Chapter 3Drugs and the Nervous SystemMaisto, Drug Use and

Chapter 3
Drugs and the Nervous System
Maisto, Drug Use and Misuse, 9th Edition. © 2022 Cengage. All
Rights Reserved. May not be scanned, copied or duplicated, or
posted to a publicly accessible website, in whole or in part.
Icebreaker
Who here has ever had something hurt, and then something
made it stop hurting, or hurt less? Raise your hand if you have
ever had this experience.
(If anyone has not raised a hand): Ever drink a cup of coffee
and then felt more alert? Raise your hand if so.
(Only if anyone has still not raised a hand): The rest of you,
think of any time you ever had a feeling or thought—any feeling
or thought.
All these things are based on the activity of your brain. The
brain is the basis of all conscious experience, as our text says.
This experience is the result of psychological processes.
In this chapter, we will explore how drugs affect those
psychological processes. [10 minutes]
Chapter Objectives (1 of 2)
After studying this chapter, you will be able to…
3-1 Describe the main components of a neuron and their
function
3-2 Explain how changes in ion channels and the movement of

ions across the neural membrane result in an action potential
3-3 Discuss how electrical signals are transmitted from one
neuron to other neurons
3-4 Differentiate between ionotropic and metabotropic receptor s
3-5 Summarize the ways drugs can affect neural transmission
3-6 Describe the major neurotransmitter systems and their
functions; then identify conditions that may result due to
abnormalities within each system
Chapter Objectives (2 of 2)
After studying this chapter, you will be able to…(cont’d.)
3-7 Identify the structure and organization of the nervous
system
3-8 Describe the main functions of the two divisions of the
peripheral nervous system
3-9 Describe the main structures that compose the hindbrain,
midbrain, and forebrain
3-10 Explain the role of the mesolimbic dopaminergic pathway
in reward and drug addiction
3-11 Summarize the techniques used in imaging the human
brain
The Neuron
3.1
Maisto, Drug Use and Misuse], 9th Edition. © 2022 Cengage.
All Rights Reserved. May not be scanned, copied or duplicated,
or posted to a publicly accessible website, in whole or in part.

The Neuron (Nerve Cell)
Neurons: Basic building blocks of the nervous system; cells that
can communicate with one another
Dendrites and axon = structures unique to the neuron
Some axons are sheathed in white, fatty myelin that insulates
them and conducts electrical signals called action potentials
An action potential is a rapid depolarization of the axon
membrane when positively charged sodium ions rush into the
axon
This occurs when the neuron is stimulated
It produces a change of c. 110 millivolts
“All or none”—either firing at full voltage or at rest
Diagram of a Neuron
Knowledge Check 1: The Neuron
Question: The part of a neuron that sends signals is the
________ and one part that receives signals is the _________.
axon; dendrites
dendrites; axon
nucleus; myelin
myelin; nucleus

Knowledge Check 1: Answer
Question: The part of a neuron that sends signals is the
________ and one part that receives signals is the _________.
axon; dendrites
dendrites; axon
nucleus; myelin
myelin; nucleus
Answer: a. axon; dendrites. The axon transmits signals and the
dendrites and cell body receive signals during an action
potential (an electrical signal).
Neural Transmission
3.2
Neural Transmission: How Signals Are Sent and Received
End branches of axons terminate in axon terminals or terminal
buttons
Most axon terminals do not touch dendrites of adjacent neurons
Junction between two neurons = a synapse, separated by a gap
called the synaptic cleft
Chemicals stored in the terminal button released into the
synapse = neurotransmitters, which trigger activity in the next
neuron
Neural transmission is an electrochemical event: Electrical
along the axon, chemical at the synapse
Drugs may interact with the nervous system at the synapse

Receptor sites: Large protein molecules on neurons
Must be “unlocked” by neurotransmitters as “keys” to trigger
neural firing
Diagram of a Synapse
Neurotransmitters and Receptors
Transmitters and their receptors have an affinity: transmitter is
attracted to receptor site
When a transmitter occupies a receptor, it is briefly attached by
binding – changes the neuron, making it more or less likely to
fire
Two types of receptors responsible for changes of binding:
Ionotropic receptors
Directly coupled with ion channels
Excitatory and inhibitory receptors
Result in rapid changes, milliseconds in duration
Metabotropic receptors
Not directly coupled with ion channels
May also be excitatory or inhibitory
Result in slightly delayed changes, relatively long-lasting
Cause release or activation of G proteins
G proteins may initiate synthesis of second messengers
(chemicals)
Second messengers make changes over extended time periods

