Download Psychopharmacology and Other Biologic Treatments

The Biologic Foundations of
Psychiatric Nursing
Chapter 8
Biological Basis of Behavior
• Most human behaviors
have a biological
basis.
• Symptom expression =
behavioral symptoms
= brain dysfunction
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
Risk Factors
• Increased risk for developing a disorder
• May be genetic, biological, psychologic
or social
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
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.
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
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.
Neuroanatomy of the CNS
• Cerebrum
• Left and right hemispheres
• Lobes of the brain
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Frontal
Parietal
Temporal
Occipital
Association Cortex
Neuroanatomy
Subcortical Structures
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Basal ganglia
Limbic system
Hippocampus
Thalamus
Hypothalamus
Amygdala
Limbic midbrain nuclei
Neuroanatomy
Other Important CNS Structures
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Extrapyramidal system
Pineal body
Locus ceruleus
Cerbebellum
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
Neurons and Nerve Impulses
(Fig. 8.8)
• Soma – cell body
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nucleus
ribosomes
endoplasmic reticulum
Golgi apparatus
vesicles
lysomes
mitrochodria
• Axons – conducts impulses
• Dendrites – receives impulses
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”
Fate of Neurotransmitter After
Action
• Removed by natural diffusion
• Reuptake into presynaptic terminal
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.).
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.
Neurotransmitters
• Excitatory – causes activity to occur
• Inhibitory – causes activity to decrease
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
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
Biogenic Amines
• Synthesized from tyrosine
– Dopamine
– Norepinephrine
– Epinephrine
• Synthesized from tryptophan
– Serotonin
• Synthesized from histidine
– Histamine
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
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
Dopamine Receptors
• Five subtypes
• D1 and D5 - cortex, hippocampus and
amygadala
• D2 found in nigrostriatal system
• D4 found mainly in cortex
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
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
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
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.
Aminobutyric Acid (GABA)
• Inhibitory transmitter
• Pathways almost exclusive in CNS,
hypothalamus, hippocampus, basal
ganglia, spinal cord and cerebellum
• Receptors:
– GABAA
– GABAB
Neurotransmitters
• Histamine
– Autonomic and neuroendocrine regulation
– Blocking – causing sedation and weight gain
• GABA
– Control of neuronal excitement
– Inhibitory
• Glutamate
– Excitatory
• Neuropeptides
New Fields of Study
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Psychoendocrinology
Psychoimmunology
Chronobiology
Diagnostic Approaches
Neurophysiologic Procedures
• Electroencephalography (EEG)
• Polysomnography
• Others