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261 Cards in this Set
- Front
- Back
what is the coronary blood supply?
|
supplies the heart with oxygenated blood and then goes back to heart to get oxygenated again
|
|
what are the two walls of the pericardium?
|
1. fibrous pericardium (pericardial sac)
2. serious pericardium |
|
where is the fibrous pericardium located?
|
it goes up around the vessels and attaches to diaphragm
|
|
what are the three main functions of the fibrous pericardium?
|
1. protects
2. anchors 3. prevents overfilling because of dense CT=prevents overstretching |
|
what are the two layers of the serous pericardium?
|
1. parietal layer (parietal pericardium)- fused to fibrous pericardium; very thin and smooth which allows mvmt of the heart
2. visceral layer (epicardium)- adheres to heart surface |
|
what are the three layers of the heart wall?
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1. epicardium
2. myocardium 3. endocardium |
|
what is the myocardium?
|
-muscular wall that forms both atria and ventricles
-75% of heart wall |
|
how are muscle cells tethered together in the myocardium?
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by crisscrossing CT fibers
|
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what is the arrangement of the myocardium?
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arranged in spiral or circular bundles
|
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what is the endocardium?
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-inner surface- lines heart chambers
-covers fibrous skeleton of valves |
|
what is the endocardium continuous with?
|
endothelial linings of blood vessels leaving and entering the heart
|
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what is the epicardium?
|
-visceral pericardium
-covers the outer surface of heart -consists of an exposed mesothelium and loose areolar CT |
|
what four characteristics differentiate cardiac muscle tissue from skeletal?
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1. small cell size
2. single, central nucleus 3. branching interconnections between cells 4. specialized intercellular connections |
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what do cardiac muscle cells obtain the energy they need to continue contracting from?
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aerobic metabolism because the sarcoplasm contains many mitochondria and myoglobin
|
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where and how are cardiac muscle cells bound together?
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at intercalated discs by desmosomes and gap junctions
|
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what do gap junctions allow?
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direct electrical connection
|
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why has cardiac muscle been called a functional syncytium?
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because the cells are mechanically, chemically, and electrically connected to one another, the entire tissue represents a single, enormous muscle cell
|
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where is the heart located?
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in the mediastium, suspended within the pericardial cavity
|
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what does the paricardial cavity contain?
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pericardial fluid that reduces friction between the opposing surfaces as the heart beats
|
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what is cardiac tamponade?
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occurs when traumatic injuries damage the pericardium or chest wall and can result in fluid accumulation in the cavity which can restrict the mvmt of the heart
|
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what are sulci?
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shallow grooves that mark the boundaries between the atria and ventricles and between the right and left ventricles
|
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what does the CT of the epicardium generally contain?
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a lot of fat
|
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explain the walls of the two atria
|
thin musclular walls that are highly expandable
|
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what is an auricle?
|
in the atrium and is an expandable extension
|
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what is the coronary sulcus?
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deep groove border between the atria and ventricles
|
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what is the ligamentum anteriosum?
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-attaches the pulmonary trunk to the aortic arch
|
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what is the anterior interventricular sulcus?
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boundary between the left and right ventricles
|
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what veins is the left atrium connected to?
|
pulmonary veins
|
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what veins is the right atrium connected to?
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coronary veins and vena cavae
|
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what is the coronary sinus?
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-carries blood collected from the myocardium
-conveys blood to right atrium |
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what is the posterior interventricular sulcus?
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boundary between left and right ventricles
|
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what does the coronary circulation supply?
|
blood to the myocardium because it needs its own separate blood supply
|
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where are coronary arteries?
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originate in the base of the aorta, where BP is highest
|
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myocardial flow is not steady. explain
|
it peaks while the heart muscle is relaxed and almost ceases when it contracts
|
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what do marginal arteries from the right coronary artery supply blood to?
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the surface of the right ventricle
|
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where does the left coronary artery supply blood to?
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the left ventricle, left atrium, and interventricular septum
|
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what supplies the posterior interventricular artery?
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the right coronary artery
|
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what does the posterior interventricular artery suuply blood to??
