Chapter 42- Circulation and Gas Exchange

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

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

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

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

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

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

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

Artery Vein Capillary Arteriole Venule

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

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!

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

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

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!

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.

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

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

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

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

Insects- Tracheal system (air tubes within body) spiracles

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

Quizlet Reviews! Ch. 42: https://quizlet.com/74212325/test Ch. 41 – Nutrition https://quizlet.com/43650236/test