The Endocrine System Flashcards
hormones
endocrine signaling involves secretion of these directly into the bloodstream
travel to distant target tissues, where they bind to receptors and induce a change in gene expression or cell function
peptide hormones
composed of amino acids and are derived from large precursors that are cleaved during post translational modification
polar and cannot pass through plasma membrane
bind to extracellular receptors where they trigger transmission of a secondary messenger
usually have rapid onset but are short-lived
travel freely in the bloodstream and do not require a special carrier
steroid hormones
derived from cholesterol
minimally polar and can pass through plasma membrane
bind to intracellular or intranuclear receptors, where they promote conformational change and bind to DNA, affecting transcription of a particular gene
usually have slow onset but are long-lived
cannot dissolve in the bloodstream and must be carried by specific proteins
amino acid-derivative hormones
modified amino acids
chemistry shares some features with peptide hormones and some features with steroid hormones; dif ones share dif features with other hormone classes
common ex’s: epinephrine, norepinephrine, triiodothyronine, thyroxine
direct hormones
have major effects in non-endocrine tissues
tropic hormones
have major effects in other endocrine tissues
hypothalamus
bridge between nervous and endocrine systems release of hormones from here mediated by a number of factors: projections from other parts of brain, chemo- and baroreceptors in blood vessels, and neg feedback from other hormones stimulates anterior pituitary gland through paracrine release of hormones into the hypophyseal portal system which directly connects the two organs antidiuretic hormone (ADH or vasopressin) and oxytocin synthesized here
negative feedback
final hormone (or product) of a pathway inhibits hormones (or enzymes) earlier in the pathway, maintaining homeostasis
gonadotropin-releasing hormone (GnRH)
promotes the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
growth hormone-releasing hormone (GHRH)
promotes release of growth hormone
thyroid-releasing hormone (TRH)
promotes release of thyroid-stimulating hormone (TSH)
corticotropin-releasing factor (CRF)
promotes release of adrenocorticotropic hormone (ACTH)
prolactin-inhibiting factor (PIF or dopamine)
inhibits release of prolactin
anterior pituitary
releases hormones in response to stimulation from hypothalamus
FSH, LH, ACTH, TSH are tropic hormones
prolactin, endorphines, growth hormone are direct hormones
follicle-stimulating hormone (FSH)
promotes development of ovarian follicles in females and spermatogenesis in males
luteinizing hormone (LH)
promotes ovulation in females and testosterone production in males
adrenocorticotropic hormone (ACTH)
promotes synthesis and release of glucocorticoids from adrenal cortex
thyroid-stimulating hormone (TSH)
promotes synthesis and release of triiodothryonine and thyroxine from the thyroid
prolactin
promotes milk production
endorphins
decrease perception of pain and can cause euphoria
growth hormone (GH)
promotes growth of bone and muscle and shunts glucose to these tissues
raises blood glucose concentrations
posterior pituitary
releases two hormones produced in the hypothalamus
antidiuretic hormone (ADH or vasopressin)
secreted in response to low blood volume or increased blood osmolarity and increases reabsorption of water in collecting duct of nephron, increasing blood volume and decreasing blood osmolarity
oxytocin
secreted during childbirth and promotes uterine contractions
also promotes milk ejection and may involved in bonding behavior
has a positive feedback loop
thyroid
located at base of neck in front of trachea
produces three key hormones
triiodothyronine (T3) and thyroxine (T4)
produced by follicular cells and contain iodine
increase basal metabolic rate and alter utilization of glucose and fatty acids
required for proper neurological and physical development in children
calcitonin
produced by parafollicular (C) cells
decreases plasma Ca concentration by promoting Ca excretion in kidneys, decreasing Ca absorption in gut, and promoting Ca storage in bone
parathyroid glands
release parathyroid hormone (PTH)
parathyroid hormone (PTH)
increases blood Ca concentration
decreases excretion of Ca by kidneys and increases bone resorption directly to increase blood Ca conc
activates vitamin D, which is necessary for Ca and phosphate absorption from gut
promotes resorption of phosphate from bone and reduces reabsorption of phosphate in kidney, but vitamin D promotes absorption of phosphate from gut; two effects on phosphate conc somewhat cancel each other out
adrenal cortex
produces three classes of steroid hormones: glucocorticoids, mineralocorticoids, cortical sex hormones
glucocorticoids
i.e. cortisol, cortisone
increase blood glucose conc, reduce protein synthesis, inhibit the immune system, and participate in the stress response
release is stimulated by ACTH
mineralocorticoids
i.e. aldosterone
promote Na reabsorption in distal convoluted tubule and collecting duct, thus increasing water reabsorption
also increases K and H ion excretion
regulated by renin-angiotensin-aldosterone system
cortical sex hormones
i.e. androgens (testosterone) and estrogens in both males and females
adrenal medulla
derived from nervous system
secretes catecholamines into bloodstream
catecholamines
i.e. epinephrine and norepinephrine (involved in fight-or-flight response)
promote glycogenolysis, increase basal metabolic rate, increase heart rate, dilate bronchi, alter blood flow
pancreas
produces hormones that regulate glucose homeostasis
glucagon
produced by alpha cells, raises blood glucose levels by stimulating protein and fat degradation, glycogenolysis, and gluconeogenesis
insulin
produced by ß-cells and lowers blood glucose levels by stimulating uptake by cells and anabolic processes
somatostatin
produced by ∂-cells and inhibits insulin and glucagon secretion
gonads
produce hormones that are involved in development and maintenance of reproductive systems and secondary sex characteristics
testes
secrete testosterone
ovaries
secrete estrogen and progesterone
pineal gland
releases melatonin
melatonin
helps regulate circadian rhythms
secretin, gastrin, cholecystokinin
produced by cells in stomach and intestine
erythropoietin
secreted by kidneys
stimulates bone marrow to produce erythrocytes (RBC’s) in response to low oxygen levels in blood
atrial natriuretic peptide (ANP)
secreted by atria of heart
promotes excretion of salt and water in kidneys in response to stretching of atria (high blood volume)
thymosin
secreted by thymus
important for proper T-cell development and differentiation
