The endocrine system

-coordinates various activities of the body by utilizing chemical messengers to coordinate

*utilizes hormones that are typically released directly to the bloodstream to then interact with cells throughout the body

-reacts pretty slowly as it takes time to travel through the circulatory system and to its desired organ

-cells have specific receptors, like a lock and key, so certain cells react to certain hormones

Hormone- an organic chemical produced by one set of cells that affects a different set of cells

*many are proteins coded by genes and synthesized at the ribosomes, then packaged into vesicles and secreted into the plasma membrane

peptide hormone- derived from proteins, peptides, or catecholamines. They activate existing enzymes in a cell. act quickly for a short time

steroid hormones- derived from cholesterol by metabolic reactions. act slowly, but for a longer time. stored in fat droplets in the cytoplasm until release at the plasma membrane. enter freely, then bind to receptors, which activates specific genes.

endocrine glands- ductless, secreting the contents directly into the bloodstream

exocrine glands- ducts that secrete their contents into an epithelial surface

primary endocrine organs- secrete hormones to chemically regulate body functions

*include the hypothalamus, pituitary gland, pineal gland, thyroid gland, parathyroid glands, adrenal glands, and pancreas

adrenal gland- located superiorly to each kidney, contains an inner portion (medulla) and an outer portion (cortex)

thyroid gland- located in the neck, attached to the trachea just below the larynx

parathyroid glands- four, embedded into the surface of the thyroid gland, produce parathyroid hormone

pancreas- long organ between the kidneys, near the duodenum of the small intestine

secondary endocrine organs- secrete organs as a secondary function

*includes the heart, kidneys, gonads, and thymus

thymus- lobular gland that lies in the upper thoracic cavity

negative feedback- how most hormones are controlled, helps maintain homeostasis by acting like a thermostat, turning it on and off as it detects it is needed.

positive feedback- enhances or increases the amount of hormone being released.

hypothalamus- portion of the brain that regulates internal environment and homeostasis

pituitary gland- lies below the hypothalamus and is divided into two sections

posterior pituitary- connected to the hypothalamus by a stalk-like structure

neurosecretory cells- neurons in the hypothalamus that produce hormones and respond to neurotransmitters. stored in and released from the posterior pituitary.

ADH- antidiuretic hormone (aka vasopressin), stored in the axon endings of the posterior pituitary, promotes absorption of water

oxytocin- induces and promotes labor

anterior pituitary- controlled by the hypothalamus, secrets growth hormone, prolactin, melanocyte stimulating hormone, thyroid stimulating hormone, adrenocorticotropic hormone, follicle stimulating hormone, and luteinizing hormone.

three tiered relationship- hypothalamus produces hormones, they travel to the anterior pituitary to produce specific hormones, those control the thyroid, adrenal cortex, and gonads, these glands then produce hormones that regulate the secretion of hormones.

growth hormone- causes cell growth and division, and protein synthesis. determines the height and bone structure of a person.

prolactin- causes the development and production of milk. also helps with carbohydrate and fat metabolism

melanocyte stimulating hormone- stimulates melanocytes to increase synthesis of melanin

thyroid stimulating hormone- stimulates the thyroid gland to produce T3 and T4

adrenocorticotropic hormone- stimulates adrenal cortex to produce cortisol

gonadotropic hormones (FSH and LH)- stimulate the gonads

thyroxin- (T4) secreted by the thyroid. contains iodine (with T3) at a large concentration. increases the metabolic rate in cells, necessary for proper growth

goiter- enlarged thyroid due to lack of iodine

congenital hypothyroidism- individuals who have had hypothyroidism since birth. shows reduced growth, sexual immaturity, and abnormal protein metabolism

calcitonin- produced by the thyroid gland, lowers the levels of calcium in the blood and deposits it into the bone

parathyroid hormone- increases calcium levels and decreases phosphate. (stimulates calcium absorption in intestines, retains calcium by excreting phosphate at kidneys, promotes osteoclast activity)

tetany- the body shakes from continuous muscle contraction. caused when PTH isn’t produced in response to low blood calcium.

adrenal medulla- secretes epinephrine and norepinephrine during stress.

adrenal cortex- essential to life. makes glucocorticoids and mineralocorticoids.

cortisol- glucocorticoid, under control of anterior pituitary, promotes hydrolysis of muscle proteins to amino acids in the blood. favors metabolism of fatty acids rather than carbohydrates, raises blood glucose levels, reduces inflammation

aldosterone- mineralocorticoid, not under control of anterior pituitary, regulates sodium (absorption) and potassium (excretion) ion levels in the kidney, maintains blood pressure

pineal gland- in the third ventricle of the brain and receives nerve impulses by the eyes, follows a circadian rhythm

melatonin- follows a circadian rhythm, levels high at night, low in the morning

pancreatic islets- endocrine tissue, produces and secretes insulin and glucagon into the blood

glucose- an energy source, should remain within normal levels

insulin- secreted by beta cells when there are high blood glucose levels. stimulates the liver, fat, and muscle cells to metabolize glucose. stimulates the liver and muscles to store glucose as glycogen, promotes the buildup of fats and proteins.

glucagon- secreted by alpha cells between eating, stimulates the breakdown of stored nutrients, raises blood glucose levels.

erythropoietin- produced by kidneys, acts on bone marrow to increase red blood cells into the bloodstream.

thymus- largest and most active in childhood. transforms some lymphocytes to T cells for immunity, produces thymosin to aid in development of T cells.

testosterone- necessary for development and functioning of sex organs in males, matures sperm, causes beard growth, voice change, and strength to increase. causes oil and sweat glands to secrete

follicle stimulating hormone- causes development of a follicle on the ovary to mature, increases estrogen production

luteinizing hormone- acts on the ovary to cause ovulation, causes progesterone to aid in potential fertilization, helps maintain pregnancy.

estrogen- stimulates growth of the uterus, matures the eggs in the ovary, distributes fat in the body