Chapter 34 Opener

Concept 34.1 Nervous Systems Consist of Neurons and Glia

Parts of a neuron

Working in pairs, draw two neurons that meet at a synapse.

Label on your diagram:

• Axon • Axon hillock• Axon terminal• Cell body• Dendrite• Nucleus• Presynaptic cell• Postsynaptic cell• Synapse

Take turns defining each term and describing the function of each part.

Concept 34.1 Nervous Systems Consist of Neurons and Glia

What do axons do?

a. The major function of an axon is to transmit electrical signals from one location to another.

b. Axons are the primary location where a neuron receives information from other neurons.

c. Axons manufacture neurotransmitter.

d. Axons are the primary location where a neuron releases neurotransmitter.

e. All of the above

Figure 34.1 A Generalized Neuron

Figure 34.1 A Generalized Neuron

Figure 34.2 Wrapping Up an Axon

Figure 34.2 Wrapping Up an Axon

Figure 34.2 Wrapping Up an Axon (Part 1)

Figure 34.2 Wrapping Up an Axon (Part 2)

Figure 34.3 Nervous Systems Vary in Size and Complexity

Figure 34.3 Nervous Systems Vary in Size and Complexity

Figure 34.3 Nervous Systems Vary in Size and Complexity (Part 1)

Figure 34.3 Nervous Systems Vary in Size and Complexity (Part 2)

Figure 34.3 Nervous Systems Vary in Size and Complexity (Part 3)

Figure 34.4 Measuring the Membrane Potential

Figure 34.4 Measuring the Membrane Potential

Figure 34.4 Measuring the Membrane Potential (Part 1)

Figure 34.4 Measuring the Membrane Potential (Part 2)

Figure 34.5 Ion Transporters and Channels

Figure 34.5 Ion Transporters and Channels (Part 1)

Figure 34.5 Ion Transporters and Channels (Part 2)

Nernst Equation

Goldman-Hodgkin-Katz Equation

These data were recorded from the large axon of a squid. They show the concentrations of four ions both inside the axon’s cytoplasm and outside the cell, in a sea water bath.

1. Use the Nernst equation to predict the equilibrium potential for each of the four ions.

2. The measured resting potential of this axon is -66 mV. How can you explain that resting potential on the basis of the equilibrium potentials you calculated.

3. Another equation, the Goldman-Hodgkin-Katz equation, includes a relative permeability of the membrane for each ion. Why is this necessary for accurately predicting membrane potential?

Apply the Concept, Ch. 34, p. 677

Figure 34.6 Membranes Can Be Depolarized or Hyperpolarized

Figure 34.6 Membranes Can Be Depolarized or Hyperpolarized

Figure 34.7 The Course of an Action Potential

Figure 34.7 The Course of an Action Potential

Figure 34.7 The Course of an Action Potential (Part 1)

Figure 34.7 The Course of an Action Potential (Part 2)

Figure 34.8 Saltatory Action Potentials

Figure 34.8 Saltatory Action Potentials

Figure 34.8 Saltatory Action Potentials (Part 1)

Figure 34.8 Saltatory Action Potentials (Part 2)

Concept 34.2 Neurons Generate and Transmit Electrical Signals

Using the Nernst equation to predict membrane potentials

Suppose a cell has the following ion concentrations:

• Calcium (Ca2+): 1 mM outside, 0.0001 mM inside• Chloride (Cl–): 100 mM outside, 10 mM inside• Potassium (K+): 5 mM outside, 150 mM inside

1. Working individually, calculate the equilibrium potential of each ion. Then check with your neighbors to see if you all got the same result.

2. Working in small groups, suppose that while at rest, the membrane is much more permeable to chloride than to any other ion. What will the cell’s resting membrane potential be (approximately)?

3. Now suppose the chloride channels close and a large number of calcium channels open, such that the cell membrane becomes much more permeable to calcium than to any other ion. Which way will calcium move? Will the cell depolarize, hyperpolarize, or neither? What will be the new membrane potential (approximately)?

