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Neurobiologic theories and Psychopharmacology
Central Nervous System
Comprises^ of^ the^ brain,^ spinal^ cord,^ and^ associated nerves that control voluntary acts Brain consist of the cerebrum, cerebellum, brain stem, and limbic system Central Fissure (Rolando) separate frontal and parietal lobe Gyri Folds: raised, ridge-like folds on the surface of the cerebral cortex;more folds=faster transmission of information Lateral Fissure (Sylvius) divides frontal and temporal CEREBRUM Divided in 2 hemisphere; all lobes and structures are found in both halves except for pineal body, or gland (located between the hemisphere) Pineal Body Endocrine gland Influences activities of the pituitary gland, islets of Langerhans, parathyroids, adrenals, and gonads Corpus Callosum Pathway connecting the two hemisphere and coordinating their functions Left hemisphere Controls the right side of the body Center^ for^ logical^ reasoning^ and^ analytic functions (reading, writing, and mathematical tasks) Right hemisphere Controls left side if the body Center for creative thinking, intuition, and artistic abilities Cerebral hemispheres are divided into 4 lobes: frontal, parietal, temporal, and occipital Frontal Lobe Organization of thought, body movement, memories, emotions, and moral behaviors Integration of this information regulates arousal, focuses attention, and enables problem-solving and decision making Abnormalities results in schizophrenia, attention-deficient/ hyperactivity disorder (ADHD), and dementia Parietal Lobes Interpret sensation of taste and touch and assist in spatial orientation Temporal Lobes Centers for the senses of smell, hearing, memory and emotional expression Occipital Lobes Assist in coordinating language generation and visual interpretation (s/a depth perception) CEREBELLUM Located below the cerebrum Center for coordination of movements and postural adjustments Inhibited transmission of dopamine in this area is associated with the lack of smooth muscle coordinated movements in diseases such as Parkinson disease and dementia BRAIN STEM Includes the midbrain, pons, medulla oblongata and the nuclei for cranial nerves III to XII Medulla Located at the top of the spinal cord Vital centers for respiration and cardiovascular functions Pons Bridges the gap both structurally and functionally, serving as primary motor pathway Midbrain Connects^ pons^ and^ cerebellum^ with^ cerebrum Includes most of the reticular activating system (influences motor activity, sleep, consciousness, and awareness) and the extrapyramidal system (relays information about movement and coordination from the brain to the spinal nerves) Locus coeruleus Small group of norepinephrine-producing neurons in the brain stems Associated with stress, anxiety, and impulsive behavior LIMBIC SYSTEM Located above the brain stem Includes thalamus, hypothalamus, hippocampus, and amygdala Regulates activity, sensation, and emotions Hypothalamus Temperature regulation, appetite control, endocrine function, sexual drive, and impulsive behavior associated with feelings of anger, rage, or excitement Hippocampus and Amygdala Emotional arousal and memory Disturbance of limbic system have been implicated in a variety of mental illness, such as the memory loss that accompanies dementia, and the poorly controlled emotions and impulses seen with psychotic or manic behavior SPINAL CORD A^ column^ of^ nerve^ tissue^ that^ runs^ from^ the^ base^ f^ the skull down the center of the back Cervical (8 nerve pairs); Thoracic (12 nerve pair); Lumbar (5 nerve pair); Sacral ( nerve pair); Caudia equina
Neurotransmitters
Chemical substances manufactures in the neuron that aid in the transmission of information throughout the body Excite or stimulate an action in the cells (Excitatory) or inhibit or stop an action (inhibitory) Type Mechanism of action Physiologic effects Dopamine Excitatory Controls complex movement, motivation, cognition; regulates In the brain stem Synthesized
emotional response from tyrosine Norepinephrine (noradrenaline) Excitatory Causes changes in attention, learning ad memory, sleep and wakefulness, mood Most prevalent neuro- transmitter in the nervous system Located primarily in the brain stem Epinephrine (adrenaline) Excitatory Controls fight or flights response Serotonin Inhibitory Controls food intake, sleep and wakefulness, temperature regulation, pain control, sexual behaviors, regulation of emotions Derived from tryptophan (dietary amino acid) Histamine Neuromodu lator Controls alertness gastric secretions cardiac stimulation, peripheral allergic responses Some psychotropic drugs block histamine, resulting in weight gain, sedation, and hypotension Acetylcholine Excitatory or inhibitory Controls sleep and wakefulness cycle; signals muscles to become alert Found in brain, spinal cord, and peripheral nervous system Synthesized from dietary choline found in red meat and vegetables Neuropeptides Neuromodu lators Enhance, prolong, inhibit, or limit the effects of principal neurotransmitters Glutamate Excitatory Results in neurotoxicity if levels are too high GABA (Gamma- Aminobutyric Acid) Inhibitory Modulates other neurotransmitters