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the interventricular septum and adjacent portions of the ventricles
|
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what do the anterior cardiac veins drain and empty into?
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drain the anterior surface of the right ventricle and empty into the right atrium
|
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what does the great cardiac vein drain blood from?
|
the region supplied by the anterior interventricular artery
|
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where does the coronary sinus open into?
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the right atrium
|
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where does the small cardiac vein recieve blood from? where does it empty into?
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recieved from the right atrium and ventricle
-empties into the coronary sinus |
|
what is elastic rebound?
|
everytime the left ventricle contracts, it forces blood into the aorta which stretches the elastic walls of the aorta
|
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where does elastic rebound push blood?
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forward into the systemic circuit and backward into the coronary arteries
|
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what separates the atria?
|
interatrial septum
|
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what separates the ventricles
|
the thicker interventricular septum
|
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what do atrioventricular (AV) valves permit?
|
blood flow in one direction only, atria->ventricle
|
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what three veins does the right atrium recieve blood from?
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the superior vena cava
the inferior vena cava the coronary sinus |
|
what what is the fossa ovalis?
|
-right atrium
-remnant of the foramen ovale in the embry -depression in the wall of the interatrial septum |
|
where are the pectinate muscles?
|
-right atrium
-the anterior wall of the right atria and continues up to the auricle of right atrium |
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from the right atrium, what does the blood pass through to the right ventricle?
|
the tricuspid valve
|
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from the right ventricle, where does blood pass through to get to the pulmonary trunk?
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the pulmonary valve
|
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what is the chordae tendineae?
|
-ventricle (right in this case)
tendinous chords that connect the AV valve (tricuspid) to papillary muscles |
|
what is trabeculae carnea?
|
raised bundles of cardiac muscle fibers on the inner surface of ventricles
|
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what are the walls of the left atrium like?
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-inside of walls are smooth
-same thickness as right atrium |
|
where does the left atrium recieve blood from?
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the lungs through 4 pulmonary veins
|
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where are the pectinate muscles in the left atrium?
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confined to the auricle
|
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from the left atrium, where does the blood pass through to get to the left ventricle?
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the bicuspid valve
|
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why does the left ventricle have the thickest wall?
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because it is pumping to the entire body
|
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what type of arteries does the left ventricle consist of?
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coronary arteries
|
|
from the left ventricle, where does the blood pass through to the aorta?
|
the aortic valve
|
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what part of the left ventricle carry blood throughout the body?
|
branches of aortic arch and descending aorta
|
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why does the right ventricle have a thin wall?
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because it doesnt need to work hard to push blood since lungs are close and pulmonary vessels are short and wide
|
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when the right ventricle contracts, where does it squeeze the blood?
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against the thick wall of the left ventricle; develops low pressures
|
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what three things happen when the left ventricle contracts?
|
1. the diameter of the ventricular chamber decreases
2. the distance between the base and apex decrease (toothpaste) 3. reduces the volume of the right ventricle (why some people can live if right ventricle is damaged) |
|
what are aortic sinuses?
|
-saclike dilations adjacent to each cusp
-where the coronary arteries originate |
|
what happens when ventricles relax?
|
when ventricles relax, so do papillary muscles. chordae tendinae are loose, valves open, and cusps project into the ventricles
|
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when ventricles contract what happens to the valves and why?
|
-they close because the papillary muscles contract to prevent valves from backflow in response to high pressure
|
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as the ventricular pressures rise above those in the pulmonary and systemic circuits, what happens?
|
the aortic and pulmonary valves open and blood flows out of the ventricles
|
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what is the cardiac skeleton?
|
dense bands of tough elastic tissue that encircle the heart valves
|
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what are the two functions of the cardiac skeleton?
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1. stabilize the positions of the heart valves and ventricular muscle cells
2. isolate the ventricular myocardium from the atrial myocardium |
|
where are the semilunar valves?
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in the pulmonary and aortic valve, each contain three semilunar valves
|
|
what do semilunar valves do?
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-allow ejection and prevent backflow
|
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explain the blood flow of the semilunar valves?
|
pressure builds up as ventricles contract, pushing blood out. as ventricles relax, cusps fill up causing closure
|
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what are the 4 steps of contraction?
