Hormones and Hormone Action

1. Homeostasis

1.1. Nervous System

1.2. Endocrine System

2. Chemical Messengers

2.1. Endocrine cells (hormone secreting cells)

2.2. Exocrine glands (releases secretions into a duct)

3. Regulation

3.1. Neurocrine: neuron hormones released near another cells

3.2. Paracrine: secretion effects adjacent cells

3.2.1. Islet of Langerhans: clustered cells in pancreas that produce hormones to regulate glucose

3.3. Autocrine: hormone has direct effect upon the cell that secreted it

4. Growth factors

4.1. Binds to plasma membrane receptors

4.2. Must be present in extracellular fluid

4.3. Cytokines: secreted by white blood cells (activates phagocytic cells)

5. Classes of Hormones

5.1. 1. Protein & peptides: inc. insulin (released by pituitary gland; regulates gonads)

5.2. 2. Amines: derived from amino acids

5.3. 3. Steroid: lipid hormones (derived from cholesterol, gonads and adrenal cortex)

6. Mechanisms of Hormone Action

6.1. 1. Reception (receive)

6.1.1. 2. Signal transduction (cell signalling)

6.1.1.1. Response (reply)

7. Sites of synthesis

7.1. Hypothalamus

7.1.1. Endocrine fuctions

7.1.2. Initiates endocrine signals

7.2. Posterior pituitary

7.2.1. Regulates pituitary gland activity

7.2.2. Secretes oxytocin and ADH

7.2.2.1. ADH increases water reabsorption

7.2.2.2. Oxytocin helps uterine contractions and milk ejections

7.3. Anterior pituitary

7.3.1. stimulates hormones from other glands

7.4. Thyroid glands

7.4.1. Located on ventral trachea

7.4.2. Secretes T3 and T4

7.4.3. Regulates cellular metabolism

7.5. Parathyroid glands

7.5.1. Controls plasma calcium levels

7.6. Endocrine pancreas

7.6.1. Comprises 1-2% pancreatic mass

7.6.2. Secretes insulin and glucagon

7.7. Adrenal glands

7.7.1. Secretes adrenalins by adrenal medulla

7.7.2. 'flight-or-fight' response

7.7.3. Also secretes sex hormones

7.8. Gonads

7.8.1. Sex hormones

7.8.1.1. Androgen (male

7.8.1.2. Estrogen (female)

7.8.1.3. Progestins

7.9. Pineal

7.9.1. Secretes melatonin

7.9.1.1. Controls sensory activity

7.9.1.2. Light-dark cycles (biological rhythms)

8. Feedback Loops

8.1. 1. Receptor detects a change in stimulus and signals control centre 2. Control centre directs an effector mechanism to respond to signal to reverse the change

8.2. Connects response to stimulus

8.3. Negative: prevents excessive fluctuations (operates in endocrine and nervous)

8.4. Positive: reinforces stimulus (e.g. milk of mother)

9. Receptors

9.1. Specific receptor binds signal molecule

9.2. Usually located in plasma membrane of target cell (depends on lipid permeability)

9.3. Signal transduction: results in cell function change

10. Hormones entering cells

10.1. Steroid hormones: readily diffused and binds to receptors (some located in the cytoplasm)

10.2. Thyroxine: is lipid soluble but is ineffective until cytoplasmic enzyme removes one iodine

10.3. Intracellular receptors (located in the nucleus)

11. Hormones not entering cells

11.1. Large/polar molecules (can't permeate plasma membrane)

11.2. 'second messenger' (indirectly modifies activity of protein kinases)