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Lecture Date _______ • Chapter 45 • Chemical Signals in Animals Regulatory systems • Hormone – chemical signal secreted into body fluids (blood) communicating regulatory messages • Target cells – body cells that respond to hormones • Endocrine system/glands~ – hormone secreting system/glands (ductless); exocrine glands secrete chemicals (sweat, mucus, enzymes) through ducts • Neurosecretory cells – actual cells that secrete hormones • Feedback mechanisms – negative and positive Local regulators: cells adjacent to or near point of secretion • Growth factors – proteins for cell proliferation • Nitric oxide (NO) – neurotransmitter; cell destruction; vessel dilation • Prostaglandins – modified fatty acids secreted by placenta and immune system; also found in semen Mode of Action: Chemical Signaling • 1- Plasma membrane reception – signal-transduction pathways (neurotransmitters, growth factors, most hormones) • 2- Cell nucleus reception – steroid hormones, thyroid hormones, some local regulators Vertebrate Endocrine System • Tropic hormones – a hormone that has another endocrine gland as a target • • • • • • • • • Hypothalamus~pituitary Pituitary gland Pineal gland Thyroid gland Parathyroid glands Thymus Adrenal glands Pancreas Gonads (ovary, testis) The hypothalamus & pituitary, I • Releasing and inhibiting hormones • Anterior pituitary: – Growth (GH)~bones • gigantism/dwarfism • acromegaly – – – – – – – Prolactin (PRL)~mammary glands; milk production Follicle-stimulating (FSH) & Luteinizing (LH) ~ ovaries/testes Thyroid-stimulating (TSH) ~ thyroid Adrenocorticotropic (ACTH) ~ adrenal cortex Melanocyte-stimulating (MSH) Endorphins~natural ‘opiates’; brain pain receptors The pituitary, II • The posterior pituitary: • Oxytocin – uterine and mammary gland cell contraction • Antidiuretic (ADH) – retention of water by kidneys The pineal, thyroid, & parathyroid • Melatonin – pineal gland; biological rhythms • Thyroid hormones: – Calcitonin - lowers blood calcium – Thyroxine - metabolic processes • Parathyroid (PTH) – raises blood calcium The pancreas • Islets of Langerhans • Alpha cells: – Glucagon - raises blood glucose levels • Beta cells: – Insulin - lowers blood glucose levels • Type I diabetes mellitus (insulin-dependent; autoimmune disorder) • Type II diabetes mellitus (non-insulindependent; reduced responsiveness in insulin targets) The adrenal glands • Adrenal medulla (catecholamines): – epinephrine & norepinephrine - increase basal metabolic rate (blood glucose and pressure) • Adrenal cortex (corticosteroids): – glucocorticoids (cortisol) - raise blood glucose – mineralocorticoids (aldosterone) - reabsorption of Na+ and K+ The gonads • Steroid hormones: precursor is cholesterol • Androgens (testosterone) – sperm formation; male secondary sex characteristics; gonadotropin • Estrogens (estradiol) – uterine lining growth; female secondary sex characteristics; gonadotropin • Progestins (progesterone) – uterine lining growth