There will be a refractory period after the cell has returned to its resting potential that means the cell can temporarily be unable to be activated again. The action potential is the electrical potential that moves down the cell axon or dendrite when the cell is activated. This is an all or none phenomena so the neuron is either activated or it is not.
PARTS OF THE NERVOUS SYSTEM There are two major divisions of the nervous system. These are the central nervous system or CNS and the peripheral nervous system or PNS. The CNS is basically just the brain and the spinal cord, while the PNS is the rest of the nervous system—namely, the peripheral nerves. Most of the peripheral nerves are axons that travel in bundles called nerves throughout the body. There are large and small nerves. There are also clusters of nerve cell bodies in the peripheral nervous system called ganglia. There are two subdivisions of the peripheral nervous system. These are the somatic nervous system and the autonomic nervous system. The somatic nervous system consists of nerves that can be motor nerves or sensory nerves. Sensory nerves pick up signals from the environment and send the signal to the central nervous system to be processed. These are referred to as afferent nerves because they go into the body. Motor nerves are efferent nerves that send signals out of the central nervous system to the muscles that move in response to voluntary thought or in response to a sensory signal. There are interneurons within the central nervous system that can connect two different types of nerves together. The autonomic nervous system is very important to psychology because its involuntary activities can be strongly influenced by stress and one s emotions. There are two subdivisions of the autonomic nervous system. These are the somewhat opposite systems of the sympathetic nervous system and the parasympathetic nervous system. Their function is to maintain the homeostasis or equilibrium of the body. Figure 8 shows the different activities of the autonomic nervous system branches:
49
