Human Anatomy & Physiology 2 (Cardiovascular System)
What factors causes blood to flow in arteries? In veins?
--Blood flow in arteries is due to high blood pressure (blood has just left heart). -Blood flow in veins is due to: *contraction of surrounding skeletal muscles "squishes" vein, forcing blood to move *valves keep blood from moving in wrong direction *vasoconstriction of venous walls *negative intrathoracic pres (from breathing
What is ischemia? Coronary infarction?
-A blockage in a coronary artery can result in the loss of oxygen to heart cell (ischemia) . -Death of cardiac muscle cells (heart attack/coronary infarction).
Distinguish between the structure and function of arteries, arterioles, capillaries, venules, and veins.
-Arteries-thick (smooth muscle), elastic walls--carry blood away from heart--high blood pressure. Thick, strong wall, thicker than walls of veins . *3 layers or tunics: - Tunica interna (intima): innermost layer - Tunica media: smooth muscle & elastic tissue - Tunica externa (adventitia): outer layer, connective tissue *Transport blood under high blood pressure *Give rise to smaller arterioles -Arterioles-thinner-lower b.p., so have to dilate & constrict to keep blood moving-precapillary sphincters are at end of arteriole to control how much blood enters capillary bed. -Capillaries-smallest-walls are made of 1 layer of squamous cells-exchange of gases, nutrients, & waste products with the tissues occurs here. *Capillaries are the smallest-diameter blood vessels *Connect the smallest arterioles and the smallest venules *They are extensions of the inner lining of arterioles *Walls consist of endothelium (simple squamous epithelium) only *They are semi-permeable *Capillary blood flow regulated mainly by precapillary sphincters: smooth muscle surrounding capillary when it branches off arteriole or metarteriole -Venules-small veins. -Veins-walls are not as thick & elastic as arteries-have valves which keep blood from backing up-carry blood back to heart. *Thinner walls than arteries (3 layers or tunics) *Tunica media less developed *Carry blood under relatively low pressure *Function as blood reservoirs *Many have flap-like valves:
How does blood pressure differ in arteries, arterioles, capillaries, venules, and veins?
-Blood pressure decreases as distance from left ventricle increase.
Distinguish between systolic and diastolic pressure.
-Blood pressure is the force exerted by blood against inner walls of vessels. In the arterial system, b.p. corresponds to ventricular cycles -Systolic pressure-pressure during ventricular contraction (artery expands) -Diastolic pressure-pressure during ventricular relaxation/filling (artery recoils)
What causes blood pressure? What is the name of the instrument which measures it?
-Blood pressure varies with cardiac output Increase in SV (stroke volume) or HR causes increase in CO(cardiac output), which increases the blood pressure (BP) -An average blood pressure of the brachial artery is 120/80 -Sphygmomanometer-instrument which is used to take blood pressure
Describe the cardiac conduction system, including the roles of the SA node, the AV node, and bundle of His, and the Purkinje fibers.
-Cardiac Conduction System: *A group of clumps and strands of specialized cardiac muscle tissue, which initiates and distributes impulses throughout the myocardium.Coordinates the events of the cardiac cycle. -SA (Sinoatrial) Node: Pacemaker; initiates rhythmic contractions of the heart -AV (Atrioventricular) Node: Conducts impulses to AV Bundle; delays impulse, so that atria finish contracting before ventricles contract -AV (Atrioventricular) Bundle (of His): Conducts impulses rapidly between AV node and bundle branches -Purkinje Fibers: Large fibers that conduct impulses to ventricular myocardium
What is a functional syncytium? How many are in the heart?
-Cardiac muscle fibers form a functional syncytium: A mass of merging cells that function as a unit 2 such masses exist in the heart: *In the atrial walls; called the atrial syncytium *In the ventricular walls; called the ventricular syncytium
Describe what happens in the heart during one cardiac cycle. What causes the heart sounds lub-dup? What causes a murmur?
-During a cardiac cycle, the pressure in the heart chambers rises and falls. Pressure changes open and close the valves. -During atrial systole and ventricular diastole: The ventricles are relaxed. The A-V valves open and the semilunar valves close. About 70% of blood flows passively from atria into ventricles. Atrial systole pushes remaining 30% of blood into the ventricles, causing ventricular pressure to increase. -During ventricular systole and atrial diastole: The A-V valves close. The chordae tendineae prevent the cusps of the valves from bulging too far backward into the atria. The atria relax. Blood flows into atria from venae cavae and pulmonary veins. The ventricular pressure increases and opens the semilunar valves. Blood flows into the pulmonary trunk and aorta. -A heart beat through a stethoscope sounds like "lubb-dupp" *Sounds are due to closing of heart valves, and vibrations associated with a sudden slowing of blood flow during contraction/relaxation of chambers "Lubb": The first heart sound Occurs during ventricular systole Associated with closing of the A-V valves "Dupp": The second heart sound Occurs during ventricular diastole Associated with closing of the pulmonary and aortic semilunar valves -Murmur: Abnormal heart sound derived from incomplete closure of a valve.
Describe the 3 layers of the heart wall.
-Epicardium-Outer layer; also called visceral pericardium;thin layer. -Myocardium-Middle layer;composed of cardiac muscle tissue;thickest layer Endocardium-Inner layer;forms inner lining of all heart chambers;thin layer
What is the name of the fibrous loose-fitting sac around the heart?
-Fibrous pericardium
Identify the P wave, QRS complex, and T wave of a cardiac cycle. What is the name of the instrument used to record the cardiac cycles?
-P wave: Atrial depolarization; occurs just prior to atrial contraction -QRS complex (3 waves): Ventricular depolarization; occurs just prior to ventricular contraction -T wave: Ventricular repolarization; occurs just prior to ventricular relaxation -electrocardiograph instrument used to record the cardiac cycles.
Describe how the cardiac center in the medulla oblongata regulates blood pressure.
-Pressoreceptors in parts of aortic arch and carotid sinuses are sensitive to changes in blood pres. If b.p. is too high, they signal the cardioinhibitor center in medulla oblongata---> increase parasympathetic impulses---> slows rate & force of contraction.
Distinguish between the pulmonary circuit and the systemic circuit.
-Pulmonary circuit transports oxygen poor blood from the heart to the lungs, and back to the heart. In the lungs blood picks up O2 and drops off CO2. -Systemic circuit transports oxygen rich blood from the heart to all body cells, and back to the heart. Blood delivers nutrients to cells, and removes wastes. -Left side oxygen rich blood -Right side oxygen poor blood
Trace the pathway that a drop of blood would travel from the vena cava to the aorta. Know when it is oxygenated and when it is deoxygenated.
-Superior/Inferior vena cava> right atrium> triscupid valve> right ventricle> pulmonary SL valve> pulmonary trunk> pulmonary artery> lungs ( blood becomes onygenated) > pulmonary veins> left atrium> biscupid valve> left ventricle> aortic SL valve> aorta> body. * Note arteries carry blood away from the heart. * Note veins carry blood toward the heart.
How do sympathetic impulses affect the heart? Parasympathetic?
-Sympathetic fibers in the accelerator nerves join SA & AV nodes. They release norepinephrine to increase heart rate and force of contraction. -Parasympathetic fibers of the Vagus nerve joins SA & AV nodes. They release acetylcholine which slows rate.
What are precapillary sphincters? Why are they so important?
-precapillary sphincters: smooth muscle surrounding capillary when it branches off arteriole or metarteriole -Capillary blood flow regulated mainly by precapillary sphincters.