Chapter 2

Question 1

In what way did Sherrington’s conclusions agree with Ramón y Cajal’s conclusions?

Answer 1

Both concluded that neurons are separate from one another.

Question 2

Sherrington based his conclusions on what type of evidence?

Answer 2

Observations of reflexive responses.

Question 3

Why did Sherrington conclude that synaptic transmission differs from conduction along an axon?

Answer 3

Reflexes are slower than axonal transmission.

Question 4

An EPSP is an abbreviation for what?

Answer 4

Excitatory PostSynaptic Potential.

Question 5

Although one pinch did not cause a dog to flex its leg, a rapid sequence of pinches did. Sherrington cited this observation as evidence for what?

Answer 5

Temporal summation.

Question 6

The extensor muscles of a leg relax when the flexor muscles contract. Sherrington saw this observation as evidence for what?

Answer 6

Inhibitory synapses.

Question 7

What channels in a neuron open during an EPSP?

Answer 7

Sodium.

Question 8

In what way were Sherrington’s conclusions important for psychology as well as neuroscience?

Answer 8

He demonstrated the importance of inhibition.

Question 9

What evidence led Sherrington to conclude that transmission at a synapse is not the same as transmission along an axon?

Answer 9

The velocity of conduction through a reflex arc is slower than the velocity of an action potential along an axon. Therefore, a delay must occur at the junction between one neuron and the next.

Question 10

How does temporal summation differ from spatial summation?

Answer 10

Temporal summation is the combined effect of quickly repeated stimulation at a single synapse. Spatial summation is the combined effect of several nearly simultaneous stimulations at several synapses onto one neuron.

Question 11

Can an inhibitory message flow along an axon?

Answer 11

No. Only action potentials propagate along an axon. Inhibitory messages—IPSPs—decay over time and distance.

Question 12

How did Loewi demonstrate chemical transmission at a synapse?

Answer 12

He transferred fluid from one frog’s heart to another’s.

Question 13

What are the brain’s most abundant excitatory and inhibitory neurotransmitters, respectively?

Answer 13

Glutamate and GABA.

Question 14

Which of these is a catecholamine?

Answer 14

Dopamine.

Question 15

Why does removing phenylalanine from circulation increase the serotonin in the brain?

Answer 15

Phenylalanine and tryptophan compete for entry to the brain.

Question 16

Suppose you want to cause the presynaptic terminal of an axon to release its transmitter. How could you do so without an action potential?

Answer 16

Inject calcium into the presynaptic terminal.

Question 17

What is a second messenger?

Answer 17

A chemical released inside a cell after it is stimulated at a metabotropic synapse

Question 18

How do the effects of neuropeptides differ from those of other transmitters?

Answer 18

Their effects last longer.

Question 19

What fact makes it possible to develop drugs with a limited effect, such as suppressing nausea?

Answer 19

Each transmitter attaches to more than one type of receptor.

Question 20

A transporter protein produces which of the following?

Answer 20

Reuptake.

Question 21

Except for the magnitude and speed of effects, methylphenidate (Ritalin) affects synapses the same way as which drug?

Answer 21

Cocaine.

Question 22

How do cannabinoids affect synapses?

Answer 22

They inhibit the release of both excitatory and inhibi-tory transmitters.

Question 23

Electrical synapses are important when the nervous system needs to accomplish what?

Answer 23

Synchrony between neurons.

Question 24

What part of the brain produces releasing hormones that control the pituitary gland?

Answer 24

Hypothalamus

Question 25

Across species, how much do neurotransmitters vary?

Answer 25

Most animals have all or nearly all the same neurotransmitters.

Question 26

Name the three catecholamine neurotransmitters.

Answer 26

Epinephrine, norepinephrine, and dopamine. Do not confuse the term catecholamine with acetylcholine.

Question 27

How do ionotropic and metabotropic synapses differ in speed and duration of effects?

Answer 27

Ionotropic synapses act more quickly and more briefly.

Question 28

Ionotropic synapses are most important for what types of behavior?

Answer 28

Ionotropic synapses are most important when precise timing is important, such as visual or auditory perception.

Question 29

How do LSD and opiate drugs influence behavior?

Answer 29

LSD binds to one type of serotonin receptor. Opiates bind to endorphin receptors.

Question 30

What happens to acetylcholine molecules after they stimulate a postsynaptic receptor?

Answer 30

The enzyme acetylcholinesterase breaks acetylcholine molecules into two smaller molecules, acetate and choline. The presynaptic neuron then reabsorbs the choline.

Question 31

What happens to serotonin and catecholamine molecules after they stimulate a postsynaptic receptor?

Answer 31

Most serotonin and catecholamine molecules are reabsorbed by the presynaptic terminal. Some of their molecules are broken down into inactive chemicals, which then diffuse away.

Question 32

How do amphetamine and cocaine influence synapses?

Answer 32

They block reuptake of released dopamine, serotonin, and norepinephrine.

Question 33

19. Which part of the pituitary—anterior or posterior—is neural tissue, similar to the hypothalamus? Which part is glandular tissue and produces hormones that control the secretions by other endocrine organs?

Answer 33

The posterior pituitary is neural tissue, like the hypo-thalamus. The anterior pituitary is glandular tissue and produces hormones that control several other endocrine organs.