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UPPERS DOWNER AND ALL
AROUNDERS
Chapter 2
Part I
How Psychoactive Drugs Affect Us
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Chapter 2 Focuses on the following:
Why do we crave a drug?
Why can’t we stop craving a drug.
Chapter 2 will also examine the
neurochemistry of craving and satiation.
• Look at different genetic factors
• Look at the role of brain chemicals
• Risk factors
How Psychoactive Drugs Affect Us
• Factors that determine effects and abuse
potential include:
– Route of administration
– Speed of transit to the brain
– Affinity for nerve cells and neurotransmitters
Routes of Drug Administration and Absorption.
5 common ways that drugs enter the body
Inhaling
Injecting
Snorting
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Orally
Transdermal
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Routes of Drug Administration and Absorption.
• Inhaling:
– Allows the vaporized
drug to enter the
lungs, the heart and
then the brain in about
7-10 seconds (Most
rapid)
Inhaling: 7 to 10 seconds
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(Pictures)
• Marijuana inhaling tent used
by the Scythians, c. 500 B.C.
• Man in India smokes ganja
(marijuana) in a “chillum”
pipe.
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Routes of Drug Administration and Absorption.
• Injecting
(Intravenous):
– Puts drugs directly
into a vein
– Put drugs into
muscles or under
skin
Intravenous (IV)
Intramuscular (IM)
Subcutaneous
15 – 30 seconds
3 – 5 minutes
3 – 5 minutes
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Routes of Drug Administration and
Absorption
• Snorting &
Mucosal
Exposure:
– Drugs can be snorted
and absorbed through
capillaries in the nasal
passages or placed on
mucosal tissues in the
gums, cheeks, or even
rectum and absorbed.
• Cocaine snorter’s
nose showing how
cocaine ate a hole
through the nasal
septum separating
the nostrils.
Snorting or Mucosal Exposure: 3 to 5 minutes
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Routes of Drug Administration and
Absorption
• Oral Ingestion:
• Drug passes
through the
esophagus and
stomach to the
small intestine
where it is absorbed
by the capillaries
lining the walls of
the small intestine.
• Hindu ascetic
prepares marijuana for
drinking.
Oral use (ingesting): 20 to 30 minutes
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Routes of Drug Administration and
Absorption
Contact or Transdermal
Absorption
Absorption through the
skin is the slowest
method of drug use. It
often takes 1–2 days
for effects to begin and
the absorption can
continue for about 7
days. Nicotine,
fentanyl, and heart
medications can also
be absorbed this way
Skin creams & ointments
absorbed through skin
Contact or
Transdermal:
1 to 2 days
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Drug Distribution
• Drugs Circulate through the bloodstream to the rest of the body where
they cause an effect, be ignored, be absorbed or be biotransformed
• Distribution depends on the drug itself and on blood volume of the
person (6-8 quarts in an adult, 3-4 in child)
• Takes 10 to 15 seconds after entering the bloodstream and has the
greatest effect on the brain and spinal cord
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Drug Distribution: Blood-brain Barrier
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The walls of the capillaries that
form a protective shield around
the nerves cells of the central
nervous system (CNS) and guard
against toxins, virus, and bacteria
can be penetrated by
psychoactive drugs
Penetration happens because
psychoactive drugs are Fatsoulable and the brain and its
barrier are fatty
Psychoactive drugs such as
heroin, nicotine, alcohol and
marijuana cross this barrier more
easily than other substances.
Cocaine (water soluble) hitchhikes
onto protein molecules to pass
through blood-brain barrier.
It takes 1–2 years for the bloodbrain barrier to develop fully in
infants.
Blood-Brain Barrier
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The Nervous System
• Principle Target of
Psychoactive drugs
• Network of 100 billion
nerve cells & 100 trillion
connections
• Nervous System is
made up of the:
– Central Nervous System
– Peripheral Nervous
System
Central
Somatic
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Autonomic
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The Nervous System
• Psychoactive drugs primarily affect the central
nervous system. The two parts of the central
nervous system are the brain and spinal cord.
• The Central Nervous System
– Includes the Brain and Spinal Cord
– Is the message center, receiving, analyzing and
responding to messages from the peripheral and
autonomic nervous systems
– Drugs alter the information sent from our
environment,
– Disrupts the processing (Thinking) of information
– Disrupts the commands sent back to various parts of
body
Peripheral Nervous System
• Is divided further into two systems:
– Autonomic Nervous System:
• Controls involuntary functions such as circulation,
digestion and respiration
• Helps body respond to stress
• Conserves the body’s resources and restores
homeostasis
• Many cells of the autonomic nervous system is
located in the brain and spinal cord.
• Psychoactive drugs that cross the brain-blood
barrier can disrupt involuntary functions
Peripheral Nervous System
• Somatic Nervous System
– Transmits sensory information from the skin,
muscles & joints to the central nervous
system (CNS),
– Then transmits instructions from the CNS
back to the skeletal muscles, allowing the
body to respond
Old Brain – New Brain
• Old Brain: Consist of the
brain stem, cerebellum and
mesocortex. Regulates
physiologic functions.
