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Chapter 45 Endocrine System 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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Chapter 45 Endocrine System 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 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-insulin-dependent; 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