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1. begins at SA node (spontaneous depolarization) across both atria and reaches AV node
2. AV node enter atrial septum and passes bundle of HIS (AV bundle) 3. travels left and right bundle branches to apex 4. signal passes upwards to base via perkinje fibers |
|
what happens if SA node is damaged during a contraction?
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AV node takes over
|
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what happens if both the SA node and AV node are damaged?
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the bundlee of HIS takes over (20-30 beats)
|
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what is systole and what does the chamber do?
|
contraction
|
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what is diastole and what does the chamber do?
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relaxation
|
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what is cardiac cycle determined by?
|
atria
|
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what happens to the phases of the cardiac cycle when HR increases?
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are shortened
|
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when heart rate increases, what phase has the greatest reduction?
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diastole by almost 75%
|
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what are the eight stages of a cardiac cycle?
|
1. chambers relaxed and ventricles partially filled
2. atrial systole 3. atrial diastole 4. ventricular systole- first phase; isovolumentric contration 5. ventricular systole- second phase 6. ventricular diastole- early 7. isovolumetric relaxation 8. ventricular diastole- late |
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what happens during atrial systole?
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atria contract filling ventricles
|
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what is atrial diastole?
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atrial systole ends and this continues until start of next cycle
|
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when does ventricular systole begin?
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when atrial systole ends
|
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what happens during the first phase of ventricular systole?
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contraction closes AV vales but not enough pressure to open semilunar valves
|
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what is isovolumetric contraction?
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when AV valves close but not enough pressure is created to open semilunar valves
|
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what happens during the second phase of ventricular systole?
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pressure rises and exceeds pressure in arteries, semilunar valves open and blood is forced out
|
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what is ventricular ejection?
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when blood is forced out during ventricular systole
|
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what happens during early ventricular diastole?
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ventricles relax, pressure drops, blood flows back and forced semilunar valves closed
|
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what is isovolumetric relaxation?
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when blood flows into the relaxed atria but AV valves are closed
|
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what happens during late ventricular diastole?
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all chambers relaxed, ventricle begins passively filling
|
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what is a dicrotic notch and when does it occur?
|
double beating; occurs when semilunar valves close, pressure rises again and the elastic arterial walls recoil
|
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what does S1 ("lubb") mark the start of?
|
ventricular contraction
|
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when does S2 occur?
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when the semilunar valves close
|
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what causes S3?
|
blood flowing into the ventricles
|
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what causes S4?
|
atrial contraction
|
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what is the best overall indicator of peripheral blood flow?
|
cardiac output CO
|
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what two factors does cardiac output depend on?
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stroke volume (SV) and heart rate
|
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what is stroke volume
|
the amount of blood pumped out of the ventricle during a single heartbeat
|
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what is the conducting system?
|
responsible for initiating and distributing the stimulus to contract
|
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how does the heartbeat begin?
|
with an AP by an SA node in the right atrium
|
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where are conducting cells in the atria found?
|
internodal pathways
|
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what do internodal pathways do?
|
distribute the contractile stimulus to atrial muscle cells toward ventricles
|
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where is the AV node located?
|
bwteen the atria and ventricles
-dont effect heart rate |
|
if SA node is damaged, at what rate ill the AV node begin generates impules?
|
40-60 beats/min
|
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what are purkinje fibers?
|
-large-diameter conducting cells that propagate action potentials rapidly
-final link in distribution network |
|
what are purkinje fibers responsible for?
|
the depolarization of the ventricular myocardial cells that triggers ventricle systole
|
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where do the AV nodes deliver the stimulus to/
|
AV bundles
|
|
what is the AV bundle?
|
only electrical connection between the atria and the ventricles
|
|
what does the AV bundle lead to?
|
the bundle branches
-left bundle branch is much bigger than right |
|
what are the five steps of distribution of the contractile stimulus?
|
1. AP generate by SA node-atrial activation
2. stimulus speads by cell-to-cell contact to AV node 3. 100-msec delay at AV node- atrial contraction 4. atrial contraction completed, impulse within AV bundle which branches to Purkinje fibers- ventricular contraction 5. purkinje cells distribute impulse and is relayed through ventricular myocardium |
|
after atrial contraction, how and where does the impulse travel?
