Chapter 45 Chemical Signals in Animals v=YI2qYRWzSZ4&featur e=related v=kIPYVV4aThM&featur e=related
Regulatory systems u Hormone~ chemical signal secreted into body fluids (blood) communicating regulatory messages u Target cells~ body cells that respond to hormones u Endocrine system/glands~ hormone secreting system/glands (ductless); exocrine glands secrete chemicals (sweat, mucus, enzymes) through ducts u Neurosecretory cells~ actual cells that secrete hormones u Feedback mechanisms ~ negative and positive
Local regulators: cells adjacent to or near point of secretion u Growth factors ~ proteins for cell proliferation u Nitric oxide (NO) ~ neurotransmitter; cell destruction; vessel dilation u Prostaglandins ~ modified fatty acids secreted by placenta and immune system; also found in semen
Mode of Action: Chemical Signaling u 1- Plasma membrane reception signal-transduction pathways (neurotransmitters, growth factors, most hormones) u 2- Cell nucleus reception steroid hormones, thyroid hormones, some local regulators
Vertebrate Endocrine System u Tropic hormones ~ a hormone that has another endocrine gland as a target u Hypothalamus~pituitary u Pituitary gland u Pineal gland u Thyroid gland u Parathyroid glands u Thymus u Adrenal glands u Pancreas u Gonads (ovary, testis)
The hypothalamus & pituitary, I u Releasing and inhibiting hormones u Anterior pituitary: u Growth (GH)~bones √gigantism/dwarfism √acromegaly u Prolactin (PRL)~mammary glands; milk production u Follicle-stimulating (FSH) & u Luteinizing (LH)~ovaries/testes u Thyroid-stimulating (TSH)~ thyroid u Adrenocorticotropic (ACTH)~ adrenal cortex u Melanocyte-stimulating (MSH) u Endorphins~natural ‘opiates’; brain pain receptors
The pituitary, II u The posterior pituitary: u Oxytocin ~ uterine and mammary gland cell contraction u Antidiuretic (ADH )~ retention of water by kidneys
The pineal, thyroid, & parathyroid u Melatonin ~ pineal gland; biological rhythms u Thyroid hormones: Calcitonin~ lowers blood calcium Thyroxine~ metabolic processes u Parathyroid (PTH)~ raises blood calcium
The pancreas u Islets of Langerhans u Alpha cells: glucagon~ raises blood glucose levels u Beta cells: insulin~ lowers blood glucose levels u Type I diabetes mellitus (insulin-dependent; autoimmune disorder) u Type II diabetes mellitus (non-insulin-dependent; reduced responsiveness in insulin targets)
The adrenal glands u Adrenal medulla (catecholamines): epinephrine & norepinephrine~ increase basal metabolic rate (blood glucose and pressure) u Adrenal cortex (corticosteroids): glucocorticoids (cortisol)~ raise blood glucose mineralocorticoids (aldosterone)~ reabsorption of Na+ and K+
The gonads Steroid hormones: precursor is cholesterol u androgens (testosterone)~ sperm formation; male secondary sex characteristics; gonadotropin u Estrogens (estradiol)~uterine lining growth; female secondary sex characteristics; gonadotropin u progestins (progesterone)~uterine lining growth
Steroid Hormone Action u ature=related ature=related