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Page 1: Homeostasis and Homeostatic Mechanisms

Homeostasis maintains a stable internal environment despite external changes.
- Involves various physiological processes and mechanisms.
Temperature regulation is vital, with mechanisms to keep body temperature within normal ranges.
Feedback systems are critical for maintaining homeostasis:
- Negative Feedback: Output reduces effect of stimulus (e.g., body temperature).
- Positive Feedback: Enhances the initial stimulus (e.g., blood clotting).
Other mechanisms involve control systems that ensure biological rhythms are maintained.
- Involves neuroendocrine cells and hormonal responses.

Different physiological processes rely on hormonal and neural mechanisms.
Example mechanisms include:
- Hormonal signals impacting metabolic processes.
- Neural signals affecting immediate responses in tissues.
Example of hormonal feedback is the regulation of insulin and glucose levels.
Endocrine and nervous systems work together for complex homeostatic control.

Body temperature regulation involves:
- Sensor (thermoreceptors) detects changes.
- Integrator (hypothalamus) processes information.
- Effectors (sweat glands, muscles) enact changes.
Adaptations to temperature changes help maintain homeostasis, such as vasodilation and vasoconstriction.

Identification of temperature-related color changes in the body can indicate homeostatic status.
Influences from the environment affect the body’s thermoregulation.
Physiological responses can vary based on temperature exposure.

Heart activity and blood pressure are affected by physiological changes:
- Factors such as age, sex, exercise, and temperature influence heart rate.
- Understanding these variations is crucial for assessing cardiovascular health.

Key processes in respiration include:
- Ventilation: in and out air movement in lungs.
- Gas Exchange: diffusion of gases in alveoli and blood vessels.
Four components of respiration: pulmonary ventilation, alveolar gas exchange, gas transport, and systemic diffusion.

Blood pressure (BP) is defined as the force exerted by circulating blood against arterial walls:
- Systolic Pressure: pressure during cardiac contraction.
- Diastolic Pressure: pressure during relaxation phase.
BP is critical for perfusion and overall health.

BP influenced by various factors:
- Cardiac output and peripheral vascular resistance.
- Influenced by blood volume and viscosity.
Normal BP parameters include systolic < 120 mm Hg and diastolic < 80 mm Hg.

Blood pressure increases with:
- Age and physical exertion.
- Hormonal influences (sex differences).
Hypertension: defined as stage 1 > 140/90 mm Hg, stage 2 > 160/100 mm Hg.