u Chapter 45 ~ Chemical Signals in Animals

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

Figure 45.3 Mechanisms of chemical signaling: a review

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

Figure 45.6b Hormones of the hypothalamus and pituitary glands

The pituitary, II u The posterior pituitary: u Oxytocin~ uterine and mammary gland cell contraction u Antidiuretic (ADH)~ retention of water by kidneys

Figure 45.6a Hormones of the hypothalamus and pituitary glands

The pineal, thyroid, & parathyroid u Melatonin ~ pineal gland; biological rhythms associated with reproduction u Thyroid hormones: –Calcitonin~ lowers blood calcium –Thyroxine~ metabolic processes u Parathyroid (PTH)~ raises blood calcium

Figure 45.9 Hormonal control of calcium homeostasis in mammals

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)

Figure Glucose homeostasis maintained by insulin and glucagon

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+ that increases blood pressure and volume. –Thought that these are what maintains body homeostasis over an extended period of time.

Figure Stress and the adrenal gland

The gonads u 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 D:\ImageLibrary40- 55\45- ChemicalSignalsInAni mals\45-03a- NonsteroidHormone. mov D:\ImageLibrary40- 55\45- ChemicalSignalsInAni mals\45-03a- NonsteroidHormone. mov D:\ImageLibrary40 -55\45- ChemicalSignalsIn Animals\45-03b- SteroidHormone.m ov