Nervous System

A nerve cell

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Main body of neuron

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• - tree-like branches
• - for input/sensory (not output)

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Impulse generators and conductors that transmit nerve impulses away from their cell body.

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Thin sheath around a nerve axon; external material

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Fatty insulating sheath that surrounds all but the thinnest nerve fibers

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Gaps in the myelin sheath

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Star-shaped glial cells of the CNS

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Glial cells derived from mesoderm; function as macrophages (scavengers) in the CNS.

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Form a simple epithelium that lines the central cavity of the spinal cord and brain.

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"few branch cells"; line up in small groups and wrap their cell processes around the thicker axons in the CNS, producing insulating coverings called myelin sheaths.

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Type of neuroglia in the PNS; surround neuron cell bodies within ganglia(clusters of cell bodies).

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Type of neuroglia in the PNS; surround all axons in the PNS and form myelin sheaths around many of these axons.

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Neurons can live and function for a lifetime, over 100 years.

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Do not divide; lose ability to undergo mitosis.

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Continuous and abundant supplies of oxygen and glucose.  Neurons cannot survive for more than a few minutes without oxygen.

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The way neurons communicate; transmit information through chemical messengers.  Some neurons in the CNS transmit signals electronically through gap junctions.

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• -brain
• -spinal cord

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• -Everything outside the CNS.
• -Divide into several functional systems
•            -visceral (autonomic)
•            -somatic
•            -motor
•            -sensory

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• -transmits impulses toward the CNS
•      -somatic sensory: controls touch, temperature, propioception in skin, body wall, and limbs

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-visceral sensory: controls stretch, pain, temperature, and chemical changes in viscera, nausea, and hunger.

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• -transmits impulses away from the CNS
•       -somatic motor: voluntary, innervates skeletal muscle

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visceral motor (Autonomic Nervous System/ANS): involuntary, innervates involuntary muscle and glands

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Sympathetic: most active when body is in excitement or emergency situations

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Parasympathetic: most active when body is at rest

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• -more than two processes
• -numerous dendrites and single axon
• -small multipolar neurons have no axon and rely on dendrites for conducting signals
• -99% of neurons belong to multipolar
• -found in the CNS as interneurons
• -exit CNS as motor neurons

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• -more than two processes
• -occur in special sensory organs (inner ear, retina of the eye, epithelium of the nose)
• -serve as sensory neurons

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• -pseudo=false
• -found in PNS as sensory neurons
• -short, single process
• -emerges from cell body and divides like an inverted T into two long branches
• -start out as bipolar first
• -make up typical sensory neurons

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carrying toward

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carrying away

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• -covers schwann cells
• -delicate layer of loose connective tissue

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Groups of axons bound into bundles

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Wrapping of connective tissue

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Whole nerve surrounded by a tough fibrous sheath.

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-determine the direction of information flow through the nervous system

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• -positive ions- sodium and potassium
• -depolarization- 
• -resting membrane-
• -repolarization-

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-no interneuron between the sensory neuron and the motor neuron

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-one or more interneurons are part of the reflex pathway between the sensory and motor neurons.

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• -autoimmune disease
• -myelin is attacked by the body's own immune system
• -symptoms: blindness, weakness, clumsiness/balance, slurred speech, bladder inconsistence, fatigue, depression
• -myelin sheaths in the CNS are destroyed, forming scleroses

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