Chapter 45

Chapter 45 - Please, Turn Your Cell Phones OFF Now. Thanks!...

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Please, Turn Your Cell Phones OFF Now. Thanks!
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Electrical Signals in Animals Neurons (nerve cells) are the basic operating unit of the nervous system Neurons transmit information via electrical signals = nerve impulses (or “action potentials”).
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Neurons Figure 42.2a
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The Anatomy of a Neuron Most neurons have a cell body , dendrites , and one or more axons
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Dendrites Collect electrical signals Cell body Contains nucleus and organelles Axon Passes electrical signals on to dendrites of another nerve cell or to an effector cell Figure 42.2b Information flow through neurons
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Sensory receptors transmit information about the internal or external environment to sensory neurons. Sensory neurons connect to interneurons in the central nervous system (CNS). Motor neurons transmit information to effectors = glands or muscles .
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The central nervous system ( CNS ) integrates information and activates motor neurons . The CNS consists of the brain and spinal cord
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Most CNS neurons are interneurons. Both the cell bodies and axons of interneurons lie inside the CNS. Cell bodies of motor neurons lie inside the spinal cord, but their axons project outside the spinal cord. Cell bodies of sensory neurons lie outsid e the spinal cord proper (in “dorsal root ganglia”)
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All of the components of the nervous system outside the CNS are part of the peripheral nervous system ( PNS ) .
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Reflexes are rapid responses that connect sensory neurons to motor neurons in a way that bypasses the brain . Sensory neuron > spinal interneuron > motor neuron.
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The Central Nervous System (CNS) in humans consists of ___________. A. motor neurons and sensory neurons B. sensory receptors and sensory nerves C. the brain and spinal cord D. interneurons and sensory receptors
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An Introduction to Membrane Potentials An imbalance of ions across a cell membrane creates an electrical potential (voltage) across the membrane. The inside of inactive (“resting”) neurons is negative relative to the outside. The resting potential for many neurons is -70 mV (1 mV = 1/1000 Volt)
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The negative-inside resting potential of nerve cells _____________. A. results from a high concentration of potassium on the outside of the cell B. is due to an influx of sodium ions during a nerve impulse C. is due to the high permeability of the resting cell membrane to potassium ions D. is about -140 millivolts E. A. and C.
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The Resting Potential When a neuron is not transmitting an electrical signal but is merely sitting in extracellular fluid “at rest,” its membrane has a voltage called the resting potential
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In resting neurons, only K + can diffuse across the membrane easily down its concentration gradient: High K + conc Low K + conc Diffusion occurs via K + channels .
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Biologists say that the resting membrane is selectively permeable it permits a much greater flow of K
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This note was uploaded on 04/07/2008 for the course BIOL 100 taught by Professor Staff during the Fall '07 term at UMBC.

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Chapter 45 - Please, Turn Your Cell Phones OFF Now. Thanks!...

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