|
travels within the AV bundle which branches to the purkinje cells through the moderator band to the papillary muscles
|
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what is the maximum rate an AV node can conduct?
|
230 beats/min- maximum normal HR
|
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what is the prepotential or pacemaker potential?
|
gradual depolarization due to an instable resting potential produced by the nodes
|
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why does the SA node establish the HR?
|
because spontaneous depolarization is fastest at the SA node so it reaches threshold first
|
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what is the effect of parasympathetic stimulation on the heart rate?
|
-K+ channels open which slows the rate of depolarization and extends the duration of repolarization
-decline in HR |
|
what is the effect of sympathetic stimulation on the heart rate?
|
-opening of ion chaneels that increase depolarization and shorten repolarization
-HR increases |
|
what is the normal range of a resting heart rate?
|
60-100 bpm
|
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where are the autonomic headquarters for cardiac control contained?
|
within the medulla oblagata
|
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what does the cardoinhibitory center control?
|
parasympathetic neurons that slow the HR
|
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what does cardiacceleratory center control?
|
sympatheric neurons that increase HR
|
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where does sympathetic innervation arrive and what do they innervate?
|
arrives in postganglionic fibers and these fiber innervate conduction system, nodes, and the atrial and ventricular myocardium
|
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where does the parasympathetic innervation arrive and what do they synapse with?
|
arrives in the vagus nerve and synapses with the ganglion cells
|
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what is innervated in parasympathetic innervation?
|
nodes and atrial musculature; ventricular musculature is very limited
|
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what is the end-diastolic volume (EDV)?
|
amount of blood in a ventricle at the end of diastole (pump is just filled)
|
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what is end-systolic volume (ESV)?
|
blood that remains in the ventricle at the end of ventricular systole
|
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what is the stroke volume in correlation with ESV and EDV?
|
it is the difference between the two
|
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what are the normal values at rest for:
1. EDV 2. ESV 3. SV 4. HR 5. CO |
1. 125 ml
2. 50 ml 3. 75 ml 4. 60-80 bpm 5. 5L/min; ~1.3 gallons |
|
what is EDV influenced by?
|
venous return and filling time
|
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what is venous return?
|
amount of venous blood delivered ti heart by the venae cavae (pulmonary veins) each minute
|
|
what factors determine venous flow?
|
-blood volume-decreased amounts decreases return
-muscular activity- contraction increases return -the rate of blood flow- accelerated blood flow increases return |
|
what is filling time?
|
the duration of ventricular diastole
|
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what does slowing the HR do to the EDV?
|
increases the EDV
|
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what is the preload?
|
-amount of myocardiac stretching
-larger the EDV, larger the preload |
|
what is the Frank-Starling law of the heart?
|
the greater the EDV the greater the SV because it produces more powerful contractions and ejects more blood
|
|
what is contractility?
|
-the amount of force produced during a contraction at a given amount of preload
|
|
what type of activation increases contractility/
|
sympathetic
|
|
what increases contractility? decreases it?
|
increase- many hormones (E, NE)
decrease- many clinical drugs |
|
what is the afterload?
|
the amount of tension the contracting ventricle must produce to force open the semilunar valve and eject blood
|
|
explain the correlation between afterload and ESV and why?
|
the greater the afterload, the longer the period of isovolumetric contraction, the short the duration of ventricular ejection, and the larger the ESV
|
|
what is the afterload increased by?
|
any factor that restricts blood flow
|
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what is ESV influenced by?
|
contractility and afterload
|
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what is the P wave?
|
depolarization of the atria
|
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what is the QRS complex?
|
appears as ventricles depolarize; strong electrical signal; complex signal
|
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what doe sthe peak of R wave mark?
|
the beginning of ventricular contraction
|
|
what is the T wave?
|
ventricular repolarization
|
|
what is the Q-T interval?
|
the time required for the ventricles to undergo a single cycle
|
|
what are cardiac arrhythmias?
