Comprehensive Study Guide on Homeostasis and Stress Response

A fight or flight response is an adaptive physiological response meant to preserve life by aiding individuals to escape dangerous situations.
Chronic, nonproductive stress may lead to various diseases over time.
Chapter Seven focuses on understanding stress, its impact, and implications on health and homeostasis.

Definition: Homeostasis refers to the purposeful maintenance of a stable internal environment within the body.
Homeostasis includes several regulating systems:
- Osmoregulation: Maintenance of constant osmotic pressure in fluids, controlling water and salt concentrations.
- Thermoregulation: Maintenance of a steady internal body temperature despite external changes.
- Blood Glucose Regulation: Maintenance of constant blood glucose levels.
- Blood Pressure Regulation: Keeping blood pressure within a normal range.
- Electrolyte Balance: Maintenance of calcium, potassium ions, and other electrolytes within a normal range.
Homeostasis requires a steady state condition, where any tendency towards change is met with mechanisms resisting that change, often through negative feedback mechanisms.

Stimulus: Initiates a chain reaction; e.g. low blood glucose, physical stress, or temperature changes.
Sensor/Receptor: Detects the stimulus; sends inputs to control centers.
Control Center: Compares data with a set point to determine an appropriate response.
Effector System: Executes a response, usually through glands or muscles to restore normalcy.

When monitored function (e.g. temperature, glucose levels) drops below the set point, feedback mechanisms prompt an increase back to normal levels.
When levels rise above set point, feedback mechanisms prompt a decrease back to normal levels.
Collaboration between multiple bodily systems (e.g., endocrine and nervous systems) often aids successful regulation.

Fasting blood glucose normal range: 99 mg/dL or lower.
Low Blood Sugar (Hypoglycemia):
- Stimulus: Drop in blood sugar level due to fasting.
- Response: Pancreas releases glucagon, activating hepatocytes in the liver to break down glycogen to glucose.
High Blood Sugar (Hyperglycemia):
- Stimulus: Increased blood glucose after eating.
- Response: Pancreas releases insulin, which enables glucose uptake to be converted into glycogen in the liver, lowering the blood sugar back to normal.

Normal Range for Blood Calcium: 8.6 to 10.3 mg/dL.
- When Blood Calcium Decreases:
- Stimulus: Blood calcium drops below 8.6 mg/dL.
- Response: Parathyroid glands secrete parathyroid hormone (PTH), which:
  - Stimulates osteoclast activity to release calcium from bones.
  - Acts on kidneys to increase calcium reabsorption to reduce urinary loss.
  - Activates vitamin D, enhancing dietary calcium absorption in intestines.
- When Blood Calcium Increases:
- Stimulus: Blood calcium rises above 10.3 mg/dL.
- Response: Thyroid releases calcitonin, which:
  - Inhibits osteoclast activity, preventing calcium release from bones.
  - Stimulates osteoblast activity to store calcium in bones.

Definition of Stress: A person experiences stress when demands exceed their coping abilities, initiating physiological and adaptive responses that can potentially become dysregulated, leading to pathophysiology (disease).
Stress responses are hardwired for protection against threats but can also arise from daily life demands.

Definition: Anything that elicits a demand for a response to maintain homeostasis.
Types of stressors:
- Noxious Stressors: Harmful physical stimuli (e.g., pain, trauma).
- Non-noxious Stressors: Joyful life events (e.g., weddings, vacations) that still induce stress.

Introduced by Dr. Hans Selye in 1936 based on experimental findings with rats, GAS outlines three stages of the stress response:
1. Alarm Stage (Fight or Flight): Instant arousal, body releases adrenaline and cortisol.
2. Resistance Stage: Body attempts to counteract alarm stage changes, reducing cortisol for normalcy, while keeping body alert.
3. Exhaustion Stage: Body's resources are depleted, leading to fatigue, depression, anxiety, and increased risk for stress-related illnesses.

Alarm Stage:
- Threat sensed by hypothalamus; triggers adrenaline (epinephrine) and cortisol release.
- Physiological responses include increased heart rate, respiration, and energy mobilization through gluconeogenesis.
- Decreased function in non-essential systems (digestive, urinary) to prioritize survival.
Hormonal Pathways:
- Immediate response via sympathetic nervous system (catecholamines).
- Longer-lasting adaptations through HPA (hypothalamus-pituitary-adrenal) axis, involving CRH and ACTH leading to cortisol release.

Potential Health Risks: Chronic stress is linked with:
- Mental Health Issues: Depression, anxiety disorders, burnout.
- Physical Health Issues: Immune dysfunction, cardiovascular diseases, metabolic issues.
Prolonged stress leads to:
- Increased hypertension, heart disease, infections, diabetes risk, and chronic inflammatory diseases.

Unhealthy Coping: Behaviors that feel good temporarily (e.g., substance abuse, social isolation) that lead to long-term negative effects.
Healthy Coping: More sustainable practices (e.g., exercise, meditation, journaling) that promote long-term resilience and wellness.

Studies interactions between psychological processes, the nervous system, and immune function.
Investigates how mental health impacts physiological responses and overall health outcomes.

Chronic stress can lead to immune suppression and increased susceptibility to infections through elevated cortisol affecting immune responses.

Stress can be beneficial in short bursts for motivation, but chronic stress leads to health deterioration.
Importance of recognizing signs of stress and effective stress management techniques to maintain homeostasis and overall health.