生理学笔记book note 2.docx

Chapter 13 Endocrine system
overview of the endocrine system
1. the endocrine system consists of all glands, organs, and tissues that contain hormone-secreting cells
Endocrine glands: ductless glands that secrete hormones(chemical messenger carried by the blood to distant target cells).
. Pituitary, thyroid, parathyroid, adrenal, and pineal glands.
Not endocrine glands but contain cells that secrete hormones: hypothalamus, skin, thymus, heart, liver, stomach, pancreas, kidneys, small intestine, ovaries, testes, adipose tissue, placenta.
2. hormones influence target cells by binding to receptors
Down-regulation: phenomenon in which there is a decrease in the number of receptors in response to an excess of a hormone or neurotransmitter.
Up-regulation
3. hormones are chemically classified as lipid-soluble or water-soluble
Lipid-soluble
Steroid hormones
aldosterone, cortisol, dehydroepiandrosterone脱氢表雄***(adrenal androgen), testosterone, estrogens, progesterone, calcitriol(active form of Vitamin D. not a steroid, but is included in this category because its structure is similar)
Most are bound to transport proteins.
-10% are not bound to pro. This free fraction diffuses out of capillaries, bind to receptors. As they leave the blood, transport pro release new ones to replenish
Thyroid hormones
T3(triiodothyronine)
T4(thyroxine)
synthesized by attaching iodine to the aa tyrosine酪氨酸
Water-soluble hormones
Amine hormones
Tyrosine—catecholamines(epinephrine, norepinephrine, dopamine)
Tryptophan色氨酸—melatonin褪黑激素
Most circulate through the watery blood plasma in a “free” form.
Peptide/protein hormones(most hormones)
Peptide hormones: Antidiuretic hormones, oxytocin,
Protein hormones: insulin, growth hormones
Glycoprotein hormones: thyroid-stimulating hormone.
4. A hormone’s mechanism of action depends on the signaling pathway that it activates
Signaling pathway→a series of relay pro→effector cell→cellular response
Mechanisms of action o