Chapter 9 biopsych

Fascinating World of Biopsychology

Overview of Acetylcholine

  • Function of Acetylcholinesterase:

    • Breaks down acetylcholine into inactive components, terminating the signal at the neuromuscular junction.

  • Consequences of Acetylcholine Persistence:

    • If not removed, nicotinic acetylcholine receptors remain open.

    • Continuous influx of sodium leads to prolonged muscle depolarization and contraction, resulting in constant muscular contraction.

  • Acetylcholine Receptors Types:

    1. Nicotinic Acetylcholine Receptors: Ionotropic receptors involved in muscle contraction.

    2. Muscarinic Acetylcholine Receptors: Metabotropic receptors associated with effects like hallucinations and euphoria.

Visual System and Neuronal Responses

  • Primary Visual Cortex:

    • Responds to complex light stimuli, specifically:

    • Complex Cells: Respond to bars of light moving in a specific orientation.

    • Retinal Ganglion Cells:

      • On-Center Off-Surround Cells: Respond to changes in light, increasing or decreasing activity based on the position of light.

Hormonal Functionality: Aromatase and Estradiol

  • Function of Aromatase:

    • Converts testosterone into estradiol in both men and women.

  • Estradiol Production:

    • In adult women (post-pubertal, premenopausal), ovaries primarily produce estradiol and progesterone during the luteal phase.

    • Testosterone is produced first in the ovaries before conversion to estradiol by aromatase.

  • Implications of Estradiol:

    • Affects brain functions, including mood, taste sensitivity, and responsiveness to external stimuli.

    • Variations in estradiol levels can significantly influence psychological studies, especially related to menstrual cycles.

Pituitary and Ovarian Hormones

  • Pituitary Gland Functions:

    • Posterior Pituitary:

    • Produces vasopressin and oxytocin.

    • Anterior Pituitary:

    • Produces LH, FSH, TSH, ACTH, and other hormones critical for various physiological processes.

  • Ovarian Hormones:

    • Estrogen vs. Estradiol:

    • Estrogen is a group of compounds; estradiol is the bioactive form predominantly discussed.

    • Estradiol production correlates with follicle maturation during the menstrual cycle.

Menstrual Cycle Dynamics

  • Follicular Phase:

    • Follicles grow, starting small, low estradiol production early on and increasing as the follicle matures over the phase.

    • Early and late follicular phases correspond to low and high estradiol production, respectively.

  • Psychological Effects:

    • Estradiol levels impact feeding behavior, mood, and sensitivity, affecting results in psychological studies involving women based on their menstrual cycle stage.

Digestive System Overview

  • Basic Digestion Process:

    • Begins in the mouth, moves through the esophagus to the stomach where initial breakdown occurs, then proceeds to the small intestine (duodenum) for absorption.

  • Nutrient Breakdown:

    • Proteins → Amino Acids; Carbohydrates → Sugars; Fats → Simpler lipids.

Regulation of Food Intake

  • Cortical Influences:

    • In humans, cortical factors significantly influence eating behaviors—much of it unrelated to hunger.

  • Ghrelin:

    • Released by an empty stomach, increases hunger.

    • Not effective alone for treating obesity due to overriding cortical control.

  • GLP-1 Analogs:

    • In contrast to ghrelin treatments, GLP-1 medications like Wegovy adjust multiple bodily functions and support reduced food intake mechanisms.

Satiety Mechanisms

  • Factors Inhibiting Feeding:

    • Physical fullness, hormonal signals (CCK, PYY), nutrient presence affecting feeding cessation.

  • Hormonal Roles:

    • Leptin:

    • Released by fat, promotes reduced feeding behavior and increases metabolism; ineffective if receptors are faulty.

    • Insulin and PYY: Both contribute to decreasing food intake through various pathways within the body and brain.

Hypothalamus and Feeding Behaviors

  • Subregions:

    • Different areas of the hypothalamus mediate distinct behaviors related to feeding, thirst, temperature regulation, etc.

  • Ablation Techniques:

    • Ablation involves destroying specific brain regions to study behavioral changes; methods include electrolytic and excitotoxic lesions, each with different implications.

  • Functional Changes Post-Lesion:

    • Ventromedial and lateral hypothalamus lesions result in major weight changes and feeding behaviors.

Hormonal Feedback Loops in Hunger Regulation

  • NPY and POMC Neurons:

    • NPY neurons stimulate hunger (orexigenic) while POMC neurons inhibit hunger (anorexigenic).

    • Ghrelin activates NPY while leptin and GLP-1 activate POMC.

GLP-1 Overview

  • Action and Characteristics:

    • GLP-1 receptors widely distributed, influencing feeding and activity levels.

    • Shows promise in managing hunger and obesity-related behaviors but requires further research to address potential side effects.

Circadian Rhythms

  • Definition:

    • Circadian (from "circa" meaning "about" and "dien" relating to a day) rhythms govern numerous biological processes over a 24-hour cycle.

  • Impact on Physiology:

    • Influences drug metabolism, bodily functions, and research interpretations—important to consider in experimental psychology studies.

Data Analysis in Circadian Rhythms

  • Actograms:

    • Visual representation of an organism’s activity patterns throughout a sustained time course, assisting in understanding biological rhythms.

Summary of Obesity and Health Implications

  • Health Risks:

    • Obesity correlates with increased risks of illnesses such as type 2 diabetes and fatty liver disease.

  • BMI as Measure:

    • BMI is used as a simple index of body fat and health risk, though it has limitations regarding individual health assessments.

  • Cultural Influences:

    • Societal perceptions of weight can affect self-esteem and psychology, noting the importance of addressing obesity as a health issue rather than purely aesthetic.