Endocrine System

Endocrine and Exocrine Endocrine functions: communication and control, via hormones Exocrine functions: secrete products into ducts that empty on a surface or into a cavity

Endocrine Secretes HORMONES into the blood Endocrine Organs are located throughout the body: head, neck, chest, abdomen, pelvis. Endocrine secretions (hormones)bind to specific cells ( target organ cell) that have receptors for that specific hormone.

Mechanisms of Hormone Action Two Major classes of hormones: Protein & Steroid Differ in mechanisms by which they influence target cells

Protein Hormones Protein hormones serve as “first messengers”..that is they send message to a specific target organ for functions to take place. Then a number of chemical reactions occur. These reactions activate molecules inside the cell…”second messengers” Second messengers provide communication within a hormones target cells.

Steroid Hormones Pass directly through cell membrane Enters the nucleus of the cell Forms hormone receptor complex that acts on the DNA New protein is formed in the cytoplasm that causes a specific effect in the target cell

Regulation of Hormone Secretion Controlled by homeostatic feedback Negative Feedback: reverses the direction of change in a physiological system. Ex: Pancreatic Insulin to lower blood sugar Positive Feedback: amplifies physiological changes. Ex: Oxytocin release during labor to advance birth

Endocrine Disease Caused by: Hypersecretion: too much hormone secreted Hyposecretion: too little hormone secreted. See Table 10-1, pages 302-303