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Lecture 18 and 19

by: Natasha

Lecture 18 and 19 Biol 202

GPA 3.9

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This is one week of notes from the class. This includes the online lecture and the the nervous tissues and organization.
Human Anatomy and Physiology I
Schoenfuss, Heiko
Class Notes
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This 4 page Class Notes was uploaded by Natasha on Sunday November 22, 2015. The Class Notes belongs to Biol 202 at St. Cloud State University taught by Schoenfuss, Heiko in Spring 2015. Since its upload, it has received 26 views. For similar materials see Human Anatomy and Physiology I in Biology at St. Cloud State University.


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Date Created: 11/22/15
Biol 202 The Nervous System The Average Neuron  Dendrites that look like tree roots  Synaptic terminal (axon terminal) communicates with the other cells  Axon hillock is where all the information comes together Starting a Nerve Impulse   Depolarization­ a stimulus depolarizes the neuron’s membrane  A depolarization membrane allows for the sodium to flow inside the membrane  The exchange of ions initiates an action potential in the neuron The Action Potential  If the action potential or nerve impulse starts, it is propagated over the entire axon  It is an all or nothing response  Potassium ions rush out of the neuron after sodium ions rush in and that repolarizes the  membrane  The sodium­potassium pump restores the original configuration and this action requires  ATP  IMPORTANT CONCEPT (read in your text book)  Look at the graph  It takes 4 milliseconds before an action potential can fire again  Threshold, stimulus, depolarization (or failed initiations), action potential, repolarization,  refractory period, resting state Nerve Impulse Propagation  The impulse continues to move toward the cell body  Impulses travel faster when fibers have a myelinated sheath  They cannot travel backwards  It travels down to the synaptic end or axon terminal of the cell  Schwann cells cannot exchange sodium and potassium ions that can only happen at the  nodes of Ranvier Saltatory Impulse Conduction   The impulse jumps (saltation­Latin) from one Node of Ranvier to the next  Stimulus can travel effectively and quickly down the length of the axon towards the axon  terminal The Voltage­Clamp Method  Squid have think neurons so you can stimulate the neurons and test them with electrodes.  Continuation of the Nerve Impulse between Neurons  Impulses are able to cross the synapse to another nerve o Neurotransmitter is released from a nerve’s axon terminal o The dendrite of the next neuron has receptors that are stimulated by the  neurotransmitter o An action potential is started in the dendrite  Nervous System Divisions  Central Nervous System o Brain o Spinal Cord  Peripheral Nervous System o Peripheral nerves  o Nerves outside the brain and spinal cord Functional Classification of Neurons  Sensory or afferent neurons o Carry impulses from the sensory receptors to the central nervous system  Cutaneous sense organs  Proprioceptors­ they detect stretch or tension   Motor or efferent neurons o Carry impulses from the central nervous system to effectors (muscles and glands)  Interneurons or associated neurons o Found in the neural pathways in the central nervous system o Connect the sensory neurons and the motor neurons  Structural Classification of Neurons  Multipolar neurons­ many processes extend from the cell body; all are dendrites except  for a single axon  Bipolar neurons­ two processes extend from the cell body; One is a fused dendrite, the  other is an axon  Unipolar neurons­ One process extends from the cell body and forms central and  peripheral processes, which together comprise an axon Nervous Tissue: Support Cells Central Nervous System  Astrocytes o Most abundant and most versatile glial cells o Star shaped o Brace neurons o Form barrier between capillaries and neurons o Control the chemical environment of the brain  Microglia o Small ovoid cells with long “thorny” processes o Spider­like phagocytes o Dispose of debris   Ependymal Cells o Line central cavities of the brain and spinal cord o Circulate cerebrospinal fluid  Oligodendrocytes  o Line up along the thicker neuron fibers in the CNS and insulate the myelin  sheaths Nervous Tissues: Support Cells in the PNS  Satellite cells o Surround neuron cell bodies located in the PNS o Protect neuron cell bodies  Schwann cells o Form myelin sheath in the peripheral nervous system Functions of the Nervous System  Sensory input­ gather information o Monitor changes occurring inside and outside the body o Changes in stimuli   Integration o Processes and interprets sensory input and decides what should be done at each  moment  Motor output o Response to stimuli o Activates effector organs­the muscles and glands Functional Classification of the Nervous System  Sensory or afferent division o Nerve fibers that carry information to the central nervous system  Motor of efferent division o Nerve fibers that carry impulses away from the central nervous system o Two divisions 1. Somatic nervous system – voluntary  Consciously control our skeletal muscles 2. Autonomic nervous system – involuntary  Heart pumping or digesting food  Two subdivisions 1. Sympathetic division 2. Parasympathetic division 


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