Term
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Definition
- lots of mitochondria
- very aerobic
- lots of capillaries, ratio of 1:1 of capillary to muscle cell |
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Term
| excitation contraction coupling in cardiac muscle: |
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Definition
| Ca++ entering the cell through channels in the sarcolemma acts as a trigger to release Ca++ from the sarcoplasmic reticulum. Ca++ binds to troponin C. The Ca++-troponin C complex interacts with tropomyosin to unblock binding sites between actin and myosin filaments. |
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Term
| 3 ways of altering cytosolic calcium: |
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Definition
1. alter calcium channel function> altered trigger calcium> alter SR release of calcium
2. alter uptake by SR> alter amount of calcium available for SR
3. alter efflux mechanisms> alter amount of calcium available for SR uptake |
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Term
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Definition
Increases cytosolic calcium by:
- decreasing activity of sodium potassium pump
- decreases calcium extrusion of calcium sodium pump
Ultimately pt gets more forceful heart contraction, decreased heart rate, and fluid cleared from body. Used to treat congestive heart failure. |
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Term
| How do catecholamines affect cytosolic calcium? |
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Definition
- phophorylate calcium channels to increase calcium influx
- phosphorylate phospholamban to increase SR uptake of calcium
- phosphorylate troponin-I to prevent binding of calcium to troponin-C
Ultimately cardiac contraction and relaxation are accelerated. |
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Term
| equation for cardiac output: |
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Definition
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Term
| equation for cardiac output: |
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Definition
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Term
| equation for stroke volume: |
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Definition
| SV= end diastolic volume- end systolic volume |
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Term
| ejection fraction equation: |
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Definition
| ejection fraction= SV/end diastolic volume |
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Term
| factors that influence cardiac output: |
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Definition
- changes in heart rate
- 4 mechanisms that change stroke volume:
- filling presure
- ventricular distensibility or compliance
- arterial pressure
- contractility |
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Term
| How does cardiac function adjust with changes in cardiac output are required? |
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Definition
1. Heart Rate
2. Changes in Force and Velocity of Contraction |
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Term
| What are two different ways the heart can change force and velocity of contraction? |
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Definition
- change preload
- change contractility
Note that these changes allow the heart to pump away increased venous return without excessive elevation of end diastolic volume. Sarcomere length does not exceed optimum length. |
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Term
| With exercise, increased heart rate allows for ___ ___ to increase without excessive change in ___ ___. |
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Definition
- cardiac output
- cardiac size |
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Term
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Definition
| preload is the initial the initial weight that determines the sarcomere length/stretch |
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Term
| Preload is the ___ on the cardiac cell prior to ___. Preload sets the ___ ___ ___ ___. . |
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Definition
- tension
- activation
- end diastolic sarcomere length |
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Term
| In the working heart, preload is determined by ___ ___ __, which is relateed to ___ ___. But preload is NOT the same as venous return. |
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Definition
- end diatolic volume
- venous return |
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Term
| Preload is influenced by: |
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Definition
heart rate
contractility
afterload
diastolic compliance
venous return |
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Term
| At sarcomere lengths less than Lmax, an increase in preload will produce an increase in ___ ___ and velocity of ____ , but NO change in ___. |
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Definition
- increase in systolic force
- increase in velocity of shortening
- NO change in contractility |
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Term
| How does an increase in sarcomere length increase force of contraction aka systolic force (NOT contractility)? |
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Definition
1. More favorable overlap b/w actin and myosin
2. Improve excitation contraction coupling. For cardiac myocytes, this is most effective. |
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Term
| Remember changing sarcomere length changes ___ ___, NOT ____. ___ is reserved for changes in ___ __. |
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Definition
- contractile force
- NOT contractility
- contractility refers to changes in mechanical function |
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Term
| Resting tension rises steeply when its near ___, this property of cardiac muscle usually keeps it from being stretched past Lmax. |
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Definition
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Term
