The Biologic Foundations of Psychiatric Nursing

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. NeuroanatomyOther 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 Parkinson’s, 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