Chapt 48 - CHAPTER 48 - NERVOUS SYSTEMS A. An Overview Of...

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CHAPTER 48 - NERVOUS SYSTEMS A. An Overview Of Nervous Systems 1. Nervous systems perform the three overlapping functions of sensory input, integration, and motor output Peripheral nervous system ( PNS ). Sensory receptors a responsive to external and internal stimuli. Such sensory input is conveyed to integration centers, here in the input is interpreted and associated with a response. Motor output is the conduction of signals from integration centers to effector cells. Effector cells carry out the body’s response to a stimulus. The central nervous system ( CNS ) is responsible for integration. The signals of the nervous system are conducted by nerves . 2. Networks of neurons with intricate connections form nervous systems Neuron Structure and Synapses. The neuron is the structural and functional unit of the nervous system. Nerve impulses are conducted along a neuron. Dentrite cell body axon hillock axon Some axons are insulated by a myelin sheath . Axon endings are called synaptic terminals . They contain neurotransmitters which conduct a signal across a synapse . A synapse is the junction between a presynaptic and postsynaptic cell . A Simple Nerve Circuit – the Reflex Arc. A reflex is an autonomic response. A ganglion is a cluster of nerve cell bodies within the PNS. A nucleus is a cluster of nerve cell bodies within the CNS. Neurons differ in terms of both function and shape. Types of Nerve Circuits. Single presynaptic neuron several postsynaptic neurons. Several presynaptic neurons single postsynaptic neuron. Circular paths. Supporting Cells (Glia). There are several types of glia . Astrocytes are found within the CNS. Structural and metabolic support. By inducing the formation of tight junctions between capillary cells astrocytes help form the blood-brain barrier . Like neurons, astrocytes communicate with one another via chemical signals.
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Oligodendrocytes are found within the CNS. Form a myelin sheath by insulating axons. Schwann cells are found within the PNS. Form a myelin sheath by insulating axons. B. The Nature Of Nerve Signals 1. Every cell has a voltage, or membrane potential, across its plasma membrane A membrane potential is a localized electrical gradient across membrane. Anions are more concentrated within a cell. Cations are more concentrated in the extracellular fluid Measuring Membrane Potentials. An unstimulated cell usually has a resting potential of -70mV. How a Cell Maintains a Membrane Potential. Cations. K + is the principal intracellular cation. Na
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This note was uploaded on 12/14/2009 for the course BIOCHEM bIO taught by Professor Professor during the Spring '09 term at École Normale Supérieure.

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Chapt 48 - CHAPTER 48 - NERVOUS SYSTEMS A. An Overview Of...

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