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Endocrinology;Immunology

Exocrine glands release enzymes/hormones to the external environment throughducts into the lumen of an organ.Endocrine glands release hormones directly into body fluids.Pancreas functions as an exocrine AND endocrine gland.Hormones act by binding to receptors, there are specific receptors for specific hormones.Even very low concentrations of hormones in blood have significant effects on the body.Generally speaking, the endocrine system alters metabolic activities, regulate growth and development and guide

reproduction.

Three Types of Hormones1) Peptide Hormones2) Steroid Hormones3) Tyrosine Derivatives

Peptide Hormonesmanufactured in the rough ER (theyre proteins, duh) as a preprohormone, that is larger thanthe active hormone, the preprophormone is cleaved in the ER lumen becomes a prohormone enters golgi iscleaved and packaged in the golgi and released via exocytosis.

Peptide Hormones are water soluble and usually bind to a receptor on the effector (target cell).Can activate a secondary messenger cAMP, cGMP or calmodulin, secondary messenger then activates/deactivates

enzymes in the cell, and or ion channels, and often creates a cascade of chemical reactions.

HORMONES FOR THE MCAT

- Anterior pituitary hormones: FSH, LH, ACTH, hGH, TST, Prolactin.- Posterior pituitary hormones: ADH and oxytocin.- Parathyroid: PTH (parathyroid hormone)- Pancreatic hormones: glucagon and insulin.

Steroid hormones come only from adrenal cortex, gonads or placenta. Steroids are lipids and can diffuse throughmembrane and act on nucleus. Steroid hormones are made in the smooth ER. Steroid hormones interact with a

receptor in the cytosol that transports the steroid into the nucleus, where the steroid acts on the transcription level

the effect of a steroid hormone increases certain membrane proteins or cellular proteins in the effector.- Are the gonadal hormones and the corticoids.Tyrosines are the thyroid hormones and the catecholamines (epinephrine, norepinephrine). Thyroid hormones are

lipid soluble. Catecholamines are water soluble, and act with a secondary messenger.

The rest are peptides.Hormones respond to a condition, so high blood insulin levels are caused by high blood glucose levels, NOT by

unremitted excretion of insulin. And high insulin levels do not typically create low blood glucose levels.

If ADH holds water in the body, decreasing urine output and increasing blood pressure (water retention), does aperson with high blood pressure have a high ADH blood level, or a low ADH blood level?The answer is low ADH level

since BP is already high, the body is hold back excretion of ADH in response to the high blood pressure.

A secondary effect of aldosterone is to increase blood pressure, would expected aldosterone levels be high or low in aperson with low blood pressure?Aldosterone levels would be high because the body would want to counteract the

low blood pressure.

SPECIFIC HORMONES

Anterior pituitary is located under the hypothalamus, the hypothalamus controls the release of the anterior pituitaryhormones with releasing and inhibitory hormones of its own.

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Anterior Pituitary Hormones

- Human growth hormone (hGH) a peptide, stimulates growth in almost all cells by increasing mitotic frequencycell size, rate of protein synthesis, mobilization of fat stores, increasing use of fatty acids, and decreasingglucose

usage.

- Adrenocorticotropic hormone (ACTH) a peptide, stimulates the adrenal cortex to release glucocorticoids viacAMP. ACTH release is stimulated by stress, glucocorticoids are stress hormones.

- Thyroid stimulating hormone (TSH) a peptide, stimulates the thyroid to release the tyrosine hormones.- Follicle stimulating hormone (FSH) stimulates gonadal production of steroid hormones.- Leutinizing hormone (LH) stimulates gonadal productin of steroid hormones.- Prolactin a peptide, promotes lactation in the breasts.

Posterior Pituitary

- Oxytocin a small peptide that increases uterine contractions during pregnancy, causes milk to be ejected from thebreats.

- Antidiuretic hormone (ADH) a small peptide that induces water reabsorption and concentrates the urine, thewater reabsorption also increases the blood pressure.

Adrenal Cortex

Adrenal glands on located on top of the kidneys. The adrenal cortex is the outer portion of the gland.The cortex secretes only steroid hormones.Two types of steroids secreted by the cortex: mineral corticoids and glucocorticoids.

- Aldosterone a steroid hormone and mineral corticoid that acts to dilute urine by increasing Na+ reabsorption andincreasing K+ secretion. This increases the number of particles in the blood plasma, which eventually increase

blood pressure. Blood pressure increasing, is a secondary affect.

- Cortisol a steroid, is a glucocorticid that increases blood glucose levels by stimulating gluconeogenesis (creationof glucose) in the liver. Also degrades adipose tissue in the use of glucose by cells. Cortisol is a stress hormone

(think of that commercial).

- Catecholamines , this is essentially just epinephrine and norepiphrine, these affect the sympatic nervous systemcausing constriction of the vessels, dilation of the pupils, slows digestion. These are the flight or fight hormones.

Thyroid- T3 and T4 (the tyrosine hormones), both are lipid soluble and function to increase basal metabolic rate.- Calitonin a large peptide released by the thyroid gland, decreases blood calcium level by increasing osteoclas

activity.

Pancreas

- Insulin a peptide hormone, released by B cells of the pancreas. Is released when blood levels of carbohydrates areor proteins are high. The net effect of insulin is to reduce blood glucose levels.

- Glucagon a peptide hormone, released by A cells of the pancreas. The effects are essentially opposite of insulin,glucagon stimulates glycogenolysis (breakdown of glycogen), and gluconeogenesis. Breaks down adipose tissue,

increasing fatty acid concentration in the blood. RAISES BLOOD GLUCOSE LEVELS.

Parathyroid

- Parathyroid hormone (PTH) increases blood calcium levels, by renal calcium reabsorption.

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MECHANISMS OF ACTION

- Hormones can act by either passing through the membrane of target cell and binding to specific target protein, orby binding to a specific receptor on the membrane.

- After a hormone is bound to a specific membrane receptor, the resulting complex undergoes a conformationachange that allows for the synthesis of an intracellular messenger. This second messenger passes the information

mediated by the hormone (the hormone was the first messenger) to some specific reaction within the cell.

- During times of stress, glucose is mobilized from its stored form (glycogen) to be used as a source of energy.

Immunology

T cells mark bacterial membrane, and macrophages do the actual killing. Injury to tissue results in inflammation, which includes dilation of blood vessels, and increased permeability o

capillaries, and the migration ofgranulocytes and macrophages to the inflamed area.

B cells make antibodies (1 b cell will one make 1 type of antibody) which recognize and bind foreign particles, B cellsare made in BONE MARROW.

T cells are made in the THYMUS.