Brain Function and Psychotropic Effects

To understand how medications effect the body in both progressive and aversive ways, you have to have a basic understanding of the brain's functions. The parts in bold are ones most commonly affected by medications:

Brain – contains

        (a)              nerve cells (neurons) – carry out all brain functions: thoughts, emotions, behavior.

                (i)                Behavior is changed due to chemistry changes but chemistry changes can occur by complex factors and cellular activities simply by experiencing an event or action

        (b)              glial cells – provides nourishment for neurons and carries away waste products

        (c)                blood vessels-  

Brain sections

       (a)              Hindbrain

(i)                Brain stem – links brain to spinal cord; maintenance of involuntary life support functions with medulla oblongata

(ii)              cerebellum – receives info from muscles and joints and controls bodily functions operating below consciousness (balance, posture, etc)

(iii)            pons – links areas of brain to each other and to central nervous system

(b)              Midbrain – located above brain stem and monitors various sensory functions and is center of visual and auditory stimulation. Collections of cells on upper surface of midbrain relay specific info from sensory organs to higher levels of brain

(c)               Forebrain – largest section of brain

(i)                Limbic System – center of emotions; responsible for maintaining homeostasis of the body (regulating body temp, blood pressure, blood sugar, heart rate)

(a)                Hypothalamus – monitors info from autonomic nervous system and influences body bx

(b)                Thalamus – sensory info from body to brain

(c)                Hippocampus – converts info from short-term to long-term memory

(d)                Cerebrum – largest portion of brain and has highest intellectual levels

(i)                 Frontal Lobes – govern personality, emotion, reasoning and learning, motor control, decision making

(ii)               Temporal lobes – gross motor skills and integration of sensory input (hearing)

(iii)              Parietal lobes – long-term memory and info processing

(iv)              Occipital lobes – visual input

(d)              Other parts of Nervous system:

(i)                Spinal Cord –

(a)                part of autonomic nervous system– regulate unconscious and involuntary activities of internal organs and blood vessels. Has 2 subsystems

(i)                 Sympathetic System which functions when there is an expenditure of energy (such as exercising)

(ii)               Parasympathetic – prominent in body’s buildup of energy reserves (resting)

(b)                Peripheral Nervous System – neurons branching from spinal cord to muscles with messages from central nervous system to control voluntary muscle activity

(i)                 Pyramidal pathways manage fine motor activities

(ii)               extraphyramidal manage gross motor activities

 Messages pass through brain and nervous systems through neurons. Neurons consist of an axon (or axons) which passes messages to cells in the body and dendrites which receive signals from other neurons. They do not touch each other however. They are separated by a small space called a synaptic cleft. Messages are generated by electrical conductivity (nerve impulse). The transmission to a receiving cell is helped by chemical neurotransmitters released by axon into synapse and attaches to specific receivers (receptors) on the dendrite - much like a puzzle. The attachment of this neurotransmitter to the receiving cell creates an impulse along that cell that creates a reaction on the axon end of the neuron. The protein or neurotransmitter is then discarded either as waste through the glial cells or  goes through reuptake where it is released to create more neurotransmitters in the future.

 Finally, how drugs work: Medication modifies the natural processes in the synapses in certain areas of the brain. It alters activity in order to prompt neurotransmitter release or affects the binding of the neurotransmitter to the receptors. It can stop the reuptake process or alters the manufacturing of receptors. In effect, it becomes an agonist that either mimics the neurotransmitter or antagonist in which binds to the receptors but decreasing effect of neurotransmitter.

             Psychotropics tend to affect the following 6 out of 40 neurotransmitters:

(i)                Acetylcholine – affects arousal, attention, memory, motivation, and movement

(ii)              Norepinephrine – created in response to stress or arousal; influences alertness, anxiety, and tension

(iii)            Dopamine – influences emotional bx; cognition; motor activity; lack can cause physical tension, rigidity, movement difficulties (creating parkinsonian effects); regulates endocrine system

(iv)             Serotonin – sensory processes, muscular activity, thinking, calms nervous system, regulates moods; affects appetite, sleep, sexual bx

(v)               Gamma-aminobutyric Acid (GABA) – anxiety & modulation; motor activity, heart reflexes, anxiety

(vi)             Glutamate – researchers think it affects development of mental d/o’s

             Four Bodily Processes:

(i)                Absorption – drug enters bloodstream. Injected medications enter bloodstream more quickly than oral medications

(ii)              Distribution – after entering the bloodstream, the drug travels to the designated area by either dissolving into the plasma or attaching to proteins. Only the unbinded portion of a drug can enter the brain however so dosage is key in providing the right amount

(iii)            Metabolism – body breaks down chemical structure of drug and can be eliminated from body (usually takes place in the liver)

(iv)             Excretion – drug is eliminated from body (lowers concentration in body)

How drugs effect body – drug action is effected by age, weight, sex, and any organ problems or diseases that might interfere with efficiency of how the body handles the drug. Therapeutic index of a drug is the ratio needed to produce the effect wanted by taking the drug compared to the lowest average that produces toxic effects. The more toxicity, the higher risk for negative side effects. A high therapeutic index creates less of a chance that the client will accidently take more and put themselves in danger. Potency is the strength of the drug (dosage) and this is different for all drugs. Dose response is the increase in therapeutic effect with increase in amount but only up to a certain point in which they are ineffective or harmful. Lag time is the time it takes for the medication to start working. Tolerance, much like tolerance in substance dependence, means the body isn’t responding to the same dosage it used to. Adverse effects are the effects of a drug that do not have therapeutic value.

It is important to note the Placebo effect of medication in which a certain percentage of people will have results by just thinking that they are taking medication that will work. This positive thinking creates the results that they want.