Diagram of an Ionotropic Receptor
Diagram of a Metabotropic Receptor
Knowledge Check 2: Neural Transmission
Question: Fill in the blanks in each description to show whether
it describes ionotropic receptors or metabotropic receptors.
Produce neuronal changes that are slightly delayed:
__________________
Produce neuronal changes that happen very rapidly:
__________________
Produce neuronal changes that last for milliseconds:
__________________
Produce neuronal changes that can be long-lasting:
___________________
Produce specialized molecules known as G proteins:
__________________
Are directly coupled with the regulatory ion channels:
__________________
Are not directly coupled with regulatory ion channels:
__________________

Knowledge Check 2: Answers
Question: Fill in the blanks in each description to show whether
it describes ionotropic receptors or metabotropic receptors.
Produce neuronal changes that are slightly delayed:
metabotropic receptors
Produce neuronal changes that happen very rapidly: ionotropic
receptors
Produce neuronal changes that last for milliseconds: ionotropic
receptors
Produce neuronal changes that can be long-lasting:
Produce specialized molecules known as G proteins:
Are directly coupled with the regulatory ion channels:
ionotropic receptors
Are not directly coupled with regulatory ion channels:
Drugs and Neural Transmission
3.3

Drug Influences on Neural Transmission
Drugs can interfere with synaptic transmission:
Mimicry: Drugs chemically resembling natural
neurotransmitters can bind to receptor sites, fooling them into
reacting the same way
Interfering with production or transport of neurotransmitters
By interfering with ability of vesicles to store neurotransmitter
substances
Enhancing release of neurotransmitter substances into synapse
Affecting enzyme activity: enzyme breakdown and reuptake
Drugs that fit receptors and prevent neurons from firing are
blocking agents
Agonists: fit receptors and activate them;
Antagonists: fit but do not activate –stop other things from
activating receptors
Indirect agonists/antagonists: enhance or inhibit
neurotransmitter activity without binding to receptors
Examples of Drug Influences on Neural Transmission
Morphine, heroin, and other opiates activate neural opioid
receptors in the same way as endorphins (the body’s
endogenous, natural opioids) do
Amphetamines are thought to act as stimulants by enhancing the
release of neurotransmitter substances into the synapse
Some antidepressant drugs alter brain levels of the
neurotransmitters, norepinephrine, dopamine, and serotonin by
inhibiting the activity of monoamine oxidase, the enzyme that
breaks them down
Some drugs, notably cocaine, block the reuptake process of
removing neurotransmitters from the synapse, so they are not

deactivated
Chronic use of some drugs can cause long-term reduction in
amounts of neurotransmitters or in number of available receptor
sites
This can result in the development of tolerance to a drug, and in
withdrawal symptoms with cessation of drug use
Neurochemical Mechanisms of Drug ActionTABLE 3.1
Neurochemical Mechanisms of Drug ActionDrug effects can be
produced by altering the following neurochemical systems:1.
Neurotransmitter synthesis. A drug may increase or decrease the
synthesis of neurotransmitters.2. Neurotransmitter transport. A
drug may interfere with the transport of neurotransmitter
molecules to the axon terminals.3. Neurotransmitter storage. A
drug may interfere with the storage of neurotransmitters in the
vesicles of the axon terminal..4. Neurotransmitter release. A
drug may cause the axon terminals to release neurotransmitter
molecules into the synapse prematurely.5. Neurotransmitter
degradation. A drug may influence the breakdown of
neurotransmitters by enzymes.6. Neurotransmitter reuptake. A
drug may block the reuptake of neurotransmitters into the axon
terminals.7. Receptor activation. A drug may activate a receptor
site by mimicking a neurotransmitter. 8. Receptor blocking. A
drug may cause a receptor to become inactive by blocking it.
Major Neurotransmitters, Agonists, and AntagonistsTABLE 3.2
Major Neurotransmitters with Representative Agonists and

