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117 Cards in this Set
- Front
- Back
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Describe a cardiocyte
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Short, branched muscle fibers that are connected via intercalated disks.
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What do intercalated disks do?
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electrically communicate and anchor cells
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The purpose of interdigitating folds
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Creates more surface area for more anchoring and contact
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Desmosomes
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Anchoring Junctions. A "protein plaque" or thickened area of protein fibers that extend across the membrane to another cell. Prevent from pulling apart--located on cardiocytes
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Gap junctions
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Communicating junctions -- channels between cells. Anything that is small enough, dissolved in cytisol can be transferred through pore. I.E. an electrical signal via ions.
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syncytium
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Everything works together in one unit -- like the heart
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Striations
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muscle fibers that work together for contraction and cause lines in muscle -- similar to cardiac muscle
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How many nuclei in one cardiocyte?
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one
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Where is the Ca++ stored?
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Sarcoplasmic reticulum
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What do the T-Tubules do?
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T-Tubules carry electrical signals and causes opening of channels of SR that releases Ca2++ to bind to troponin and allows tropomyosin to move away from binding site so that a contraction can occur.
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Where are the two sources of Ca++?
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Sarcoplasmic Reticulum and the cytisol via diffusion and specian Na+ Ca++ channels
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What are the primary energy supplies of ATP to the heart?
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At rest, the heart uses primarily fatty acids and glucose and lactic acid can be used during more stressful periods of time.
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What are some reasons the heart is resistant to fatigue?
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Relies on slow-oxidative fibers and aerobic respiration, are rich in myglobin and glucose, Have their own resources for a short period of time, abundant in mitochondria, and can produce ATP from creatine phosphate.
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What are the functions of the conduction system of the heart?
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Coordinate electrical and functional activities, Produce cyclical contraction of atria and ventricle (systole and diastole), and to provide a path of excitation for the heart in a specific fashion
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How many cardiocytes are self-excitable?
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1%
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How does autorhytmicity work?
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self-excitable cardiocytes lack a resting membrane potential and thus spontaneously depolarize. They contain special voltage-gated channels that repolarize immediately after depolarization occurs. Different regions depolarize at different rates, and since cardiocytes are branched, they stimulate nearby cardiocytes to contract as well through electrical activity.
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Where is the sinoatrial node located?
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On the wall of the right atrium near the vena cavae
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How does the sinoatrial node work?
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It is known as the pacemaker and generally depolarizes at a rate off 100 bpm, although heartrate is only around 70 bpm. It initiates the contraction of each cycle, and then sends it to the left atrium and to the atrioventricular node.
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Where is the atrioventricular node located?
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In the interatrial septum.
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How does the atrioventricular node work?
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It is the electrical gateway between the ventricals due to the low conductivity of the fibrous skeleton in the interatrial septum. It slows down the AP of cells and allows the ventricles to fill before they contract. Far less gap junctions in this area due to slowed rate of contraction.
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What does the atrioventricular bundle do, and where is it located?
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It is located at the superior end of the interventricular septum. It is the site of entry for ventricular stimulation --> known as "beginning of funnel"
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Where are the bundle branches located and what do they do?
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They transmit signals through the itnerventricular septum to the apex. This is much more rapid due to the increase in gap junctions.
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Where are the purkinje fibers located and what do they do?
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They spread into the ventricular myocardium. They aid in spreading a rapid signal to contract starting at the apex and moving toward the base.
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What happens first when the AV valves close?
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papillary muscles contract and keep the chordae tendinae resistance in order to keep flaps from going up into the atria.
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What are the two fibers that make up the pacemaker?
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Autorhytmic conduction system and the contractile fibers
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Membrane potential
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Separation of charge across a membrane. Autorhythmic cardiocytes have no stable resting membrane potential.
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Resting membrane potential
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When a membrane is negative on the inside, postive on the outside, no outside stimulation to be changed. Negative voltage number.
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How is an action potential initiated on the pacemaker?
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Because there is no resting membrane potential, at -60 mV, it starts to depolarize again. This causes a spontaneous depolarization as Na+ enters the cell through special voltage-gated channels. Needs no signal.
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Describe the two phases of Action Potential in the pacemaker.
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Depolarization -- happens fast. Ca++/Na+ channels open and ions enter the cell. Rapid depolarization of the cell.
Repolarization -- K+ channels open and K+ leave the cell. Becomes more positive inside the cell. |
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What is Arrhythmia?
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Anytime you have an abnormal rhythm in your heartbeat. For example, when your atria and ventricles are out of sync, fibrilation, a very dangerous situation. Can help to shock the heart.
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What is an Ectopic Focus?
