chapt44_lecture1

chapt44_lecture1 - The Nervous System Chapter 44 Nervous...

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The Nervous System Chapter 44
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2 Nervous System Organization All animals must be able to respond to environmental stimuli - Sensory receptors = Detect stimulus - Motor effectors = Respond to it -The nervous system links the two -Consists of neurons and supporting cells
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3 Nervous System Organization Vertebrates have three types of neurons - Sensory neurons (afferent neurons) carry impulses to central nervous system (CNS) - Motor neurons (efferent neurons) carry impulses from CNS to effectors (muscles and glands) - Interneurons (association neurons) provide more complex reflexes and associative functions (learning and memory)
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4
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5 Nervous System Organization The CNS consists of the brain and spinal cord The peripheral nervous system (PNS) consists of sensory and motor neurons - Somatic NS stimulates skeletal muscles - Autonomic NS stimulates smooth and cardiac muscles, as well as glands - Sympathetic and parasympathetic NS -Counterbalance each other
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7 Nervous System Organization Neurons have the same basic structure - Cell body = Enlarged part containing nucleus - Dendrites = Short, cytoplasmic extensions that receive stimuli - Axon = Single, long extension that conducts impulses away from cell body
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8 Nervous System Organization
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9 Nervous System Organization Neurons are supported both structurally and functionally by cells called neuroglia - Schwann cells and oligodendrocytes produce myelin sheaths surrounding axons -In the CNS, myelinated axons form white matter -Dendrites/cell bodies form gray matter -In the PNS, myelinated axons are bundled to form nerves
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10 Nervous System Organization
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11 Nerve Impulse Transmission A potential difference exists across every cell’s plasma membrane -Negative pole = Cytoplasmic side -Positive pole = Extracellular fluid side When a neuron is not being stimulated, it maintains a resting potential -Ranges from -40 to -90 millivolts (mV) -Average about -70 mV
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12 Nerve Impulse Transmission The inside of the cell is more negatively charged than the outside because of: 1. Sodium-potassium pump = Brings two K + into cell for every three Na + it pumps out 2. Ion leakage channels = Allow more K + to diffuse out than Na + to diffuse in
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14 Nerve Impulse Transmission There is a buildup of positive charge outside and negative charge inside the membrane -This electrical potential is an attractive force to bring K + ions back into the cell -Balance between diffusional and electrical forces leads to the equilibrium potential The resting membrane potential can be viewed using a voltmeter and two electrodes
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15 Nerve Impulse Transmission
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16 Nerve Impulse Transmission There are two types of potentials: -Graded potentials and action potentials Graded potentials are small transient changes in membrane potential due to activation of gated ion channels -Most are closed in the normal resting cell
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17 Nerve Impulse Transmission Chemically-gated or ligand-gated channels -Ligands are hormones or neurotransmitters -Induce opening and cause changes in cell membrane permeability
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chapt44_lecture1 - The Nervous System Chapter 44 Nervous...

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