BIOL 1051H Lecture Notes - Lecture 4: Antigen, Leukotriene, Positive Feedback
Document Summary
Lecture 4: endocrine system (chapter 17) & blood (chapter 18) Endocrine system- glands, tissues and cells that secrete hormones. Hormones- chemical messengers that are transported by the bloodstream and stimulate physiological responses in cells of another tissue or organ, often a considerable distance away. In humans, the endocrine and nervous systems specialize in communication and coordination. The endocrine system uses hormones; the nervous system uses neurotransmitters. Nervous: reacts quickly (msec timescale), stops quickly. Endocrine: reacts slowly (seconds or days), effect may continue for days or longer. Endocrine: general, widespread, widespread effects (many organs) Steroids: derived from cholesterol, hydrophobic/lipophylic, sex steroids (e. g. estrogen) from gonads and corticosteroids (eg cortisol) from adrenals. Monoamines (biogenic amines: made from the amino acids, tryptophan and tyrosine, catecholamines (dopamine, norepinephrine, epinephrine). Occurs after long exponsure to high levels of hormones. Subsequent exposure to the same hormone produces a lesser respons. Due to decrease in # of receptors on targets.
