The peripheral nervous system (PNS) is the counterpart to the central nervous system. It contains the nerves that carry information to and from the rest of the body.
http://www.indiana.edu/~p1013447/images/pns_cnsc.gif
The basic units of the PNS are neurons, just like the CNS. The neurons in the peripheral nervous system make up nerves and ganglia, instead of making up the brain or the spinal cord. Nerves are cable-like bundles of neuron fibers tightly wrapped in connective tissue. Ganglia are clusters of neuron cell bodies.
In order for an action or reflex to occur, the PNS and the CNS must work together.
In order for an action or reflex to occur, the PNS and the CNS must work together.
Step 1:Sensory input
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Step 2: Integration
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Step 3: Motor output
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http://www.biologymad.com/nervoussystem/reflaxarc.gif
Example: A knee is tapped. A sensory receptor detects this tap. A sensory neuron sends this information to the central nervous system. In the central nervous system, an interneuron receives this information. The interneuron creates a response and sends it to the motor neuron. The motor neuron brings the new message to an effector cell, which causes the leg to jerk forward. This example uses one neuron of each type, but in reality, many of each of these cells are involved in body activities.
Each axon attached to a neuron ends in a cluster of branches. Each branch is called a synaptic terminal. The site of communication between each synaptic terminal and another cell is called a synapse.
http://www.hermes-press.com/nervous_system.gif