Experiences basic emotions
& cravings. Imprints survival
memories
• New Brain: Consist of the
neocortex and processes
information from the old
brain. Allows us to reason,
speak, create and remember.
• Craving is often located in
the old brain and is a
powerful primitive impulse
that can override the
rationality of the new brain.
Evolution of the New Brain
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Reward / Reinforcement Center
• Part of the Old Brain that
encourages a person to
remember and repeat an
action.
• It is also affected by
drugs and is thus
responsible for craving
• Drugs act on the reward
pathway to trigger
craving for euphoria or
pain relief
• AKA “mesolimbic
dopaminergic reward
pathway”
Reward System of the Brain
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Reward / Reinforcement Center
Nucleus Accubens & Satiation Center
Necleus Accumbens
Small group of nerve cells
call the “medial forebrain
bundle”
Psychoactive drugs stimulate
this area and the longer the
use, the stronger the “do it
again”
Satiation Center: keeps balance
• When activated by drugs, the
impact is so strong that it can
imprint emotional memory of
euphoria or pain relief more
deeply than survival
memories
• Induce strong cravings
• Connected with the
physiologic regulatory center
of body like heart rate and
respiration
Reward System of the Brain
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Neuroanatomy
• Nerve cells: Consisting of
dendrites, the cell body, the
axon and terminals transmit
impulses by sending
neurochemicals AKA
“neurotransmitters” across
the synaptic gap between
the nerve cells or neurons
• Messages travel in multiple
directions but with purpose,
enabling the senses to
transmit messages to the
brain that, in turn, send
messages and commands
back to the appropriate
muscles, tissues, and
organs. A single nerve cell
can receive signals from
hundreds, even thousands
of other nerve cells.
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Neuroanatomy
• They move holding
sacs in one nerve cell,
across the synaptic
gap, slot into rector
sites, trigger an
impulse, and then
move back to the
sending cell.
• The rapid signals are
reflex reactions
• Slower signals allow
time for thought
Message Arrives
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Neurotransmitters
• The released
neurotransmitters cross
the synaptic gap and slot
into receptor sites on the
postsynaptic neuron,
causing the retransmission
of the message. The
slotted neurotransmitters
are then released and
either metabolized in the
synaptic gap or more likely
reabsorbed through
reuptake ports in the
sending terminal, ready to
be transmitted again. (p.
53)
Message
Transmitted
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Neurotransmitters & Receptors
• Endorphins & enkephalins are the body’s
own opiods or (Endogenous Opiods)
• Exogenous opiods are external opiod
drugs such as heroin and morphine
• Psychoactive drugs cannot create
sensations or feelings that don’t have a
natural counterpart in the body
– So psychoactive drugs duplicate or mimic the
natural counterpart in the body to a higher
degree
Major Neurotransmitters
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Acetycholine
Norepinephrine
Epinephrine
Dopamine
Histamine
Serotonin
Enkephalins
Endorphins
Dynorphins
GABA
Glycine
Glutamic Acid (Glutamate, Glutamine)
Subtance PA
Anandamide
Corticotrophines (cortisone)
Nitric Oxide
100 more have been discovered
If the cells senses too many neurotransmitters, then it closes down
ports.
If there is too few neurotransmitters, then the cell opens more ports
• Cocaine forces the
release of extra
neurotransmitters,
especially dopamine,
epinephrine, and
norepinephrine.
Cocaine Forces
Neurotransmitter
Release
• It then also blocks the
reuptake ports so the
neurotransmitters
cannot be reabsorbed
by the sending neuron
thus causing excess
stimulation of the user.
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Heroin & Neurotransmitters
• When heroin is taken, it
slots into receptor sites
on the edge of the
pain-transmitting nerve
cell, causing a
reduction in the amount
of substance “P” that
gets across the gap.
• The heroin also slots
into receptor sites on
the receiving neuron,
blocking the substance
“P” that gets through.
When heroin or opioid
use is discontinued, the
pain returns unless that
tissue or organ has
been repaired. (p. 57)
Heroin Inhibits
Substance “P”
Pain Message
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Agonist & Antagonist
• Drugs disrupt neutral message
transmission
– Agonist are those drugs that enhance neutral
signals mimic or facilitate the effects of
neurotransmitters
– Antagonist are those drugs that block
neurotransmitters
• Heroin will act like a second
messenger and slot into the
opiod (enkeohlin) receptors
and block the release of
Substance “P”
neurotransmitters
• Heroin can also slot into the
Substance “P” receptor
sites without causing pain.
• Cocaine forces the release
of norepinepherine &
dopamine neurotransmitters
by entering the presynaptic
neurons causing an
exaggerated effect
• Ecstacy works this way with
serotonin
Heroin Inhibits
Substance “P”
Pain Message
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Cocaine Forces
Neurotransmitter
Release
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