|
abnormal patterns of cardiac electrical activity
|
|
what is cardiac reserve?
|
in abdomen and skin (in capillary beds)
-the difference between resting and maximal CO |
|
what are the normals of cardiac reserve for rest, light exercise, heavy exercise, and trained athlete?
|
rest: 5-6 L/min (1.5 gal)
light: 9.5 L/min (2.5 gal) heavy: 17.5 L/min (4.5 gal) trained: 30 L/min (7.5 gal) |
|
what is myocardial contractility?
|
contractile strength achieved at any given muscle length (independent of muscle stretch and EDV)
|
|
what happens to calcium influx during AP?
|
greater influx to get more to sarcolemma from cytoplasm
|
|
what effect does enhanced contractility have on SV? ESV?
|
SV- increase
ESV- decrease |
|
what two factors play a role in the extrinsic regulation of SV?
|
1. increased sympathetic stimulation
2. glucagon, thyroxine, and high levels of Ca+ |
|
what happens with sympathetic stimulation such as NE/E in regulating SV
|
increase in Ca+ entry which promoted cross bridge binding
|
|
when does sympathetic system release NE?
|
when activated by emotional or physical stressors
|
|
in general what happens when symp. nervous system is activated?
|
-pacemaker fires more rapidly, heart beats faster
-enhances contractility speeds relaxation |
|
how does the sympatheric system enhance contractility which speeds relaxation?
|
-enhances Ca+ movements in cells
-ESV falls as a result so SV doesnt decline |
|
what effect does parasympathetic division have on contractility?
|
no effect
|
|
what are the three layers of blood vessels?
|
1. tunica intima
2. tunica media 3. tunica externa |
|
what is the tunica intima?
|
-innermost, interna
-includes endothelial lining -elastic fibers |
|
what is the internal elastic membrane?
|
-in arteries of the tunica intima
-contain thick layer of elastic fiber |
|
what is the tunica media?
|
-middle layer
-contains smooth muscle tissue |
|
what is vasodilation?
|
when smooth muscles relax and diameter increases
|
|
what is vasoconstriction?
|
smooth muscles contract, vessel diameter decreases
|
|
what is the tunica externa?
|
-outermost layer; tunica adventida
-connective tissue sheath |
|
what does the tunica externa contain in arteries?
|
collagen fibers with scattered bands of elastic fibers
|
|
what does the tunica externa contain in veins?
|
-thicker than tunica media
-network of elastic fibers and smooth muscle cells |
|
what is a large vein?
|
-includes the superior and inferior vena cavae
-tunica externa consists of elastic and collagen fibers |
|
how big are medium-sized veins?
|
-2-9mm
|
|
what does the tunica externa contain of medium sized veins?
|
smooth muscle cells, elastic and collagen fibers
|
|
what are venules?
|
-they collect blood from capillary beds
-smallest venous vessels -lack a tunica media and resemble expanded capillaries |
|
what are elastic arteries?
|
-transport blood away from heart
-pulmonary trunk and aorta |
|
what are muscular arteries?
|
medium sized arteries that distribute blood to the bodys skeletal muscles and internal organs
|
|
what are arterioles?
|
-have poorly defines tunica externa
-tunica media consists of only one or two layers of smooth muscle cells |
|
what are capillaries?
|
only blood vessel whos walls permit exchange between the blood and surrounding interstsitial fluids
|
|
why can exchange in capillaries occur quickly?
|
because the walls are thin and diffusion distances are short
|
|
what are the five general classes of blood vessels?
|
1. arteries
2. arterioles 3. capillaries 4. venules 5. veins |
|
what are arteries?
|
they carry blood away from the heart and branch repeatedly forming arterioles
|
|
what are arterioles?
|
smallest arterial branches that pushes blood into capillaries
|
|
fromthe capillaries, where does the blood flow?
|
enters small venules that form veins
|
|
what are veins?
|
return blood to the heart
|
|
what does a typical capillary consist of?
|
-a tube of endothelial cells within a delicate basal lamina
-lacks a tunica media and a tunica externa |
|
what two types of capillaries are there?
