Anatomical Organization of the Nervous System Pt 2

Anatomical Organization of the Nervous System Pt 2 -...

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Anatomical Organization of the Nervous System -Part II Cells of the Nervous System Neurons: Neurons are the basic cellular unit of the nervous system. They are the cells that conduct information from the periphery to the CNS or from the CNS out to effectors (muscles, glands, organs). The basic elements of a neuron are its cell body (soma), one or more branching cytoplasmic extensions termed dendrites, and typically a single axon. Axons may be long (more than a meter) or short (just a few microns). Neurons have a few basic types of morphology . A unipolar neuron has the dendrite and axon coming off the same process. A pseudounipolar neuron has a single process that runs a short distance and then branches into a relatively long axon. However, one branch of the axon is significantly longer than the other. Sensory neurons traveling from the periphery into the spinal cord are an example. Cell bodies of these neurons lie within the dorsal root of the spinal nerve and typically have few, if any, dendrites. Multipolar neurons have a single axon with two or more dendrites. This is typical for motor neurons and most neurons intrinsic to the brain and spinal cord. Bipolar neurons have a centrally located soma with a single axon and a single dendrite projecting in opposite directions. Bipolar neurons in the retina of the eye, and olfactory cells are examples. Neurons can also be classified by what they do. Sensory neurons bring information from the periphery to the CNS. Motor neurons travel from the CNS to muscle, glands, or other effectors. Interneurons typically are small multipolar CNS neurons with relatively short axons. They may connect sensory to motor neurons or connect with other interneurons. Most interneurons are inhibitory and release GABA or glycine as their neurotransmitter. However some are excitatory and release glutamate or aspirate. Associative neurons are interneurons in the CNS that connect one region of the brain or spinal cord to another region.
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Neuroglial Cells: These cells support the neurons. Their four primary functions are to provide nutrients and oxygen to neurons, provide structural support to neurons, provide electrochemical insulation around axons, and help to destroy invading microorganisms and clean up cellular debris. They are not directly involved in the propagation of a nerve impulse. CNS supportive cells: Astrocytes are star-shaped cells of variable size with extensive cytoplasmic processes. Fibrous astrocytes are found in the white matter while protoplasmic astrocytes are found in the grey matter. They function in structural support for neurons, help provide nutritional and metabolic support for neurons, may aid in the processing of neurotransmitters, help limit the spread of electrochemical excitation into the surrounding brain substance (neuropil), and help maintain the extracellular ion concentrations. Oligodendrocytes are responsible for producing and maintaining the myelin sheaths of axons in the central nervous system.
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This note was uploaded on 04/05/2011 for the course APC 100 taught by Professor Kelliewhited during the Spring '07 term at UC Davis.

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Anatomical Organization of the Nervous System Pt 2 -...

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