Concept 34.2 Neurons Generate and Transmit Electrical Signals

If calcium channels suddenly open,

a. there will be a net movement of calcium into the cell.

b. there will be a net movement of calcium out of the cell.

c. there will be no net movement of calcium.

d. the cell will hyperpolarize.

e. Both a and d

Concept 34.2 Neurons Generate and Transmit Electrical Signals

How does the pufferfish kill?

The Japanese pufferfish produces a highly potent neurotoxin called tetrodotoxin (TTX). TTX binds to voltage-gated sodium channels. Ingestion of TTX causes numbness of the lips and tongue, followed rapidly by weakness, loss of coordination, and a sensation of limpness and weakness throughout the body. Relatively small doses of TTX can kill a person.

Working in pairs, develop a hypothesis to explain the symptoms of TTX poisoning in terms of TTX’s effect on sodium channels. How exactly do you think TTX kills?

Concept 34.2 Neurons Generate and Transmit Electrical Signals

Blockage of voltage-gated sodium channels in a neuron will cause which of the following?

a. The neuron’s resting membrane potential will become more negative.

b. The neuron’s resting membrane potential will become less negative.

c. The neuron will be unable to produce action potentials.

d. Both a and c

e. Both b and c

Figure 34.9 Chemical Synaptic Transmission

Figure 34.9 Chemical Synaptic Transmission

Figure 34.10 Chemically Gated Channels

Figure 34.10 Chemically Gated Channels

Figure 34.11 The Postsynaptic Neuron Sums Information

Figure 34.11 The Postsynaptic Neuron Sums Information

Neurons Communicate with other cells at synapses

How do we know that Ca2+ influx into the presynaptic nerve ending causes the release of neurotransmitter? Because the squid giant axon and its nerve endings are so large, they are a convenient system for experiments. It is possible to inject substances into both the presynaptic and postsynaptic cells near the synapse. Some of the substances that can be injected are Ca2+ ions and BAPTA, a substance that binds Ca2+ ions. Also, channel blockers can be added to the culture medium. For example, cadmium blocks Ca2+ channels.

Here are the results of a series of experiments using these substances.

Apply the Concept, Ch. 34, p. 683

1. What is happening during the delay between the pre- and post synaptic membrane events in the control condition?

2. Explain the postsynaptic response in the absence of a presynaptic response in experiment 1?

3. Explain why there is a presynaptic but no postsynaptic response in experiment 2?

4. Why are there no pre- or postsynaptic responses in experiment 3?

Concept 34.3 Neurons Communicate with Other Cells at Synapses

An acetylcholinesterase inhibitor would cause which of the following?

a. No action potentials in the postsynaptic cell

b. Too many action potentials in the postsynaptic cell

c. No change in action potentials in the postsynaptic cell

d. I don’t know.

Concept 34.3 Neurons Communicate with Other Cells at Synapses

Sequence of events at a synapse

Working in pairs, put the following steps in the correct sequence:

a. ACh binds to membrane receptors.

b. Vesicles containing ACh fuse with the cell membrane.

c. A graded potential spreads through the postsynaptic cell.

d. Action potential arrives at the axon terminal.

e. Na+ and K+ enter the postsynaptic cell.

f. Postsynaptic cell fires an action potential.

g. Calcium enters the presynaptic cell.

h. Voltage-gated calcium channels open.

i. ACh diffuses across the synaptic cleft.

j. Ligand-gated channels on the postsynaptic cell open.

Concept 34.3 Neurons Communicate with Other Cells at Synapses

Biology of a weapon of mass destruction

In Tokyo, Japan, on a Monday morning in 1995, at rush hour, five terrorists dropped bags containing a chemical compound called sarin into five subway cars. The perpetrators punctured the bags with sharpened umbrella tips, and then left the cars. Over 5,000 people were affected. Thirteen people died, several dozen became critically ill, and several hundred more suffered vision impairment (in some cases lasting over a decade). Sarin is classified as a weapon of mass destruction.

