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
• Natural selection modified according to activity
levels
2 chambers
Single circulation
3 chambers
Partial 4 chambers
Double circulation
4 chambers
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, Circulation and Gravity
• Veins must work against
gravity
– One way valves
– Skeletal muscle sandwich
• Standing on mats
– ‘Cankles’
• Blood pressure
– Highest at heart level
• Fainting
• Raising wounds
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