Transcript Chapter 12, part 3

Anatomy & Physiology
SIXTH EDITION
Chapter 12, part 3
Neural tissue
PowerPoint® Lecture Slide Presentation prepared by
Dr. Kathleen A. Ireland, Biology Instructor, Seabury Hall, Maui, Hawaii
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Frederic H. Martini
Fundamentals of
SECTION 12-5
Synaptic Activity
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Nerve impulse
• Action potential travels along an axon
• Information passes from presynaptic neuron to
postsynaptic cell
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General properties of synapses
• Electrical
• Rare
• Pre- and postsynaptic cells are bound by
interlocking membrane proteins
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General properties of synapses
• Chemical synapses
• More common
• Excitatory neurotransmitters cause
depolarization and promote action potential
generation
• Inhibitory neurotransmitters cause
hyperpolarization and suppress action potentials
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Cholinergic synapses
• Release acetylcholine (ACh)
• Information flows across synaptic cleft
• Synaptic delay occurs as calcium influx and
neurotransmitter release take appreciable
amounts of time
• ACh broken down
• Choline reabsorbed by presynaptic neurons
and recycled
• Synaptic fatigue occurs when stores of ACh are
exhausted
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Figure 12.19 The Function of a Cholinergic
Synapse
PLAY
Animation: Overview of a cholinergic synapse
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Figure 12.19.1
Figure 12.19 The Function of a Cholinergic
Synapse
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Figure 12.19.2
Other neurotransmitters
• Adrenergic synapses release norepinephrine (NE)
• Other important neurotransmitters include
• Dopamine
• Serotonin
• GABA (gamma aminobutyric acid)
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Neuromodulators
• Influence post-synaptic cells response to
neurotransmitter
• Neurotransmitters can have direct or indirect
effect on membrane potential
• Can exert influence via lipid-soluble gases
PLAY
Animation: Synaptic potentials, cellular integration, and synaptic transmission
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Figure 12.21 Neurotransmitter Functions
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Figure 12.21a
Figure 12.21 Neurotransmitter Functions
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Figure 12.21b
Figure 12.21 Neurotransmitter Functions
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Figure 12.21c
SECTION 12-6
Information Processing
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Information processing
• Simplest level of information processing
occurs at the cellular level
• Excitatory and inhibitory potentials are
integrated through interactions
between postsynaptic potentials
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Postsynaptic potentials
• EPSP (excitatory postsynaptic potential) =
depolarization
• EPSP can combine through summation
• Temporal summation
• Spatial summation
• IPSP (inhibitory postsynaptic potential) =
hyperpolarization
• Most important determinants of neural activity
are EPSP / IPSP interactions
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Figure 12.22 Temporal and Spatial Summation
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Figure 12.22a
Figure 12.22 Temporal and Spatial Summation
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Figure 12.22b
Figure 12.23 EPSP – IPSP Interactions
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Figure 12.23
Presynaptic inhibition
• GABA release at axoaxonal synapse inhibits
opening calcium channels in synaptic knob
• Reduces amount of neurotransmitter released
when action potential arrives
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Figure 12.24 Presynaptic Inhibition and
Facilitation
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Figure 12.24
Presynaptic facilitation
• Activity at axoaxonal synapse increases amount
of neurotransmitter released when action
potential arrives
• Enhances and prolongs the effect of the
neurotransmitter
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Figure 12.24 Presynaptic Inhibition and
Facilitation
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Figure 12.24
Rate of generation of action potentials
• Neurotransmitters are either excitatory or
inhibitory
• Effect on initial membrane segment reflects
an integration of all activity at that time
• Neuromodulators alter the rate of release of
neurotransmitters
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Rate of generation of action potentials
• Can be facilitated or inhibited by other
extracellular chemicals
• Effect of presynaptic neuron may be altered by
other neurons
• Degree of depolarization determines frequency
of action potential generation
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You should now be familiar with:
• The two major divisions of the nervous system
and their characteristics.
• The structures/ functions of a typical neuron.
• The location and function of neuroglia.
• How resting potential is created and maintained.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
You should now be familiar with:
• The events in the generation and propagation of
an action potential.
• The structure / function of a synapse.
• The major types of neurotransmitters and
neuromodulators.
• The processing of information in neural tissue.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings