A&P 8 - Chapter 8: Nervous System Chapter Three...

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Chapter 8: Nervous System Chapter 8: Nervous System Three specific functions that work to maintain homeostasis: Sensory input: receptors in the skin and organs respond to external and internal stimuli. Integration: brain and spinal cord interpret the data received from sensory receptors and signal the appropriate nerve responses. Motor output: nerve impulses from the brain and spinal cord are sent to effectors , which are muscles, glands, and organs.
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Nervous System Nervous System Divisions of the Nervous System Central nervous system (CNS) Brain Spinal cord Peripheral nervous system (PNS) – includes all the cranial and spinal nerves Afferent (sensory) division Efferent (motor) division
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Nervous System Nervous System
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Nervous System Nervous System
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Nervous System Nervous System
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Types of Neurons Types of Neurons Motor neurons: take nerve impulses from the CNS to muscles, organs, or glands, where they stimulate muscle contraction, glands to secrete, and organs to function. These neurons are classified as multipolar (many dendrites and a single axon).
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Types of Neurons Types of Neurons Sensory neurons: take nerve impulses from sensory receptors to the CNS. These are unipolar (a single extension from the cell body that divides into a branch that goes to the dendrite and axon).
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Types of Neurons Types of Neurons Interneurons: known as associated neurons, they are entirely within the CNS and convey nerve impulses between from sensory to motor neurons from one side of the spinal cord to the other. Interneuron
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Neuron Structure Neuron Structure Cell body – contains nucleus and other organelles Dendrite – receive signals from sensory receptors or other neurons Axon Conducts nerve signals away from cell body Nerve – bundle of parallel axons in the PNS Tract – bundle of parallel axons in the CNS May be covered by myelin (lipid coating) Formed by Schwann cells or neurolemmocytes in PNS Formed by oligodendrocytes in CNS
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Nerve Signal Conduction Nerve Signal Conduction Resting potential Neuron possesses potential energy The cell membrane is polarized positively charged outside the cell negatively charged inside Action potential Process of conduction of nerve signals Occurs in the axons Begins with a stimulus Channels in the cell membrane opens and sodium ions rush into the cell ( depolarization ) Sodium channels close and the cell repolarizes
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Nerve Signal Conduction Nerve Signal Conduction Conduction of action potentials (APs) In unmyelinated axons Slow (~1 meter/second) Each section of the axon must be stimulated In myelinated axons Called saltatory conduction An AP at one node of Ranvier can “jump” over myelinated portion of axon Much faster (>100 meters/second) Is an all-or-none event Refractory period Axon cannot conduct an AP Ensures one-way direction of an impulse
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Nerve Signal Conduction Nerve Signal Conduction
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Nerve Signal Conduction Nerve Signal Conduction
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This note was uploaded on 11/26/2011 for the course PHY 220 taught by Professor Thomas during the Summer '10 term at N.C. State.

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A&P 8 - Chapter 8: Nervous System Chapter Three...

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