AntagonistsNeurotransmitterAgonistAntagonistAcetylcholineNi
cotineAtropineDopamine/norepinephrineCocaine/amphetamines
ChlorpromazineSerotoninLysergic acid diethylamide
(LSD)ChlorpromazineEndorphinsMorphine NaloxoneGamma
aminobutyric acid
(GABA)BarbituratesBicuculineGlutamateAspartic
acidKetamineAnandamideTetrahydrocannabinol
(THC)Rimonabant
Knowledge Check 3: Drugs and Neural Transmission
Question: The antidepressant Prozac (generic name fluoxetine)
is classified as a serotonin-specific reuptake inhibitor (SSRI).
By applying what you learned in this section, you can determine
that Prozac __________ the __________ of the __________
called serotonin.
inhibits; deactivation; neurotransmitter
activates; breakdown; enzyme activity
stimulates; reuptake; neurotransmitter
inhibits; release; endogenous receptor
Question: The antidepressant Prozac (generic name fluoxetine)
is classified as a serotonin-specific reuptake inhibitor (SSRI).
By applying what you learned in this section, you can determine
that Prozac __________ the __________ of the __________
called serotonin.
inhibits; deactivation; neurotransmitter
activates; breakdown; enzyme activity

stimulates; reuptake; neurotransmitter
inhibits; release; endogenous receptor
Answer: a. inhibits; deactivation; neurotransmitter. A serotonin-
specific reuptake inhibitor like Prozac inhibits the reuptake,
i.e., deactivation, of the neurotransmitter called serotonin.
Major Neurotransmitter Systems
3.4
Acetylcholine
One of the first neurotransmitters discovered: found in neurons
outside the brain* that activate skeletal muscles
Neuromuscular junction: where nerves meet muscles
When nerves that synapse with muscle fibers fire, they release
acetylcholine into the neuromuscular junction: muscle contracts
The disease myasthenia gravis is caused by blockage of
acetylcholine
Botulinum toxin causes muscle paralysis by blocking release of
acetylcholine
Neurons containing acetylcholine are cholinergic; drugs that
block acetylcholine are anticholinergic
*Acetylcholine is also important in the brain
Alzheimer’s disease is related to loss of neural function in some
cholinergic pathways
Some drugs reduce Alzheimer’s symptoms temporarily by
elevating acetylcholine levels, through inhibiting the enzyme
acetylcholinesterase

Alzheimer’s Disease
Late President Ronald Reagan retreated from public life after it
was revealed that he suffered from Alzheimer’s disease.
Monoamines
Norepinephrine (noradrenaline), dopamine, and serotonin
Norepinephrine: discovered early – found outside as well as
inside the brain
Outside the brain – mediates the physical changes of emotional
arousal
Inside the brain – important in regulating hunger, alertness, and
arousal
Serotonin – important in regulating sleep
Dopamine – regulates coordinated motor movements
Dopamine insufficiency may be the basis of Parkinson’s
disease: this hypothesis led to treatment with L-dopa, a
dopamine precursor
While dopamine does not cross the blood-brain barrier, L-dopa
does: it is converted to dopamine in the brain
Monoamine dysregulation is implicated in psychiatric disorders
like depression and schizophrenia
Drugs that influence the monoamine systems have
revolutionized modern psychiatry

Endorphins, Amino Acids, Others
Endorphins: Large molecules in the peptide family: functionally
like morphine, heroin, other opiates
endorphins
Endorphins modulate pain relief
GABA (gamma aminobutyric acid): among most abundant of
known neurotransmitters in brain tissue and most significant
inhibitory one: impedes neural firing
Depressants, barbiturates, tranquilizers, alcohol - thought to act
on GABA system
Glutamate: among most abundant of excitatory
neurotransmitters; important in learning and memory processes
Hallucinogenic drugs PCP and ketamine act on glutamate
receptors in some parts of the brain
Anandamide: active chemical in marijuana seems to mimic
anandamide, a lipid
Many more neurotransmitters have been and will be discovered
Parkinson’s Disease
Boxing legend Muhammad Ali pretends to punch actor Michael
J. Fox. Both developed Parkinson’s disease.
Knowledge Check 4: Major Neurotransmitter Systems

