8.2 THE HEART

-valves are necessary to ensure one-way flow through the circulatory system-ventricular pressure is very high

-arterial pressure is very low

-valves throughout the venous system

-this is necessary b/c in passing through the capillaries, blood loses its pressure --> not much of a driving force pushing it toward the heart

-contraction of skeletal muscle becomes important, b/c normal body movements push and squeeze the veins, pressurizing venous blood and pushing it along

-venous valves prevent backflow

-when the venous valves fail - varicose veins result (suffered by pregnant women b/c fetus presses against the inferior vena cava --> venous pressure in the legs to rise)

-"lub" results from the closure of the AV valves @ the beginning of systole

-"dup" sound of the semilunar valves closing @ the end of systole

-stronger heart pumps more blood each time it contracts and thus may beat fewer timers per minute and still provide adequate circulation

-venous return - return of blood to the heart by the vena cava

-force of contraction in the ventricles and atria is generated by the cardiac muscle cells that form the muscular walls of the chambers of the heart-syncytium is a tissue in which the cytoplasm of different cells can communicate via gap junctions

-the atria and ventricles are separate syncytia

-transmission of AP is slightly delayed as it passes through the part of the conduction system known as the AV node

-contractility - rate and strength of contraction

-SA node has the most sodium leak channels of all of the conduction system --> it reaches threshold before any other region of the heart does, and sets the rate of heart contractions (pacemaker)

-each heartbeat begins as an AP in the SA node then spreads throughout the atria (causing contraction and fill the ventricles with blood)

-AP also spreads down the special conduction pathway which transmits AP very rapidly without contracting

-impulse travels to the AV node almost instantaneously

-impulse spreads through the atria more slowly because contracting heart muscle cells pass the impulse more slowly than specialized conduction fibers

-at the AV node the impulse is delayed slightly then passes from the node to the ventricles via the conduction pathway again (known as AV bundle/bundle of His)

-purkinje fibers allow the impulse to spread rapidly and evenly over both ventricles

-autonomic nervous system does regulate the rate of contraction-role of the parasympathetic system in controlling the heart is to modulate the rate of inhibiting rapid automaticity

-at rest, most nervous input is form the vagus

-any regulatory system, three components are required: input (afferent information), integration (central NS), and output (efferent information)

-when pressure is too high, baroreceptors notify the central nervous system --> increased vagal tone and decreased sympathetic input

-when pressure is too low, baroreceptors notify the central nervous system --> decreased vagal tone and increased sympathetic input8.3 HEMODYNAMICS

-hemodynamics - the study of blood flow

-driving force is a difference in pressure from arteries to veins

-force opposing flow is friction, which results when blood squeezes through many tiny branching vessels

-principal determinant of resistance is the degree of constriction of arteriolar smooth muscle

-if arteriolar smooth muscle contracts, it becomes more difficult for blood to flow from arteries to capillaries --> resistance goes up

-sympathetic activation causes precapillary sphincters in the gut to contract while arterioles supplying skeletal muscle are allowed to relax --> blood flow is diverted from the gut to skeletal muscle which facilitates the fight or flight response-throughout the cardiac cycle the pressure in the vena cava is about zero mm Hg

-result of all the branching is that the pressure generated by the heart is dissipated

-by the time blood reaches the vena cava it depends on valves to prevent backflow because the driving pressure is negligible

8.4 COMPONENTS OF BLOOD

-blood pH is 7.4

-oncotic pressure in the capillaries due only to plasma proteins-plasma - liquid portion of blood-combinations of the ABO alleles and the Rh alleles determine the overall blood type of an individual

-person with A+ blood produces anti-B antibodies

-transfusion reaction - clumping and destruction of red blood cells bearing the incorrect antigen

-sensitization - person with Rh- blood is exposed to Rh+ blood leading the to development of Rh antigens

-mother's blood and baby's blood do not mix during pregnancy

-on delivery some Rh+ cells from the child can mix with the mother's Rh- blood and lead to her sensitization

-future Rh+ babies are then at risk since anti-Rh antibodies can cross the placenta barrier to clump and/or destroy the Rh+ baby's red blood cells

-hemolytic disease of the newborn (erythroblastosis fetalis) - crossing of anti-Rh antibodies across the placenta barrier and destroy the baby's Rh+ red blood cells

-can be prevented by injecting the mother at the time of birth with anti-Rh antibodies can clump and lead to the destruction of any stray Rh+ cells from the baby --> prevent sensitization of the mother and protect any future unborn Rh+ children-while blood cell's role is to fight infection and dispose of debris

8.5 TRANSPORT OF GASES

-tissues have low levels of oxygen due to oxidative phosphorylation-dietary fats bypass the hepatic vein-fluid, proteins and while blood cells in the tissues are returned to the bloodstream via the lymphatic system8.6 THE LYMPHATIC SYSTEM

-lymphatic system is a one-way flow system which begins with tiny lymphatic capillaries in all the tissues of the body that merge to form large lymphatic vessels

-lymphatic vessels have valves

-lymphatic vessels merge to form large lymphatic ducts

-lymphatic ducts have smooth muscle in their walls

8.7 THE IMMUNE SYSTEM

-innate immunity - general non-specific response the body provides; simplest being the skin-humoral immunity - specific protection by proteins in the plasma called antibodies (Ab) or immunoglobulins (Ig)

-most circulating class of immunoglobulins is IgG class-variable regions are responsible for specificity of antibodies in recognizing foreign particles

-antigens are often large molecules which have many different recognition sites for different antibodies

-immature B cells are derived from precursor stem cells in the bone marrow

-the genes that encode antibody proteins are assembled by recombination from many small segments during B cell development

-thus there are many different B cell clones, each with a different variable region-role of T helper is to activate B cells, T killer cells, and other cells of the immune system

-T helper is the central controller of the whole immune response

-T helper cell is the host of HIV

-T cells can cause an autoimmune response

-bone marrow stem cell - the cell that gives rise to all the various blood cells-neither the tonsils or the appendix are required for survival and are often removed if they become infected