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SECOND REVISED
M07_EBY6927_02_SE_C07.QXD
12/17/07
12:02 PM
Page 95
Chapter 7
Psychobiology and Psychopharmacology
95
TABLE 7-1
Brain Anatomy and Function
BRAIN STRUCTURE
FUNCTION
Cerebral Cortex
IMPLICATIONS FOR MENTAL DISORDERS
The frontal lobes are affected in schizophrenia, which causes disordered thought
processes, lack of motivation.
Frontal Lobes
Prefrontal Area
Prefrontal area controls thought, inhibition,
goal-oriented behavior.
Motor Cortex
Motor cortex controls voluntary movement.
Pyramidal System
Pyramidal system or corticospinal tract
affects voluntary movement.
Extrapyramidal System
Extrapyramidal system affects movement
patterns, automatic motor functioning of
walking, and inhibits lower motor neurons
from overactivity (involuntary movement).
Basal Ganglia
In the basal ganglia, complex motor skills
(driving a car, activities of daily living [ADLs])
become so memorized that the ability to
perform them persists even after damage to
memory in the frontal lobes.
Abnormalities in the motor area (for
example, Parkinson’s disease) cause
movement disorders: rigidity, resting
tremor, slow movement, shuffling gait,
sudden jerky movement, and athetosis
(meaningless unintentional motions).
These movement disorders can also be
medication side effects (called
extrapyramidal side effects).
Temporal Lobes
Auditory receptive and auditory association areas, olfactory function, language
expression and interpretation
Aphasia (receptive or expressive) is
caused by damage in the temporal lobes.
Parietal Lobes
Sensory association
Occipital Lobes
Visual reception and visual association
Damage to occipital lobes can cause
blindness.
Controls feeling pleasure, feeding and drinking behavior, the fight or flight response,
aggression, submission, memory, body temperature, sexual behavior, emotions, and
motivation for behavior. It is responsible for
physical reactions to emotions. Limbic system also interprets olfactory sensations.
Hippocampus converts short-term memories to long term.Thalamus also has sensory
relaying and stimulus filtering functions.
Schizophrenia decreases limbic system
function (anhedonia, polydipsia [an
abnormal, persistent increase in thirst],
loss of motivation). Cocaine may stimulate
limbic system to provide pleasure.
Thiamine deficiency in alcoholics
(Korsakoff’s syndrome) affects limbic
function and causes loss of short-term
memory. Hippocampus degenerates in
Alzheimer’s disease.
Most of brain dopamine is synthesized
here.
Reduced dopamine activity causes the
extrapyramidal movement disorders of
Parkinsonism. Increased dopamine activity in schizophrenia.
Limbic System
Refers to limbic lobe and structures
that function with it: hippocampus,
amygdala, thalamus, hypothalamus,
brainstem nuclei, autonomic system
Brainstem
Midbrain
(continued)
SECOND REVISED
M07_EBY6927_02_SE_C07.QXD
96
Unit I
12/17/07
12:02 PM
Page 96
Foundations of Mental Health Nursing
TABLE 7-1
Brain Anatomy and Function (continued)
BRAIN STRUCTURE
FUNCTION
IMPLICATIONS FOR MENTAL DISORDERS
Pons
Conducts motor and posture information
to cerebellum. Controls reflexes.
Norepinephrine is made in the pons.
Norepinephrine activity is decreased in
depression and increased in
schizophrenia.
Medulla Oblongata
The medulla controls respiration, regulation
of blood pressure, partial regulation of
heart rate, vomiting, and swallowing.
Cerebral motor fibers collect here in the
shape of pyramids. Here the motor fibers
that begin in the cerebral cortex cross to
the opposite side of the corticospinal motor
pathway.
Damage to the medulla can stop spontaneous breathing.The fact that motor
fibers cross at the medulla explains why a
stroke affects the movement of the opposite side of the body from where the brain
damage occurred.
Reticular Formation
Sensory input is integrated in the reticular
formation and conducted to other brain
areas. It affects sensory, motor, and visceral
functions.The RAS allows screening/filtering of stimuli so the brain does not have to
react to all stimuli. RAS controls the sleepwake cycle.
Reticular formation may be involved in
attention deficit disorder (may be due to
an inability to filter sensory stimuli normally). If the RAS is disrupted and a person cannot sleep, psychosis can result.
Cerebellum mainly coordinates muscle
activity and function, and maintains equilibrium. It may be involved in
cognitive and behavioral functions
because of its connections to other brain
areas.
Cerebellar disorders cause ataxia (awkward
gait and uncoordinated intentional movement), intention tremor, decreased reflexes,
and nystagmus. Cerebellar ataxia may be
caused by malnutrition in severe, prolonged alcoholism.
Reticular Activating System
(RAS)
Cerebellum
at relieving client symptoms, and not because their mechanism of action is fully understood.
Figure 7-2. ■ Electron micrograph of brain neurons. Source:
Photo Researchers, Inc.
NEUROTRANSMITTERS
Neurotransmitters are chemical messengers that conduct
impulses from one neuron to the next. Figure 7-3 ■ illustrates neurotransmitter function. Review it carefully
because it is the basis for understanding treatment of
mental disorders with psychotropic drugs.
Human consciousness, behavior, learning, memory,
emotion, and creativity are all the result of physiological
brain functions. Neurotransmission is the communication between neurons conducted by neurotransmitter
chemicals. Neurotransmission must occur for the brain to
perform normally (Keltner, 2000).
The building materials for neurotransmitters are
brought into the body in food. The intake of adequate