Homeostatic system and Drugs

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Homeostatic system and Drugs
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You have to think

• How do drugs work in your body?
• Why is your body susceptible to the influence of
  drugs and other substances?
• Why do human beings like to abuse drugs?

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Key Terms

• Homeostasis maintenance of internal stability or
  equilibrium
• Neurotransmitters chemical messengers released
  by neurons
• Hormones chemical messengers released into the
  blood by glands
• Endocrine system relating to hormones, their
  functions, and sources
• Neurons specialized nerve cells that make up the
  nervous system and release transmitters

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Learning Objectives

• The role of receptors in mediating the effects of
  drugs, hormones, and neurotransmitters.
• Distinguish between receptor agonists and
  antagonists.
• Neurotransmitters associated with drug addition.
• Identify which brain areas are most likely to be
  affected by drugs of abuse.
• How and why anabolic steroids are abused and the
  health impact attributed to abuse?

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Nerve cells (neurons)

• They can conduct bioelectric signals for long
  distances without any loss of signal strength.
• They possess specific intercellular connections
  with other nerve cells and with innervated
  tissues such as muscles and glands.
• Neurons can send discrete excitatory or
  inhibitory messages to their target cells.

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How do neurons communicate ?

• Neurotransmitters
• Receptors

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Common neurotransmitters

• Acetylcholine mild euphoria
• Norepinephrine excitation
• Epinephrine excitation
• Dopamine euphoria
• Serotonin (5HT) aggressiveness
• GABA (gamma-aminobutyric acid) sedation
• Endorphins mild euphoria, blockade of pain

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Plasma membrane barrier

• The membranes of cells (3-6 nm) are effectively
  impermeable to ions and polar molecules.

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Receptors

• Receptors proteins inserted in the plasma
  membranes of cells.
• They permit external chemical signaling
  molecules, the first messengers, to direct the
  activities of cells in a variety of ways with
  high specificity and precise control in terms of
  extent and duration.

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Key Terms

• Opiate receptors receptors activated by opioid
• Endorphins neurotransmitters that have
  narcotic-like effects
• Agonist a type of substance that activates a
  receptor
• Antagonists a type of substance that blocks a
  receptor
• Neurons specialized nerve cells that make up the
  nervous system and release transmitters

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Neurotransmitters in brain-Drugs of abuse

• Acetylcholine tobacco, nicotine
• Dopamine amphetamines, cocaine
• Endorphins narcotics
• GABA alcohol, diazepam, barbiturates
• Serotonin LSD (lysergic acid diethylamide)

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The PRP includes the dopaminergic pathway from
the ventral tegmental area (VTA) to the nucleus
accumbens (NA) and extending to the prefrontal
cortex. Dopaminergic pathways are activated by
the neurotransmitter, dopamine.
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The serotonin pathways in the brain
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Distribution of acetylcholine receptors in the
brain
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Stress and anxiety affect nicotine tolerance and
dependence. The stress hormone corticosterone
reduces the effects of nicotine therefore, more
nicotine must be consumed to achieve the same
effect. This increases tolerance to nicotine and
leads to increased dependence. Studies in animals
have also shown that stress can directly cause
relapse to nicotine self-administration after a
period of abstinence.
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In 1992, WHO for the first time, included tobacco
smoke in the chapter dedicated to "MENTAL and
BEHAVIOURAL DISORDERS caused by psychoactive
substances." Nicotine, which is responsible for
nicotine addiction, may be defined as a
psycoactive substance whose action consists
mainly in the activation of cerebral centers1)
The dopaminergic mesolimbic system is regarded as
the cerebral centre of pleasure and
gratification, since the subject tries to recover
the exhilarative effect of the product (CRAVING).
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• The central nervous system
• Reticular activating system
• Basal ganglia
• Limbic system
• Cerebral cortex
• Hypothalamus

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• The RAS is the attention center in the brain. It
  is the key to "turning on your brain," and seems
  to be the center of motivation. The RAS is
  connected at its base to the spinal cord where it
  receives information projected directly from the
  ascending sensory tracts. The brain stem
  reticular formation runs all the way up to the
  mid brain. As a result, the Reticular Activating
  System is a very complex collection of neurons
  which serve as a point of convergence for signals
  from the external world and from interior
  environment.
• RAS is very susceptible to the effects of drugs
• LSD, cocaine, amphetamine, alcohol,
  barbiturates

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BG are the primary centers for involuntary and
finely tuned motor functions, posture and muscle
tone. Damage to BG may cause Parkinsons disease.
Heavy use of tranquilizers for psychotic patients
can produce Parkinson-like syndromes.
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Limbic system It appears to contribute to the
characteristics of the individual and the
continuation of human life. The limbic system is
responsible for feeding behavior, fight and
flight reactions, aggression, the formation of
memories and the emotional life. The limbic
system receives input from many parts of the
cerebral cortex and contains association areas
where various aspects of sensory experience come
together to form a single experience.
Self-administration of stimulant drugs
(amphetamine cocaine) occurs in Limbic
system. Limbic systems transmitters dopamine,
NE, 5-HT.
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The endocrine system

• The endocrine system consists of glands which
  release hormone into the bloodstream.
• Regulation of metabolism, growth, tissue repair,
  sexual behavior, etc.
• Hormone has a slower onset, a longer duration of
  action, and a more generalized target.

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The abuse of hormones

• Androgens testosterone (natural androgen)
• Anabolic steroids
• They are abused by many athletes trainers
• Side effects early heart disease, sudden death,
  the increase of LDL, lower HDL, an increase in
  tendon injuries, liver tumors, testicular
  atrophy, gynecomastia, male pattern baldness,
  severe acne, premature closure of growth plates
  in adolescents, emotional disturbances and other
  significant health risks.
• Designer steroids tetrahydrogestrinone (2003),
  gastrinone, trenbolone

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ANABOLIC STEROIDSTHE ROAD TO THE GOLD OR THE
ROAD TO THE GRAVE