1. The cone snail is a deadly predator. Why?
Figure 48.1 What makes this snail such a deadly predator?
For the Discovery Video Novelty Gene, go to Animation and Video Files.

2. Squid Nervous System Nerves with giant axons Ganglia Brain Arm Eye
Mantle
Nerve
Figure 48.2 Overview of the squid nervous system

3. Information Processing
Sensory input
Sensor:
Detects stimulus
Integration
Processing
Motor output
Figure 48.3 Summary of information processing
Effector:
Does response
Peripheral nervous
system (PNS)
Central nervous
system (CNS)

4. Neurons Dendrites Presynaptic cell Axon Synapse Postsynaptic cell
Stimulus
Nucleus
Presynaptic cell
Axon
hillock
Cell
body
Axon
Synapse
Synaptic terminals
Figure 48.4 Neuron structure and organization
For the Cell Biology Video Dendrites of a Neuron, go to Animation and Video Files.
Postsynaptic cell
Neurotransmitters

5. Structural diversity of neurons
Dendrites
Axon
Cell
body
Portion
of axon
Figure
80 µm
Cell bodies of
overlapping neurons
Sensory neuron
Interneurons
Motor neuron

6. Key Na+ Sodium- potassium Potassium Sodium pump channel channel K+
OUTSIDE
CELL
Figure 48.6b The basis of the membrane potential
INSIDE
CELL

7. Graded potentials and an action potential in a neuron
Stimuli
Stimuli
Strong depolarizing stimulus
+50
+50
+50
Action
potential
Membrane potential (mV)
Membrane potential (mV)
Membrane potential (mV)
–50
Threshold
–50
Threshold
–50
Threshold
Resting
potential
Resting
potential
Resting
potential
Figure 48.9
Hyperpolarizations
Depolarizations
–100
–100
–100 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 6
Time (msec)
Time (msec)
Time (msec)
(a) Graded Hyperpolarizations
(b) Graded Depolarizations
(c) Action potential

8. Membrane potential (mV)
Stimuli
+50
Membrane potential (mV)
–50
Threshold
Figure 48.9b Graded potentials and an action potential in a neuron
Resting
potential
Depolarizations
–100 1 2 3 4 5
Time (msec)
(b) Graded depolarizations – magnitude of the change varies
with the strength of the stimulus.

9. Action potential Threshold Resting potential
Strong depolarizing stimulus
+50
Action
potential
Membrane potential (mV)
–50
Threshold
Figure 48.9c Graded potentials and an action potential in a neuron
Resting
potential
–100 1 2 3 4 5 6
Time (msec)
(c) Action potential = change in membrane voltage

10. The role of voltage-gated ion channels in the generation of an action potential
Key
Na+ K+ 3
Rising phase of the action potential 4
Falling phase of the action potential
+50
Action
potential 3
Membrane potential
(mV) 2 4
Threshold
–50 1 1 5
Resting potential 2
Depolarization
Figure The role of voltage-gated ion channels in the generation of an action potential
–100
Time
Extracellular fluid
Sodium
channel
Potassium
channel
Plasma
membrane
Cytosol
Inactivation loop 5
Undershoot 1
Resting state

11. Conduction of an Action Potential Signal Transmission Action potential
Axon
Action
potential
Plasma
membrane
Na+
Cytosol
Action
potential K+
Na+
Figure 48.11 K+
Action
potential K+
Na+ K+

12. Schwann cells and the myelin sheath
Node of Ranvier
Layers of myelin
Axon
Schwann
cell
Schwann
cell
Figure Schwann cells and the myelin sheath
Nodes of
Ranvier
Nucleus of
Schwann cell
Axon
Myelin sheath

13. Saltatory conduction Schwann cell Depolarized region (node of Ranvier)
Cell body
Myelin
sheath
Axon
Figure

14. Chemical synapse neurotransmitter Ca2+ Ligand-gated ion channels5
Na+ K+
Synaptic vesicles
containing
neurotransmitter
Presynaptic
membrane
Voltage-gated
Ca2+ channel
Postsynaptic
membrane
Ca2+ 1 4 2 6
Figure
Synaptic
cleft 3
Ligand-gated
ion channels

15. Summation of postsynaptic potentials
Terminal branch
of presynaptic
neuron E1 E1 E1 E1 E2 E2 E2 E2
Postsynaptic
neuron
Axon
hillock I I I I
Threshold of axon of
postsynaptic neuron
Action
potential
Action
potential
Membrane potential (mV)
Resting
potential
Figure Summation of postsynaptic potentials
–70 E1 E1 E1 E1
E1 + E2 E1 I
E1 + I
(a) Subthreshold, no
summation
(b) Temporal summation
(c) Spatial summation
(d) Spatial summation
of EPSP and IPSP

16. Table 48.1

17. Action potential Resting potential Review Threshold (–55)
+50
Falling
phase
Rising
phase
Membrane potential (mV)
Threshold (–55)
–50
Resting
potential
–70
Depolarization
Undershoot
–100
Time (msec)

18. You should now be able to:
Distinguish among the following sets of terms: sensory neurons, interneurons, and motor neurons; membrane potential and resting potential; ungated and gated ion channels; electrical synapse and chemical synapse; EPSP and IPSP; summation.
Explain the role of the sodium-potassium pump in maintaining the resting potential.

19. Describe the stages of an action potential; explain the role of voltage-gated ion channels in this process.
Explain why the action potential cannot travel back toward the cell body.
Describe saltatory conduction.
Describe the events that lead to the release of neurotransmitters into the synaptic cleft.

20. Explain the statement: “Unlike action potentials, which are all-or-none events, postsynaptic potentials are graded.”
Name and describe five categories of neurotransmitters.