Brain & Behavior Ch. 2

Which of the following is an accurate statement about neural networks?

Neural networks are responsible for a lot of the processing that is done in the brain.

Which of the following is true of the firing patterns of neurons?

Neurons can fire action potentials with varying intervals between spikes.

Identify the principal structures of a neuron and describe the functions of each.

Neurons contain a cell body or soma, which contains much of the machinery of the cell. The nucleus is within the cell body and contains the chromosomes of the cell. The dendrites of a neuron receive signals from presynaptic neurons. The axon of a neuron extends from the cell body and is responsible for carrying signals to the end of the neuron. At the end of the neuron are the axon terminals, which contain vesicles in which neurotransmitter is packaged. Signals are sent from the axon terminal to postsynaptic neurons via the synapse, which is the space between neurons.

Describe three different ways that chemical transmission at the synapse results in more complexity than action potentials along an axon.

Neurotransmitters are not all-or-none events. Instead, neurotransmitters can have effects that vary in intensity and duration, which contributes to complexity in the nervous system. For example, once released into the synapse, the action of a neurotransmitter can be limited through removal of the neurotransmitter from the synapse, which can occur through enzymes that break down the neurotransmitter, reuptake of the neurotransmitter, or absorption by glial cells. The amount of neurotransmitter that is released into a synapse can be modified through axoaxonic synapses, so that inhibitory or excitatory signals from other neurons can impact the amount of calcium that comes into the axon terminal, and thus the amount of neurotransmitter that is released once an action potential reaches the axon terminal. Autoreceptors on a presynaptic neuron can also detect the amount of neurotransmitter in a synapse and adjust release based on this. Glial cells can release gliotransmitters, which can alter release of neurotransmitter by the presynaptic neuron or responses by the postsynaptic neuron. Not all neurotransmitters have the same effects on postsynaptic neurons; some are inhibitory, reducing the chances of an action potential occurring, and others are excitatory, increasing the chances of an action potential occurring. Even the same neurotransmitter can have different effects at different receptors. Through spatial and temporal summation, where the inputs from even thousands of different neurons over a period of time can be added together, any one neuron's activity can be impacted by stimulation or inhibition coming from multiple different sensory inputs. In addition, ionotropic receptors respond quickly to neurotransmitters with direct opening of ion channels, while metabotropic receptors respond more slowly and have less direct impact on ion channels.

Which of the following is true about neurotransmitters?

Neurotransmitters can have different effects on postsynaptic neurons depending on which receptor they bind to.

The gaps in the myelin sheaths on axons are known as ______.

Nodes of Ranvier

Name and describe the functions of three different types of glial cells.

Oligodendrocytes are glial cells that produce myelin on the axons of neurons in the brain and spinal cord, while Schwann cells are glial cells that produce myelin on axons of neurons in the rest of the nervous system. Myelin serves the function of speeding conduction of signals within neurons and making neurons function more efficiently. Radial glia assist newly generated neurons in reaching the final destination in the brain. Microglia respond to injury and disease in the nervous system by removing waste, and these glial cells also provide energy for to neurons. Astrocytes support synaptic connections between neurons and release gliotransmitters, which can impact neurotransmitter functioning.

The cells that produce myelin in the parts of the nervous system outside of the brain and spinal cord are called ______.

Schwann cells

The seawater-like solution inside neurons and bathing their outside are known respectively as ______.

intracellular and extracellular fluid

Which of the following is prompted by a neurotransmitter docking with a receptor site?

ion channels open, directly or indirectly

_____ are charged atoms that have gained or lost one or more electrons.

ions

Many people are concerned about eating too much salt, yet table salt (sodium chloride) plays which important role in your nervous system?

it breaks down into ions that are needed for neuron signaling

Which of the following is true of depolarization?

it is a change in the resting neuron's polarity toward zero

Which of the following is true of local potential but not action potential?

it is decremental

Which of the following is true of the resting membrane potential?

