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A&P II Exam 6
Terms in this set (78)
Epicardium (Heart Layer)
Outer layer of the heart
Myocardium (Heart Layer)
Striated, branched muscle cells joined by intercalated discs and gap junctions, middle part
Endocardium (Heart Layer)
Inner part of the heart.
Systematic loops (Circulation)
Ejection of oxygenated blood from the left ventricle, to cells of the body, and then return to the right atrium
Pulmonary loops (Circulation)
Ejection of deoxygenated blood from the right ventricle, to the lungs for oxygenation, and then return to the left atrium
Trace Flow of Blood
*This is deoxygenated
-Right Atrium: Receives blood from vena cava, inferior vena cava, and coronary sinus
-Through tricuspid valve: Right AV
-Right Ventricle: Pumps blood to the lungs. Most of the anterior surface of the heart.
-Through Pulmonary Semilunar Valves
-Through pulmonary arteries
*This is Oxygenated
-Lungs oxygenation in pulmonary capillaries
-Through pulmonary vein
-Left Atrium: Receives blood from the lungs through four pulmonary veins.
-Through bicuspid valve: Left AV
-Left Ventricle: Sends blood throughout the body: Blood flows through the aortic valve to the aorta.
Ensure one way flow of blood.
Atrioventricular Valve (AV)
Valves between the atria and the ventricles
-Left AV valve is also called the bicuspid (2 flaps) or mitral
-Right AV valve is also called the tricuspid (3 flaps)
Valves Leading away from the ventricles
-Pulmonary semilunar = valve between right ventricle and the pulmonary artery (deoxygenated)
-Aortic semilunar = valve between the left ventricle and the aorta (oxygenated)
Holds the AV valves to prevent them from prolapsing back into the atria during the high pressure that the ventricles put on the blood when they contract (prolapsing means the valve flaps go the wrong way)
Sound 1 (lubb): Atrioventricular valves and surrounding fluid vibrations as valves close at beginning of ventricular systole
Sound 2 (dupp): Results from closure of aortic and pulmonary semilunar valves at beginning of ventricular diastole, lasts longer
Sound 3 (occasional): Caused by turbulent blood flow into ventricles and detected near end of first one-third of diastole
Turbulent Flow and Laminar Flow
Blood flow to the myocardium to provide the heart muscle with oxygen and nutrients. Blood flows directly out of the aorta through the left and right coronary arteries, branches into capillaries to bathe the heart muscle (myocardium) in nutrients, then flows back to the right atrium via the coronary veins that meet at the coronary sinus- Blood flow interruption to the coronary arteries and their branches is a heart attack (myocardial infarction).
Conduction and Contraction
Cardiac muscle cells of the myocardium
intercalated disks, gap junctions
-Every muscle cell of the atrial and ventricle myocardium contracts at the same time (first atria, then ventricles)
Specialized cell-cell contacts.
Cell membranes interdigitate (like fingers of clasped hands)
Desmosomes hold cells together
-A special kind of junction that holds individual heart muscle cells together (only found in heart muscle, not skeletal).
Allow action potentials to move from one cell to the next.
Electrically, cardiac muscle of the atria and of the ventricles behaves as single unit
-Allow the inside of every cell to share the cytoplasm - This means if one depolarizes, they all will since they essentially share their cytoplasm and act as one giant cell (also unique to heart muscle).
Autorythmic Cells (Pacemaker Cells)
A small group of cells (NOT muscle cells) that are leaky to cations (mainly sodium through "funny channels") so they automatically and repeatedly reach threshold and then fire without any external signals. These small groups of cells then cause the myocardium to depolarize by communicating through gap junctions.
Path of conductance of electrical
SA Node (Conducting System)
Primary pacemaker - Depolarizes 60-90 times per minute- fibers send signal to the rest of the atria and to the AV node
Chronic failure of the SA node may require an artificial pacemaker
AV Node (Conducting System)
Depolarizes 40-60 times per minute but only depolarizes if the SA node fails. After the signal from the SA node reaches the AV node, there is a short pause before it sends the signal to the AV bundle (bundle of His). This is necessary to let the atria contract and fill the ventricles. Damage to this area or the AV bundle can delay or stop the signal from going to the ventricles (extended PR interval, or heart block)
AV Bundle and Purkinje Fibers
30-40 times per minute. Network of fibers that causes the ventricles to depolarize all at the same time. The depolarization and subsequent contraction starts at the apex and moves up to squeeze the blood toward the aorta and pulmonary artery.
Heart muscle, calcium, and refractory period
Voltage gated Calcium channels on the cell membrane open during a heart muscle action potential which allows extracellular calcium into the cells. The positively charged calcium offsets the repolarizing effect of potassium and keeps the cell in a depolarized state for a longer period of time. This has the effect of lengthening the refractory period which prevents the cell from depolarizing too quickly following the previous depolarization event. If not for this, the heart muscle could contract and stay contracted.
