Module 2 Notes: Biological Basis for Mental Illness

Brain Structures

  • Cerebrum
    • Frontal Lobe: conscious movement, problem solving, and speech
    • Parietal Lobe: most anterior part; moderates social behaviors, goal setting, planning, and personality
    • Occipital Lobe: vision and visual processing
    • Temporal Lobe: hearing, language perception, and language comprehension
  • Brainstem
    • Composed of midbrain, pons, and medulla
    • Regulates heart rate, breathing, and sleep
  • Cerebellum
    • Involved in motor control and cognitive processing
    • Helps maintain balance by coordinating muscles from various muscle groups for complex tasks
    • Involved in coordination of eye movement
    • Benzodiazepines and alcohol can alter cerebellar function
  • Limbic System (the emotional brain)
    • Constituents: hippocampus, amygdala, basal ganglia, hypothalamus, thalamus
    • Role: integrates emotion with cognition and behavior; supports memory, motivation, and autonomic responses
    • Hippocampus: interacts with the prefrontal cortex (PFC) in forming new memories
    • Amygdala: processes fear and anxiety
    • Basal ganglia: supports motor responses via the extrapyramidal motor system and relies on dopamine to maintain muscle tone and motor stability
    • Movement involves basal ganglia control of muscles including the diaphragm, throat, tongue, and mouth

Thalamus and Hypothalamus; Autonomic Regulation

  • Thalamus
    • Filters sensory information before it reaches the cerebral cortex
  • Hypothalamus
    • Maintains homeostasis; regulates temperature, blood pressure, perspiration, libido, hunger, thirst, and circadian rhythms
  • Hypothalamic–Pituitary–Thyroid (HPT) Axis
    • Involved in regulation of nearly every organ system because hormones and catecholamines depend on thyroid status
    • Thyroid hormones can be used to treat depression or rapid-cycling bipolar I disorder
    • Thyroid hormones are also used as replacement therapy for hypothyroidism caused by lithium treatment
  • Autonomic Nervous System (ANS)
    • The hypothalamus sends instructions to the ANS, which is divided into the sympathetic and parasympathetic nervous systems

Limbic System and Its Functional Significance

  • The limbic system supports both physical and emotional needs
    • Hippocampus–PFC interactions are crucial for forming and retrieving memories
    • Amygdala’s role in processing fear and anxiety influences emotional responses
    • Basal ganglia influence motor control via the extrapyramidal system; dopamine maintains proper muscle tone and motor stability
    • Movement regulation also involves diaphragm, throat, tongue, and mouth muscles through basal ganglia circuits

Structure and Function of Nerve Cells (Neurons)

  • Neurons initiate signals and conduct electrical impulses along their length (neurotransmission)
  • Electrical signals within neurons are converted to chemical signals at synapses through the release of neurotransmitters
  • Neurotransmitters cross the synapse and bind to receptors on the postsynaptic neuron to either excite or inhibit it

Major Neurotransmitters and Their Functions

  • Dopamine (DA)
    • Fine muscle movement and integration of emotions and thoughts
    • Decision making
    • Stimulates the hypothalamus to release hormones (sex, thyroid, adrenal)
  • Serotonin (5-HT)
    • Mood regulation
    • Sleep regulation
    • Hunger regulation
    • Pain perception
    • Aggression and libido; hormonal activity
  • Norepinephrine (NE)
    • (Not detailed in depth in the transcript excerpt for this section; typically involved in arousal and attention; integrates with mood and stress responses)
  • Acetylcholine (ACh)
    • Learning and memory
    • Regulates mood; implicated in mania and sexual aggression
    • Affects sexual and aggressive behavior
    • Stimulates the parasympathetic nervous system
  • Gamma-aminobutyric acid (GABA)
    • Inhibitory neurotransmitter
    • Reduces anxiety, excitation, and aggression
    • May play a role in pain perception
    • Has anticonvulsant and muscle-relaxant properties
    • May impair cognition and psychomotor functioning

Synapses and Neurotransmission in Detail

  • Electrical signals within neurons become chemical signals at synapses via neurotransmitter release
  • Neurotransmitter release occurs at the presynaptic terminal and diffuses across the synapse
  • Neurotransmitters bind to receptors on the postsynaptic neuron, either exciting or inhibiting the postsynaptic cell

