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Unformatted text preview: MEDICAL-SURGICAL NURSING By: Anthony T. Villegas R.N. Overview of structures and functions: NERVOUS SYSTEM • The functional unit of the nervous system is the nerve cells or neurons • The nervous system is composed of the ff: Central Nervous System • Brain • Spinal Cord – serves as a connecting link between the brain & the periphery. Peripheral Nervous System • Cranial Nerves –12 pairs; carry impulses to & from the brain. • Spinal Nerves – 31 pairs; carry impulses to & from spinal cord. Autonomic Nervous System subdivision of the PNS that automatically controls body function such as breathing & heart beat. Special senses of vision and hearing are also covered in this section • Sympathetic nervous system – generally accelerate some body functions in response to stress. • Parasympathetic nervous system – controls normal body functioning. CELLS A. NEURONS • Primary component of nervous system • Composed of cell body (gray matter) , axon, and dendrites • Basic cells for nerve impulse and conduction. Axon • Elongated process or fiber extending from the cell body • Transmits impulses (messages) away from the cell body to dendrites or directly to the cell bodies of other neurons • Neurons usually has only one axon Dendrites • Short, blanching fibers that receives impulses and conducts them toward the nerve cell body. • Neurons may have many dendrites. Synapse • Junction between neurons where an impulse is transmitted Neurotransmitter • Chemical agent (ex. Acetylcholine, norepinephrine) involved in the transmission of impulse across synapse. Myelin Sheath • A wrapping of myelin (whitish, fatty material) that protects and insulates nerve fibers and enhances the speed of impulse conduction. o Both axons and dendrites may or may not have a myelin sheath (myelinated/unmyelinated) o Most axons leaving the CNS are heavily myelinated by schwann cells Functional Classification 1. Afferent (sensory) neurons • Transmit impulses from peripheral receptors to the CNS 2. Efferent (motor) neurons • Conduct impulses from CNS to muscle and glands 3. Internuncial neurons (interneurons) • Connecting links between afferent and efferent neurons Properties 1. Excitability – ability of neuron to be affected by changes in external environment. 2. Conductility – ability of neuron to transmit a wave of excitetation from one cell to another. 3. Permanent Cell – once destroyed not capable of regeneration. TYPES OF CELLS BASED ON REGENERATIVE CAPACITY 1. Labile • Capable of regeneration. • Epidermal cells, GIT cells, GUT cells, cells of lungs. 2. Stable • Capable of regeneration with limited time, survival period. • Kidney cells, Liver cells, Salivary cells, pancreas....
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This note was uploaded on 02/10/2010 for the course ADN 105 taught by Professor Aaa during the Spring '07 term at 東京大学.

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