Chapter 9 Nervous System_Spinal Cord and Nerves

Chapter 9 Nervous System_Spinal Cord and Nerves - Nervous...

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1 Chapters 9: The Nervous System Nervous System (NS) Functions: Sensory input Integration Motor output NS is classified by structure and function Structural Classification Functional Classification of PNS Nervous Tissue: Neurons Functional cells of the NS Specialized to transmit stimuli Cytoplasmic extensions from the cell body form Dendrites Axons Long, thin single fibers Conduct impulses away from the cell body End in axon terminals Most axons are myelinated Myelin : a white fatty material surrounding most axons Synaptic end bulbs contain vesicles with neurotransmitters Nerve impulses may be delivered to another neuron, muscle or gland Neuron Anatomy: Axons
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2 Typically short, highly branched & unmyelinated Conduct impulses towards the cell body Receptors of stimuli Neuron Anatomy: Dendrites Neuroglia (Glial Cells) protect the neurons aid in cell repair act as phagocytes regulate the composition of interstitial fluids Continue to multiply throughout life Neuroglia (Glial Cells) Astrocytes : Star-shaped cells attached to brain capillaries Form a barrier between blood & neurons Regulate nutrients & wastes Neuroglia (Glial Cells) Microglia : Small spider-like phagocytes Processes contact blood vessels Immune effector cells of the CNS exhibit pinocytotic activity function to cleanse the ECF to maintain central homeostasis Neuroglia (Glial Cells) Ependymal cells : Line fluid-filled cavities in the CNS Circulate within the cerebrospinal fluid (CSF) Micro-villi involved in the directional movement of CSF thought to facilitate the transport of nutrients into the brain and the removal of toxic metabolites. Neuroglia Oligodendrocytes: Most common glial cell Form myelin sheath around axons in the CNS Schwann cells : Form the myelin sheath around axons in the PNS Satellite cells : protect neuron cell bodies in PNS
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3 Neurilemma: Outermost membrane of schwann cells Important role in the regeneration of damaged nervous tissue in the PNS Not present in oligodendrocytes (in CNS) Nodes of Ranvier: Gaps in the myelin sheath Speed the conduction of nerve impulses The Myelin Sheath Interneuron Sensory Neuron Motor Neuron Types of Neurons Sensory/ Afferent neurons carry impulses from the sensory receptors to the CNS Motor/ Efferent neurons carry impulses from the CNS to muscles or glands Interneurons/ Association neurons relay information between sensory & motor neurons within the CNS Types of Neurons NS Terms White matter : composed of myelinated axons Gray matter : composed of cell bodies, dendrites, Ganglion : a collection of cell bodies outside CNS Nerve : a bundle of neuron fibers
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Chapter 9 Nervous System_Spinal Cord and Nerves - Nervous...

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