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When the AV node isn't working, the heart is stimulated by anything except the AV node, or a total heart block. This spontaneously produces signals. 40-60 beats per minute, ventricles beat very slow, not enough to sustain brain functioning
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How do epinephrine and norepinephrine affect heart functioning?
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They speed up heartrate. By decreasing the length in time for pacemaker potential. Beta blockers interfere with NE and EP functioning to slow heartrate down.
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Describe and AP of a contractile fiber of the heart.
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Resting potential at -90 mV. Depolarize to 30 mV with Ca++ and Na+. "Plateau Phase." K+ outflow causes depolarization and restores resting membrane potential.
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What happens during the plateau phase of the contraction?
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Channels open from sarcoplasmic reticulum called calcium induced calcium released. Ca++ binds to troponin, releases troponin and tropomyosin so that actin can bind to myosin. There is some K+ outflow to coutnerbalance and level off the plateau phase.
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How does an electrocardiogram work?
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Records the electrical events associated with the heart by measuring the depolarization and repolarization associated with the heart through electrodes. In this way, it assumes contraction and relaxation and can detect certain ailments such as abnormal rhythm, enlargement of the heart, damage, abnormal conduction pathways.
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What are the different waves associated with the electrocardiogram?
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P wave -- atrial depolarization (SA node), QRS complex is ventricular depolarization (AV node) and atrial repolarization, T wave is ventricular repolarization.
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What is hypertrophy?
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Heart enlargement of a ventricle. Can be detected by a larger interval or a wavelength
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Holter Moniter
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ECG that you wear all day
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How do valves open?
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Based on a pressure gradient of blood from one side to another
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What marks the new phase in the beginning of a cardiac cycle?
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The opening and closing of valves in response to a change in the pressure gradient
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When does pressure rise and fall?
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Pressure rises during systole and falls during diastole.
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What is the first phase in the cardiac cycle?
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Ventricular filling
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What happens during ventricular filling?
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Pressure in atria rise above ventricles, AV valves open. passive filling for 2/3 of blood. Atrial contraction. Ventricles in diastole. Semilunar valves are closed. Volume of blood in ventricles rises.
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What is the EDV?
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The amount of blood in the ventricle at the end of the phase ventricular filling phase. The amount of blood you can move at the end of a contraction. Usually a small amount of reserve. 130 mL of blood.
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Describe the isovolumetric contraction.
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Ventricle begins to contract, therefore in early systole, the AV valves close, but the semilunar valves close. Pressure rises in the ventricles but doesn't exceet the aorta and pulmonary trunk, therefore blood doesn't move.
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When is the first heart beat sound heard?
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When the AV valve closes.
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What happens during ventricular ejection?
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Ventricular systole, blood is ejected from the ventricles because the pressure exceeds that of the aorta and the pulmonary trunk.
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What is stroke volume?
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The amount of blood that is available to circulate through the circulatory system as a result from the cardiac cycle. About 70 mL.
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What is ejection traction.
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The ratio of the EDV and the stroke volume. 70/130 mL which is 54%. Measures cardiac health. Vigorous excercise can increase this to 90%.
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What happens during isovolumetric relaxation?
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Ventricles relax, then expand a bit. Semilunar valves close. (AV valves close, so all the valves are closed). By the end of the cycle, atria are filled with blood again in order to fill ventricles with blood.
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What is the dicrotic notch and when is it observed?
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Slight drop in pressure before the semilunar valves close due to the backflow of blood, then rapid rise after closing the valves. This causes a notch in the diagram.
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When is the second heart beat heard?
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When the semilunar valves close (beginning of isovolumetric relaxation)
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What is Cardiac output?
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varies from person to person, measures the pumping ability of the heart. Amount of blood ejected per ventricle per minute. (Both ventricles should be pumping the same amount of blood per minute). At rest, 75 bpm/ 70 ml = 5.25 L per minute. Circulates all your blood each minute.
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What is the formula for Cardiac output?
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Heart Rate x Stroke Volume = Cardiac Output
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What is the cardiac reserve?
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The cardiac output measured when maximally active - resting cardiac output = cardiac reserve.
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How does autonomic innervation effect the heart?
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ANS sends information to the cardiac control center of the heart. Sympathetic speeds up the heart and parasympathetic slows down the heart.
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How does the ANS speed up or slow down the heart?
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If you increase the permeability to Ca++ or Na++ ions, you will shorten the length between depolarization and thus increase heartrate. If you increase permeability to K+ you will decrease permeability to Ca++ you will hyperpolarize the heart and lengthen signals between the heart and thus slow down heartbeat.
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Where are the cardiac centers located?
