Description
Activity: Public health officials are concerned about how high-potency cannabis will affect teens. After reviewing: https://www.snexplores.org/article/teen-brain-vulnerable-harms-cannabis-thc-marijuana discuss what parts of the brain are affected, and how potency has changed and apply what we’ve learned in chapter four to discuss why this is of concern,
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Chapter 4
Pharmacology
& Physiology of
Drug Use
H L E D 2 4 | LO N G B E A C H C I T Y C O L L E G E
Chapter Objectives
Describe
Describe how neurons communicate electrically and chemically
Contrast
Contrast a dendrite and an axon
Explain
Explain the effects of various neurotransmitters
Summarize
Summarize the functions of the reticular activating system, hypothalamus, cerebral cortex, limbic system, basal ganglia, and brain stem
List and provide
List and provide examples of the different factors that alter the effects of drugs
Describe
Describe how drugs interact with different systems of the body
Contrast
Contrast the sympathetic and parasympathetic branches of the autonomic nervous system
Describe
Describe the additive, antagonistic, and synergistic effects of drugs
Contrast
Contrast between pharmacological tolerance, behavioural tolerance, cross-tolerance, and reverse tolerance
List
List the mechanisms of how drugs can be administered and discuss the effects of these different routes have on absorption rates
Pharmacology
Pharmacology: the interaction between drugs and the living organism
Relates to the way drugs are:
• Administered, absorbed, distributed, metabolized and excreted
Dependent on:
• The properties of the drug itself
• The route of administration
• Amount or dosage
• Other drugs in the system
• Previous experience with the drug
Generally, drugs that act quickly and produce profound effects are more likely to be abused compared to drugs that act slowly.
Drug Actions
Drugs affect the nervous system, which consists of:
• Central nervous system (CNS)- brain and the spinal cord
• Peripheral nervous system (PNS)
• Autonomic nervous system (ANS)
Neurons- “messengers”
• transmit information via chemical and electrical processes
Contains two types of nerve fibers
• Dendrites- receive nerve impulses
• Axons – send impulses away from the cell
Neurons sends messages electrochemically
Neurons
• Messages between neurons are accomplished chemically
• Information within the neuron occurs electrically
o Neurotransmitters- chemical substances used to transmit messages
• Electrical impulses originate in the dendrite and pass through the cell through the axon
Action Potential- procedure of how nerve impulses are transmitted
Synapse- the space between an axon and a dendrite
Neuron
Neurotransmitters- manufactured in the vesicle of the neuron
and travel to the synaptic space
– Causes the receiving cell to start an electrical impulse
Actions of drugs
Drugs are most likely to have their major effect in the
synaptic space
Presynaptic drugs
– Drugs that impact the neuron responsible for causing the
neurotransmitter to be released
Postsynaptic drugs
– Drugs that impact the release, storage, and synthesis of
neurotransmitters
Synaptic Transmission
Neurotransmitters
▪ Most drugs affect brain activity by increasing or decreasing the
activity of various neurotransmitters
▪ Neurotransmitters affect our emotions, movement and cognition
▪ Some drugs mimic the action of neurotransmitters, and others
block their action.
▪The functions of selected neurotransmitters are described on the
following slides
One of the most common
neurotransmitters in the brain
• Drugs that block the action of ACH receptors are called
anticholinergic
Acetylcholine
(ACH)
Functions
• Excitatory transmitter in the skeletal muscles
• Inhibitory in the heart muscle
• Processing memory and learning
A number of hallucinogenic drugs impact the action of ACH and are
referred to as anticholinergic hallucinogens
Serotonin
Inhibitory neurotransmitter
Plays a role in:
– Regulating pain, sleep, eating, sensory perception, body temperature
Research suggests a link between low serotonin levels and depression
– Many depression medication are serotonin reuptake inhibitors which reduce the amount of serotonin
being absorbed→ increasing the amount of serotonin
Serotonin syndrome is a potentially life-threatening condition resulting from too much serotonin
Gamma-aminobutyric
acid (GABA)
Inhibits nerve cells being sent from one neuron
to another
Drugs that stimulate GABA production leaves
one feeling relaxed
– Alcohol
Low levels of GABA are linked with:
– Anxiety, epilepsy, chronic pain
Affect the emotional state
Catecholamines
Function repeatedly because they are
reabsorbed by the neuron that discharges
them→ reuptake
Examples include:
• Dopamine
• Epinephrine
• Norepinephrine
Dopamine
Plays a significant role
in emotional, mental,
and motor functions
Dopamine activates the
pleasure system in the
brain
Overproduction of
dopamine produces
feelings of euphoria→
strongly related to
drug-seeking behavior
Drugs that influence
dopamine are:
Dopamine has also been
associated with:
• Marijuana, nicotine, heroin,
and amphetamines
• Pathological gambling,
compulsive shopping, and
hypersexuality
Epinephrine
• During acute stress, epinephrine
(AKA: adrenaline) is released
• Part of the fight-or-flight system
• Speeds up coronary blood flow
and heart rate
Norepinephrine
• Inhibits target neurons
• Increases motor activity
Epinephrine & Norepinephrine
Substances of linked amino acids
Endorphins
Peptides
– Enkaphalins are endorphins in the brain
Actions are similar to morphine and heroin
Moderates one’s perception of pain
Brain emits endorphins during stress and pain
Also emits during strenuous exercise (i.e. runner’s high)
Central Nervous System
CONSISTS OF THE BRAIN AND SPINAL CORD
Located in the brain stem
Reticular
Activating
System
Plays a role in sleep and wake cycles
Filters out information as it enters the brain
– Allows a person to focus on important stimuli
Susceptibility to drugs are high
Implicated in hyperactivity
– Stimulants activate the RAS system which may help those
with hyperactivity disorder focus
Located near the base of the
brain
Comparable to a central
computer
Hypothalamus
Maintains
homeostasis
Stress, heart rate, body
temperature
Linked to chemical and
behavioral dependence
Part that
distinguishes
humans from
animals
Located in the
cerebellum
Essential for
thought
processes and
understanding
information
Influences
personality
and how we
interpret
emotions
Cerebral
Cortex
Limbic
System
The emotional center of the brain
Sorts and stores memory related to emotions
Brain’s reward circuit
Limbic System
T H E L I M B I C S Y S T E M R E G U L AT E S E M OT I O N S .
