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

Figure 8-26

Axon terminalsof presynaptic

neurons

Axon

Glial cellprocesses

Dendrite ofpostsynaptic

neuron

Integration: Purkinje cell

• The highly branched dendrites of a Purkinje cell (neuron) demonstrate convergence

Figure 8-27

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

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

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

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

Integration: Spatial Summation

Figure 8-28b, step 1

1 One inhibitory and twoexcitatory neurons fire.

Inhibitoryneuron

Trigger zone

(b)No

action potential

1

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

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

Integration: Temporal Summation

Figure 8-29a

Integration: Temporal Summation

Figure 8-29b

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

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

Figure 8-33

Integration: Growth Cones of a Developing Axon

• Survival of neurons depend on neurotrophic factors

Integration: Injury to Neurons

Figure 8-34

Axon Myelin

Proximal stump Distal stump

Site of injury

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