Waveforms on an electrocardiogram (EKG or ECG)
P-wave, QRS Complex, and T-wave
Is a small upward deflection - represents atrial depolarization
(Spreads from SA node throughout the atria)
Large, upright, triangular wave flanked by two smaller downward waves - represents rapid ventricular depolarization - Atrial repolarization occurs here too but it is masked by the larger depolarization signal of the ventricles.
Small, wider upward deflection - represents ventricular repolarization
A heart block is indicated by a delay in getting the signal from the atria to the ventricles (increased PR interval) and usually indicates damage to the area of the AV node and/or AV bundle (Bundle of His).
Very rapid, random, inefficient, and irregular contractions of the heart (350 beats or more per minute) or
quick, uncoordinated contraction of the ventricles or atria
Increased heart rate (usually over 100 beats per minute
Slow heart rate (usually under 60 bpm)
Cardiac Cycle stage 1
1. Atrial systole: active ventricular filling. The atria contract,
Increasing atrial pressure and completing ventricular filling
while theventricles are relaxed. (Semilunar Valves Closed and AV Valves opened.
Cardiac Cycle stage 2
2. Ventricular systole: period of isovolumetric contraction. The
atria are relaxed, and blood flows into them from the veins.
ventricular contraction causes ventricular pressure to increase
and causes the AV valves to close, which is the beginning
of ventricular systole. The semilunar valves were closed in
the previous diastole and remain closed during this period
(Semilunar Valves closed and AV Valves opened)
Cardiac Cycle stage 3
3. Ventricular systole: period of ejection. Continued ventricular
Contraction causes agreater increase inventricular
pressure, which pushes blood out of the ventricles,
Causing the semilunar valves to open.
(Semilunar Valves opened and AV Valves closed)
Cardiac Cycle stage 4
4. Ventricular diastole: period of isovolumetric relaxation. As the
ventricles begin to relax at the beginning of ventricular
diastole, blood flowing back from the aorta and pulmonary
trunk toward the relaxing ventricles causes the semilunar
valves to close. Note that the AV valves are closed also.
(Both Semilunar and AV Valves are closed)
Cardiac Cycle 5
5. Ventricular diastole: passive ventricular filling. As ventricular
relaxation continues, the AV valves open, and blood flows from
the atria Into the relaxing ventricles, accounting for most of the
(Semilunar Valves closed and Av Valves opened)
Contraction of the atria to finish filling the ventricles with blood (about 70% of ventricular filling happens without the atria even contracting) - AV valves are open to allow blood to flow from the atria to the ventricles
After the ventricles are full, they begin to contract. For a very brief period of time, the pressure pushes the AV valves closed and the semilunar valves are also closed. Then the semilunar valves pop open and blood is squeezed out of the ventricles which is the period of ejection
This period is called Isovolumetric contraction (contraction with no change in volume).
relaxation of the ventricles to allow them to once again fill with blood - At first, all valves are closed so no blood moves (isovolumetric relaxation). But this is very brief before the AV valves open and blood begins to flow in from the atria again. The semilunar valves are closed so no blood leaks back in, but the AV valves are open to allow blood to flow in from the atria.
Volume of blood ejected by each ventricle during each contraction - near 100% stroke volume is possible
Cardiac Output is the volume of blood ejected from the left or right ventricles into the aorta or pulmonary trunk each minute (heart rate X stroke volume) - About 5 L/min is an average number (about the volume of blood in your body every minute)
Maximum cardiac output minus cardiac output at rest (how much more blood your heart is capable of pumping compared to when it is at rest). It may change with the health of the heart. Severe heart disease patients have little or no reserve... their heart is working as hard as it can.
Mean arterial pressure (MAP)
The average blood pressure in the aorta - Cardiac Output X Peripheral resistance. It's usually about the average of systole and diastole, but just a little lower (because you spend more time in diastole). When your mean arterial pressure falls below 60, your organs may not be getting the blood flow and therefore, the oxygen they need (associated with "shock").
Intrinsic Control: Preload
A high volume of blood stretches the ventricles. According to the Frank Starling law, more stretching results in a more forceful contraction to eject the extra blood (see diagram). (A diuretic may reduce blood volume to reduce a high preload)
Intrinsic Control: Afterload
The pressure caused by resistance of the aorta. When the ventricle tries to eject its blood, the pressure in the aorta might resist it so not all blood is ejected. (A drug that dilates the vessels may reduce a high afterload)
Important facts to remember
-Blood moves from higher pressure to lower pressure (arteries have the highest pressure, veins have the lowest pressure)
-Velocity of blood is lowest in the capillaries since that is where nutrient exchange takes place
-Most of the blood volume at any one time is in the veins (about 65%).
