FEEDBACK MECHANISM

FEEDBACK MECHANISM

  • Endocrine system activities control growth and development

    • Most actions maintain homeostasis

  • Feedback mechanism explained

    • Two types: negative and positive feedback

  • Negative feedback examples

    • The last step (response) inhibits the first step (stimulus), the feedback mechanism is controlled negatively

    • Regulation of body temperature, blood glucose, etc.

    • Negative feedback processes control the secretion of most hormones

  • Positive feedback mechanism

    • Last step stimulates the first step

    • Examples: blood clotting, birth labor, Na2+ influx causing depolarization, arousal state, and hemorrhagic shock.

  • Homeostasis maintains a constant internal environment

    • The term 'homeostasis' is derived from Greek words, "Homeo", which means Increase unchanging," and Stasis which means "standing." In its simplest form, it means "staying the same."

  • Various organs involved in maintaining homeostasis

  • Body temperature regulation

    • Skin's role in maintaining body temperature

  • Mechanisms for overheating and overcooling

  • Hypothalamus contains sensors that monitor the body temperature.

  • External temperatures vary by as much as 40°C . However, the human body temperature stays at about 37°C. Sweating, vasodilation, vasoconstriction, and shivering are used to accomplish this.

Overheating

  • Sweating

    • When the body temperature increases, the sweat glands in the skin are stimulated.

Overcooling

  • Vasodilation

    • As the bod temperature increases, the skin’s blood vessels dilate (become wider) and allow more blood to circulate near the surface.

  • Vasoconstriction

    • If the temperature of the body falls, the blood vessels in the skin are constricted.

  • Shivering

    • An uncontrollable burst of rapid muscular contraction in the limbs releases heat due to respiration in the muscles

  • Tissue fluid and Blood

    • The cells can absorb oxygen and food from it. It also accepts the carbon dioxide and other waste products produced by the cells. The blood system keeps the composition of the tissue fluid stable

Glucose Level Regulation

  • The pancreas contains cells that generate digestive enzymes.

  • When the concentration of glucose rises, the beta cells release insulin.

  • Insulin triggers the liver and muscles to remove any excess glucose from the blood and store it as glycogen.

  • It is secreted into the portal blood before glucose absorption.

  • As a result, glucose given orally stimulates more insulin than glucose given intravenously

  • When the concentration of glucose falls, the alpha cells release glucagon.

    o Glucagon stimulates the liver to burn its stored glycogen into glucose, then released into the bloodstream.

  • The gastro-intestinal tract controls the rate of glucose absorption.

  • It protects the body from a sudden and excessive increase in blood glucose in different ways.

  • The gradual evacuation of gastric contents allows a good time for absorption and utilization of glucose.

  • The secretion of gastro-intestinal hormones stimulates insulin secretion by B-cells of the pancreas.

  • The liver is the main organ responsible for glucose homeostatic mechanisms.