Medial
Forebrain
Bundle (MFB)
Along each side of the hypothalamus
Serves as a communication route between
the limbic system and the brain stem
The sensation of an orgasm starts here
When the MFB is stimulated, a person feels
pleasure
Located on both side
of the brain below
the cerebral cortex
Basal Ganglia
Maintains
involuntary muscle
control
Periventricular System
Comprised of nerve
cells above and to
either side of the
hypothalamus
Associated with
punishment and
avoidance behavior
People experience
discomfort when
the periventricular
system is activated
Brain Stem
Connects the brain and spinal cord
Consists of medulla oblongata, pons, and
midbrain
Regulates vital functions (heartrate, breathing,
blood pressure, vomiting reflex)
Serve as transmitting agents that link the body’s
extremities to the brain and spinal cord
▪ Somatic Nervous System
▪ Control skeletal muscles
Peripheral
Nervous
System
▪ Relay sensory information to the CNS
▪Autonomic Nervous System
▪ Regulates blood pressure, gastrointestinal and
urinary functioning, body temperature
▪ Sympathetic Nervous System
▪ Fight-or-Flight Response
▪ Parasympathetic Nervous System
▪ Allows the body to achieve a resting state following an
emergency
Endocrine System
• Release hormones
• Controlled by the hypothalamus
Cardiovascular System
Body Systems
• Consists of the heart and blood
vessels
• Alcohol can cause the heart muscle
to degenerate
• Cocaine increases heart rate and
blood pressure
• Smoked drugs interfere with ability
of the blood to deliver oxygen
Respiratory System
– Depressants slow down respiration
– Combing depressants can cause a synergistic
effect
Body Systems
– Stimulants increase respiration
Gastrointestinal System
– Consists of esophagus, stomach, and intestines
– Alcohol irritates and inflames the stomach,
small intestine, esophagus and pancreas
– Alcohol mixed with aspirin can cause excessive
internal bleeding→ the two shouldn’t be mixed
Factors
Influencing the
Effects of Drugs
(1 of 6)
The effects of a drug are based on their pharmacological or
chemical make-up. There are other factors that impact the effects
of a drug.
What do you think the other factors are?
Factors Influencing the Effects of Drugs
(2 of 6)
Age
• Infants and the elderly are more susceptible to the effects of drugs
• Tolerance for alcohol lessens as people age
Gender
• Females and males respond to drugs differently
• Women generally have a higher percentage of body fat and lower percentages of water
making them more sensitive to drugs
• Fat stores drugs and water dilutes the drugs
• Hormones impact the effects of drugs
Dosage
Factors
Influencing the
Effects of Drugs
• The amount of the drug consumed
• Threshold dose: smallest amount of the
drug required to produce the desired effect
• Effective dose: the amount of the drug
required to produce a specific response
• Lethal dose: the amount of the drug
required to result in death
(3 of 6)
Purity and Potency
• Purity: quality of a drug
• Potency: drug’s ability to produce a desired
effect
Dose-Response
Curve
A dose response curve refers to the
relationship between an effect of a
drug and the amount of drug given.
Dose response curves are essential to
understand the drug’s safe and
hazardous levels, so that the
therapeutic index can be determined,
and dosing guidelines can be created.
Drug Interactions
Factors
Influencing the
Effects of Drugs
(4 of 6)
– Some drugs cannot be mixed
– An estimated 25% of hospital admissions result from interactions
between alcohol and some other medication
– Effects can be additive, antagonistic, or synergistic
• Additive: the cumulative effects of two drugs
• Antagonistic: drugs that negate the effects of other drugs
• Synergistic: the combined effects of two drugs are greater than if they were
added together
Factors
Influencing the
Effects of Drugs
(5 of 6)
Tolerance
§ A state of progressively decreasing responsiveness of a drug
• Pharmacological tolerance: body adjusts to the presence of the drug
• Behavioral tolerance: a person learns to adjust to the presence of the drug
• Cross tolerance: people who develop tolerance to a drug will develop tolerance
to chemically similar drugs
• Reverse tolerance: a drug user will feel the desired effects from lesser amounts
Set and Setting
Factors
Influencing the
Effects of Drugs
(6 of 6)
• Set refers to the drug user’s psychological makeup, personality,
mood, and expectations when using the drug
• Setting refers to the social and physical environment in which
drugs are taken.
• Placebos- inert substances capable of producing an effect
• May provide relief for 30-40% of the patients they are prescribed for
• They are effective because of the expectations for the drug
Methods of Administration
Oral Ingestion
Injection
Topical
application
• primary site
of drug
absorption is
usually the
small
intestine
• Intravenous:
• transdermal:
into veins
• Intramuscular:
into muscle
• Subcutaneous:
under skin
applied to the
skin and
absorbed into
the bloodstream
Inhalation
• absorbed into
the bloodstream
via the lungs
• inhaled drugs
reach the brain
in 5 to 8 seconds
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