Neurotransmitter
Question: Match the neurotransmitter on the left with a
characteristic on the right.
Acetylcholine _________
Dopamine _________
Serotonin _________
Norepinephrine________
Endorphins ________
GABA ________
Glutamate ________
Anandamide ________
Characteristic
Depressants act on this system
Marijuana’s active chemical mimics this lipid
Regulates sleep
Excitatory; important in memory, learning
Its deficiency is implicated in Parkinson’s disease
Its deficiency is implicated in Alzheimer’s disease
Mediates physical changes of emotional arousal
Naturally occurring pain relievers
Neurotransmitter
Question: Match the neurotransmitter on the left with a
characteristic on the right.
Acetylcholine f
Dopamine e
Serotonin c
Norepinephrine g
Endorphins h
GABA a

Glutamate d
Anandamide b
Characteristic
Depressants act on this system
Marijuana’s active chemical mimics this lipid
Regulates sleep
Excitatory; important in memory, learning
Its deficiency is implicated in Parkinson’s disease
Its deficiency is implicated in Alzheimer’s disease
Mediates physical changes of emotional arousal
Naturally occurring pain relievers
The Nervous System
3.5
A Microscopic View of the Nervous System
Major distinction: Between central nervous system (CNS) and
peripheral nervous system (PNS)
CNS: brain and spinal cord
PNS: all nervous tissue outside or peripheral to CNS
Sensory nerves: Nerves that send input from senses brain
Motor nerves: Nerves that send output from brain to muscles
Autonomic nervous system (ANS): regulates
nonconscious/automatic functions
Sympathetic branch: activated during emotional arousal by
release of epinephrine and norepinephrine from adrenal glands
(“fight-or-flight”)

Cocaine, amphetamines, LSD mimic this: sympathomimetic
drugs
Parasympathetic branch: balances action of sympathetic branch
by exerting opposite effects
Organizational Structure of the Nervous System
Knowledge Check 5: The Nervous System
Question: The sympathetic and parasympathetic branches are
parts of the __________, which in turn is a part of the
___________.
Autonomic nervous system; peripheral nervous system
Peripheral nervous system; autonomic nervous system
Central nervous system; peripheral nervous system
Autonomic nervous system; central nervous system
Question: The sympathetic and parasympathetic branches are
parts of the __________, which in turn is a part of the
___________.
Autonomic nervous system; peripheral nervous system
Peripheral nervous system; autonomic nervous system
Central nervous system; peripheral nervous system

Autonomic nervous system; central nervous system
Answer: a. Autonomic nervous system; peripheral nervous
system. The central nervous system includes the brain and
spinal cord. The peripheral nervous system includes sensory and
motor nerves and the autonomic nervous system. The autonomic
nervous system includes the sympathetic and parasympathetic
branches.
The Brain
3.6
The Hindbrain
Major divisions of the brain: hindbrain, midbrain, and forebrain
Three main components of hindbrain: medulla oblongata,
cerebellum, pons
Medulla: Just above (= enlargement of) the spinal cord; controls
breathing, heart rate, blood pressure, swallowing, digestive
processes, vomiting – its normal functioning is critical
Farther up is the pons: Provides pathways for input up and
output down along the spinal cord; plays a role in the control of
sleep and wakefulness
Reticular activating system: Pathway running along pons and
through medulla; critical for alertness, arousal
Barbiturates, tranquilizers, sedatives are thought to act in this
system
Cerebellum: Critical for motor control, balance, coordination,
speech

The Midbrain
Includes the Inferior colliculi, superior colliculi, and substantia
nigra
Inferior colliculi form part of the auditory system
Superior colliculi function in localizing visual stimuli
These structures are specific in localizing stimuli and mediating
reflexes
Recognition and interpretation of visual and auditory stimuli are
elsewhere, in the cerebral cortex
Parkinson’s disease involves damage to substantia nigra and
nigrostriatal motor pathway, when neurons in this region begin
to degenerate
The substantia nigra produces dopamine: Deterioration of the
substantia nigra causes a shortage of dopamine for
neurotransmission
Toxins (e.g., rotenone, permethrin) may kill neurons in the
substantia nigra and trigger Parkinson’s disease
The Forebrain
Contains the most important regions related to complex human
behavior: cerebral cortex, thalamus, hypothalamus, limbic
system, basal ganglia
Thalamus: like a relay station – receives incoming sensory
stimuli, relays information to relevant centers throughout the
brain
Hypothalamus: Critical in the motivation of behavior –
regulation of eating and drinking, control of body temperature,