|
continuous and fenestrated
|
|
what are continuous capillaries?
|
-endothelium is the complete lining
-in all tissues except epithelia and cartilage |
|
what do continuous capillaries permit?
|
the diffusion of water, small solutes, and lipid soluble materials
|
|
what do continuous capillaries prevent?
|
the loss of blood cells and plasma proteins
|
|
in specialized continuous capillaries, how are endothelial cells bound together?
|
by tight junctions causing permeability to be restricted and regulated
|
|
what do fenestrated capillaries contain?
|
"windows" or pores that penetrate the endothelial lining
|
|
what do fenestrated capillaries permit?
|
the rapid exchange of water and solutes between the plasma and interstitial fluid
|
|
what are sinusoids?
|
-resemble fenestrated capillaries flat and irrgeularly shaped
-have gaps between adjacent cells -basal lamina is thin or absent |
|
what do sinusoids permit?
|
free exchange of water and solute between slow-moving blood and interstitial fluid
|
|
where domany sinusoids occur?
|
liver, bone marrow, spleen, and many endocrine organs
|
|
what are collateral arteries?
|
when capillary bed recieves blood from more than one artery
-fuse before giving rise to arterioles |
|
what is arterial anastomosis?
|
like an insurance policy; if one artery is compressed or blocked, capillary circulation will continue
|
|
what is a precapillary sphincter?
|
the band of smooth muscle that guards the entrance to each capillary
|
|
what is arteriovenous anastomosis?
|
-a direct connection between arteriole and a venule
-when dilated, will flow directly into venous circulation |
|
what are these anastomoses regulated by?
|
sympatheric innervation
|
|
what do capillary beds contain?
|
-direct connections between arterioles and venules
|
|
what is a metarteriole?
|
the wall in the initial part of the direct passageway (provided by the capillary beds)
|
|
what is the thoroughfare?
|
the rest of the passageway
|
|
what is vasomotion?
|
the cycling of contraction and relaxation of the smooth muscles that control the blood flow through the capillary beds
|
|
what are valves?
|
-fold of the tunica intima that project from vessel valls and point in the direction of blood flow
|
|
what happens if the walls of the veins near the valves weaken, stretch, or become distorted?
|
valves may no longer work properly
|
|
what are varicose veins?
|
superficial in the thighs and legs that causes mild discomfort and cosmetic problems
|
|
what are hemorrhoids?
|
painful distortion of tissues in the anal canal
|
|
how do valves ddivide the weight of the blood?
|
through compartmentalizing
|
|
what do valves above the contracting muscles do?
|
open and allow blood to move toward the heart
|
|
what do valves below the contracting muscles do?
|
close and prevent backflow
|
|
how does the body maintain blood volume with the arterial system at near-normal levels?
|
by reducing the volume of the blood in the venous system through venoconstriction
|
|
what is venoconstriction?
|
reducing the blood diameter of the veins and the amount of blood contained in the venous system
|
|
where does blood enter the general circulation from?
|
liver, bone marrow, and skin
|
|
(endocrine2) what three factors regulate the heart rate?
|
1. ANS
2. parasympathetic division 3. chemicals |
|
what chemicals regulate the heart rate?
|
hormones such as epinephrine (adrenal medulla), thyroxine (thyroid), and ions
|
|
what does thyroxine do?
|
-causes a slower but more sustained increase in HR
-enhances effects of NE/E |
|
how do ions regulate heart rate?
|
plasma electrolyte balance must be maintained
|
|
what does hypocalcemia do?
|
supresses the heart; too little calcium
|
|
what does hypercalcemia do?
|
prolongs the plateau phase of AP
|
|
what does hyperkalemia do?
|
interferes with depolarixation (lowers resting potential)- cardiac arrest
|
|
when does blood pressure fall progressively?
|
as the distance from the left ventricle increases
|
|
what is capillary exchange?
|
primary focus of the cardiovascular system; pressures are very low so blood flows slowly allowing plenty of time for diffusion
|
|
what is total peripheral resistance?
|
resistance of the entire cardiovascular system
|
|
what three factors does total peripheral resistance depend on?
