1. Chapter 45
Endocrine System
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 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: Beta 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