Circulation

Chapter 23

Molecular Exchange

• O2 & nutrients into all cells

• CO2 & 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 chambers 4 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 O2 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 O2 = 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