aggression, sexual behavior
“Neural basis of reward”: Mesolimbic dopaminergic pathway
Includes the nucleus accumbens; travels through ventral
tegmental area to the frontal cortex – related to release of
dopamine
Limbic system: contains amygdala – regulates fear, aggression,
other emotional experiences
Hippocampus – critical in memory storage
Basal ganglia: include caudate nucleus, putamen, globus
pallidus: critical for motor movements
The Cerebral Cortex
A greatly enlarged cerebral cortex distinguishes the human
brain from those of most other animals – involved in most
complex psychological functions
Occipital lobe at the back: “visual projection area” – perceives
visual stimuli
Temporal lobes at sides: perceive auditory stimuli, important in
language
Damage to left temporal lobe causes severe language
impairment
Damage to right temporal lobe often causes dysregulation of
emotions
Mediation of language and emotions is reversed in some left-
handed people
Frontal lobe: important in initiation of movement and
emotionality, intelligence, personality
Parietal lobe: registers tactile stimuli
Prefrontal cortex: important in planning, impulse control,
considering long-term consequences of behavior
Some suggest that prefrontal cortex dysregulation found in
drug-dependent individuals may be critical to understanding

neurobiology of addiction
Dorsal View and Cross-Section of Human Brain
Sagittal View of the Human Brain
Dorsal View and Cross Section of the Human Brain
Sagittal view of the Human Brain

Imaging the Human Brain
Electroencephalography (EEG): Measures electrical brain waves
through scalp
Computerized axial tomography (CT/CAT scan): Passes X-rays
through head in circular pattern for three-dimensional image of
the brain
Positron-emission tomography (PET) scan: Intravenous
injection of radiotracers; measured to see where isotopes are
absorbed, absorption rate, etc., to assess changes (including
drug-induced) in activity in various brain regions [Closely
related: single-photon emission computed tomography (SPECT)
scan]
Magnetic resonance imaging (MRI): passes strong magnetic
field through the head, generating radio waves causing brain
molecules to emit energy of different frequencies depending on
their properties – creates localized, detailed brain image
Functional MRI (fMRI): permits very rapid imaging,
measurement of oxygen levels in brain blood vessels, correlated
with brain region metabolism: can use to make inferences about
brain regions most active during a specific psychological
activity
Imaging techniques help to learn about neural mechanisms of
drug action, dependence, brain changes from long-term drug
exposure
Imaging of the Human Brain: CAT Scan
A technician monitors a patient during a CAT scan.

Knowledge Check 6: The Brain
Place each of the listed structures in the brain region where they
are found:
Medulla oblongata; superior colliculi; inferior colliculi;
substantia nigra; thalamus; reticular activating system;
hypothalamus; hippocampus; pons; cerebellum; limbic system;
basal ganglia; cortex.
Hindbrain
Midbrain
Forebrain
Question: Place each of the listed structures in the brain region
where it is located:
Medulla oblongata; superior colliculi; inferior colliculi;
substantia nigra; thalamus; reticular activating system;
hypothalamus; hippocampus; pons; cerebellum; limbic system;
basal ganglia; cortex.
Hindbrain
Medulla oblongata

Pons
Cerebellum
Reticular activating system
Midbrain
Superior colliculi
Inferior colliculi
Substantia nigra
Forebrain
Thalamus
Hypothalamus
Hippocampus
Limbic system
Basal ganglia
Cortex
Self-Assessment
Which parts of this chapter did you find most challenging, and
thus need to review?
Which things in this chapter did you find the most interesting,
and would like to study further? What do you find interesting
about them?
What are some things you learned from this chapter that you did
not know before, and which may have surprised you?
What things do you think you can best take from this chapter
and apply in real life, like at school, at work, or at home? How
would you apply them?
Summary

Summary (1 of 2)
Now that the lesson has ended, you should be able to…
Describe the main components of a neuron and their function
Explain how changes in ion channels and the movement of ions
across the neural membrane result in an action potential
Discuss how electrical signals are transmitted from one neuron
to other neurons
Differentiate between ionotropic and metabotropic receptors
Summarize the ways drugs can affect neural transmission
Describe the major neurotransmitter systems and their
functions; then identify conditions that may result due to
abnormalities within each system
Summary (2 of 2)
Now that the lesson has ended, you should be able to…(cont’d.)
Identify the structure and organization of the nervous system
Describe the main functions of the two divisions of the
peripheral nervous system
Describe the main structures that compose the hindbrain,
midbrain, and forebrain
Explain the role of the mesolimbic dopaminergic pathway in
reward and drug addiction
Summarize the techniques used in imaging the human brain

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Chapter 3: Drugs and the Nervous System
Key Terms
acetylcholine (-’se-t l-’k -l n): A neurotransmitter linked with
cognitive processes and memory that is found both in the brain
and in the parasympathetic branch of the autonomic nervous
system.
action potential: The electrical impulse along the axon that
occurs when a neuron fires.
agonist (‘a-gә-nist): A substance that occupies a neural receptor
and causes some change in the conductance of the neuron.

