chapter 8c neurons: cellular and network properties
TRANSCRIPT
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Chapter 8c
Neurons: Cellular and Network Properties
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Integration: Divergence
Figure 8-25a
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Integration: Convergence
Figure 8-25b
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Integration: The Abundance of Synapses on a Postsynaptic Neuron
Figure 8-26
Axon terminalsof presynaptic
neurons
Axon
Glial cellprocesses
Dendrite ofpostsynaptic
neuron
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Integration: Purkinje cell
• The highly branched dendrites of a Purkinje cell (neuron) demonstrate convergence
Figure 8-27
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Integration: Spatial Summation
Figure 8-28a, step 1
1 Three excitatory neurons fire. Their graded potentials separately are all below threshold.
Trigger zone
Presynapticaxon terminal
Actionpotential(a)
1
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Integration: Spatial Summation
Figure 8-28a, step 2
1 Three excitatory neurons fire. Their graded potentials separately are all below threshold.
Graded potentials arrive at trigger zone together and sum to create a suprathreshold signal.
Trigger zone
Presynapticaxon terminal
Actionpotential(a)
1
2
2
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Integration: Spatial Summation
Figure 8-28a, step 3
1 Three excitatory neurons fire. Their graded potentials separately are all below threshold.
An action potential is generated.
Graded potentials arrive at trigger zone together and sum to create a suprathreshold signal.
Trigger zone
Presynapticaxon terminal
Actionpotential(a)
1
2
2 3
3
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Integration: Spatial Summation
Figure 8-28a
1 Three excitatory neurons fire. Their graded potentials separately are all below threshold.
An action potential is generated.
Graded potentials arrive at trigger zone together and sum to create a suprathreshold signal.
Trigger zone
Presynapticaxon terminal
Actionpotential(a)
1
2
2 3
3
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Integration: Spatial Summation
Figure 8-28b, step 1
1 One inhibitory and twoexcitatory neurons fire.
Inhibitoryneuron
Trigger zone
(b)No
action potential
1
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Integration: Spatial Summation
Figure 8-28b, step 2
1
The summed potentials are below threshold, so no action potential is generated.
One inhibitory and twoexcitatory neurons fire.
Inhibitoryneuron
Trigger zone
(b)No
action potential
1
2
2
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Integration: Spatial Summation
Figure 8-28b
1
The summed potentials are below threshold, so no action potential is generated.
One inhibitory and twoexcitatory neurons fire.
Inhibitoryneuron
Trigger zone
(b)No
action potential
1
2
2
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Integration: Temporal Summation
Figure 8-29a
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Integration: Temporal Summation
Figure 8-29b
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Integration: Presynaptic Inhibition
Figure 8-31a
321
3
21
An action potentialis generated.
An excitatory neuronfires.
An inhibitory neuron fires, blockingneurotransmitter release at one synapse.
(a) Presynaptic inhibition
Presynapticaxon terminal
Action potential
Target cell
No neurotransmitterrelease
No response
Neurotransmitterreleased
Inhibitory neuron
Excitatoryneuron
Response
Response
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Integration: Postsynaptic Inhibition
Figure 8-31b
1 2 34
Modulated signal inpostsynaptic neuronbelow threshold.
One excitatory and oneinhibitory presynapticneuron fire.
No action potentialinitiated at trigger zone. No response in
any target cell.
Inhibitory neuron modulates the signal.
Excitatoryneuron
(b) Postsynaptic inhibition
No response
No response
No response
IPSP+
EPSP
PLAY Interactive Physiology® Animation: Nervous II: Synaptic Potentials and Cellular Integration
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Figure 8-33
Integration: Growth Cones of a Developing Axon
• Survival of neurons depend on neurotrophic factors
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Integration: Injury to Neurons
Figure 8-34
Axon Myelin
Proximal stump Distal stump
Site of injury
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Summary
• Organization of the nervous system• CNS – brain and spinal cord• PNS – peripheral nerves and ganglia, sensory
receptors• Afferent – sensory• Efferent motor• Somatic• Autonomic
• Autonomic• Sympathetic• Parasympathetic
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Summary
• Cells of the nervous system• Cell body, dendrites, axon, and axon terminal• Interneurons, synapse, postsynaptic cell,
presynaptic cell, synaptic cleft, and axonal transport
• Glial cells, Schwann cells, satellite cells, microglial, oligodendrocytes, astrocytes, and ependymal cells
• Myelin sheaths, nodes of Ranvier, and neural stem cells
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Summary
• Electrical signals in neurons• GHK equation, graded potentials, local current
flow, action potentials, trigger zone, threshold, and all-or-none depolarizations
• Activation gate, inactivation gate, absolute refractory period, relative refractory period, and conduction
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Summary
• Cell-to-cell communication• Electrical synapses, chemical synapses, and
synaptic vesicles• Cholinergic neurons, adrenergic neurons,
acetylcholine, norepinephrine, glutamate, GABA, serotonin, adenosine, and nitric oxide
• Fast synaptic potentials and slow synaptic potentials
• Integration of neural information transfer• Divergence, convergence, spatial summation,
temporal summation, presynaptic modulation, postsynaptic modulation, and long-term potentiation