4 Lecture Neurobiological Theory

4th Lecture
Neurobiological Theory
 As our understanding of the brain grows, evidence accumulates that most
human behaviors have a biological basis. So when common psychiatric
symptoms manifest as abnormal behaviors (eg, seeing things that are not there,
attempting suicide, talking in odd or unusual ways), we look to the brain.
 Because symptoms of psychiatric illness looks mainly as behavioral
disturbance, and because the behavioral symptoms are linked to anomalies in
brain functioning, psychiatric–mental health nurses need to understand disease
symptoms in relationship to brain function.
 Psychiatric–mental health nurses must be able to make the connection between
(1) patients’ psychiatric symptoms, (2) the probable alterations in brain
functioning linked to those symptoms, and the (3) rationale for treatment and
care practices. Knowledge of the CNS is an inescapable aspect of modern
psychiatric nursing.
 The study of molecular genetics in psychiatric disorders is in its infancy.
Because the exact genetic basis of psychiatric disorder remains unclear This
technique, called population genetics, involves the analysis of genetic
transmission of a trait within families and populations to determine risks and
patterns of transmission.
 The risk for a given disorder occurring in the general population can then be
compared with the risk within families and between groups of relatives
 These studies rely on the initial identification of an individual who has the
disorder and include the following principal methods:
 Family studies—analyze the occurrence of a disorder in first-degree relatives
(biologic parents, siblings, and children), second-degree relatives
(grandparents, uncles, aunts, nieces, nephews, and grandchildren), and so on.
 Twin studies—analyze the presence or absence of the disorder in pairs of
twins. The concordance rate is the measure of similarity of occurrence in
individuals with similar genetic makeup.
 Adoption studies—compare the risk for the illness developing in offspring
raised in different environments.
 Although no conclusive evidence exists for a complete genetic cause of most
 disorders, significant evidence suggests strong genetic contributions exist for
most psychiatric disorders are polygenic.
 This means that more than one gene is involved in producing a psychiatric
disorder and that the disorder develops from genes interacting, which produces
a risk factor, and environmental influences that lead to the expression of the
 The environmental factors may include stress, infections, poor nutrition,
catastrophic loss, complications during pregnancy, and exposure to toxins.
 Two basic neuroimaging methods are structural and functional neuroimaging.
 Structural neuroimaging techniques were the first form of neuroimaging that
allowed visualization of brain structures
 Structural images show what normal structures of the brain look like and
allow clinicians to identify tissue abnormalities, changes, or damage
Commonly used structural neuroimaging techniques include computed axial
tomography (CT) scanning: used to diagnoses tumors, effusions and
determine the size of the ventricles of the brain some sch. Persons have been
shown to have enlarged ventricles
 magnetic resonance imaging (MRI). Produce more tissue details. It can be
used to measure the size and thickness of the brain structures . It was found
that 7%reduction in cortical thickness in person with sch.
 Although these techniques are useful in identifying what the brain looks like,
they do not reveal anything about how the brain works.
 Functional Neuroimaging: Although structural imaging identifies what the
brain looks like, the scans do not show how the brain is working.
Functional neuroimaging techniques measure physiologic activities,
providing insight into how the brain works.
 Single photon emission computed tomography (SPECT) and positron
emission tomography (PET) are the primary methods used to observe
metabolic functioning.
Central Nervous System
 Cerebrum is divided into two hemispheres with four lobes each:
1. Frontal lobe (organization of thought, movement, memories, emotions,
moral behavior; arousal; attention; problem-solving and decision-making)
2. Parietal (taste, touch, spatial orientation)
3. Temporal (smell, hearing, memory, expression of emotions)
4. Occipital (coordination of language generation, visual interpretation)