Chapter 43 Assessment of the Nervous System.docx

Chapter 43 Assessment of the Nervous System.docx - Chapter...

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Chapter 43 Assessment of the Nervous System Structures and Functions of Nervous System Central nervous system (CNS) o B rain o Spinal cord o Cranial nerves I and III Peripheral nervous system (PNS) o Cranial nerves III to XII o Spinal nerves o Autonomic nervous system (ANS) Neurons o Primary functional unit o Characterized by Excitability : Ability to generate a nerve impulse Conductivity: Ability to transmit an impulse Influence: Ability to influence other neurons, muscle cells, or glandular cells by transmitting nerve impulses to them o function: carries impulses to other neurons or other organs o Myelin sheath: a white, lipid substance that acts as an insulator for the conduction of impulses o Nonmitotic Glial cells: (glia or neuroglia) provide support, nourishment, and protection to neurons. Glial cells constitute almost half of the brain and spinal cord mass and are 5 to 10 times more numerous than neurons o Microgli a: specialized macrophages capable of phagocytosis, protect the neurons. These cells are mobile within the brain and multiply when brain is damaged. o Macroglia: Astrocytes: (Most Abundant) Found primarily in gray matter and provide structural support to neurons. are found primarily in gray matter and provide structural support to neurons. Their delicate processes form the blood-brain barrier with the endothelium of the blood vessels. Play a role in synaptic transmission (conduction of impulses between neurons). When the brain is injured, astrocytes act as phagocytes for neuronal debris. They help restore the neurochemical milieu and provide support for repair. Proliferation of astrocytes contributes to the formation of scar tissue (gliosis) in the CNS. VOLUNATARY MOTOR NEURONS Oligodendrocytes: Specialized cells that produce the myelin sheath of nerve fibers in the CNS and are `primarily found in the white matter of the CNS. (Schwann cells myelinate the nerve fibers in the periphery.) Ependymal cells : line the brain ventricles and aid in the secretion of CSF o Mitotic: Neuroglia are mitotic and can replicate. When destroyed, the tissue is replaced by proliferation of neuroglial cells. o AFFERENT- AFFECTS SOMETHING o EFFERENT- EFFECT FROM SOMETHING. Nerve regeneration (repair) o Attempt to grow back by sprouting many branches from the damaged ends of their axons o PNS more successful than CNS
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Injured nerve fibers in the PNS can regenerate by growing within the protective myelin sheath of the supporting Schwann cells if the cell body is intact. The final result of nerve regeneration depends on the number of axon sprouts that join with the appropriate Schwann cell columns and reinnervate appropriate end organs. Nerve impulse: Purpose is to initiate, receive, and process messages about events both within and outside the body. Initiation involves the generation of an action potential. Once an action potential is initiated, a series of action potentials travels along the axon. When the impulse reaches the end of the nerve fiber, it is
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  • Spring '17
  • Acevedo
  • Nervous System

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