15.1 homeostasis

biology

Homeostasis

Homeostasis

Maintenance of stable internal environment within restricted limits in organisms.

Importance of Homeostasis

Keeps internal environment constant for metabolic reactions + ensures cells function properly to avoid damage.

Control Mechanisms

Homeostasis coordinated by receptors, coordinators + effectors throughout body.

Receptors

Sensory receptors detect stimuli and send signals to the brain about changes in the internal environment.

Coordinator

Receives and interprets information from receptors and sends instructions to an appropriate effector.

Effectors

Muscles or glands that act on signals from the brain to cause responses that reverse changes and regain equilibrium.

Negative Feedback Systems

Involve coordination between receptors and effectors to control conditions around set optimum points.

How Negative Feedback Works

Receptors detect change, triggering effectors to produce responses that reverse the initial change.

Blood Glucose Regulation

insulin + glucagon adjust blood glucose conc to maintain healthy supply of glucose.

Blood pH Regulation

Adjustments made to acid-base balance in blood to maintain optimum pH, preventing enzyme impairment.

Temperature Regulation

Adjustments like sweating or shivering maintain optimum temperature to prevent enzyme impairment.

Water Regulation

Water is removed or reabsorbed from blood/tissue fluid to maintain optimum water potential, preventing cell damage.

Positive Feedback Systems

Amplify changes rather than reversing them, leading to greater deviation from the optimum point.

How Positive Feedback Works

Initial change stimulates effectors, enhancing the change until an endpoint is met.

Blood Clotting

Clotting factors activate further clotting, demonstrating a positive feedback mechanism.

Childbirth

Oxytocin stimulates more uterine contractions, illustrating a positive feedback mechanism.

Cell Signalling

Process by which cells communicate, occurring between adjacent or distant cells.

Hormonal Communication

Hormones travel in blood to signal target cells that may be far away.

Cell-Surface Receptors

Allow cells to recognize and respond to hormones, facilitating communication.