Alzheimer’s disease (‘alts-’hıˉ-mәrz): One of the most common
forms of dementia involves a progressive loss of memory and
other cognitive functions.
anandamide: A lipid neurotransmitter mimicked by marijuana.
antagonist: A substance that occupies a neural receptor and
blocks normal synaptic transmission.
autonomic nervous system (ANS): Part of the PNS has two
branches: sympathetic and parasympathetic.
enzyme breakdown: One process by which neurotransmitters are
inactivated. Chemicals called enzymes interact with the
transmitter molecule and change its structure so that it no
longer is capable of occupying receptor sites.
axon (‘ak-’sän): A long cylindrical extension of the cell body of
the neuron; conducts electrical charge from the cell body to the
axon terminals.
axon terminals (or terminal buttons): Enlarged button-like
structures at the ends of axon branches.
beta-blockers: Drugs that block beta-adrenergic receptors of the
sympathetic system and thus act to relieve high blood pressure.
blood-brain barrier: The system that “filters” the blood before it
can enter the brain.
central nervous system (CNS): The brain and the spinal cord.
cerebellum (‘ser-ә-’be-lәm): Hindbrain structure important in
motor control and coordination.
computerized axial tomography (CT): Technique that produces a

three-dimensional X-ray image of the brain.
norepinephrine (‘no˙r-’e-pә-’ne-frәn): A neurotransmitter in the
brain that is also involved in activity of the sympathetic branch
of the autonomic nervous system.
cortex: The outermost and largest part of the human brain.
dendrites (‘den-’drïts): Spiny branchlike structures that extend
from the cell body of a neuron, typically contain numerous
receptor sites and are thus important in neural transmission.
dopamine (‘do–-pә-’mën): A neurotransmitter in the brain that
is involved with movement and reward.
electroencephalography (EEG): Technique used to measure
electrical activity in the brain.
endorphins (en-’do·r-fәnz): Neurotransmitters in the brain that
are mimicked by opiate drugs.
forebrain: The largest part of the human brain; includes the
cerebral cortex, thalamus, hypothalamus, and limbic system.
GABA: Short for gamma aminobutyric acid; the most abundant
inhibitory neurotransmitter in the brain.
glutamate: An excitatory amino acid neurotransmitter.
hindbrain: The lower part of the brain, including the medulla,
pons, and cerebellum.
hippocampus (‘hi-p ә’kam-pәs): A structure of the limbic
system thought to be important in the formation of memories.
hypothalamus: (‘h
ī-po–-tha-lә-mәs): Forebrain structure that regulates

eating, drinking, and other basic biological drives.
inferior colliculi (ko-’lik-yü–-lï): Midbrain structures that
control sound localization.
ionotropic receptors: Receptors that are coupled to ion channels
and affect the neuron by causing those channels to open.
L-dopa (‘el-’dö–pә): A chemical precursor of dopamine used in
the treatment of Parkinson’s disease.
limbic system: Forebrain structures including the amygdala and
hippocampus.
magnetic resonance imaging (MRI): Technique that creates a
high-resolution, three-dimensional image of the brain.
medulla oblongata (mә-’dә-lә-’-ä-bl˙oŋ-gä-tә): The lowest
hindbrain structure of the brain; important in the regulation of
breathing, heart rate, and other basic life functions.
mesolimbic dopaminergic pathway: Pathway that is rewarding
when stimulated.
metabotropic receptors: Receptors that act through a second
messenger system.
midbrain: Part of the brain that includes the inferior and
superior colliculi and the substantia nigra.
monoamines (‘mä-n–öә-’mëns): A class of chemicals
characterized by a single amine group; includes the
neurotransmitters norepinephrine, dopamine, and serotonin.
myelin (‘mıˉ-e-len): A fatty white substance that covers the

