1. Chapter 42- Circulation and Gas Exchange

2. Background
The lowest inverts (jellyfish, etc…) have only a gastrovascular cavity where circulation AND digestion take place simultaneously.

3. Open vs. Closed Circulatory Systems
All have:
- Circulatory fluid (blood)
- Tubes (blood vessels)
- Muscular pump (heart)

4. Open circulation Insects/Arthropods/Mollusks - Metabolically cheap
- Sinuses- Area surrounding the organs
- Blood bathes the organs (not kept separate in distinct tubes)

5. Closed circulation Blood is contained within vessels *tubes
(all mammals)
- Metabolically expensive
- Called cardiovascular system in mammals
Heart  Arteries Arterioles  Capillaries (site of gas exchange) 
Venules  Veins  Heart

7. Animal Fishes- Heart is 2 chambers Amphibians and Reptiles- 3 chambers
Mammals and Birds - 4 chambers

8. The Human Heart
- Pathway of blood through heart (and body)

9. The Human Heart
Cardiac cycle- The complete sequence of pumping and filling
- Contraction- systole
- Relaxation- diastole
Valves in the heart prevent backflow
SA Node- Pacemaker of the heart. *sinoatrial node
Receives original signal then passes signal to the AV node, *atrioventricular node which delays the pulse and then sends it out
Animation

12. Artery
Vein
Capillary
Arteriole
Venule

13. Blood Vessels - Veins have valves to prevent backflow, arteries do not
- Arteries are thicker than veins

14. Blood Vessels Layers of blood vessels (from the outside to the inside)
- Elastic connective tissue
- Smooth muscle
- Endothelium- Smooth surface for blood to flow over
- Capillaries only have a “basement membrane” and an endothelium *only one cell thick!

16. Blood Vessels
- Normal blood pressure 120 (systole)/70 (diastole) *denominator on bottom! - Fluid is lost through the capillaries, but returns to the circulatory system by entering into the lymphatic system (direct connection to circulatory system) *animation

17. Blood Called hemolymph and is a connective tissue - 90% of it is water
- pH of 7.4
- Plasma is the fluid that all of the cells are suspended in

20. Cells found in blood *NO NUCLEUS! Erythrocytes (red blood cells)
- Carry oxygen by having hemoglobin proteins
- Each hemoglobin has 4 subunits each with a heme group and an associated iron atom.
Iron binds to the O2
*NO NUCLEUS!

22. Blood
- Cooperative binding- when one O2 binds, it makes it easier for more O2 to attach and when one O2 leaves, it makes it easier for more O2 to leave
- Each erythrocyte can contain up to 250 million hemoglobin molecules and each can carry four O2 molecules = 1 billion O2 molecules per erythrocyte.

23. The lower the pH, the lower the affinity to O2 = Bohr Shift.
pH lowers when CO2 levels are high (ie: rigorous exercise *more carbonic acid forms = lower pH) and hemoglobin will be more likely to release O2 to the tissue that needs it.
The Bohr effect

24. Blood Leukocytes (white blood cells)- Fight infection
Platelets- Blood clotting factor

25. Gas Exchange
Gas exchange (O2 uptake and CO2 release- flow of molecules is because of diffusion)
- The “respiratory medium” is the source of O2
- The “respiratory surface” is the location of gas exchange
- Water must be present for the gas exchange to occur

26. Groups of Animals and Gas Exchange
Worms- Diffusion through skin (reason they are often flat and long)
Aquatic animals- Gills. Countercurrent exchange
ANimation

28. Insects- Tracheal system
(air tubes within body)
spiracles

29. Large animals and birds- Lungs
- Tidal flow- The volume of air inhaled and then exhaled. Animation

30. Quizlet Reviews! Ch. 42: https://quizlet.com/74212325/test
Ch. 41 – Nutrition