Exam 1 Study Guide - Homeostasis and Stress Response System

Exam 1 Study Guide

Homeostasis

• Homeostasis: The purposeful maintenance of a stable internal environment.
  • Purpose:
  • Keeps cells alive and functioning.
  • Protects against disease.
  • Adapts to changes in the environment.
  • Examples of homeostatic variables:
  • Body temperature: 37°C (98.6°F).
  • Blood sugar levels.
  • Water balance.

Feedback Mechanisms

• Negative feedback: A process that counteracts change.

  • If a functional value increases or decreases, the feedback mechanism does the opposite.
  • Example:
    • Body becomes too hot → initiates sweating to cool down.
    • Blood sugar increases → pancreas releases insulin to lower sugar levels.

• Positive feedback: A process that amplifies change to promote a specific outcome.

  • Example:
  • Childbirth → stronger uterine contractions stimulate the release of oxytocin, leading to increased contractions to push the baby out.

Selye’s Stress Response System

• Stages of Stress Response:
  1. Alarm stage (fight or flight):
  • Generalized stimulation of the sympathetic nervous system and the Hypothalamic-Pituitary-Adrenal (HPA) axis.
  • Release of catecholamines and cortisol.
  1. Resistance stage:
  • The body selects the most effective and economical channels of defense.
  1. Exhaustion stage (emotional stage):
  • Resources are depleted, leading to a