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Lecture 8

Week/Lecture 8: Nervous System.pdf

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BIOL 171

Nervous System Nervous Tissue controls and integrates all body activities within limits that maintain life general functions: communication between brain and body control body functions 3 basic functions sensing change brain must know what is happening in body interpreting, remembering change brain learns that pain is bad reacting to change brain returns body to homeostasis Major Structures brain cranial nerves not part of spinal cord; sensory and control enteric plexus network of neurons/nerves that are important for controlling gastrointestinal (GI) function brain does not have direct control over plexus sensory receptors not necessarily part of nervous system, but are made of nervous tissue Classification see notes (diagram pg 7) Neuron: nerve cell Nerve: bundle of nerve cells (axons of neurons) Mixed nerves: 2 different types of nerves Peripheral Nervous System: Cranial and Spinal Nerves sensory fibres (send msgs from sensory receptors to CNS) motor fibres (send msgs from CNS to muscles, glands) Functional Divisions Somatic voluntary sensory neurons gathering info from somatic receptors and special sense receptors (sight, taste, balance, smell, etc) to the CNS motor neurons to skeletal muscle tissue Autonomic involuntary sensory neurons from visceral organs to CNS (heart beating) motor neurons to smooth muscle, cardiac muscle, glands (sweat secretion) Sympathetic fight or flight heart rate, breathing rate, blood pressure increase Parasympathetic resting Enteric network of sensory, motor neurons within the wall of the GI tract functions independently of ANS and CNS controls GI function Nervous Tissue composed of: neurons and neuroglia Neurons (nerve cells) functional unit of the nervous system electrically excitable (able to produce nerve impulses/AP) Parts: cell body (high concentration of cytoplasm) nucleus cytoplasm with usual organelles plus: Nissl bodies (clusters of rough ER) neurofilaments (give shape and support) microtubules (intracellular transport; ex: from soma to axon) lipofuscin pigment granules (brown pigment as cells age; no known purpose) processes (protruding) dendrites short, highly branched (branching of other branches) unmyelinated specialized for contact with other neurons conduct impulses/information towards the cell body contain neurofibrils and Nissl bodies axon long, slender process arising from axon hillock contains mitochondria, microtubules, neurofibrils conducts impulses away from cell body axon terminals (branching) contain vesicles filled with neurotransmitter functional classification sensory (afferent) neurons transmit sensory info from skin, muscles, joints, sense organs and viscera to CNS information to CNS ganglion: group of cell bodies outside CNS motor (efferent) neurons transmit motor nerve impulses from CNS to muscles and glands information to glands/muscles interneurons (association) 90% of neurons connect neurons within the CNS structural classification based on number of processes (proje
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