Homeostasis and Chemical Control in Mammals

• Mode of action of estrogen

  Estrogen, a steroid hormone, diffuses through the cell membrane and forms a hormone-receptor complex with the ER 𝛼 receptor in the cytoplasm. This complex then enters the nucleus and acts as a transcription factor.
• Mode of action of adrenaline

  Adrenaline acts through a secondary messenger model: 1. Adrenaline binds to its receptor forming a hormone-receptor complex. 2. This complex activates a G-protein, leading to a conformational change in the receptor. 3. The activated receptor activates adenylate cyclase, which converts ATP to cyclic AMP (cAMP). 4. cAMP activates the protein kinase A pathway, resulting in glycogenolysis.
• Time lag in hormone response


  The time required for hormone production, transport in the blood, and causing the required changes to the target proteins.
• Separate negative feedback mechanisms


  Additional negative feedback mechanisms that provide more control, especially in cases of 'overcorrection', which could lead to deviations in the opposite direction from the original one.
• General stages of negative feedback

  The process of negative feedback involves the detection of a deviation from the normal conditions by receptors, coordination of corrective mechanisms by a coordinator, and the action of effectors to restore the internal environment to its normal conditions.
• Hormones

  Proteins secreted by endocrine glands, transported in the bloodstream, and having a specific tertiary structure that complements receptors on certain cells.
• Positive feedback


  A mechanism in which a fluctuation or deviation from the normal level triggers changes that result in an even greater deviation from the normal level.
• Negative feedback


  Self-regulatory mechanisms that act to counteract any fluctuations or deviations from the normal conditions, bringing the internal environment back to its optimal state.
• Blood water potential stability

  The prevention of osmotic lysis or crenation of cells by maintaining a stable water potential in the blood.
• Blood pH stability

  The regulation of the pH level in the blood to maintain an optimal environment for enzyme-controlled reactions and other protein functions, preventing acidic pH conditions.
• Core temperature stability

  The maintenance of a stable body temperature to ensure that enzyme-controlled reactions occur at an optimal rate and to prevent temperature extremes that could be harmful to the body.
• Homeostasis


  The process of maintaining a stable internal environment within set limits around an optimum in order to support proper bodily functions.