Brain Imaging Technology
Procedure Imaging method Results Duration Computed tomography (CT) Serial x-rays of brain Structural image 20-40 mins Magnetic Resonance Imaging (MRI) Radio waves from brain detected from magnet Structural image 45 minutes Positron Emission Tomography (PET) Radioactive tracer injected into bloodstream and monitored as client performs activities Functional 2-3 hrs Single-photon emission computed tomography (SPECT) Same as PET Functional 1-2 hrs Limitations of Brain Imaging Techniques Use of radioactive substances in PET and SPECT limits the number of times a person can undergo these tests. There is risk that the client will have an allergic reaction to substances. Some clients may find receiving IV doses of radioactive material frightening or unacceptable Imaging equipment is expensive to purchase and maintain; availability is limited Some persons cannot tolerate these procedures because of the fear or claustrophobia Many of the changes in disorders such as schizophrenia are at the molecular and chemical and chemical levels and cannot be detected with current imaging techniques
Neurobiologic Causes of Mental Illness
Genetics and Heredity Several mental disorders may be linked to a specific gen or combination of genes Non genetic factirs also play important roles Three types of studies are commonly conducted to investigate the genetic basis of mental illness Twin^ studies:^ to^ compare^ the^ rates^ of^ certain mental illnesses or traits in monozygotic (identical) twins, who have an identical genetic makeup, and dizygotic (fraternal) twins, who have a different genetic makeup Adoption studies: to determine a trait among biologic versus adoptive family members Family studies: to compare whether a trait is more common among first degree relatives (parents, siblings, and children) than among more distant relatives or the general population Stress and Immune System (Psychoimmunology) Examines the effect of psychosocial stressors on the body’s immune system Compromised immune system could contribute to the development of a variety of illnesses, particularly in populations already genetically at risk Immune system and the brain can influence neurotransmitters When^ the^ inflammatory^ response^ is^ critically^ involved^ in illnesses such as multiple sclerosis or lupus erythematosus, mood dysregulation and even depression are common Infection as a Possible Cause Existence of a virus that has an affinity for tissues of the CNS, the possibility that a virus may actually alter human genes, and maternal exposure to a virus during critical fetal development of the nervous system
Nurse’s Role In Research and Education
Reports in the media regarding new research and studies are confusing, contradictory, or difficult for clients and their families to understand Ensure that clients and families re well informed about the progress in these areas Help them to distinguish between facts and hypothesis Explain if or how new research may affects a client;s treatment or prognosis Be a good source for providing information and answering questions
Psychophramacology
Efficacy Maximal therapeutic effect that a drug can achieve Potency Amount of drug needed to achieve the maximum effect;
unnecessary facial movements are characteristics Anticholinergic side effects: include orthostatic hypotension, dry mouth, constipation, urinary hesitance or retention, blurred near vision, dry eyes, photophobia, nasal congestion, and decreased memory Using calorie-free beverages or hard candy may alleviate dry mouth and stool softener, adequate fluid intake, and the inclusion of grains and fruits in the diet may prevent constipation Increased blood prolactin levels: cause breast enlargement and tenderness in men and women; diminished libido, erectile and orgasmic dysfunction, and menstrual irregularities; may contribute to weight gain Metabolic Syndrome: increase risk for heart disease, diabeted, and stroke
Antidepressant Drugs
Monoamine hypothesis states that depression results from deficiency on one or more of the three monoamines namely serotonin, norepinephrine and domapine this monoamine depletion could also cause the postsynaptic receptors to upregulate thus leading to depression Monoamine hypothesis of gene repression suggest that there might be an abnormal functioning gene that is responsible for causingdepression Primarily used in the treatment of major depressive illness, anxiety disorders, the depressed phase of bipolar disorder and psychotic depression Off label uses: chronic pain, migraine headaches, peripheral and diabetic neuropathies, sleep apnea, dermatologic disorders, panic disorder, and eating disorders Interacts with the two neurotransmitters norepinephrine and serotonin (regulates mood, arousal, attention, sensory, processing, appetite) TRICYCLIC