255 nervous system - Two subdivisions of the nervous system...

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Two subdivisions of the nervous system o Central nervous system Brain Spinal cord o Peripheral Nervous system Cranial nerves Spinal nerves Ganglia 3 main functions of the nervous system o Collecting information o Processing and evaluating information o Responding to information 2 functional divisions of nervous system o Sensory nervous system o Motor nervous system Sensory nervous system o Afferent- Receives sensory information from receptors in PNS and transmits it to CNS o 2 subdivided systems Somatic sensory Voluntary (touch, pain, pressure, vibration) Visceral sensory Involuntary (impulses from viscera) Motor nervous system o Efferent- Send impulses from CNS to muscles and glands o 2 subdivided systems Somatic motor Voluntary o Impulses from the CNS that cause contraction of skeletal muscles Autonomic motor Involuntary o Impulses from CNS that regulate smooth and cardiac muscle and glands Cytology o Neurons (nerve cells) Electrically excitable cells that initiate, transmit, and receive nerve impulses o Glial cells Nonexcitable cells that support and protect neurons
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Neurons o Basic structural unit of nervous system o Conduct nerve impulses from one part of the body to another part o Features High metabolic rate Extreme longevity Nonmitotic Neuron structure o Cell body Contains: Nucleus Nucleolus Mitochondria Ribosomes and ER o Dendrites Toward cell body Short processes o Axon Away from cell body to other cells Anaxonic: do not have axon Axon hillock: region where axon connects to cell body o Axon collaterals Side branches of main axon o Telodendria Fine terminal extensions at end of the axon and its collaterals o Synaptic knobs Expanded regions at tip of telodendria Aka synaptic bulb, axon terminals, or synaptic button Structural Classification of neurons o Unipolar Single short process that branches like a T o Bipolar 2 processes, one dendrite and one axon o Multipolar Many dendrites and single axon Most common Functional Classification of neurons o Sensory Afferent Impulses from sensory receptors to CNS o Motor Efferent
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From CNS to muscles or glands o Interneurons Facilitate communication between sensory and motor neurons Glial cells o Aka neuroglia o Found in CNS and PNS o Smaller than neurons and capable of mitosis o Physically protect and nourish neurons o More numerous than neurons Brain tumors more likely to be derived from glial cells than neurons o 4 types Astrocytes Ependymal Microglial cells Oligodendrocytes Astrocytes o Type of glial cell o Most abundant glial cell in CNS o Functions Maintain blood-brain barrier/regulate blood flow Regulate tissue fluid composition Form structural network Replace damaged neurons Assist neuronal development Ependymal o Ciliated cuboidal epithelial cells o
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