1. Chapter 45 ~ Chemical Signals in Animals

2. Internal regulation
Interstitial fluid: internal fluid environment of vertebrates; btw cells exchanges nutrients and wastes
Homeostasis: “steady state” or internal balance – Regulator (moderates internal temp) vs Conformer (int. temp varies w/ external)
Control System – 3 components
Receptor (sensor) - detects change
Control center - directs response
Effector - carries out response

3. Negative feedback: change in a physiological variable that is being monitored triggers a response that counteracts the initial fluctuation
Maintaining body temperature, blood sugar
Positive feedback: physiological control mechanism in which a change in some variable triggers mechanisms that amplify the change
Uterine contractions at childbirth

4. 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~ specialized nerve cells that secrete hormones

5. Local regulators: cells adjacent to or near point of secretion (local signaling)
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

6. 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

7. 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)

8. The hypothalamus & pituitary, I
Releasing and inhibiting hormones
Anterior pituitary:
Growth (GH) ~ bones
Prolactin (PRL) ~ mammary glands; milk production
Follicle-stimulating (FSH) & Luteinizing (LH) ~ ovaries/testes
Thyroid-stimulating (TSH) ~ thyroid
Melanocyte-stimulating (MSH)
Endorphins ~ natural ‘opiates’

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

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

11. The pancreas 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)

12. 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+

13. The gonads Steroid hormones: precursor is cholesterol
Regulated by FSH and LH
Androgens (testosterone)
sperm formation; male secondary sex characteristics
Estrogens (estradiol)
uterine lining growth; female secondary sex characteristics
Progestins (progesterone)
uterine lining growth