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Medulla oblongata
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Compare cardiostimulatory/cardioinhibitory.
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Cardiostimulatory increases heartrate via sympathetic nervous system through the release of Na+ and Ca++. Cardioinhibitory decreases heartrate via the parasympathetic nervous system through the release of K+ .
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Where do the cardiac centers recieve input from?
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cerebral cortex, the limbic system, and sensory receptors.
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What are the three types of sensory receptors and what do they do?
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Proprio -- from the joins and skeletal muscle, send messages to cadio center when active to increase heart rate. Baro -- from walls of blood vessels to detect pressure difference and trigger either para or sympathetic pathways. Chemo -- monitor CO2 and O2 and blood pH. Increases the sympathetic ti increase blood O@ and raise blood pH.
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What does the atrial reflex do?
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Increased venous return causes an increase in heart rate monitored by the stretch receptors in the right atrium.
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What are the neurotransmitters of the sympathetic division?
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Norepinephrine and epinephrine. They trigger Ca+ release which elevate heart rate.
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Hyperkalemia
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inhibits reploarization -- slow heart rate due to excess K+ in the blood, positive ions in the blood and prolonged AP.
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Hypokalemia
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Too little K+ in the blood. Thus the muscle hyperpolarizes and has a strong AP. The positive ions move out of faster and cause the heart rate to slow....can make the heart stop.
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What are the three factors that affect stroke volume?
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Preload, Contractility, Afterload.
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What is the preload?
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Amount of tension in the ventricular myocardium immediately before it contracts. If you increase the preload, you increase the stroke volume. Works due to the optimum stretch relationship of the sarcomeres.
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Why isn't the heart overstretch with increased preload?
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The pericardial sac prevents overstretching.
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What is contractility?
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Responsiveness to the fibers to electrical stimulation. Influenced by inotropic agents -- positive inotropic agents elevate blood calcium levels which mean increased contraction strength. Epinephrine and norepinephrine stimulate release of Ca++ . Relates to muscles, not pacemaker.
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What happens if contractility is upregulated too much or too little?
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If too much Ca++, create strong, prolonged contractions, then Can go into cardiac arrest in systole. If too little Ca++, then harder to produce contraction and can go into cardiac arrest in diastole.
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What is the afterload?
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It decreases stroke volume. When blood vessels just distal to semilunar valves are resistant to blood flow. Decrease in stroke is due to the force needed to open the semilunar valves.
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What causes a change in afterload?
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Hypertension, impediments in arterial tissue (scar tissue), causes the blood to work that much harder to get out.
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What is Anaphalactic shock?
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Blood capillaries fill with blood and blood vessels shut off and open constantly
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What are the three layers of a blood vessel?
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Tunica interna, tunica media, tunica externa.
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Describe the tunica interna.
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Inner layer of simple squamous epithelium formed into a tubular structure. This lines the entire blood vessels and is what is exposed to the blood. Is continuous with the endocardium. Selectively-permeable barrier and therefore is basically all capillaries consist of.
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Describe the tunica media.
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Middle layer and usually the thickest layer in larger vessels. Consists of smooth muscle, collage, and elastic tissue in some. Strengthens the vessel to prevent rupture. Also produces vasomotion (responsible for the pressure).
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Describe the tunica externa.
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Sometimes merges with the tunica externa of other blood vessels. Consists of collagen and elastic fibers. Innervated and has tiny little vessels that supplies it with O2-- known as vasa vasorum. Anchors vessels and
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Describe continuous capillaries.
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Contain tight junctions between the capillary cells. Hold cells together and "zip up" the cells so it creates an impermeable layer. Materials pass through narrow intercellular clefts. In brain, there are no intercellular clefts (blood-brain barrier).
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Describe fenestrated capillaries.
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Have pores in cells called fenestrae that filter. Have lots of pores therefore allow for rapid passage of substance. Works for filtration, reabsorption and readsroption. Platelets don't pass through -- found in kidneys and secretory glands and plexuses.
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Describe sinusoid capillaries.
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Contain wide clefts between fenestrated cells. Form wide, twisted passages that are enough for RBC to pass through and are found where RBC and WBC are made. (Liver, kidney)
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Describe the difference between efferent and afferent.
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Efferent is when vessels are carrying blood away from the heart and afferent is when they are carrying blood toward the heart.
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Describe venules.
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Range from capillaries that have some fibroblast material to having a some muscles and a tunica externica. They are small in diameter and have a thin wall.
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Describe conducting arteries.
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Also called elastic arteries due to the high proportion of elastic fibers in the tunica media. Expand and recoil. Functions as the "Pressure Resevior" in order to maintain a constant pressure.
