Conservation of mass: the total blood volume is (nearly) constant.

1. Conservation of mass: the total blood volume is (nearly) constant. That means all of the blood passing though the aorta has to equal all of the blood passing though the capillaries in every second! Cardiac Output = Area*Velocity = Total Area * Velocity Aorta

2. From heart Capillaries Return to heart Figure 44-30 Velocity Total area

3. Cardiac Output = PA-PV/R R = 8 h L/p r4 What is blood? 40% RBC, 60% Plasma How does the viscosity of blood vary with hematocrit (fraction rbc) ? h 0 20 40 60 80 hematocrit

4. Closed system: Blood never leaves vessels. Figure 44-3 Single heart Open system: Hemolymph leaves vessels and comes into direct contact with tissues. Tubular heart

5. Other circulatory systems Open versus closed

6. Is it really “closed”? Plasma and lymphatic exchange : a consequence of the balance of mechanical and osmotic pressures. Figure 44-23 Blood enters capillary from arteriole (a small artery) Blood leaves capillary to venule (a small vein) Blood pressure 32 mm Hg Blood pressure 15 mm Hg Net pressure 10 mm Hg out Net pressure 7 mm Hg in Capillary Osmotic pressure 22 mm Hg Osmotic pressure 22 mm Hg Fluid returns Fluid leaves Lymphatic duct Excess fluid in interstitial space enters lymphatic duct Lymph leaves tissue Interstitial fluid

7. Environmental oxygen: Earth’s atmosphere today: Nitrogen 78% Oxygen 21% CO2 0.03% Other gases (H, Ar …) Gas concentrations measured as Partial Pressure: 250 mmHg 760 mmHg

8. Strategies for getting oxygen to tissues Simple diffusion: Protozoa, plankton, tiny insects And small cold creatures..

9. Strategies for getting oxygen to tissues FISH GILLS : COUNTER CURRENT EXCHANGERS

10. Strategies for getting oxygen to tissues Fick’s Law: Rate of diffusion = k A P2-P1 D FISH GILLS : COUNTER CURRENT EXCHANGERS 100 90 70 50 100 90 70 50 O2 O2 0 10 30 50 90 60 30 5

11. Strategies for getting oxygen to tissues BIRD LUNGS : COUNTER CURRENT EXCHANGERS

12. Human gas exchange: tidal respiration. D = 0.2 um Trachea Bronchi Bronchioles Lung

13. D = 0.2 um Red blood cells represent about 40% of the total blood volume in humans.

14. Hemoglobin Transports Oxygen to Tissues Hemoglobin O2 from lung 98.5% of oxygen loads to hemoglobin in red blood cells 1.5% of oxygen loads to blood plasma O2 to tissues

15. Hemoglobin Transports Oxygen to Tissues Heme group 98.5% of oxygen loads to hemoglobin in red blood cells

16. The Oxygen-Hemoglobin Equilibrium Curve

17. CO2 Handling by red blood cells -- Hemoglobin buffers pH changes.

18. Key characteristics of nervous systems Contrast to endocrine system • Fast • Not long lasting • Highly specific • Transmission in the form of action potentials (fast and electrical) • Chemical transmission largely restricted to synapses with very small distances. • Slow (long lasting). • Can have both specific and broad actions. • Transmission via circulatory system. • Chemical transmission dominates and occurs over long distances. • Specificity determined by receptors.

19. Six categories of chemical signaling Examples Autocrine signals Paracrine signals Endocrine signals Neural signals Neuroendocrine signals Pheromones

20. Three categories of chemical signals And the signals are amplified! Protein Insulin Growth hormone Amio Acid Norepinephrine Epinephrine Serotonin Steroid Estradiol Testosterone Cortisol

21. Amplification via two different mechanisms MODEL FOR EPINEPHRINE ACTION 1. Epinephrine binds to receptor Epinephrine Adenylyl cyclase Receptor 2.Activation of G protein 3. Activated adenylyl cyclase catalyzes formation of cAMP Transmission of message from cell surface STEROID HORMONE ACTION Nucleus Hormone receptor Proteins mRNA DNA Steroid hormone Hormone- response element RNA polymerase Hormone-receptor complex Ribosome

22. The major components of the endocrine system

24. Hypothalamus Neurosecretory cells of the hypothalamus Hypothalamic hormones Posterior pituitary Blood vessels Hormone ADH Oxytocin Kidney nephrons Mammary glands, uterine muscles Target Response Aquaporins activated; H2O reabsorbed Contraction during labor; ejection of milk during nursing

25. The anterior pituitary Neurosecretory cells of the hypothalamus Hypothalamic hormones Blood vessels Anterior pituitary Pituitary hormones Hormone ACTH Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) Growth hormone (GH) Prolactin (PRL) Thyroid- stimulating hormone (TSH) Adrenal cortex Testes or ovaries Many tissues Mammary glands Thyroid Target Response Production of glucocorticoids Production of sex hormones; control of menstrual cycle Growth Mammary gland growth; milk production Production of thyroid hormones

26. Three pathways regulated by feedback inhibitionAmplification again. Endocrine pathway Neuroendocrine pathway Neuroendocrine-to-endocrine pathway Stimulus Stimulus Stimulus Endocrine cell Sensor cell Sensor cell Endocrine signal Feedback inhibition Feedback inhibition Feedback inhibition Effector cell Neural signal Neural signal Response CNS CNS Neuroendocrine signal Neuroendocrine signal Effector cell Endocrine cell Endocrine signal Response Effector cell Response