it is the difference in electrical charge inside and outside the inactive neuron

When depolarization of the cell membrane reaches threshold, which of the following occurs?

sodium ion channels open

_____ are concentrated primarily outside of the neuron, in the extracellular fluid, which contributes to the negative resting membrane potential of neurons.

sodium ions

_____ would tend to move into the neuron based on both their electrostatic pressure and force of diffusion.

sodium ions

Which of the following occurs during an EPSP?

sodium ions enter the cell

Following an action potential, the _____ returns the ions to their resting state concentrations.

sodium-potassium pump

In a resting neuron, which force pushes potassium ions into the cell?

sodium-potassium pump

Which part of the neuron works less due to myelination reducing the places where sodium can enter a neuron?

sodium-potassium pump

The largest part of a neuron is the ______.

soma

The part of a neuron that contains the nucleus is called the ______.

soma

At the last home football game, Joel started a taunting chant that slowly spread to more and more fans. Eventually, all those in the stadium picked up the chant and made a roar so deafening that the opposition had to call a timeout. What Joel and fellow fans performed is analogous to the process of ______ at axon hillocks.

spatial summation

If different postsynaptic potentials occur at the same time but from different inputs, ______ will occur.

spatial summation

Just as many people want to mistakenly compare the brain's "information processing" capability and speed to that of a computer, the speed of neural impulses is often erroneously compared to the ______.

speed of electrical charge

The ______ is the difference in electrical potential between the inside and outside of an inactive neuron.

resting potential

Which of the following mechanisms of terminating transmitter action involves the reabsorption of a neurotransmitter by the axon terminals?

reuptake

While listening to drug users describe the subjective effects of cocaine, BJ took a few notes to himself to remember that cocaine's effects are due to blocking the ______.

reuptake of dopamine

The fact that action potentials occur only at the nodes of Ranvier is the basis for ______.

saltatory conduction

One function of the specialized protein channels in a cell membrane is to ______.

selectively allow substances to enter or leave the cell

Which of the following is a true statement about neuron type?

sensory neurons are typically unipolar or bipolar

Which of the following is true of sensory neurons?

sensory neurons gather information from the environment and convey it into the central nervous system

Muscles contain ______ receptors.

excitatory nicotinic

Sodium ions are most concentrated in the ______ fluid.

extracellular

The most common type of neuron in the brain is the ______.

interneuron

Potassium ions are most concentrated in the ______ fluid.

intracellular

After a few too many cups of coffee and having to find a restroom, Sal ironically remembered the meaning of the term vesicle, as in ______.

"little bladder"

An action potential from beginning to end lasts about ______.

1 millisecond

The effect of myelination on an axon's conduction speed is the equivalent of increasing an axon's diameter by ______ times. a. 25

100

If the partial depolarization arriving at an axon is sufficiently large, typically ______, it can cause normally closed sodium ion channels to open.

10mV or more

The sodium-potassium pump accounts for ______ of the neuron's energy expenditure.

40%

Describe the electrical and chemical events that underlie an action potential.

Action potentials are generated when the summed signal entering a neuron is excitatory enough to hypopolarize/depolarize the cell membrane approximately 10 mV compared to the resting membrane potential. That excitatory signal comes from neurotransmitters that bind to specific receptors on a neuron. Following that initial graded potential, voltage-gated sodium channels open, and sodium ions enter the neuron. Since sodium ions carry a positive charge, this prompts the next segment of the axon to become depolarized, and the action potential is propagated down the axon in this manner. The depolarization also opens voltage-gated potassium channels, allowing potassium ions to leave the neuron. Since potassium ions carry a positive charge, this results in hyperpolarization of the cell membrane as the neuron's electrical charge becomes slightly more negative than at rest. Movement of sodium ions into the neuron and potassium ions out of the neuron results in the rapid depolarization and then hyperpolarization of the cell's membrane during the action potential.

Which of the following is the order of events that prompts release of neurotransmitters into the synapse?

An action potential reaches the axon terminals, calcium ions enter the terminals, vesicles fuse with cell membrane, neurotransmitter is released.