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Describe Distributing arteries
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Arteries continue to branch form conducting arteries. more muscle fibers. Distribute to the organs. More muscle and less elastic tissue in tunica media. Can depress the size of the lumen and channel blood flow.
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Describe the resistance arteries.
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Smallest of the arteries and arterioles, therefore much pressure and resistance. supply parts of organs with O2.
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What is the role of metarterioles?
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To connect the resistance arteries with the capillaries. Connect thoroughfare channels that bypass capillary beds, regulate whether or not blood moves into a capillary bed which is regulated by a precapillary sphincter and primarily involved in the control of the organ blood flow and mean arterial pressure.
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What do arterial sense organ control?
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heart rate, respriation, and vasomotion.
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Why are veracose veins formed?
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Blood sits and pools in veins
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Describe the portal system.
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the blood passes through two capillaries instead of one.
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What are the three types of portal systems?
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hepatic -- goes from digestive system to liver to heart to absorb nutrients and detoxify them.
hypophyseal goes from the hypothalamus to the anterior pituitary glands. Kidneys filter fluid solutes and another resorbes the liquid. |
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What is anastamosis?
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When an artery connests to an artery or a vein connests to a vein. can bypass arteris or shunt veins
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What is collateral circulation?
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An alternat route of supply to an organ in case of blockage
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What is venous enastimosis?
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An alternate route of drainage from an organ in case of blockage.
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What is the most important capillary exchange mechanism?
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Diffusion through intercellular clefts, fenestrations, and plasma membrane.
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Describe transcytosis.
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Vesicles form to transfer substancs across the pm and merge with the EF. This is important for larger molecules like insulin and glycogen.
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Describe bulk flow.
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This is a pressure driven movement (based on a pressure gradient). It involves filtration and resorption. Ideally, don't lose blood volume.
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What are the three pressures involved in bulk flow?
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Hydrostatic pressure, interstitial fluid hydrostatic pressure, and oncotic pressure.
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Describe hydrostatic pressure
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Fluid pressing on the wall of the vessel itself. Directly related to blood pressure. Always higher at arterial end than at venous end. The primary driving force for filtration.
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Describe interstitial fluid hydrostatic pressure (IFHP).
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Generally creates a negative pressure (suction ). Filtration favored at the atrial end. Flows through lymphatic tissues.
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Describe Oncotic Pressure.
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Due to the presence of proteins in the blood. Unable to cross capillary wall at higher osmotic pressure. More likely to be drawn into the compartment.
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What are the two types of oncotic pressure.
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Blood colloid oncotic pressure (BCOP) and interstitial fluid colloid oncotic pressure (IFCOP)
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Describe BCOP
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Type of oncotic pressure. Primarily due to plasma proteins, favors resorption. More proteins in the plasma, the more reabsorption we see. Opposing force of the filtration. Most important force of resorption at the venous end of the capillary.
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Describe IFCOP
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Type of oncotic pressure. Concentration of proteins in interstitial fluid. Typically lowers the force of blood plasma but doesn't negat it. Favors Filtration.
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What is the only force that opposes filtration and favors reabsorption?
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Plasma protein concentration in the blood.
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What is the net filtration pressure?
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Measure of the net movement of fluid between blood and interstitial fluid. Describe what's happening to a changing volume. May show if you are not recovering blood components.
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What is NFP and how can we measure it?
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Net hydrostatic pressure, positive number means movement out of capillary, negative number means net movement into the capillary.
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What happens to the fluid that is not taken up by the capillaries?
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They are recaptured by the lymphatic vessels. About 15 % is returned by resorption.
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What is edema?
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swelling accumulation in interstitial space. Cells can become impaired and die if surrounded by too much fluid. Can cause a drop in blood volume.
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What causes edema?
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Lymphatic drainage is blocked, filtration pressure greatly exceeds reabsorption pressure. (hypertension, increased capilarly permeability, decreased concentration of plasma proteins)
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What is blood flow?
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mL per minute that passes through a given tissue per minute. Total blood flow = cardiac output. The larger the gradient, the faster the blood flows from place to place.
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What is blood pressure?
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pulsatile -- pressure exerted on the walls of the blood vessels, generated by ventricle contraction.
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How is blood pressure effected?
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High sodium diet elevates blood pressure, quality of blood vessels can affect bp, and blood volume.
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How is blood volume controlled?
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By the kidneys. Can be a long term regulation mechanism.
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A pacemaker potential is aresult of what ion inflow?
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Na+
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Stroke volume is proportional to what?
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EDV
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What is the stroke volume?
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End diastolic volume - end systolic volume.
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What will a decrease in afterload result in?
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An increase in stroke volume.
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