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1. resistance
2. viscosity 3. turbulence |
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what is peripheral resistance?
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resistance of the arterial system as a whole
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what is vascular resistance?
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resistance of the blood vessels
-largest component of total peripheral resistance -results from friction between blood and the vessel walls |
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what two factors does the amount of friction depend on?
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1. vessel length
2. vessel diameter |
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what is the relationship between friction and vessel length?
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-friction occurs between moving blood and the walls of the vessel
-longer the vessel, greater the surface area in contact with the blood, and the greater the resistance |
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when do you see the most dramatic changes in blood vessel length?
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birth and maturity
-considered constant in adults |
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what is the relationship between friction and vessel diameter?
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-friction occurs between layers of fluid moving at different speeds
-in small diameter vessel, blood is slowed and resistance is high vise versa with large diameter |
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what does R=1/r4 mean?
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vessel radius (r), resistance (R)
-means that a small change in vessel diameter produces a large chain in reistance |
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so how do vasomotor centers primarily control peripheral resistance and blood flow?
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by altering the diameters of the arterioles
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what is viscosity?
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resistance to flow caused by interactions among molecules in a liquid (molasses); low viscosity=low pressure
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what is turbulence?
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-when the flow of the blood is disturbed by high flow rates, irregular surfaces, and sudden changes in vessel diameter
-increases resistance and slows blood flow |
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when in normal individuals, where does turbulence occur?
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1. when blood flows between the atria and the ventricles
2. between the ventricles and the aortic and pulmonary trunks |
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what is turbulent flow responsible for?
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the production of the third and fourth heart sounds
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what is a pressure gradient?
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the difference in pressure from one end of the vessel to the other
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where is the largest pressure gradient found?
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between the base of the aorta and the ends of peripheral capillary beds
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what happens to the diameter of arteries as blood proceeds towards the capillaries? toward the heart?
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decreases; increases
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why does blood flow accelerate in the venous system even though pressures are falling?
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because vessels are merging into large diameter passages with very low resistance
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what is systolic pressure?
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highest pressure attainted in arteries during systole (110 mmHg)
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what is diastolic pressure?
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the lowest arterial pressure during diastole (70 mmHg)
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what is the pulse pressure?
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difference between systolic and diastolic pressures
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what is the mean arterial pressure (MAP)
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used to measure how much blood is being pumped out of the heart
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what thee things does capillary exchange involve?
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1. diffusion
2. filtration 3. reabsorption |
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what is capillary hydrostatic pressure (CHP)
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-the blood pressure within the capillary beds
-provides driving force for filtration -pushes water and small soluble molecules out of the bloodstream and into the interstitial fluid |
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when is diffusion most rapid?
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1. when distances are short
2. small ions or molecules are involved |
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what is diffusion important for?
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solute exchange
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why do rates of filtration and reabsorption gradually change as blood passes along the capillary?
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because in a capillary, blood pressure declines as blood flows from arterial end to venous end
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where does filtration predominate?
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-at the arterial end where CHP is highest
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what is blood colloid osmotic pressure (BCOP)?
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plasma osmolarity
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as filtration occurs, what happens to the BCOP?
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it increases because water is depearting leaving the larger solutes behind
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what is filtration important for?
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the regulation of relative volumes of blood and interstitial fluid
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what is the net filtration pressure (NFP)?
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difference between the CHP and the BCOP; large at start of capillary then CHP decreases as water moves out and BCOP increase
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when CHP falls below BCOP in the final segment, what happens?
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water flows into the capillary
-more water leaves the blood during filtration than gets retrieves through reabsorption |
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what is interstitial fluid colloid osmotic pressure (ICOP) involved in?
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filtration; 0 mmHg
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what is reabsorption?
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-pressure driven from interstitial fluid into blood capillaries
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what two mechanisms are involved in reabsorption?
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1. BCOP 25 mmHg
2. interstitial fluid hyrostatic pressure (IHP) 0 mmHg |
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what does net filtration pressure (NFP) indicate?
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the direction of fluid movement
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what is starling law of capillaries?
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overall the volume of fluid and solutes reabsorbed is almost as large as the volume filtered
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