1. I cdnuolt blveiee that I cluod aulaclty uesdnatnrd what I was rdanieg
The phaonmneal pweor of the hmuan mnid is icrebdinle. Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it deosn’t mttaer in what odrer the ltteers in a wrod are, the only iprmoatnt thing is that the frist and lsat ltteer be in the rghit pclae. The rset can be a ttaol mses and you can still raed it wouthit a porbelm. This is bcuseae the hmuan mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.
Amzanig huh? Yaeh and I awlyas thought slpeling was ipmorantt!
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3. Introduction to Information Processing
Nervous systems process information in three stages
Sensory input
Integration
Motor output
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4. Siphon Sensory input Integration Sensor Motor output Processing center
Figure 37.4
Siphon
Sensory input
Integration
Sensor
Motor output
Proboscis
Figure 37.4 Summary of information processing
Processing center
Effector
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5. Sensory neurons transmit information about external stimuli or internal conditions (usually PNS)
This information is sent to the processing center (usually CNS), where interneurons integrate (analyze and interpret) the sensory input
Neurons that extend out of the processing centers trigger muscle or gland activity to elicit response. (usually PNS)
For example, motor neurons transmit signals to muscle cells, causing them to contract
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7. Concept 37.2: Ion pumps and ion channels establish the resting potential of a neuron
The inside of a cell is negatively charged relative to the outside
This difference is a source of potential energy, termed membrane potential
The resting potential is the membrane potential of a neuron not sending signals
Changes in membrane potential act as signals, transmitting and processing information
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8. Functional Properties of Neurons
Irritability – ability to respond to stimuli
Conductivity – ability to transmit an impulse
The plasma membrane at rest is polarized
Fewer positive ions are inside the cell than outside the cell
The resting potential of an actual neuron is about –60 to –80 mV

9. Concept 37.3: Action potentials are the signals conducted by axons
Changes in membrane potential occur because neurons contain gated ion channels that open or close in response to stimuli
A voltage-gated ion channel opens or closes in response to a shift in the voltage across the plasma membrane of the neuron
Change in
membrane
potential
(voltage)
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10. Starting a Nerve Impulse
Depolarization – a stimulus depolarizes the neuron’s membrane
Gated Na+ channels open allowing sodium (Na+) to flow inside the membrane
If a depolarization shifts the membrane potential sufficiently, (threshold) it results in a massive change in membrane voltage, called an action potential
Figure 7.9a–c

11. Figure
(c) Action potential triggered by a depolarization that reaches the threshold
Strong depolarizing stimulus
+50
Action
potential
Membrane potential (mV)
Threshold
-50
Figure Graded potentials and an action potential in a neuron (part 3: action potential)
Resting
potential
-100 1 2 3 4 5 6
Time (msec)
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12. When stimulus depolarizes the membrane
Some gated Na+ channels open first, and Na flows into the cell
During the rising phase, the threshold is crossed, and the membrane potential increases
During the falling phase, voltage-gated Na channels become inactivated; voltage-gated K channels open, and K flows out of the cell
During the undershoot, membrane permeability to K is at first higher than at rest, and then voltage-gated K channels close and resting potential is restored
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13. The sodium-potassium pump restores the original configuration
During the refractory period after an action potential, a second action potential cannot be initiated
The refractory period is a result of a temporary inactivation of the Na channels
The sodium-potassium pump restores the original configuration
This action requires ATP
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14. Continuation of the Nerve Impulse between Neurons
Impulses are not able to cross the synapse to another nerve
Neurotransmitter is released from a nerve’s axon terminal
The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter
An action potential is started in the dendrite

15. © 2016 Pearson Education, Inc.

16. containing neurotransmitter
Figure 37.16
Presynaptic cell
Postsynaptic cell
Axon
Synaptic vesicle
containing neurotransmitter
Synaptic
cleft
Postsynaptic
membrane
Presynaptic
membrane
Figure A chemical synapse K+
Ca2+
Voltage-gated
Ca2+ channel
Ligand-gated
ion channels
Na+
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