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Lecture #20 Date _______

Lecture #20 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

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Lecture #20 Date _______

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  1. Lecture #20 Date _______ • Chapter 45 ~ Chemical Signals in Animals

  2. 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

  3. 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

  4. 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

  5. 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)

  6. 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

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

  8. The pineal, thyroid, & parathyroid • Melatonin~ pineal gland; biological rhythms • Thyroid hormones: Calcitonin~ lowers blood calcium Thyroxine~ metabolic processes • Parathyroid (PTH)~raises blood calcium

  9. 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-insulin-dependent; reduced responsiveness in insulin targets)

  10. 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+

  11. 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

  12. Steroid Hormone Action

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