9 - General principles of the humoral control of the physiologic functions. Telecrinia and paracrinia. Classification, synthesis and mechanism of action of the hormones. Control on the hormone secretion.

section

what is humoral stimulus

telecrinia and paracrinia

hormone classification

traditional classification

lipid soluble

water soluble

control of hormone secretion

other facts about hormones

what is humoral control

• control of hormone release in response to changes in extracellular fluids, e.g. ion concentration in the blood.

• E.g., increase in blood glucose levels → pancreatic release of insulin. → Blood glucose decreases→ signals pancreas to stop producing insulin.

telecrinia and paracrinia

• Telecrinia is related to the action of a hormone distant from its site of secretion.

• Paracrinia is the activity of cellular secretes on nearby cellular receptors.

hormone classification

1. 1. Lipid derivatives: → , estradiol testosterone

   • Steroid hormones (aldosterone, cortisol, androgens, estrogens, and progesterone) -derived from cholesterol.

   • Eicosanoids are derived from a fatty acid. ➢ Two families: prostaglandins and leukotrienes act as local hormones in most tissues of the body.

2. Amino acid derivatives (thyroid hormones, epinephrine, and norepinephrine)

3. Peptides and proteins (insulin, glucagon, oxytocin, ADH, all hypothalamic releasing and inhibiting hormones, and all anterior pituitary gland hormones).

traditional classification

1. classical hormones-secreted by endocrine cells into intestinal fluid from here they diffuse into the bloodstream

2. Neurohormones- provided by neuroendocrine cells and secreted at nerve terminals

3. Local hormones- secreted into interstial fluid and out in to the lungs.

4. Some act locally on neighbouring cells, some act on the cells they are secreted by- autocrine

lipid soluble

bind to receptors within the target cells. The activated receptor then alters function by turning specific genes on or off.—complex formed

water soluble

bind to receptors in a target cell’s membrane. “second messenger” (cAMP) is produced which, in turn, activates several enzymes that produce physiological responses.

control of hormone secretion

• Coordinated by positive and negative feedback mechanisms

• Negative feedback- hormones involved cause and effect. The cells that make the hormone detect a change and increase production of that hormone. Eg, when blood glucose low → causes to Blood glucose rise

• Positive feedback, effect of this causes more of it to be released → e g. oxytocin

• Neuroendocrine reflex-symp

other facts about hormones

1. Hormone will only affect certain cells called target cells.

2. Most body cells have receptors (proteins) that bind to hormones.

3. Only target cells for a certain hormone have receptors that bind and recognize that hormone.

4. Therefore, each hormone will influence only its target cells but not other cells in the body.

5. Once a hormone binds to a target cell, it causes that cell to respond in a manner that will maintain some characteristic of the internal environment in homeostasis.

6. After a hormone performs its function, it is broken down by target cell and eliminated from the body by the liver or kidneys.