-Most arteries and veins are innervated (they have to be for sympathetic and parasympathetic signals to tell them to constrict or dilate)
How easily something can be stretched
How well something returns to it's original size after being stretched
Arteries and Veins General structure: Tunica adventitia
Outer part merges with the outer connective tissue
Arteries and Veins General structure: Tunica media
Middle layer containing smooth muscle and elastic tissue
Arteries and Veins General Structure: Tunica Intima
Inner layer containing a layer of epithelial cells
Arteries and Veins General Structure: Vas vasorum
Blood vessels that supply the walls of arteries and veins with oxygen and nutrients
Vessels in Order
Nearest the heart - Larger diameter - More elastin - Expand and contract to act as pressure reservoirs (valves keep blood from moving backward so the elasticity of these arteries pushes blood forward)
Deliver blood to specific organs - Contain the most smooth muscle and are very active in vasoconstriction and dilation to control blood flow and blood pressure to these regions.
Smallest arteries - Control blood flow into capillary beds since capillaries have no smooth muscle - varying thickness, but smaller ones have only a single layer of smooth muscle
-Metarterioles are the branches from the arteriole to the capillary beds. These control blood flow to very small areas via precapillary sphincters (bands of smooth muscle)
Single layer of epithelial cells called endothelium - some are barely wider than a blood cell and are very delicate, but good for molecule exchange to exchange gasses and nutrients with the extracellular environment. Found everywhere cells are. (Very small capillaries are often damaged or destroyed from excess glucose in diabetes - i.e. in the eyes and around nerves)
Drain capillary networks - contain no muscle or just a few muscle cells
Small Veins and medium veins get larger and contain more and more smooth muscle
Have thin tunica layers including smooth muscle but pressure is low in veins so they can still effectively contract. The thin layers allow veins to have very high compliance so they can hold a great deal of blood (60-70% of total blood volume)
Valves in veins function
Because blood pressure is so low in veins, they contain valves which prevent the backward movement of blood. Movement of muscles squeezes the veins, applying pressure like a pump. The valves keep it moving forward (prevent it from flowing backward)
Carry 90% of return blood and superficial veins carry the remaining 10%.
Deep Vein Thrombosis
Pooling of blood leading to a clot. Often caused by low movement
Insufficient valves that block blood movement and cause a visible collection of blood at the surface (spider veins)
Movement of substances into and out of capillaries
Lipid soluble molecules move right through the capillary walls (i.e O2, CO2, steroid hormones, fatty acids)
Water soluble (hydrophilic) molecules diffuse through spaces or fenestrations of capillaries (i.e. glucose and amino acids)
Fluid movement from capillaries to extracellular fluid - fluid can move into and out of capillaries through spaces between cells.
Is the pressure from blood pushing (blood pressure)
Colloid osmotic pressure
Is the movement of water back into the capillary to an area of high concentration of large molecules that can't diffuse across the membrane
A build up of extracellular fluid or is part of the Inflammatory Process.
A chronic disease characterized by abnormal thickening and hardening of the arterial walls with resulting loss of elasticity
Changes in the walls of large arteries consisting of lipid deposits on the artery walls.
Resistance in relation to blood pressure
Decreasing diameter of blood vessels increases resistance to flow and therefore increases blood pressure
As resistance increases, flow decreases (and vice versa)
Resistance of a liquid to flow (thicker blood, such as that with more red blood cells, is more resistant to flow)
Measuring Blood pressure - laminar vs turbulent flow, Karotkoff sounds
The pressure generated by the contracting ventricle at systole causes the arteries to expand. The amount of pressure required to block this expansion is determined by the amount of pressure being generated by the heart during systole. Applying the exact same pressure as systole (systolic pressure) will block blood flow and thereby the pulse beyond that point. Anything below this point creates turbulent flow so it can be heard with a stethoscope
The pressure at diastole, or the relaxation phase, is the point at which the cuff is putting no additional pressure on the artery beyond its 'at-rest' pressure. Since no additional pressure is being applied, no turbulent blood flow is being caused and therefore no pulse sound can be heard.
Vasodilation and Vasoconstriction
Vasodilation: Dilation of blood vessels. Decreases BP
Vasoconstriction: Constriction of blood vessels. Increases BP
Provides a rapid negative feedback loop in which an elevated blood pressure reflexively causes the heart rate to decrease and also causes blood pressure to decrease.
Good to know
Adrenal gland releases epinephrine and norepinephrine into the blood
Regulates respiration, cardiac output, and regional blood flow, ensuring that proper amounts of oxygen are delivered to the brain and heart.
Control by the kidneys for long-term regulation
Kidneys control fluid volume of the body.
Diuretics increase urine volume leaving less blood in the body and decreasing blood pressure
Vasopressin (antidiuretic hormone)
Atrial Natriuretic Peptide (ANP)
Good to know
Note that of the three long-term, kidney related mechanisms to control blood pressure, ANP is the only one that DECREASES blood pressure when it is activated. Renin/angiotensin/aldosterone and Vasopressin mechanisms both INCREASE blood pressure when they are activated.
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