Transcript Fig. 48.1 Peripheral nervous system

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
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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
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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.
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• 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
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Nervous systems show diverse patterns
of organization
• Nerve nets.
• With cephalization come more
complex nervous systems.
Fig. 33.33
Fig. 48.15
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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
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• 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.
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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
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• 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.
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• 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.
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