Download Chapter 8c

Chapter 8c
Neurons: Cellular
and Network
Properties
Integration: Divergence
Figure 8-25a
Integration: Convergence
Figure 8-25b
Integration: The Abundance of Synapses on a
Postsynaptic Neuron
Axon terminals
of presynaptic
neurons
Dendrite of
postsynaptic
neuron
Glial cell
processes
Axon
Figure 8-26
Integration: Purkinje cell
• The highly
branched dendrites
of a Purkinje cell
(neuron)
demonstrate
convergence
Figure 8-27
Integration: Spatial Summation
Presynaptic
axon terminal
1
1 Three excitatory neurons
fire. Their graded potentials
separately are all below
threshold.
Trigger zone
(a)
Action
potential
Figure 8-28a, step 1
Integration: Spatial Summation
Presynaptic
axon terminal
1
1 Three excitatory neurons
fire. Their graded potentials
separately are all below
threshold.
2 Graded potentials arrive at
trigger zone together and sum
to create a suprathreshold
signal.
2
Trigger zone
(a)
Action
potential
Figure 8-28a, step 2
Integration: Spatial Summation
Presynaptic
axon terminal
1
1 Three excitatory neurons
fire. Their graded potentials
separately are all below
threshold.
2 Graded potentials arrive at
trigger zone together and sum
to create a suprathreshold
signal.
2
3
An action potential is
generated.
Trigger zone
3
(a)
Action
potential
Figure 8-28a, step 3
Integration: Spatial Summation
Presynaptic
axon terminal
1
1 Three excitatory neurons
fire. Their graded potentials
separately are all below
threshold.
2 Graded potentials arrive at
trigger zone together and sum
to create a suprathreshold
signal.
2
3
An action potential is
generated.
Trigger zone
3
(a)
Action
potential
Figure 8-28a
Integration: Spatial Summation
1 One inhibitory and two
excitatory neurons fire.
Inhibitory
neuron
1
Trigger zone
(b)
No
action potential
Figure 8-28b, step 1
Integration: Spatial Summation
1 One inhibitory and two
excitatory neurons fire.
Inhibitory
neuron
2 The summed potentials
are below threshold, so
no action potential is
generated.
1
2
Trigger zone
(b)
No
action potential
Figure 8-28b, step 2
Integration: Spatial Summation
1 One inhibitory and two
excitatory neurons fire.
Inhibitory
neuron
2 The summed potentials
are below threshold, so
no action potential is
generated.
1
2
Trigger zone
(b)
No
action potential
Figure 8-28b
Integration: Temporal Summation
Figure 8-29a
Integration: Temporal Summation
Figure 8-29b
Integration: Presynaptic Inhibition
(a) Presynaptic inhibition
Inhibitory neuron
3
No neurotransmitter
release
Target cell
Presynaptic
axon terminal
Excitatory
1
neuron
No response
2
Response
Action potential
Neurotransmitter
released
Response
1
An excitatory neuron
fires.
2
An action potential
is generated.
3 An inhibitory neuron fires, blocking
neurotransmitter release at one synapse.
Figure 8-31a
Integration: Postsynaptic Inhibition
(b) Postsynaptic inhibition
No response
Inhibitory neuron modulates the signal.
Excitatory
neuron
IPSP
+
EPSP
No response
No response
1
One excitatory and one
inhibitory presynaptic
neuron fire.
PLAY
2
Modulated signal in
postsynaptic neuron
below threshold.
3 No action potential
initiated at trigger zone.
4
No response in
any target cell.
Interactive Physiology® Animation: Nervous II:
Synaptic Potentials and Cellular Integration
Figure 8-31b
Integration: Growth Cones of a Developing Axon
• Survival of neurons
depend on
neurotrophic factors
Figure 8-33
Integration: Injury to Neurons
Site of injury
Proximal stump
Axon
Distal stump
Myelin
Figure 8-34
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
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
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
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