Contrast the terms agonist and antagonist using acetylcholine as an example.

An agonist is a chemical that mimics or enhances the function of a neurotransmitter at its receptors, while an antagonist is a chemical that reduces the effects of a neurotransmitter at its receptors. For example, nicotine and muscarine act like acetylcholine at the nicotinic and muscarinic acetylcholine receptors, respectively. The plant toxin curare acts as an antagonist at nicotinic acetylcholine receptors, which is why this toxin produces paralysis.

______ gated ion channels open and close based on the presence of neurotransmitters or hormones.

Chemically

Compare and contrast EPSPs and IPSPs. How do they contribute to triggering an action potential?

EPSPs (excitatory postsynaptic potentials) are signals that hypopolarize postsynaptic neurons, making the neuron less negative (moving closer to a membrane potential of zero), and making an action potential more likely to occur. IPSPs (inhibitory postsynaptic potentials) are signals that hyperpolarize postsynaptic neurons, making those neurons more negative in charge (moving farther from a membrane potential of zero), and making action potentials less likely to occur. EPSPs and IPSPs can be summed through temporal and spatial summation to have more complex effects on action potentials being triggered.

Explain the two forces that produce the resting membrane potential.

Force of diffusion results in ions moving across the cell membrane to areas of low concentration, while electrostatic pressure results in ions being attracted to the side of the cell membrane that carries an opposite charge. At rest, there is a negative charge across the cell membrane because many negatively charged protein anions are trapped inside the cell. Positively charged sodium ions exist in larger concentrations outside the cell membrane but are not able to enter the neuron because the sodium channels are closed, even though both electrostatic pressure and force of diffusion would prompt these ions to enter the neuron. Negatively charged chloride ions exist in greater concentrations outside of the cell membrane and would be repelled from the cell by electrostatic pressure. Positively charged potassium ions exist in greater concentration inside the neuron but do not leave the neuron in large quantities during the resting state because the potassium channels are closed. The sodium-potassium pump also works to maintain the cell's resting membrane potential by returning sodium to the extracellular space and potassium to the intracellular space.

What function of glial cells shows why they should be considered "active partners in neural transmission"?

Glial cells release gliotransmitters into the synapse.

Explain how greater brain complexity can arise from groups of neurons working together than can occur if neurons only communicated in chains in which each neuron only communicated with one presynaptic and one postsynaptic neuron.

Groups of neurons working together as networks generate greater complexity because they can create patterns of activity such as bursts in which neurons are extremely active, and those bursts can occur for varying lengths of time. In addition, there can be varying time intervals between high-amplitude activity. These patterns do contain information, as demonstrated in the study of taste perception in rats that was conducted by Patricia Di Lorenzo and Gerald Hecht.

______ are released from axon terminals and are detected by protein receptors on an adjacent neuron.

Hormones

Which of the following is true of action potentials in axons?

Many action potentials are generated next to each other along the length of an axon.

Describe two properties of the nervous system that disprove Dale's principle.

Many neurons have been shown to release multiple different neurotransmitters, such as GABA, glutamate, and dopamine. Multiple different neurotransmitters can be released at different times through corelease (in which the neurotransmitters are packaged in the same vesicles, but molecules of different size are released at different times) or cotransmission (in which transmitters are packed in separate vesicles and vesicles differ in their sensitivities to calcium). Different neurotransmitters can also be released from different axon terminals of the same neuron.

Explain the all-or-none law in the generation of an action potential.

The all-or-none law means that action potentials either occur or fail to occur, and action potentials occur with the same strength each time they are generated. Action potentials do not differ in strength, even if a signal coming into a neuron differs in strength. Once the threshold potential for the cell membrane is reached, an action potential will always be generated.

