Circulation Chapter 23

Molecular Exchange O 2 & nutrients into all cells CO 2 & wastes out of all cells Necessary for large SA to volume ratio – Folds – Alternate structures Internal transport system facilitates

No Circulatory System Exchange across PM directly with environment Gastrovascular cavity – Digestion, gas exchange, and distribution

Open Circulatory System Mollusks and arthropods Heart pumps hemolymph – Blood/interstitial fluid mixed – Valves prevent backflow Fluid directly bathes organs – Body movements help circulate – No pigment = only carries nutrients

Closed Circulatory System Annelids, cephalopods, and vertebrates Heart pumps blood in vessels – Distinct from interstitial fluid – Control flow Vessels enter organs – Capillaries – Respiratory pigments Allows higher pressure – Larger, more complex organisms

Evolution of Cardiovascular Systems Single circulation Double circulation 2 chambers4 chambersPartial 4 chambers3 chambers Natural selection modified according to activity levels

The Mammalian Heart

Human Cardiovascular System Process is continuous Double circulation – Circuits are simultaneous – Each loop/circuit must pass through the heart Be able to diagram/explain

The Working Heart Electrocardiogram (EEG) measures activity of heart – SA node is pacemaker – AV node relays signals to ventricles Cardiac cycle – Rhythmic contraction and relaxation of heart 0.8 sec = 72 bpm – Systole = ventricle contract – Diastole = ventricle relax Listening to your heart – Lub-dub, lub-dub is AV-semilunar contraction – Heart murmurs Blood moves backward Myocardial infarction (heart attack) – Lack of O 2 kills cardiac muscle fibers Stroke – Artery blockage kills brain tissue

Blood Vessels Direction determines – Away from or towards the heart Layers vary – Endothelium Single cell later – Middle layer Smooth muscle – Outer layer Elastin protein

Types of Blood Vessels Arteries and arterioles – Thicker walls, smaller diameter – High pressure Capillaries – Lowest velocity (speed) – Allows diffusion – Regulate pressure Venules and veins – Thinner walls, larger diameter – Lowest pressure – One way valves

Controlling Blood Flow Capillaries – Sphincters to regulate flow – Active or inactive tissues Thoroughfare channel always open Arterioles (smooth muscle) – Neural and hormonal control Vasodilation Vasoconstriction

Arteriole Blood Flow Blood pressure: force of blood against vessel (arteriole) walls – Pulse: stretching of arteries Systole: increased velocity in vessels – Smaller vessels = up resistance = up pressure Dystole: decreased velocity, but pressure maintained Velocity correlates with changing vessel types (size and number) – Capillaries allow time for diffusion Veins compensate for drop in pressure

Veins must work against gravity – One way valves – Skeletal muscle sandwich Standing on mats – ‘Cankles’ Blood pressure – Highest at heart level Fainting Raising wounds Veins, Circulation and Gravity

Blood Composition Plasma (55%) – Water (90%) – Ions (balance/homeostasis) – Proteins (clotting and immunity) – Transport substances Cellular componenets (45%) – Red blood cells (rbc’s) – White blood cells (wbc’s) – Platelets

RBC Count 3-4 month life span Formed in bone marrow – Low O 2 = kidney’s make erythropoietin (EPO) = stimulate bone marrow Athletic training at high altitudes Injections  illegal Altering RBC numbers – Anemia is low RBC or hemoglobin – Blood doping

Blood Clotting Damaged vessel constricts Platelets form a temporary plug Fibrin threads trap cells to seal