BIOPSYCH - Chapter 2 - Synapses

Which structure within an animal cell contains the chromosomes?

nucleus

The two kinds of cells in the nervous system are __________, which receive and transmit information to other cells, and __________, which do not transmit information.

neurons, glia

The outer surface of a cell is called the __________ and the fluid inside the cell is the __________.

membrane, cytoplasm

The main feature that distinguishes a neuron from other cells is the neuron's...

varied shape

Which part of a neuron contains the nucleus?

cell body

Neurons have one __________, but can have any number of __________.

axon, dendrites

An axon hillock is

a swelling at the start of an axon, next to the cell body.

As a general rule, axons convey information

away from the cell body.

One way to tell the difference between a dendrite and an axon is that dendrites usually...

taper in diameter toward their periphery.

An interneuron is...

a neuron that receives all its information from other neurons and conveys impulses only to other neurons.

A neuron that conveys information toward the hippocampus is considered a (an) __________ cell, with regard to the hippocampus.

afferent

A neuron that conveys information away from the hippocampus is considered a (an) __________ cell, with regard to the hippocampus.

efferent

A neuron that has an axon and dendrites that branch diffusely, but only extend within a small radius, is probably a(n)_________.

interneuron

In the human brain, glia cells are...

more numerous than neurons.

One function NOT performed by glia is to...

transmit information.

Keeping animals in a varied environment with much stimulation leads to which change in neuronal structure?

Increased branching of dendrites.

How does the structure of neurons change when an older person becomes senile?

Many neurons die and dendrites branch less widely in the remainder.

The difference in voltage between the inside and the outside of a neuron that typically exists is called the...

resting potential.

What is meant by the term "concentration gradient"?

Potassium ions are more concentrated inside the cell and sodium ions are more concentrated outside.

The sodium potassium pump pumps sodium ions __________ and potassium ions __________.

out of the cell, into the cell

The sodium potassium pump makes possible which of the following features of a neuron?

Resting potential.

When the neuron is at rest, which of the following forces tends to move potassium ions OUT OF the cell?

Concentration gradient.

If a stimulus shifts the potential inside a neuron from the resting potential to a more negative potential, the result is...

hyperpolarization.

If a stimulus shifts the potential inside a neuron from the resting potential to a potential slightly closer to zero, the result is known as...

depolarization.

A membrane produces an action potential whenever the potential across it reaches...

the threshold.

According to the all or none law...

the size of the action potential is independent of the strength of the stimulus that initiated it.

For a given neuron, the resting potential is 70 mV and the threshold is 55 mV.

Stimulus A depolarizes the membrane to exactly 55 mV.

Stimulus B depolarizes the membrane to 40 mV. What can we expect to happen?

Stimulus A and stimulus B will produce action potentials of the same size.

How can a neuron signal the difference between an intense stimulus and a stimulus that just barely reaches the threshold for an instant?

Frequency of action potentials.

During the entire course of events from the start of an action potential until the membrane returns to its resting potential, the net movement of ions is...

sodium in, potassium out.

The refractory period of a neuron is a period of time when...

the neuron is unable to fire another action potential due to inactivation of sodium channels.

No stimulus can excite a membrane to produce an action potential if...

the membrane is in its absolute refractory period.

Which feature of a neuron limits the number of action potentials it can produce per second?

Refractory period.

Suppose we find that the maximum firing rate of a given neuron is 50 action potentials per second. What is the refractory period of that cell?

1/50 sec.

Most action potentials begin

at the axon hillock.

Once an action potential starts,

it is regenerated at various points along the axon, the same way that it began.

The velocity of an action potential is

1 100 m/sec.

On which of the following would action potentials travel the slowest?

A thin, unmyelinated axon.

The function of a myelin sheath is to

increase the velocity of transmission along an axon.

What are the nodes of Ranvier?

Interruptions in the myelin sheath.

Saltatory conduction refers to...

transmission of an impulse along a myelinated axon.

True or False: By an IPSP (Inhibitory Postsynaptic Potential), electric potential differences across the postsynaptic membrane increase.

True

True or False: By an EPSP (Excitatory Postsynaptic Potential), electric potential differences across the postsynaptic membrane increase.

False

True or False: By an IPSP, electric potential differences across the postsynaptic membrane decrease.

False

True or False: By an EPSP, electric potential differences across the postsynaptic membrane decrease.

True

Suppose that the brains of two adult rats are to be investigated.

The first rat was raised in an environment full with fellow rats and sensory stimuli (enriched environment), and the second was raised singly in a small empty cage (impoverished environment). It will appear that the brain of the first rat in comparison with the second:

contains almost the same number of nerve cells; on the other hand, the number of synapses of nerve cells is increased.

Assume that the duration of an action potential is 1 msec and the duration of the refractory period is also 1 msec. What is the largest number of action potentials that can be transported over the axon per second?

500.

Which of the following statements related to nerve and glia cells is NOT true?

Nerve cells, just as glia cells, have the power to divide.

By the creation of action potentials, shifts in the concentrations of sodium and potassium ions play an essential role. If we follow these changes over a certain period, we note the following:

first sodium ions enter the cell, somewhat later potassium ions leave the cell.

The speed that an action potential travels down an axon is increased by

the presence of a myelin sheath.

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

Both concluded that neurons are separate from one another.

Sherrington based his conclusions on what type of evidence?

Observations of reflexive responses

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

Reflexes are slower than axonal transmission.

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?

Temporal summation

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

Inhibitory synapses

What channels in a neuron open during an EPSP?

Sodium

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

He demonstrated the importance of inhibition.

How did Loewi demonstrate chemical transmission at a synapse?

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

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

Glutamate and GABA

Which of these is a catecholamine?

Dopamine

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

Phenylalanine and tryptophan compete for entry to the brain.

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

Inject calcium into the presynaptic terminal.

Which type of synapse is better suited for vision and hearing, and why?

Ionotropic synapses, because they produce quick, brief effects

What is a second messenger?

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

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

Their effects last longer.

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

Each transmitter attaches to more than one type of receptor.

A transporter protein produces which of the following?

Reuptake

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

Cocaine

How do cannabinoids affect synapses?

They inhibit the release of both excitatory and inhibitory transmitters.

Electrical synapses are important when the nervous system needs to accomplish which of the following?

Synchrony between neurons

Which of these is composed of neural tissue, as opposed to glandular tissue?

The posterior pituitary

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

The hypothalamus