An action potential occurs at a specific amplitude for that neuron, regardless of the stimulus intensity or how much higher than threshold the stimulus is; this is known as the ______.

all-or-none law

Which of the following can prompt an electrically gated ion channel in the cell membrane to open?

a change in the electrical potential of the membrane

One property of action potentials is that they move in one direction down the axons of neurons. This occurs due to the ______.

absolute refractory period

Nicotinic and muscarinic receptors are two types of ______ receptors.

acetylcholine

When your Aunt Desirae skeptically asks you how a stimulant can slow down and calm a hyperactive child, you answer that stimulants ______.

act to stimulate underactive frontal areas of the brain

The ______ is the neuron's means of transmitting information over long distances. a. depolarizing potential

action potential

Which of the following is a brief, rapid reversal of the neuron's potential from -70 mV to +30 or +40 mV and back?

action potential

Most local anesthetics result in numbness because they block sodium channels in cell membranes. What impact does this blocking have on the activity of nerve cells?

action potentials cannot occur because the membrane cannot fully depolarize

Which property of action potentials results in their ability to transmit information over long distances?

action potentials do not become smaller as they occur down the length of an axon

Which of the following would be a consequence of the sodium-potassium pump being inactivated?

action potentials would not be able to generated

A drug that mimics the effects of a neurotransmitter is called a(n) ______.

agnoist

Smoking cigarettes can impact a person's mood and behavior because an active ingredient in cigarettes acts as a(n) ______ at a receptor for acetylcholine.

agonist

Harry came home to find his brother unconscious from an overdose of hydrocodone. When the paramedics arrived, they administered naloxone, because this drug is an opiate ______.

anatgonist

Where can sodium ions enter a myelinated axon?

at the nodes of Ranvier

The part of a neuron that transmits information over long distances is the ______.

axon

The conduction speed of neurons is largely a function of ______.

axon diameter and myelination

Contrary to Dale's principle, presynaptic neurons show a great deal of flexibility in releasing different neurotransmitters from different ______.

axon terminals

Where are vesicles stored?

axon terminals

_____ can be long enough to provide a direct connection between the spinal cord and the toes of a giraffe.

axons

Which of the following is true of both chloride ions and anions?

both carry a negative charge

The gap between two adjacent neurons was first observed by ______.

cajal

Neurotransmitters that open ion channels do so by docking on ______.

chemical receptor

Which of the following is one reason why chemical signals sent through the synapse lead to greater complexity than the signals of action potentials?

chemical signals sent through the synapse can be either excitatory or inhibitory

If you have ever awoken from sleep to scribble down a brilliant idea, you can probably relate to Loewi, whose own sleep was interrupted with notes with an insight about ______.

chemical transmission at the synapse

During a neuron's resting state, channels for potassium and sodium ions are ______.

closed

Most neurons fire spontaneously. IPSPs ______ the rate of firing.

decrease

The action potential spreads through an axon by ______.

depolarizing adjacent membrane to threshold, triggering another action potential

After Debbie's car accident, as the doctor asked her if it hurt here or if it hurt when he pressed this hard, Debbie understood why she could tell the differences in amount of pressure the doctor used; her sensory neurons coded the different pressures via ______.

different rates of firing neurons

The condition in which ions of a similar charge repel each other and thus spread evenly through a solution is called ______.

electrostatic pressure

All synapses use chemical neurotransmitters.

false

Myelinated axons require more energy to transmit action potentials than unmyelinated axons.

false

Reuptake and inactivation are two mechanisms that prolong synaptic responses.

false

The relative refractory period precedes the absolute refractory period.

false

The resting potential of a neuron is +70 mV.

false

The signal sent to neurons via the synapse can only be influenced by the amount and type of neurotransmitter that is released by the presynaptic neuron.

false

The force by which high concentrations of ions disperse away from each other and thus spread evenly through a solution is called ______.

force of diffusion

When making dinner, you add salt to a pot of boiling water. At first, the salt remains in one spot, but eventually spreads throughout the water due to the ______.

force of diffusion

Which nervous system cells got their name for one of their previously believed roles, to hold neurons together?

glia

Electricity flowing in power lines drops in voltage over distance, requiring your power company to use transformers to boost the voltage back to the original amplitude. This loss over distance is similar to the behavior of ______ potentials.

