rav65819_ch44_869-896

rav65819_ch44_869-896 - ; 20 mm chapter 44 The Nervous...

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;;;;;;;; 20 m m chapter 44
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The Nervous System introduction ALL ANIMALS EXCEPT SPONGES use a network of nerve cells to gather information about the body’s condition and the external environment, to process and integrate that information, and to issue commands to the body’s muscles and glands. As we saw in chapter 43, homeostasis of the animals body is accomplished by negative feedback loops that maintain conditions within narrow limits. Negative feedback implies not only detection of appropriate stimuli but also communication of information to begin a response. The nervous system, composed of neurons, such as the one pictured here, is a fast communication system and a part of many feedback systems in the body. 44.4 The Central Nervous System: Brain and Spinal Cord A postsynaptic neuron must integrate input from many synapses Neurotransmitters play a role in drug addiction concept outline 44.1 Nervous System Organization The central nervous system is the “command center” The peripheral nervous system collects information and carries out responses The structure of neurons supports their function Supporting cells include Schwann cells and oligodendrocytes 44.2 The Mechanism of Nerve Impulse Transmission An electrical difference exists across the plasma membrane
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Graded potentials are small changes that can reinforce or negate each other Action potentials result when depolarization reaches a threshold Action potentials are propagated along axons There are two ways to increase the velocity of nerve impulses 44.3 Synapses: Where Neurons Communicate with Other Cells The two types of synapses are electrical and chemical Many different chemical compounds serve as neurotransmitters As animals became more complex, so did their nervous systems Vertebrate brains have three basic divisions The human forebrain exhibits exceptional information-processing ability Complex functions of the human brain may be controlled in speciFc areas The spinal cord conveys messages and controls some responses directly 44.5 The Peripheral Nervous System: Sensory and Motor Neurons The PNS has somatic and autonomic systems The somatic nervous system controls movements The autonomic nervous system controls involuntary functions through two divisions G proteins mediate cell responses to autonomic signals 869 rav65819_ch44_869-896.indd 869 rav65819_ch44_869-896.indd 869 12/6/06 11:53:41 AM 12/6/06 11:53:41 AM 44.1 Nervous System Organization An animal must be able to respond to environmental stimuli. A fly escapes a flyswatter; the antennae of a crayfish detect food and the crayfish moves toward it. To accomplish these actions, animals must have sensory receptors that can detect the stimulus and motor effectors that can respond to it. In most invertebrate phyla and in all vertebrate classes, sensory receptors and motor effectors are linked by way of the nervous system. The central nervous system is the “command center”
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This note was uploaded on 10/15/2010 for the course BIO BIO1 taught by Professor Lipke during the Fall '09 term at CUNY Brooklyn.

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rav65819_ch44_869-896 - ; 20 mm chapter 44 The Nervous...

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