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  • 1.The Biologic Foundations of Psychiatric Nursing Chapter 8

2. Biological Basis of Behavior Most human behaviors have a biological basis. Symptom expression = behavioral symptoms = brain dysfunction 3. Foundation of Biological Basis of Behavior Animal modeling Resembles humans in structure, function or genetics Can induce disorders Usually rats, mice Genetics Populations genetics Risk factors 4. Risk Factors Increased risk for developing a disorder May be genetic, biological, psychologic or social 5. Current Approaches to Studying Neuroanatomy and Neurophysiology Comparative compared with other life forms Developmental changes in nervous system throughout the life span Cytoarchitectonic distribution and arrangement of cells within various parts of brain Chemoarchitecture identification of neurotransmitters or chemicals Functional localization of functioning 6. Plasticity Ability of the brain to change Compensates for loss of function in specific area Nerve signals may be rerouted. Cells learn a new function. Nerve tissues may be regenerated. 7. Structural Neuroimaging Allows for visualization of the brain Commonly used techniques Computed tomography (CT) X-rays and computers Iodinated contrast materials administered IV Magnetic resonance imaging (MRI) Place patient in long tube with magnets Can reconstruct three-dimensional structures More costly and complicated than CT 8. Functional Neuroimaging Measurement of physiologic activities Two primary imaging procedures (Both require administration of radioactive materials.) Positron emission tomography (PET) Single photon emission computed tomography (SPECT) Patient can perform functions during this time. 9. Neuroanatomy of the CNS Cerebrum Left and right hemispheres Lobes of the brain Frontal Parietal Temporal Occipital Association Cortex 10. Neuroanatomy Subcortical Structures Basal ganglia Limbic system Hippocampus Thalamus Hypothalamus Amygdala Limbic midbrain nuclei 11. Neuroanatomy Other Important CNS Structures Extrapyramidal system Pineal body Locus ceruleus Cerbebellum 12. Autonomic Nervous System (Fig. 8.7) Neurons of ANS Efferent or motor system nerves (nerves moving away from CNS) Afferent or sensory (nerves moving toward CNS) Sympathetic Parasympathetic 13. Neurons and Nerve Impulses (Fig. 8.8) Soma cell body nucleus ribosomes endoplasmic reticulum Golgi apparatus vesicles lysomes mitrochodria Axons conducts impulses Dendrites receives impulses 14. Synaptic Transmission Neurotransmitters - Small molecules directly or indirectly responsible for opening or closing ion channels Neuromodulators - Chemical messengers that make the cell membrane more or less susceptible to effects of primary neurotransmitter Influx of CA++ into the neuron stimulates release of neurotransmitters into synapse. Receptors - Proteins for specific neurotransmitter, lock and key 15. Fate of Neurotransmitter After Action Removed by natural diffusion Reuptake into presynaptic terminal 16. Receptors Sensitivity can change, developing either a greater or lesser response to the neurotransmitter. Receptor subtypes Each major neurotransmitter has several different subtypes for the chemical, allowing for different effects on the brain. Each major neurotransmitter has several different subtypes (e.g., Dopamine, D1, D2, etc.). 17. Neurotransmitter Criteria Synthesized inside the neuron Present in the presynaptic terminal Released into the synaptic cleft, causing a particular effect on the postsynaptic receptors An exogenous form of the chemical is administered as a drug causes identical action. Chemical is removed from the synaptic cleft by a specific mechanism. 18. Neurotransmitters Excitatory causes activity to occur Inhibitory causes activity to decrease 19. Cholinergic Neurotransmitter Acetylcholine (ACh) Primary neurotransmitter of parasympathetic nervous system Part of sympathetic system Excitatory neurotransmitter Follow diffuse projections throughout the cerebral cortex and limbic system ACh involved in higher intellectual functioning and memory 20. Cholinergic Receptor Muscarinic receptors Many psychiatric medications block the muscarinic receptors (anticholinergic). Blocking the effects causes common side effects, including: dry mouth, blurred vision constipation, urinary retention, and tachycardia Nicotinic receptors 21. Biogenic Amines Synthesized from tyrosine Dopamine Norepinephrine Epinephrine Synthesized from tryptophan Serotonin Synthesized from histidine Histamine 22. Neurotransmitters Acetylcholine High intellectual functioning Dopamine Mesocortical and Mesolimbic Cognition, memory, emotion, auditory reception Nigrostriatal Influences extrapyramidal system Subserve voluntary movement Allows involuntary movement Tuberoinfundibular Endocrine functions 23. Dopamine (DA) Excitatory neurotransmitter Involved in cognition, motor and neuroendocrine functions Decreased in Parkinsons, increased in schizophrenia Pathways (Figure 8.11) Mesocortical, mesolimbic Nigrostriatal Tuberoinfundibular 24. Dopamine Receptors Five subtypes D1 and D5 - cortex, hippocampus and amygadala D2 found in nigrostriatal system D4 found mainly in cortex 25. Norepinephrine Widely distributed in the peripheral nervous system Excitatory neurotransmitters play a major role in mood states. Decreased NE associated with depression, increased NE associated with mania Pathways are named noradrenergic and are less delineated than dopamine pathways. Pathways in locus cereulus so involve in sleep, wake 26. Neurotransmitters Norepinephrine (Fig. 8.12) Sympathetic nervous system functions Sleep, wakefulness Reinforce learning Serotonin (5-HT) (Fig. 8.13) Sleep, wakefulness Control of food intake, hormone secretion, sexual behavior, mood and emotion, thermoregulation 27. Serotonin (5-HT) Excitatory neuron distributed within the cerebral cortex, limbic system, an basal ganglia, hypothalamus and cerebellum. Involved in regulation of emotion, cognition, sensory perceptions, sleep and appetite. Involved in control of food intake, hormone secretin, sexual behavior, thermoregulation and cardiovascular regulation Numerous subtypes of receptors 28. Histamine Recently identified as a neurotransmitter Originates in hypothalamus and projects to all major structures in cerebrum, brain and spinal cord Functions not well known Blocking produces side effects, such as sedation, weight gain and hypotension. 29. Aminobutyric Acid (GABA) Inhibitory transmitter Pathways almost exclusive in CNS, hypothalamus, hippocampus, basal ganglia, spinal cord and cerebellum Receptors: GABAA GABAB 30. Neurotransmitters Histamine Autonomic and neuroendocrine regulation Blocking causing sedation and weight gain GABA Control of neuronal excitement Inhibitory Glutamate Excitatory Neuropeptides 31. New Fields of Study Psychoendocrinology Psychoimmunology Chronobiology Diagnostic Approaches 32. Neurophysiologic Procedures Electroencephalography (EEG) Polysomnography Others