Biological Psychology Lecture Notes

Biological Psychology Notes

Course Overview

  • Course Code: PSY 1202

  • Instructor: Norman Paul M. Deg-Aoan, RPM

  • Image Source: http://brainpiemedia.com/

Internal Regulations

  • Key Areas of Internal Regulation:

    • Temperature Regulation

    • Thirst

    • Hunger

Temperature Regulation

Definition and Purpose

  • Homeostasis: Regulation of body temperature to keep bodily variables within a fixed range.

    • Set Point: The ideal value for a given variable, which can change based on various factors (i.e., allostasis).

    • Negative Feedback: Mechanisms that reverse deviation from a set point to maintain homeostasis.

Mechanisms

  • Basal Metabolism: Involves maintaining a constant body temperature.

    • Types of Temperature Regulation:

    1. Poikilothermic: Body temperature matches the environment.

    2. Homeothermic: Body maintains a constant internal temperature.

    • Heat Generation and Loss:

    • Humans generate heat relative to body mass but lose heat based on surface area.

    • Mechanisms for heat loss include radiation and evaporation.

Brain Mechanisms

  • Preoptic Area (POA)/Anterior Hypothalamus (AH):

    • Located near the optic chiasm, it monitors body temperature and receives signals from skin and spinal cord temperature receptors.

    • Sends output to the raphe nucleus to facilitate physiological responses related to temperature.

Defense Against Illness

  • Role of Leukocytes: White blood cells respond to pathogens by releasing cytokines.

  • Cytokines and Fever:

    • They stimulate the vagus nerve, which signals the hypothalamus to increase body temperature by raising the set point through the synthesis of prostaglandin.

Thirst

Mechanisms of Water Regulation

  • Water Conservation:

    • The body conserves water by producing more concentrated urine and reducing sweat.

  • Vasopressin Release:

    • Produced by the posterior pituitary gland, it constricts blood vessels, raising blood pressure and balancing blood volume.

    • Known as antidiuretic hormone (ADH), it allows kidneys to reabsorb water, particularly during sleep, to preserve body water.

Types of Thirst

  1. Osmotic Thirst: Arises from the consumption of salty foods.

  2. Hypovolemic Thirst: Triggered by blood loss or sweating.

Osmotic Thirst Mechanism

  • Osmotic Pressure: Water moves across semipermeable membranes from areas of low solute concentration to areas of high solute concentration:

    1. Solutes become concentrated on one side of the membrane.

    2. Salty foods raise extracellular fluid sodium levels, causing water to leave cells into the extracellular fluid.

    3. Neurons detect water loss from cells and stimulate osmotic thirst.

    4. The kidneys work to excrete concentrated urine to remove excess sodium.

Thirst Regulation via Receptors

  • OVLT (Organum Vasculosum Laminae Terminalis):

    • Detects osmotic pressure and sodium levels in the blood, providing feedback on thirst needs prepares the digestive tract for potential water needs.

  • Subfornical Organ:

    • Regulates thirst by integrating signals from OVLT and other areas impacting vasopressin release and drinking behavior.

Allostasis in Thirst

  • Anticipation of Needs: Drinking patterns adjusted based on anticipated levels of salt intake and hydration needs during meals.

  • Cooling the Tongue: Reduces activity in the subfornical region, influencing both thirst and temperature regulation.

Hypovolemic Thirst Mechanism

  • Response to Blood Volume Drop:

    • Kidneys release renin, which converts angiotensin to angiotensin I and II, stimulating thirst and regulating blood pressure.

    • Receptors in the third ventricle respond to blood pressure changes, influencing thirst and behavior.

Sodium-Specific Hunger

  • Low Sodium Levels:

    • Trigger release of aldosterone, which aids in the retention of salt and water.

    • Impacts the tongue’s sensitivity to salt, influencing dietary choices and hunger signals.

Summary: Osmotic vs. Hypovolemic Thirst

  • Osmotic Thirst: High sodium concentration outside cells; relieved by drinking plain water.

    • Receptor location: OVLT in the third ventricle; hormone influence: vasopressin.

  • Hypovolemic Thirst: Triggered by low blood volume; relieved by water with solutes.

    • Receptor locations: Blood pressure receptors and the subfornical organ; hormone influence: Angiotensin II.

Hunger

Overview of the Digestive System

  1. Mouth: Chewing and mixing with saliva begin carbohydrate digestion.

  2. Esophagus to Stomach: Food is mixed with hydrochloric acid and enzymes for protein digestion.

  3. Stomach: Stores food; sphincter muscle opens to send food to the small intestine.

  4. Small Intestine: Digests carbohydrates, proteins, and fats; absorbs nutrients into the bloodstream.

  5. Large Intestine: Absorbs remaining water and minerals, preparing waste for excretion.

Common Misconceptions About Food

  • Impact of Sugar: No significant impact on activity or school performance; more linked to perception than actual effects.

  • Tryptophan and Sleep: Not solely responsible for sleepiness post-turkey consumption; largely tied to overeating.

Facts Regarding Food Consumption

  • Nutritional Impacts of Tryptophan: Essential for melatonin production, altered by carbohydrate intake to enhance brain access.

    • Seafood consumption linked to improved cognitive abilities in children; potential protective effects against cognitive decline in the elderly.

Short- and Long-Term Regulation of Feeding

  • Oral Factors: Evidence shows strong satisfaction from chewing; taste influences satiety, but satisfaction is complex.

  • Stomach and Intestinal Feedback:

    • Stomach distension signals fullness; vagus and splanchnic nerves convey nutrient availability to the brain.

    • Hormonal signals from the duodenum, such as CCK, play role in meal size control.

Hormonal Regulation of Feeding

  • Glucose Regulation: Glucose levels rise post-meal; insulin helps cells absorb glucose, while glucagon raises blood glucose when low.

    • Anomalous Feeding: High insulin, chronic hunger; diabetes leads to inadequate glucose absorption by cells, influencing eating behavior.

Theories of Hunger and Eating

  • Set Point Theory: Body maintains a set point for body fat levels; homeostatic signals drive compensatory actions to maintain weight.

  • Glucostatic Theory: Blood glucose levels directly influence hunger; dips below set point activate hunger responses.

  • Lipostatic Theory: Body fat levels control long-term hunger; involves adaptability in calorie intake.

  • Positive Incentive Perspective: Desire for food is driven by anticipated pleasure, influenced by various external factors like flavor and environment.

Brain Mechanisms in Hunger Regulation

  • Arcuate Nucleus: Regulates hunger and satiety via hormones like ghrelin (hunger signal) and CCK (satiety signal).

  • Paraventricular Nucleus: Modulates fuel utilization; damage leads to insensitivity to satiety signals.

  • Lateral Hypothalamus and Ventromedial Hypothalamus:

    • Lateral hypothalamus activates feeding behaviors; damage leads to aversion to food.

    • Ventromedial hypothalamus inhibits feeding; lesions cause overeating.

Eating Disorders

  • Anorexia Nervosa: Characterized by extreme underconsumption of nutrients, distorted body image, and extreme weight loss. Risks include high mortality due to starvation-related complications.

  • Bulimia Nervosa: Features cycles of bingeing followed by purging; can occur in individuals of any body weight; carries approximately a 4% mortality rate.

  • Obsessions regarding body image and extreme dieting behaviors reveal shared patterns between anorexia and bulimia, including psychological distress and compulsive behaviors.

Sources

  • Images from various educational sources related to neuroscience, psychology, and biology.

  • Comprehensive understanding influenced by literature on hunger and eating behaviors, including theories, regulations, and psychological perspectives.