Stress, Brain Function, and Mental Disorders

  • Brain structures and functions can be altered by stress and in mental disorders
  • Structural changes due to chronic or severe stress
    • Dendritic retraction and reduced synaptic connectivity in the prefrontal cortex and hippocampus
    • Impaired memory, decision-making, and concentration; potential volume loss and functional decline in these regions
    • Amygdala often shows increased neuronal activity and growth, contributing to heightened anxiety and fear responses
    • Oligodendrocyte dysfunction and reduced neurogenesis reduce neural adaptability
  • Functional consequences of stress
    • Altered dopamine, serotonin, and glutamate neurotransmitter systems
    • Emotional dysregulation, impaired executive function, and increased vulnerability to depression, anxiety disorders, and schizophrenia
  • Neurobiological presentation of mental disorders (as discussed by Varcarolis)
    • Cognitive problems such as attention, memory, and decision-making related to neurobiological disruptions
    • Clinical assessment tools and evidence-based care strategies highlighted by Varcarolis
  • Mental disorders and neurobiology (examples)
    • Major depressive disorder, bipolar disorder, schizophrenia show structural changes (e.g., ventricular enlargement, cortical thinning) and functional deficits (e.g., reduced prefrontal activity, abnormal limbic activation)
  • Clinical implications for nursing
    • Assessment, diagnosis, and intervention planning are guided by understanding these neurobiological changes
    • Use of patient scenarios, case vignettes, and evidence-based care strategies
  • PANSS
    • The Positive and Negative Syndrome Scale is used in schizophrenia assessments to evaluate symptomatology

Brain Imaging and Its Clinical Utility

  • Functional neuroimaging modalities
    • PET (Positron Emission Tomography) and SPECT (Single Photon Emission Computed Tomography)
    • Use ionizing radiation to localize brain regions associated with perceptual, cognitive, emotional, and behavioral functions
    • Based on activity-related increases in local blood flow
    • Findings: decreased metabolism in unmedicated depression or schizophrenia; increased metabolism in OCD
    • PET/SPECT show dopamine system dysregulation in schizophrenia and monoamine loss in depression
    • fMRI (functional Magnetic Resonance Imaging)
    • Measures how well two brain regions communicate with each other (functional connectivity)
  • Clinical implications
    • In first-episode schizophrenia, striatal connectivity indices may predict response to antipsychotic medications

Psychotropic Drugs and Neurotransmitter Modulation

  • Pharmacokinetic interactions
    • Occur when one drug alters absorption, distribution, metabolism, or elimination of another, affecting plasma concentrations
    • Most arise from inhibition or induction of CYP450 enzymes
    • CYP450 inhibitors can increase drug concentrations and toxicity risk
    • CYP450 inducers can decrease concentrations, reducing efficacy unless the dose is increased
  • Pharmacogenetics
    • Tests provide information on which medications an individual can metabolize properly
    • Focus on pharmacokinetic genes (CYP450 family) and pharmacodynamic genes related to neurotransmitter regulation
  • Pharmacodynamic interactions
    • Occur when drugs act at the same or related receptor sites, leading to synergistic or antagonistic effects

Preparation and Readings (Learning Guide)

  • Before the course/lab: Concepts Relating to the Biological Basis of Mental Illness
    • Begin with reviewing the module objectives
    • Complete the assigned reading in the textbook
    • Review the PowerPoint presentation
  • Optional enrichment
    • Supplemental learning material provided
    • Videos: What Is Mental Illness? (NAMI) and Understanding the Biology of Mental Illness
    • Complete the Quiz for Modules 1 and 2; review in class
    • Complete Things to Know (review during class)
  • Readings
    • Varcarolis’ Essentials of Psychiatric-Mental Health Nursing, 5th Edition, Chapter 4, pages 33-42 (stop at antidepressant drugs)
  • Supplemental (enrichment only)
    • Neurotransmitters (document and additional related readings)
  • Additional resources referenced
    • What Is Biopsychology?
    • What Is Mental Illness: NAMI video (1:53)
    • Understanding the Biology of Mental Illness video (8:47)
  • Quizzes
    • Quiz for Modules 1 and 2 (2021 version) for review
  • Things to Know
    • Five things for Module 2 and five to start Module 3

Key Takeaways and Connections

  • The brain’s biological underpinnings of mental illness span structure, chemistry, and function, influencing assessment, diagnosis, and nursing care
  • Emotion, memory, and action are interlinked through the limbic system, hippocampus, amygdala, basal ganglia, hypothalamus, and thalamus
  • The HPT axis links neuroendocrine regulation to mental health, with thyroid status affecting mood and cognition
  • Stress can structurally and functionally alter brain regions, underpinning risk for mood and psychotic disorders
  • Imaging technologies provide insight into brain activity and connectivity that inform treatment decisions and prognostic expectations
  • Pharmacokinetic and pharmacodynamic interactions, plus pharmacogenetics, guide safe and effective psychotropic medication use
  • The nursing focus includes using cognitive, behavioral, and emotional symptom assessment to infer neurobiological status and plan care; case vignettes and evidence-based approaches (as highlighted by Varcarolis) support clinical decision-making