graded

When you call your sleeping dog, his eyelids flutter; you call louder and his ears perk up; you call even louder and he wakes up. Why?

greater stimulus intensities produce higher rates of action potentials

Excitatory postsynaptic signals result in partial depolarization, while inhibitory postsynaptic signals result in ______.

hyperpolarization

If the resting potential of a membrane changed from −70 mV to −75 mV, this would be ______.

hyperpolarization

The change in electrical charge from -70 mV to the peak of the action potential is due to ______.

inflow of sodium ions

A(n) ______ would be found bridging between a sensory neuron and a motor neuron in the spinal cord.

interneuron

Many business deals involve a "middle man" who communicates between buyer and seller. The "middle man" between a sensory neuron and a motor neuron is a(n) ______.

interneuron

While action potentials provide simple all-or-none responses, synapses have responses that are ______.

more complex

______ neurons control movements and actions of organs.

motor

A disease that destroys myelin is ______.

multiple sclerosis

As Francine slowly lost motor function and suffered increasing sensory deficits, she could almost picture her ______ being destroyed by the multiple sclerosis.

myelin

Saltatory conduction occurs only in ______.

myelinated axons

You have been given the task of designing an animal that needs to have an efficient nervous system, and the animal can be no larger than a human. What feature can you include in the animal's nervous system to ensure that it can respond quickly to its environment?

myelinated axons

Which of the following statements about neuronal conduction in myelinated neurons is correct?

myelinated axons uses saltatory conduction

By stimulating taste pathways in the brains of rats who were not exposed to sucrose but using firing patterns of neurons that were recorded from rats who were drinking a sucrose solution, researchers determined that ______.

neural firing patterns can encode taste stimuli

Cells that convey environmental information, carry out the functions underlying thought, emotion, and movements, and transmit commands out to the body's organs and muscles are called ______.

neurons

William, a philosophy major, asked Ian the psychology major what type of cell contributes the most to Ian's "being" who he is. Without hesitation, Ian replied ______.

neurons

______ are one of the cell types composing the nervous system.

neurons

______ are released from axon terminals and are detected by protein receptors on an adjacent neuron.

neurotransmitters

Which of the following is a true statement about what occurs when an axon transmits an action potential?

nothing physically moves down the axon

The soma of a neuron contains the ______.

nucleus

The cells that produce myelin in the brain and spinal cord are called ______.

oligodendrocytes

Dale's principle, a recently discounted theory about synaptic function, stated that a neuron ______.

only released a single neurotransmitter

The sodium-potassium pump forces sodium ions ______ and potassium ions into the cell.

out of the cell

The change in electrical charge from the peak of +30 or +40 mV back to -70 mV is due to ______.

outflow of potassium ions

If the resting potential of a membrane were to change from −70 mV to −65 mV, this would be ______.

part of EPSP

The fact that the cell membrane is highly permeable to some substances and much less so to other substances is one factor that contributes to the cell being ______.

polarized

When it is said that the cell membrane has a difference in electrical charge between its inside and the outside, this means the membrane is ______.

polarized

The change in a neuron's potential caused by the arrival of neurotransmitter is called ______.

postsynaptic potential

______ tend to exit a neuron based on weaker electrostatic pressure than their force of diffusion.

potassium ions

Which of the following occurs during an IPSP?

potassium ions leave the cell

What ionic movement is responsible for pulling the membrane potential back to a negative voltage during an action potential?

potassium ions move out of the cell

Signals are sent from ______ neurons.

presynaptic

The cell membrane of a neuron is a double layer made up of ______.

protein and lipid(fat)

Which of the following is a type of glia that helps new neurons reach their final destination in the brain?

radial glia

Which of the following explains a neuron's means of encoding various intensities of stimuli?

rate law

The neurotransmitter fits into a very precisely shaped location on the postsynaptic neuron called a ______.

receptor

The connection point between two neurons is called the ______.