Sarin forms a covalent bond with the enzyme acetylcholinesterase.In small groups, discuss:

• How exactly could sarin kill a person? (What is the cause of death?)

• What might the symptoms of sarin poisoning be?• Contrast sarin’s mechanism of action with that of pufferfish toxin.

Figure 34.12 Organization of the Nervous System

Figure 34.13 The Autonomic Nervous System

Figure 34.14 The Spinal Cord Coordinates the Knee-jerk Reflex

Figure 34.14 The Spinal Cord Coordinates the Knee-jerk Reflex

Figure 34.15 The Limbic System

Figure 34.15 The Limbic System

Figure 34.16 The Human Cerebrum

Figure 34.16 The Human Cerebrum

Figure 34.16 The Human Cerebrum (Part 1)

Figure 34.16 The Human Cerebrum (Part 2)

Figure 34.17 The Body Is Represented in Primary Motor and Primary Somatosensory Cortexes

Figure 34.17 The Body Is Represented in Primary Motor and Primary Somatosensory Cortexes

Concept 34.4 The Vertebrate Nervous System Has Many Interacting Components

Reviewing the divisions of the nervous system

Working in pairs and not looking at your notes, make a chart showing the relationships of these parts of the nervous system:

• Sympathetic nervous system• Parasympathetic nervous system• Central nervous system• Enteric nervous system• Peripheral nervous system• Autonomic nervous system• Brain• Spinal cord• Voluntary division• Afferent pathways• Efferent pathways• Sensory nerves• Motor nerves

Concept 34.4 The Vertebrate Nervous System Has Many Interacting Components

The sympathetic nervous system is a part of the

a. autonomic nervous system.

b. peripheral nervous system.

c. parasympathetic nervous system.

d. Both a and b

e. All of the above

Concept 34.4 The Vertebrate Nervous System Has Many Interacting Components

Where was the damage?

Suppose a woman suffers a stroke (bleeding within the brain) and suffers some brain damage. Her symptoms are as follows:

• Inability to speak• Inability to move the right side of her body• Some deficits in sensation on the right side of the body• Inability to recognize faces

She still retains the following abilities:• Normal sensation on the left side of her body• Normal vision in both sides of both eyes• Unchanged personality• Normal ability to plan and reason

Which lobes of her cerebrum were most likely affected by the stroke? On what side? Explain.

Concept 34.4 The Vertebrate Nervous System Has Many Interacting Components

Which of the following is associated with the parietal lobe?

a. Control of the voluntary muscles

b. The sense of vision

c. The sense of hearing

d. Ability to make decisions

e. Perception of three-dimensional space

Figure 34.18 Imaging Techniques Reveal Active Parts of the Brain

Figure 34.19 Stages of Sleep

Figure 34.19 Stages of Sleep (Part 1)

Figure 34.19 Stages of Sleep (Part 2)

Concept 34.5 Specific Brain Areas Underlie the Complex Abilities of Humans

Which of the following brain areas is associated with understanding of speech in humans?

a. Broca’s area

b. Wernicke’s area

c. The hippocampus

d. The insula

e. The thalamus

Concept 34.5 Specific Brain Areas Underlie the Complex Abilities of Humans

A new ape

Suppose a previously unknown species of ape is discovered in Africa. To everybody’s astonishment, the new apes turn out to use a fairly complex form of verbal communication - something never before observed in any non-human ape. Tests reveal that the new apes appear capable of highly advanced planning and decision-making, and appear to recognize themselves in a mirror.

What brain areas would you predict might be especially well-developed in these apes, compared to other mammals and compared to other apes (chimpanzee, gorilla)? Why?

Finally, would your answer be the same if the new species were an intelligent bird, rather than an intelligent mammal? Why or why not?

Figure 34.20 Source of the Fear Response