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speed of the endocrine system
pretty slow
the endocrine system
coordinates various activities of the body by utilizing chemical messengers (hormones)
hormone
an organic chemical produced by one set of cells that affects a different set of cells
hormone production
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
primary endocrine organs include
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 gland
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
secondary endocrine organs include
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) *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.It plays a crucial role in regulating various physiological processes including growth, metabolism, and reproduction.
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 (GH)
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 (MSH)
stimulates melanocytes to increase synthesis of melanin
Thyroid stimulating hormone (TSH)
stimulates the thyroid gland to produce T3 and T4
adrenocorticotropic hormone (ACTH)
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
congenial 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
*targets the bones
parathyroid hormone (PTH)
increases calcium levels and decreases phosphate. (stimulates calcium absorption in intestines, retains calcium by excreting phosphate at kidneys, promotes osteoclast activity)
*targets the bones
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
*found in most cells
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 (FSH)
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