Chapter 4 Hormonal Control

Second Messenger

A molecule (e.g., cAMP) inside the cell that relays the signal from a non-steroid hormone (which cannot enter the cell) to the cellular machinery.

Major Glucose Regulatory Hormones

1. Glucagon (Pancreas): Increases blood glucose.2. Epinephrine/Norepinephrine (Adrenal Medulla): Increases glycogenolysis.3. Cortisol (Adrenal Cortex): Increases gluconeogenesis.4. Insulin (Pancreas): Decreases blood glucose (uptake).

Hormonal Response to Exercise

Insulin decreases, while Glucagon, Epinephrine, Norepinephrine, and Cortisol all increase to maintain blood glucose and fuel availability.

Adrenal Hormones

Medulla: Catecholamines (Epi/Norepi) → Fight or flight.Cortex: Cortisol (Stress/Metabolism) and Aldosterone (Fluid balance).

Aldosterone

Produced in the Adrenal Cortex. Promotes Sodium (Na+) retention in the kidneys (water follows sodium), increasing blood volume/pressure.

ADH (Antidiuretic Hormone)

Produced in the Posterior Pituitary. Promotes direct water reabsorption in the kidneys to prevent dehydration.

Thyroid Hormones (T3/T4)

Regulate metabolic rate (BMR), protein synthesis, and sensitivity to other hormones (permissive action).

Anorexigenic Hormones

Hormones that suppress appetite (e.g., Leptin, PYY, GLP-1).

Homeostasis Maintenance

Achieved primarily through Negative Feedback Loops (hormone secretion inhibits further secretion once the desired effect is achieved).