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Download Fig. 48.1 Peripheral nervous system
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CHAPTER 48 NERVOUS SYSTEMS Section A: An Overview Of Nervous Systems 1. Nervous systems perform the three overlapping functions of sensory input, integration, and motor output 2. Networks of neurons either intricate connections form nervous systems Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings 1. Nervous systems perform the three overlapping functions of sensory input, integration, and motor output Fig. 48.1 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Peripheral nervous system (PNS). – Sensory receptors a responsive to external and internal stimuli. • Such sensory input is conveyed to integration centers. Where 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. Fig. 48.2 Fig. 48.5 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.7 Fig. 48.6a The illustrations in this slide are provided to give a better understanding of nerves and their function but are not part of the course material Fig. 48.9 Fig. 48.12 The illustrations in this slide are provided to give a better understanding of nerves and their function but are not part of the course material Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Nerve impulses propagate themselves along an axon • The action potential is repeatedly regenerated along the length of the axon. – An action potential achieved at one region of the membrane is sufficient to depolarize a neighboring region above threshold. • Thus triggering a new action potential. • The refractory period assures that impulse conduction is unidirectional. Fig. 48.10 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings 2. Networks of neurons either 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 neuron. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • A Simple Nerve Circuit – the Reflex Arc. – A reflex is an autonomic response. Fig. 48.3 A ganglion is a cluster of nerve cell bodies within the PNS. A nucleus is a cluster of nerve cell bodies within the CNS Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Nervous systems show diverse patterns of organization • Nerve nets. • With cephalization come more complex nervous systems. Fig. 33.33 Fig. 48.15 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 33.23 http://www.colorado.edu/epob/epob3730rlynch/image/figure5-4.jpg http://www.bio.davidson.edu/people/jeputnam/companat/restricted/CA4_Ne_5BrainEvol.jpeg From Pictorial Anatomy of the Dogfish, Stephen G. Gilbert, University of Washington Press, Seattle, WA, USA Figure 48.16 The nervous system of a vertebrate Figure 48.17 Functional hierarchy of the peripheral nervous system Figure 48.18 The main roles of the parasympathetic and sympathetic nerves in regulating internal body functions The illustrations in this slide are provided to give a better understanding of nervous system and its function but are not part of the course material Fig. 48.24b The illustrations in this slide are provided to give a better understanding of nervous system and its function but are not part of the course material Fig. 48.21 Fig. 48.25 CHAPTER 49 SENSORY AND MOTOR SYSTEMS Section B: Introduction To Sensory Reception 1. Sensory receptors transduce stimulus energy and transmit signals to the nervous system 2. Sensory receptors are categorized by the type of energy they transduce • Sensations are action potentials that reach the brain via sensory neurons. • Perception is the awareness and interpretation of the sensation. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Sensory receptors transduce stimulus energy and transmit signals to the nervous system Fig. 49.2 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Sensory reception begins with the detection of stimulus energy by sensory receptors. – Exteroreceptors detect stimuli originating outside the body. – Interoreceptors detect stimuli originating inside the body. – Sensory receptors convey the energy of stimuli into membrane potentials and the transmit signals to the nervous system. • This involves: sensory transduction, amplification, transmission, and integration. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Sensory Transduction. The conversion of stimulus energy into a change in membrane potential Amplification. The strengthening of stimulus energy that is can be detected by the nervous system. Transmission. The conduction of sensory impulses to the CNS. Integration. The processing of sensory information. Begins at the sensory receptor. For example, sensory adaptation is a decrease in responsiveness to continued stimulation. For example, the sensitivity of a receptor to a stimulus will vary with environmental conditions. Sensory receptors are categorized by the type of energy they transduce Fig. 49.3 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Mechanoreceptors respond to mechanical energy. – For example, muscle spindles is an interoreceptor that responds to the stretching of skeletal muscle. – For example, hair cells detect motion. • Pain receptors = nocioceptors. – Different types of pain receptors respond to different types of pain. – Prostaglandins increase pain by decreasing a pain receptors threshold. • Anti-inflammatories work by inhibiting prostaglandin synthesis. • Thermoreceptors respond to heat or cold. – Respond to both surface and body core temperature. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Chemoreceptors respond to chemical stimuli. – General chemoreceptors transmit information about total solute concentration. – Specific chemoreceptors respond to specific types of molecules. – Internal chemoreceptors respond to glucose, O2, CO2, amino acids, etc. – External chemoreceptors are gustatory receptors and olfactory receptors. • Electromagnetic receptors respond to electromagnetic energy. – Photoreceptors respond to the radiation we know as visible light. – Electroreceptors: some fish use electric currents to locate objects. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings