APK3110_Chapter7_Spring12_part+A+and+B

APK3110_Chapter7_Spring12_part+A+and+B - THE NERVOUS...

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Unformatted text preview: THE NERVOUS SYSTEM: STRUCTURE AND CONTROL OF MOVEMENT Chapter 7 Part A Objectives 1. Discuss the general organization of the nervous system. 2. Describe the structure and function of a nerve. 3. Define depolarization, action potential, and repolarization. General nervous system functions Control of the internal environment Nervous system works with the endocrine system Voluntary control of movement Programming spinal cord reflexes Memory and learning Central Nervous System (CNS) & Peripheral Nervous System (PNS) Figure 7.2 Sensory nerve fibers: called afferent fibers conduct information towards the CNS Motor nerve fibers: called efferent fibers, conduct impulses to effector organs Organization of the nervous system Central nervous system (CNS) Brain and spinal cord Peripheral nervous system (PNS) Neurons outside the CNS Sensory division Afferent fibers transmit impulses from receptors to CNS Motor division Efferent fibers transmit impulses from CNS to effector organs Subdivided into somatic motor division (innervates skeletal muscle) and autonomic motor division (innervates involuntary effector organs) Anatomical divisions of the nervous system Figure 7.1 touch, pain, temperature, body position Visceral pain (angina, IBS, appendicitis) Vision, hearing, balance Skeletal muscle Glands, vascular smooth muscle, cardiac muscle Structure of a neuron 1. Cell body (soma): center of operation Contains the nucleus 2. Dendrites: receptive area Conduct electrical impulses toward cell body 3. Axon (nerve fiber) Carries electrical impulse away from cell body towards another neuron or effector organ Figure 7.3 1 2 3 Synaptic Transmission Figure 7.4 Synapse contact point between axon of one neuron and dendrite of another neuron synaptic cleft- small gap between presynaptic neuron and postsynaptic neuron for an impulse to cross from one neuron to another it must cross the synaptic cleft at a synapse. Nerve Axon Varies in length from a few mm to a meter Each neuron has only one axon but can be divided into collateral branches that terminate at other neurons, muscle cells or glands. In large nerve fibers like those that innervate skeletal muscle the axons are covered by Schwann cells Schwann cells form a discontinuous insulating layer ( myelin sheath ) along the length of axon Gaps or spaces between myelin segments along the axon called Nodes of Ranvier aid neural transduction Axons with large myelin sheath conduct impulses more rapidly than small nonmyelinated fibers. Damage of myelin results in nervous system dysfunction. Clinical Applications 7.1 Multiple sclerosis Neurological disease that destroys myelin sheaths of axons Has genetic component Due to immune attack on myelin Results in progressive loss of nervous system function Fatigue, muscle weakness, poor motor control, loss of balance, mental depression Exercise can improve functional capacity Leads to improved quality of life Electrical activity in neurons...
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APK3110_Chapter7_Spring12_part+A+and+B - THE NERVOUS...

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