synapse

If you could surgically remove a single neuron from the brain and place it on a slide, what structure(s) would you have to destroy?

synapses

Which of the following is true about the lipids that compose the cell membrane? a. The "heads" are in contact with extracellular and intracellular fluid and the "tails" are oriented away from these fluids.

the "heads" are in contact with extracellular and intracelluar fluid and the "tails" oriented away from these fluids

Intensity of a stimulus, such as the intensity of noise that a person experiences, can be communicated through ______.

the # of neurons that fire action potentials

Which of the following is true about the action potential in a myelinated neuron?

the action potential travels faster than in an unmyelinated neuron

The release of neurotransmitter from axon terminals into the synaptic cleft depends on ______.

the entry of calcium ions into the axon terminal

Which of the following is true of a neuron at rest?

the inside of the neuron is negatively charged with respect to the outside

Which statement characterizes the relative refractory period?

the neuron can fire again but only a stronger-than-threshold stimulus

Which statement characterizes the absolute refractory period?

the neuron cannot fire again because the sodium channels are unable to open

What reduces the chances of an action potential being fired during the relative refractory period?

the neuron's membrane is slightly more negative than at rest

You awake to your phone ringing. What will need to be true of the next stimulus in your environment if it is going to be detectable to you?

the next stimulus must be strong enough to overcome a slightly hyperpolarized membrane if it occurs immediately following the phone ringing

Which of the following influences the rate at which a neuron fires?

the relative strength of excitatory and inhibitory inputs it receives

Which of the following concepts does the all-or-none law describe?

the size of an action potential does not depend on the amplitude of the stimulus that started it

Myelinated axons consume less energy than unmyelinated axons because ______.

the sodium-potassium pumps have less work to do

The type of postsynaptic potential produced by a neurotransmitter depends on which neurotransmitter is released and ______.

the type of receptor that it binds to

The disorder multiple sclerosis results in destruction of myelin. Why do people with this disorder experience motor and sensory disturbances?

their neurons lose the ability to send signals

Which of the following is true about oligodendrocytes?

there are the most common glial cells in the brain

A neuron's cell membrane could become positive through either an inflow of positive ions or an outflow of negative ions. Why is the inflow of positive ions the most logical method for this depolarization?

they are already too many chloride ions outside of the cell

Which of the statements about cell membranes is correct?

they contain specialized protein channels

Which of the following is true of the axons of neurons?

they end in swellings known as terminals

Which of the following is true of glial cells?

they guide new neurons in fetal development

Selective serotonin reuptake inhibitors are used to treat depression and have which effect on the nervous system?

they increase the availability of serotonin at the synapse

Which of the following is true of axon terminals of neurons?

they release neurotransmitters from vesicles

Which of the following is true of the axon terminals of neurons?

they release neurotransmitters from vesicles

With a bigger fire, a larger-diameter water hose will be needed to put out more water per second. Likewise, ______ axons have evolved to provide less resistance to the conduction of neural potentials.

thicker

Which of the following is an implication of the absolute refractory period?

this limits how often action potentials can occur

What is one function of hyperpolarization in the nervous system?

this serves to keep excitatory signals in check

The dendrites of a neuron ______.

transit information to the cell body

An inhibitory message received by a neuron decreases the likelihood that it will send a message down its axon.

true

Dale's principle has been disproven through scientific investigations of the nervous system.

true

Local potentials decay as they spread.

true

Neurons gather information, process it, and control muscle movements.

true

Spatial summation, by definition, can only occur on a multipolar neuron.

true

The most numerous type of neuron in the central nervous system is the interneuron.

true

The myelin sheath is formed by either oligodendrocytes or Schwann cells.

true

The sodium-potassium pumps of a neuron are major consumers of energy.

true

Sarah threw rocks of different sizes into a pond. Just as ripple size was a function of size of rock, graded potentials ______ as a function of stimulus intensity.

vary in magnitude

The depolarization arriving at an axon from a dendrite is called a graded potential because it can ______.

vary in magnitude