ANTIDEPRESSANTS “T for Tulog/ Tonight” Take at night First choice of drugs to treat depression even though they cause varying degrees of sedation, orthostatic hypotension, and anticholinergic side effects Mechanism of action: Inhibit reuptake of both serotonin and norepinerine by blocking both of their transporter Drugs : Amitriptyline, amoxapine, clomipramine, desipramine, doxepin, imipramine, maprotiline, nortripyline, protriptyline Indication : depression, migraine (amitriptyline,nortriptyline), prevention and treatment of neuropathic pain, insomnia (doxepin) Side effects: orthostatic hypotension(d/t inhibition of alpha receptors), dizziness, sedation(d/t inhibition of histamine receptor), anticholinergic effects (s/a blurred vision, dry mouth, constipation urinary retention) ,weight gain, and cardiac conduction abnormalities (due to blocking sodium channels and producing affects similar to antiarrhytmic agents) If missed dose: take it within 3 hrs of the missed dose or omit the dose for that day MONOAMINE OXIDASE INHIBITORS (MAOIs) Monoamine oxidase is a mitochondrial enzyme that degrades monoamines such as serotonin and norepinephrine Monoamine oxidase subtype A: preferentially metabolizes serotonin but also metabolize norepinephrine and dopamine Monoamine Oxidase subtype B: preferentially metabolizes dopamine “M for Morning” take in morning Low^ incidence^ of^ sedation^ and^ anticholinergic^ effects but need to use with caution because: A life-threatening effects, hypertensive crisis, may occur if the client ingest foods containing tyramine while taking MAOIs MAOIs^ cannot^ be^ given^ in^ combination^ with^ other MAOIs, tricyclic antidepressants, meperidine (Demerol), CNS Depressants, many antihypertensives, or general anesthetics MAOIs are potentially lethal in overdose and pose a potential risk in clients with depression who may be considering suicide Last choice due to high incidence of drug-drug interactions and drug food interaction Inhibited MAO enzymes can’t metabolize tyramine →built-up tyramine is taken up into synaptic nerve terminal where it acts as catecholamine releasing agents→large amount of catecholamine leads to hypertensive crisis Mechanism of action: Norepinephrine, serotonin, and dopamine are removed from the synapses after release by reuptake into presynaptic neurons; MAOIs inhibit the activity if MAO enzymes preventing breakdown of monoamine neurotransmitters==increasing their availability Drugs: isocarboxazid, phenelzine and tranylcypromine; Selegiline (selective inhibitor of MAO subtype B; depletes dopamine) Side Effects: daytime sedation, insomnia, weight gain, dry mouth, orthostatic hypotension, and sexual dysfunction Foods to avoid: mature or aged cheeses or dishes/ fermented foods, aged meats, beer, soy sauce or soybean condiments, yogurt, sour cream, peanuts, brewer’s yeast,monosodium glutamate SELECTIVE SEROTONIN REUPTAKE INHIBITOR (SSRI) “S for Sunrise” take first thing in the morning; if missed, take it up 8 hours after missed dose Replaced the cyclic drugs as the first choice in treating depression because they are equal in efficacy and produce fewer troublesome effects Drugs : Citaloparam, escitalopram, fluocetine, fluvoxqmine, paroxetine, sertraline Mechanism of action : Block the reuptake of serotonin in SERT→serotonin stuck outside→↑serotonin→improved mood Indication : SSRI and clomipramine are effective in the treatment of OCD; Treats depression, OCD, bulimia, panic disorder, PTSD
Prozac Weekly is the first and only medication that are given once a week as maintenance therapy for depression after the client has been stabilized on fluoxetine Side Effects : (Remember S for SSRI) Sleep disturbance (Insomnia), Sexual dysfunction(erectile dysfunction), Stomach Issues (nausea and vomiting), Serotonin Syndrome (too much serotonin= high BP, HR, muscle tremor and spasm) Meds with food for nausea; beta-blocker for akathisia; sedative--hypnotic or low-dosage trazodone for insomnia Serotonin Syndrome: result from taking an MAOI and an SSRI at the same time or if the client takes one of these drugs too close to the end of therapy with the other Symptom include agitation, sweating, fever, tachycardia, hypotension, rigidity, hyperreflexia, and in extreme reactions even coma and death SEROTONIN NOREPINEPHRINE REUPTAKE INHIBITORS (SNRI) Mechanism of action: Inhibit reuptake of serotonin via inhibition of serotonin transporter ; have the ability to additionally inhibit norepinephrine transporter which results in increased levels of both serotonin and norepinephrine which can then bind to the postsynaptic receptors ; enhances noradrenergic activity within CNS Side efffects: increased BP, HR Drugs : Venlafaxine, desvemlfaine, duloxetine, levomilnacipran Indication : depression, anxiety, and panic disorders; pain associated fibromyalgia; other pain causedby neuropathy REFERENCES: Pharmacology-Antidepressants-SSRis, SNRIs, TCAs, MAOIs,Lithium (MADE EASY) Speed pharmacology
