Biological Science

Scott Freeman, Kim Quillin, Lizabeth Allison

Chapter 43

Animal Nervous Systems - all with Video Answers

Educators

Chapter Questions

Problem 1

Which ion most readily leaks across a neuron's membrane, helping to establish the resting potential?
a. $\mathrm{Ca}^{2+}$
b. $\mathrm{K}^{+}$
c. $\mathrm{Na}^{+}$
d. $\mathrm{Cl}^{+}$

Joanna Quigley

Joanna Quigley

Numerade Educator

Problem 2

How does myelination affect the propagation of an action potential?
a. It speeds propagation by increasing the density of voltage-gated channels all along the axon.
b. It slows propagation by increasing electrochemical gradients favoring Na $^{+}$ entry.
c. It speeds propagation by preventing cations from leaking out across the membrane as they spread down the axon.
d. It slows propagation by restricting voltage-gated $\mathrm{Na}^{+}$ channels to gaps in the myelin (nodes of Ranvier)

Shazia Naz

Numerade Educator

Problem 3

In a neuron, what creates the electrochemical gradient favoring the outflow of $\mathrm{K}^{+}$ when the cell is at rest?
a. $\mathrm{Na}^{+} / \mathrm{K}^{+}$ -ATPase
b. voltage-gated $\mathrm{K}^{+}$ channels
c. voltage-gated Na $^{+}$ channels
d. ligand-gated $\mathrm{Na}^{+} / \mathrm{K}^{+}$ channels

Amy Adkisson

Numerade Educator

Problem 4

Which of the following brain regions is responsible for formation of new memories?
a. brain stem
b. cerebellum
c. frontal lobe
d. hippocampus

Amy Adkisson

Numerade Educator

Problem 5

Explain the difference between a ligand-gated $\mathrm{K}^{+}$ channel and a voltage-gated $\mathrm{K}^{+}$ channel.

Amy Adkisson

Numerade Educator

Problem 6

Describe the role of summation in postsynaptic cells.

Amy Adkisson

Numerade Educator

Problem 7

Compare and contrast the somatic nervous system and autonomic nervous system.

Joanna Quigley

Numerade Educator

Problem 8

Why is memory thought to involve changes in particular synapses?
a. At some synapses, more neurotransmitters are released after learning takes place.
b. At some synapses, a different type of neurotransmitter is released after learning takes place.
c. When researchers stimulated certain neurons electrically, individuals replayed memories.
d. When researchers changed synapses in the brains of patients during surgery, the patients' memories changed.

Joanna Quigley

Numerade Educator

Problem 9

Explain why drugs that prevent neurotransmitters from being taken back up by a presynaptic neuron have dramatic effects on the activity of postsynaptic neurons.

Joanna Quigley

Numerade Educator

Problem 10

Alzheimer's disease is a common form of dementia affecting millions of people, especially the elderly. Two regions of the brain are particularly affected, often shrinking dramatically and accumulating large deposits of extracellular material. Based on your knowledge of memory, what two brain regions do you think these are? Explain.

Joanna Quigley

Numerade Educator

Problem 11

Certain species of frogs in the genus Phyllobates have a powerful defensive adaptation-their skin can secrete a milky fluid that contains an extremely toxic compound called batrachotoxin (BTX). These frogs, which are found in Colombia, are known as poison dart frogs because some indigenous Colombian hunters coat the tips of their blowgun darts with the frogs' skin secretions. An animal hit by one of these darts dies quickly. What is the mechanism of action of BTX?
The graph below shows the effect of BTX on the membrane potential of a squid giant axon.
Which of the following is the most likely explanation for the effect of BTX on the squid giant axon?
a. Inactivation of $\mathrm{Na}^{+} / \mathrm{K}^{+}$ -ATPase
b. Closing of sodium channels
c. Opening of sodium channels
d. Opening of potassium channels

Joanna Quigley

Numerade Educator

Problem 12

Certain species of frogs in the genus Phyllobates have a powerful defensive adaptation-their skin can secrete a milky fluid that contains an extremely toxic compound called batrachotoxin (BTX). These frogs, which are found in Colombia, are known as poison dart frogs because some indigenous Colombian hunters coat the tips of their blowgun darts with the frogs' skin secretions. An animal hit by one of these darts dies quickly. What is the mechanism of action of BTX?
Identify a research technique that could be used to discover how BTX affects specific membrane proteins. Based on the graph in Question 11 , what would you expect this technique to show?

Joanna Quigley

Numerade Educator

Problem 13

Certain species of frogs in the genus Phyllobates have a powerful defensive adaptation-their skin can secrete a milky fluid that contains an extremely toxic compound called batrachotoxin (BTX). These frogs, which are found in Colombia, are known as poison dart frogs because some indigenous Colombian hunters coat the tips of their blowgun darts with the frogs' skin secretions. An animal hit by one of these darts dies quickly. What is the mechanism of action of BTX?
As shown by the graph in Question 11 , BTX depolarizes the membrane and prevents repolarization. What effect would this have on electrical signaling by the nervous system?

Joanna Quigley

Numerade Educator

Problem 14

Certain species of frogs in the genus Phyllobates have a powerful defensive adaptation-their skin can secrete a milky fluid that contains an extremely toxic compound called batrachotoxin (BTX). These frogs, which are found in Colombia, are known as poison dart frogs because some indigenous Colombian hunters coat the tips of their blowgun darts with the frogs' skin secretions. An animal hit by one of these darts dies quickly. What is the mechanism of action of BTX?
Like neurons, cells in skeletal and cardiac muscle also
produce action potentials. Create a concept map (see BioSkills 12 ) showing how BTX could kill a mammal through its effects on nervous and muscle tissues.

Joanna Quigley

Numerade Educator

Problem 15

Certain species of frogs in the genus Phyllobates have a powerful defensive adaptation-their skin can secrete a milky fluid that contains an extremely toxic compound called batrachotoxin (BTX). These frogs, which are found in Colombia, are known as poison dart frogs because some indigenous Colombian hunters coat the tips of their blowgun darts with the frogs' skin secretions. An animal hit by one of these darts dies quickly. What is the mechanism of action of BTX?
Predict the effects of each of the following on the membrane potential of a neuron simultaneously poisoned with BTX: (a) removing extracellular sodium; (b) increasing the intracellular potassium concentration; and (c) adding tetrodotoxin from puffer fish.

Joanna Quigley

Numerade Educator

Problem 16

Certain species of frogs in the genus Phyllobates have a powerful defensive adaptation-their skin can secrete a milky fluid that contains an extremely toxic compound called batrachotoxin (BTX). These frogs, which are found in Colombia, are known as poison dart frogs because some indigenous Colombian hunters coat the tips of their blowgun darts with the frogs' skin secretions. An animal hit by one of these darts dies quickly. What is the mechanism of action of BTX?
BTX is a powerful antipredator poison. However, one snake species in Colombia eats poison dart frogs. Suggest a hypothesis that explains how the snake is resistant to the toxin.

Joanna Quigley

Numerade Educator