• Endocrine vs Exocrine– Overview of hormone function:

• Regulation of growth & development• Homeostatic control• Control of reproductive system

– Three Characteristics are:• Host Gland• Hormones• Target Cells

– Nature of Hormones• Derived from steroid compounds

• Derived from amino acids

• Lipid-based hormones

• Control of Hormone Secretion– Hormonal – Ex. Hypothalamus secretes

hormones that affect the pituitary gland– Humoral – blood levels, bile and ion

concentrations stimulate hormone release– Neural – Adrenal Medulla

• Steroid Hormones-Lipid soluble- Diffuse through cell membranes; receptors

located within cell-Chemical structure is derived from or is similar to

cholesterol

Secreted by adrenal cortex, ovaries, testes

Nonsteroid Hormones

- Hormones travel in the blood to their specific target organs.

- Receptors are specific to hormones such that only the correct hormone will "fit" in the correct receptor.

• Each cell has 2,000 to 10,000 specific receptors

Alteration in Number of Receptors

Down-regulation—Decrease in number of cell receptors; less hormone can bind to the cell and higher concentrations of the hormone remain in the blood plasma

Up-regulation—Increase in number of cell receptors; more hormone can bind to the cell and lower concentrations of the hormone remain in the blood plasma

Key Points about Hormones

Hormones are classified into steroidal types (lipid soluble and formed from cholesterol) or nonsteroidal types (nonlipid soluble and formed from amino acids, peptides, or proteins).

Hormones are secreted in the blood and travel to sites where they exert an effect on only those target cells that have receptors specific to that hormone.

• Steroid hormones pass through cell membranes and bind to receptors within the cell. They synthesize protein via a process called direct gene activation.

THE PITUITARY GLAND

• Hormones of the Pituitary Gland

Posterior lobe Anterior lobe

Hormones of the Thyroid Gland

Triiodothyronine (T3) and Thyroxine (T4)

• Increase protein and enzyme synthesisPromote rapid cellular uptake of glucose

• Increase FFA availability for oxidation

The parathyroid gland produces parathyroid hormone (PTH), which regulates plasma calcium concentration and plasma phosphate by targeting the bones, intestines, and kidneys.

Hormones of the Adrenal Medulla

• Catecholamines—epinephrine and norepinephrineStimulated by sympathetic nervous system to prepare

you for immediate actionIncrease rate and force of heart contraction, blood

pressure, and respirationIncrease metabolic rate, glycogenolysis, and release of

glucose and FFA into blood

Hormones of the Adrenal Cortex

• Mineralocorticoids Maintain electrolyte balance in extracellular

fluids Include aldosterone• Glucocorticoids Maintain consistent plasma glucose levels

between meals Include cortisol• Gonadocorticoids Released in addition to those released by

reproductive organs but in lesser amounts

Hormones of the Pancreas

Insulin—secreted when plasma glucose levels are elevated (hyperglycemia)

Glucagon—secreted when plasma glucose concentrations are below normal (hypoglycemia); Increases blood glucose levels

Reproductive Hormones

Androgens Estrogens Testosterone

Opioids

• Endorphins– Exercise High or Runner’s High

Last Key Points about Hormones, Metabolism and Energy

Glucagon, epinephrine, norepinephrine, and cortisol help promote glycogenolysis and gluconeogenesis, thus increasing plasma glucose levels when needed.

Insulin facilitates glucose transport to the muscle fibers.

Cortisol accelerates lipolysis, releasing FFAs into the blood so they can be taken up by the cells and used for energy production.