Lesson 11 - Circulation PDF

Circulation DISP Biology Circulation Transport throughout organism and/or between organism and environment: O2, CO2 Nutrients/Waste Hormones Immune factors Heat  Circulation – 2 transport mechanisms 1. Diffusion over short distances (~1mm) –if cells in close contact wi...

Circulation DISP Biology Circulation Transport throughout organism and/or between organism and environment: O2, CO2 Nutrients/Waste Hormones Immune factors Heat  Circulation – 2 transport mechanisms 1. Diffusion over short distances (~1mm) –if cells in close contact with environmentIn flatworms, diffusion is sufficient 2. Convection Bulk flow of body fluids over longer distances (driven by a pump) n most organisms there is a combination of diffusion and convection General design of circulatory systems 1. Pump (muscular heart, or cilia) – to move circulatory fluid (i.e. blood) 2. Distribution system – tubes for circulatory fluid Closed circulatory systems: blood vessels (arteries, capillaries, veins) Open circulatory systems: body sinuses 3. Exchange areas (i.e. capillaries) – diffusion in and out of circulatory fluid, tissues Capillaries are small blood vessels 1-2 cell layers thick – allows Open vs closed circulatory systems Open circulation Closed circulation Fluid is not confined to blood Fluid confined to blood vessels vessels Fluid in body sinuses (spaces in Create more pressure in closed tissue) system, for more efficient delivery Fluid bathes cells and organs to tissues directly Examples: annelids, vertebrates Examples: arthropods  Closed circulatory system aka cardiovascular system od vessels are specialized for different functions Arteries – blood from heart to capillaries Branch to arterioles which branch to capillaries Capillaries – exchange surface for diffusion between blood and tissue cells Blood flow ~200 x slower in capillaries Converge into venules which converge into veins Veins – blood from capillaries to heart Blood vessel structure matches function Arteries and veins have 3 layers: 1. Endothelium – cells that line vessel 2. Smooth muscle – contractions help pump blood 3. Connective tissue – elastic fibres allow stretch/recoil Artery Arteries thicker walled (experience high pressure blood from heart) Vein Thick connective tissue allows artery to resist stretching, return to original shape (like a reinforced garden house) Veins thinner walled (experience low pressure) Smooth muscle contractions assist blood  Blood vessel structure matches function endothelium Capillaries have thin walls to facilitate exchange of materials between blood and interstitial fluid basal lamina (fluid bathing tissues) Narrow diameter slows flow for effective exchange Note that ~4-8L fluid is lost from capillaries to surrounding fluid daily. Lost fluid becomes “lymph”. It is returned to blood vessels Capillaries only via the lymphatic system. slightly wider than a red blood cell  Modeling fluid flow in blood vessels minar flow in blood vessels yers (laminae) of fluid move past each other, overcoming friction rrow lengths proportional to velocity yers in center are fast but layers next to vessel wall don’t move Poiseulle’s law Change in radius has biggest effect on flow rate Blood flow can be regulated by adjustive vessel diameter 1) Vasoconstriction - contract smooth muscle in arteriole walls 2) Vasodilation - relax smooth muscles in the arteriole walls 3) Contract precapillary sphincters smooth muscle rings at entrance to capillaries Modify blood flow to organs as needed: i.e. skin, digestive tract, skeletal muscles Only 5-10% capillaries have blood flowing through at a given time  Plaques (fatty deposits) narrow blood vessels Coronary artery supplies oxygenated blood to heart cells https://learning-center.homesciencetools.com/article/heart- dissection-project/ ↓ ____radius →↓ ____ flow rate↓ → ___ O2 to heart cells (heart attack if damaged)  Closed circulation: Single vs double circulation Deoxygenated blood Oxygenated blood Fish Mammals Potential problems Benefits 1. Heart supplied with low O2 1. Blood supplied to tissues and heart is blood freshly oxygenated 2. No pump to give fresh energy 2. Pumping blood from left side of the to oxygenated blood leaving heart imparts fresh energy en route to gills tissues Mammalian Heart – structure and function 2 Atria – left and right relatively thin walls collection chambers for returning blood 2 Ventricles – left and right thicker walls contract forcefully Valves prevent backflow atrioventricular valves AND semilunar valves Mammalian cardiovascular system Body tissues Blood leaving (systemic _________________________ tissues) (tissues) is low ________ in O2. vena Blood returns to heart via cavae the_____________ In heart blood goes into right atrium ___________________, then right ventricle ______________________ low Blood ________ in O2 is pumped out by contraction ofright ventricle ______________________. Blood leaves through the Pulmonary artery and travels to the __________________________ lungs _______ and picks O2up _______. lungs Blood leaving the _________________________ high is _______ in O2. Blood returns to heart via the __________________________________ pulmonary vein In the heart blood goes into left atrium the _______________, left __________________________. then ventricle high _________ in Blood O2 is pumped out by contraction of the ____________________________________. left ventricle Spread of depolarization across heart allows coordinated contraction Cardiac action potential ~100-500ms. Allows heart to contract long enough to pump blood Gap junctions (protein-lined channels between adjacent cells) allow spread of depolarization Areas with concentrated gap junctions are “intercalated disks” Gap Junctions: protein channels connect neighbor cell cytoplasm Animation: Gap Junctions Right-click slide / select “Play”  Pacemaker cells in Sinoatrial node in right atrium set rate of heart contraction by having most frequent action potentials Depolarization spreads over heart chambers via gap junctions and depolarized muscle cells contract. Purkinje fibres are specialized muscle cell bundles penetrate fibrous layers to send electric impulse to other chambers Electrocardiog ram (EKG) detects electric currents as they spread across the heart. Heart contracts and relaxes in rhythmic cardiac cycle Systole = contraction phase Diastole = relaxation/filling phase Valves ensure directionality of blood flow Atrioventricular valves - separate atrium/ventricle Closed by – ventricle contraction Open when – ventricle relaxed, blood flows from atrium to ventricle Sound – “lub” from blood recoil against closed AV valve during ventricle contraction Semilunar valves - control flow to aorta/pulmonary artery Opened by – ventricle contraction Closed when – ventricle relaxed Sound – “dub” from vibrations caused by closing semilunar valves