulating the stomach and intestines to complete digestion. A diagram of a typical neuromuscular junction is shown below: The Autonomic Nervous SystemĪs mentioned above, the autonomic nervous system is divided into the parasympathetic and sympathetic systems. Once there, channels open to allow an influx of charged particles that signal the release of calcium, starting the contraction process. Ach travels across the cleft until it reaches the Ach receptors in the membrane of the muscle fiber. For example, the mechanism of signaling muscular contraction begins when the neuron that is part of the motor unit releases a neurotransmitter called acetylcholine (Ach) into the synaptic cleft. The neurotransmitter then travels across the synapse until it reaches another neuron’s dendrites or the target cell/tissue.
The vesicle fuses with the membrane of the axon terminal, releasing the neurotransmitter into the synaptic cleft, or synapse. When the signal reaches the terminal it causes the release of synaptic vesicles that carry a neurotransmitter (chemical messengers). Once through the axon the signal travels down each axon terminal. The dendrites of the first neuron in the signal chain receives the stimulus and transmit the signal through the axon. The process of sending a signal begins with a stimulus. Just like you send a text to a friend, your neurons send messages to one another. In contrast, the PSNS relaxes the body, bringing it back to normal after an exciting stimulus. The SNS preps the body for action, creating the flight or fight response to stimuli. Finally, within the autonomic nervous system are the sympathetic (SNS) and parasympathetic (PSNS) systems. The somatic nervous system controls voluntary body movements, like muscular contractions, and the autonomic nervous system controls involuntary movements, like the dilation of your pupils or rhythm of your heartbeat. Within the PNS are the somatic nervous system and the autonomic nervous system. The PNS is responsible for linking the body to the CNS so that signals created by the CNS are able to reach their targets. Nerves in the brain and nerves that extend from the spinal cord to the various regions of the body create the peripheral nervous system (PNS). The CNS houses the brain and spinal cord that act as the central command for all actions of the body. The nervous system has several divisions, all branching from the central nervous system (CNS). The nervous system allows you to communicate, show emotion, and interact with others.
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