axons of some neurons.
neurons (‘nü-’räns): Individual nerve cells that are basic
building blocks of the nervous system.
neuromuscular junction: Junction between neuron and muscle
fibers where release of acetylcholine by neurons causes muscles
to contract.
neurotransmitters: Chemical substances stored in the axon
terminals that are released into the synapse when the neuron
fires. Neurotransmitters then influence activity in postsynaptic
neurons.
norepinephrine basal ganglia (‘ba–sel-’ga
η -glē–ә): Forebrain structures important for motor
control; they include the caudate nucleus, the putamen, and the
globus pallidus.
parasympathetic branch: Branch of the ANS that is responsible
for lowering heart rate and blood pressure.
Parkinson’s disease: A disease that involves a progressive
deterioration of motor control.
peripheral nervous system (PNS): Sensory nerves, motor nerves,
and the autonomic nervous system.
pons (‘pänz): Hindbrain structure important in the control of
sleep and wakefulness.
positron-emission tomography (PET): Technique used to
measure activity in selected brain regions.
receptor sites: Specialized structures located on dendrites and
cell bodies for neurons that are activated by neurotransmitters.

reticular activating system: Pathway running through the
medulla and pons that regulates alertness and arousal.
reuptake: One process by which neurotransmitters are
inactivated. Neurotransmitter molecules are taken back up into
the axon terminal that released them.
serotonin (‘sir-ә-tö-nәn): A neurotransmitter in the brain that is
involved with sleep and mood.
substantia nigra (sәb-’stan(t)-shә-’n
ī-grә): Literally “black substance,” this basal ganglia
structure is darkly pigmented and produces dopamine. Damage
to this area produces Parkinson’s disease.
superior colliculi: Midbrain structures that control visual
localization.
sympathetic branch: Branch of the ANS that is activated during
emotional arousal and is responsible for such physiological
changes as increased heart and respiratory rate, increased blood
pressure, and pupil dilation.
sympathomimetic: Drugs such as cocaine and amphetamines that
produce the physiological effects of sympathe tic activity.
synapse (‘si-’naps): The junction between neurons.
thalamus (‘tha-lә-mәs): Forebrain structure that organizes
sensory input.
vesicles (‘ve-si-kәls)
: Tiny sacs in axon terminals that store
neurotransmitters.

True or False Questions Answer Key
1. Certain cells in the nervous system have the unique ability to
communicate with each other.
TRUE. Neurons are able to communicate with each other
through an electrochemical process known as neural
transmission.
2. The effects of drugs always involve naturally occurring
physiological processes.
TRUE. Drugs act by making defined natural functions of the
brain or body either more or less active.
3. Some drugs work by blocking the reuptake of
neurotransmitters into the axon terminals.
TRUE. Some drugs work by blocking the reuptake of
neurotransmitters into the axon terminals, thereby changing the
levels of neurotransmitter in the brain.
4. All drugs have the same basic effect on a cellular level; that
is, they all block neural firing.
FALSE. Although some drugs, called antagonists, do block
receptor sites and prevent activation of the receptor, other
drugs, called agonists, activate the receptor.
5. The brain is shielded from many toxic substances by a
protective barrier.
TRUE. The brain is protected from toxic compounds that might
enter the bloodstream by a blood-brain barrier that screens
many, but not all, chemicals.
6. The two main branches of the nervous system are the
peripheral nervous system (PNS) and the autonomic nervous
system (ANS).

FALSE. The two main branches of the nervous system are the
central nervous system (CNS) and the peripheral nervous system
(PNS).
7. An excess of dopamine is associated with Parkinson’s
disease.
FALSE. Dopaminergic neurons in the substantia nigra
degenerate in Parkinson’s disease, which leads to a deficiency
of dopamine.
8. The brain is firmly attached to the inside of the skull by
tough membranes known as the meninges.
FALSE. The brain floats within the skull in a liquid known as
cerebrospinal fluid.
9. The autonomic nervous system is responsible for regulating
food and water intake.
FALSE. Food and water intake appears to be regulated by the
hypothalamus, a structure found in the brain.
10. Animals will work for the electrical stimulation of certain
parts of the brain.
TRUE. The mesolimbic dopaminergic pathway is sometimes
called the pleasure center of the brain.

Chapter 3Drugs and the Nervous SystemMaisto, Drug Use and

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