Endocrine System

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Exocrine Glands

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Release enzymes to the external environment through ducts. Examples: sweat glands, sebaceous glands, mucous glands, digestive glands.

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Endocrine Glands

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Release hormones directly into body fluids.

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Endocrine System vs. Nervous System

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Have a slower, less direct, and longer lasting effect than the actions of the nervous system do. Do not move directly to the target, but rater are released into general circulation. All hormones need a receptor, whether it is on the the surface of the cell or inside.

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Peptide Hormones (General)

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Derived from peptides. Made in the Rough ER. Water soluble, therefore move freely in the blood, but cannot cross the plasma membrane. As a result, peptide hormones must bind to receptors on the membrane of the target cells.

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Potential actions of membrane bound receptors

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The receptor can become ion channels themselves, or they they can trigger an intracellular second messenger.

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Peptide Hormones (Specific - List)

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Anterior Pituitary: FSH, LH, ACTH, hGH, TSH, Prolactin. Posterior Pituitary: ADH, Oxytocin. Parathyroid: PTH, Pancreatic: Glucagon and Insulin.

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Steroid Hormones (General)

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Similar to cholesterol. Produced in the Smooth ER and the Mitochondria. Are lipids, therefore they require protein transport molecules in the blood, but can diffuse across the plasma membrane, and combine with a receptor in the cytosol. Receptor transports steroid to the nucleus, and it acts at the transcription level. Typical effect: increase certain membrane or cellular proteins within the effector (target cell).

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Steroid Hormones (Specific - List)

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Glucocorticoids and mineral corticoids of the adrenal cortex: cortisol and aldosterone. Gonadal hormones: estrogen, progesterone, testosterone.

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Tyrosine derivatives

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Thyroid hormones and Catecholamines of the adrenal medulla. Thyroid hormones are lipid soluble, the catecholamines are water soluble. Act accordingly with regard to the location of the receptor and means of working on the effector (target cell)

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Tyrosine Derivatives

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Thyroid: T3, T4 .Catecholamines: Epinephrine, Norepinephrine

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Anterior Pituitary

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Location: Brain beneath the hypothalamus. Hypothalamus controls the release of the AP hormones (via releasing/inhibitory hormones - travel to AP capillaries - their release controlled by nervous system)

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Anterior Pituitary Hormones

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hGH, ACTH, TSH, FSH, LH, Prolactin.

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Human Growth Hormone

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hGH: peptide. Stimulates growth in almost all body cells. Increases mitosis, cell size, rate of protein synthesis. Mobilizes fat stores, increases use of fatty acids for energy. Decreases use of glucose. Increases amino acid transport across cell membrane. Increases translation, transcription. Decreases protein and amino acid breakdown.

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ACTH (Adrenocorticotropic hormone)

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Peptide. Stimulates adrenal cortext to release glucocorticoids through second messenger system using cAMP. Release is stimulated by different types of stress. Glucocorticoids - Stress hormones.

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TSH (thyroid-stimulating hormone)

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Peptide. Stimulates thyroid to release T2 and T4 through a second messenger system (cAMP) Increases thyroid cell size, number, rate of secretion of the hormones.

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FSH

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Peptide. Growth of follicles in females. Sprem production in males.

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LH

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Peptide. Causes ovulation. Stimulates estrogen and testosterone secretion.

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Prolactin

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Peptide. Promotes lactation. Hypothalamus inhibits the release of prolactin. Suckling - stimulates hypothalamus to stimulate anterior pituitary to release prolactin - inhibts menstruation.

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Posterior Pituitary

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Located near the hypothalamus. Called neurohypophysis - made of support tissue for nerve endings that extend from the hypothalamus. Within these neural cell bodies of the hypothalamus oxytocin and ADH are produced and transported down axons to posterior pituitary where they are released. Both hormones = small peptides.

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Oxytocin

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Small Peptide. Increases uterine contractions during pregnancy. Causes milk to be ejected from the breasts.

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ADH

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Antidiuretic Hormones, vasopressin - small peptide. Causes collecting ducts of the kidney to become permeable to water. This reduces the amount of urine. Concentrates the urine. ADH increases blood pressure. Coffee and beer/alcohol - ADH blockers, which increase urine volume.

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Adrenal Glands

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Found on top of the kidneys. Consist of: Adrenal cortex and adrenal medulla.

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Adrenal Cortex

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Found atop the kidney. Outside portion of the gland. Secretes only steroids. Secretes small amount of sex hormones - significant for females, not males.

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Aldosterone

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Steroid. Mineral corticoid. Acts in the distal convoluted tubule and colecting duct. Increases Na+ and Cl- reabsorption and K+/H+ secretion. Creates net gain of particles in the plasma. This results in an eventual increase in blood pressure. Main effect: Na+ reabsorption and K+ secretion in collecting tubule. Blood pressure increase: secondary effect.

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Cortisol

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Steroid. Glucocorticoid. Increases blood glucose. Stimulates gluconeogenesis in the liver. Degrades adipose tissue to fatty acids for use in cellular energy. Decrease in use of glucose. Stress hormone. Diminishes capacity of immune system.

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Catecholamines

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Tyrosine derivatives of adrenal medulla. Epinephrine and norephinephrine.

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Epinephrine and norepinephrine.

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vasoconstrictors for internal organs and skin. Vasodilators of skeletal muscle. Longer effects in endocrine system than in the nervous system. Stress hormones.

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Thyroid

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located along the trachea in front of the larynx

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T3 and T4

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Lipid soluble tyrosine derivatives. Effect: increase the baal metabolic rate. Regulated by TSH. Difference between the two: one has 3 iodine atoms, the other has four.

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Calcitonin

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Large peptide hormone of the thyroid gland. Decreases blood calcium by decreasing osteoclast activity and number.

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Pancreas

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Insulin and Glucagon. Both peptide hormones.

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Insulin

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Peptide. Released by beta cells. Associated with abundance of energy - high energy nutrients in blood Released when blood levels of carbohydrates/proteins are high. Affects carb, fat, protein metabolism. With insulin: carbohydrates stored as glycogen in liver and muscles, fat stored in adipose tissue, amino acids taken up and made into proteins. Effect: lowers blood glucose level. Cells become highly permeable to glucose when insulin binds to receptors. Amino acids too.

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Glucagon

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Peptide hormone. Released by alpha cells. Opposite effect to insulin. Stimulates glycogenolysis: glycogen break down, and gluconeogenesis in the liver. Breaks down adipose at high concentrations. Raises blood glucose level.

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Parathyroid

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Four small parathyroid glands at the back of the thyroid. Releases PTH (parathyroid hormone)

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PTH

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Parathyroid hormone. Peptide. Increases blood calcium. Increases osteocyte absorption of calcium and phosphate from the bone. Stimulates proliferation of osteoclasts. Increases renal calcium reabsorption and renal phosphate excretion. Increases Ca/Ph uptake from gut. Regulated by calcium ion plasma concentration.