Biological Basis for Understanding Psychopharmacology

Chapter 4

Biological basis related to number of factors-Genetics, neurodevelopment, drugs, infections,

psychosocial experience; there will eventually be an alteration in cerebral function that accounts for disturbances in pt’s behavior and mental experience

Psychiatric Mental Health Nursing-Goal is to understand biological basis of normal and

abnormal brain function and apply this understanding to care of individuals treatment with drugs

Psychiatric illness

Brain structures and functions Composed of interconnected specialized nerve cells

called neurons Cerebrum: mental activities, conscious sense of being,

conscious perception of external world, emotional status, memory, voluntary motor ability, language and ability to communicate

4 major lobes -Frontal: motor strip, supplemental motor area, Broca

area (voluntary movement and language) + prefrontal cortex (goal directed activities

-Parietal: sensory and motor -Occipital: vision -Temporal: auditory, memory processing and emotion

Brain structures and functions

Subcortical structures-Basal ganglia (4)

Striatum, pallidum, substantia nigra + subthalmic nucleus

Gray matter nuclei allows for smooth integration of emotions, thoughts + physical movement

Play a role in motor responses via extrapyramidal motor system which relies on neurotransmitter dopamine to maintain proper muscle tone and motor stability

Thalmus-Major sensory relay station to cortex

Hypothalmus-Maintains homeostasis (temp, BP, perspiration, sex drive, hunger,

thirst, circadian rhythms)-Send instructions to the autonomic nervous system which is

divided into sympathetic and parasympathetic systems -Sympathetic: increases HR, RR, BP to prepare for “fight or

flight.” Highly activated by amphetamines and cocaine, withdrawal from alcohol, benzodiazepines and opiates

-Parasympathetic: decreases HR +begins digestion Brainstem: made up of midbrain, pons + medulla

-Controls vital life functions Cerebellum (located posterior to brainstem)

-Controls balance and smooth muscle movement

Brain structures and functions

Measure structure, function and chemistry in brain-CT scan: series of x-rays to view brain structure-MRI: uses magnetic field and radio waves-higher

resolution than CT and can visualize smaller brain lesions

-PET: uses radioactive material to assess regional brain glucose and to secure images brain function (use in schizophrenia, depression and OCD)

-SPECT: similar to PET, poor resolution, less cost-fMRI: relies on magnetic properties , use is similar to

PET, higher resolution than PET.

Neuroimaging of brain structures and functions

Neurons (nerve cells)-Brain is composed of 100 billion-Essential feature of neurons is ability to conduct

electrical impulse from one end of cell to other (neurotransmission)

-Electrical signals within neurons are converted at synapse into chemical signals through release of molecules called neurotransmitters, which elicit electrical signals on other side of synapse, which enable information processing in the brain

Cellular composition of the brain

Chemical messengers between neurons by which one neuron triggers another

-4 major groups in brain Monoamines

-Dopamine, norepinephrine, serotonin, histamine Amino Acids

-GABA, glutamate Cholinergics

-Acetylcholine Peptides

-Substance P, somatostatin, neurotensin

Neurotransmitters

Produce effects through alteration of synaptic concentrations of neurotransmiters (dopamine, acetylcholine, norepinephrine, serontonin, histamine, GABA or glutamate)

Changes results from receptor antagonists (interfering with an action), agonists (mimicking an action), interference with neurotransmitter reuptake, enhancement of neurotransmitter release, or inhibition of enzymes

How psychotropics work

Typical (Neuroleptics): -Cause significant neurological effects-Also known as dopamine receptor antagonists (DRA)

because they bind to D2 receptors and reduce dopamine transmission

-D2 blockade can cause extrapyramidal side effects (dystonia, akathesia, tardive dyskinesia and neuroleptic malignant syndrome)

Chlorpromazine (Thorazine) low potency Haloperidol (Haldol) high potency Fluphenazine (Prolixin) high potency

Standard or typical antipsychotics

Atypical antipsychotics

Known as serotonin dopamine antagonists (SDA’s) because they have higher ratio of serotonin type D2 receptor blockade than typical DRA’s-Clozapine (Clozaril): one of 1st, not used due to

agranulocytosis-Olanzapine (Zyprexa): causes weight gain and

necessitates metabolic monitoring (wt, BMI, waist circumference, fasting glucose, lipid profile)

-Risperidone (Risperdal): can cause low BP/sedation