| factors that interact to affect ventricular preload: |
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Definition
- venous return
- heart rate
- end systolic volume following the preceding ejection, a function of afterload and contractility
- chamber stiffness |
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Term
| Myocardial contractility is a change in ___ __ ___ (force and velocity of contraction) which is NOT due to a change in ___/___ ___. Note that preload, afterload, and contractility can all change at once and sometimes in different directions. Contractility is sometimes referred to as an ____ state. |
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Definition
- cardiac mechanical function
- preload/sarcomere length
- inotropic |
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Term
| Changes in contractility are associated with altered ___ ___. |
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Definition
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Term
| Cardiac function graph: A variable of cardiac function(CO, SV) is plotted as a function of a variable of ___ ___ at ___ ___ ___(ventricular volume or pressure, atrial pressure). These graphs illustrate the effects of changes in ___ on cardiac performance. They are also used to illustrate changes in ___ when preload is constant. These graphs are called ___ ___. |
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Definition
- sarcomere length at the end of diastole
- preload
- contractility
- Starling Curves |
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Term
| Norepinephrine increases ___ ___. |
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Definition
| ventricular contractility so stroke volume is increased |
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Term
| With heart failure, ___ is ___so that stroke volume is decreased at any given length. |
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Definition
| contractility is decreased |
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Term
| Digitalis raises ___ ____ ___ and thus restores the ___ of the failing ventricle. |
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Definition
- intracellular calcium concentration
- contractility |
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Term
| before you start to exercise your heart rate ___ b/c of sympathetic innervation,but cardiac output stays the same, this means that stroke volume must have ___ |
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Definition
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Term
| when you begin to exercise you get further sympathetic innervation so ___ ___ and ___ ___ increase. |
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Definition
- venous return
- cardiac output |
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Term
| With intense exercise, you increase the __ ____ ___, so you increase ___ and ___. |
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Definition
- end diastolic volume
- contractility
- stretch |
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Term
| Factors that increase myocardial contractility: |
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Definition
- sympathetic innervation
- catecholamines
- force frequency relationship
- extracellular calcium concentration
- digitalis
- other positive ionotropic agents |
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Term
| Factors that have negative effects on myocardial contractility: |
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Definition
- parasympathetic nerve stimulation
- ischemia- hypoxia, acidosis
- toxins and other negative ionotropoic agents |
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Term
| Explain the force frequency relationship of the heart. |
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Definition
- during isometric contractions, if frequency of stimulation is increased, force increases
- and if frequency of stimulation decreases, force decreases
- this is b/c increased frequency of activation increases intracellular calcium |
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Term
| B/c of the force frequency relationship, we can assume that as heart rate increases, ___ also increases. |
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Definition
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Term
| Measurements of myocardial contractility: |
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Definition
- ejection fraction= stroke volume/end diatolic volume
- velocity of ventricular ejection
- velocity of ventricular wall motion
- max dP/dt |
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Term
| steep rise in ventricular pressure means a steep rise in ___. |
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Definition
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Term
| ___ is the tension the cardiac cell must develop to shorten. In the working heart, this is determined by the ___ which must be exceeded for ejection to take place and by the ___ of the chamber. |
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Definition
- Afterload
- pressure
- radius |
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Term
| pressure and radius help determine afterload b/c wall tension = |
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Definition
| wall tension= chamber pressure x chamber radius |
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Term
| As the heart fails it gets bigger b/c it has to increase ____ to compensate for its decreased ___. This increases the ___ of the heart b/c the radius has increased. |
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Definition
- fiber length/preload
- contractility
- afterload |
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Term
| A normal heart and a heart with left ventricular failure may eject against similar aortic pressures, but the afterload on the heart in failure will be greater, because its left ventricle is larger. Recall that the failing ventricle resorts to longer sarcomere lengths to compensate for depressed contractility. |
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Definition
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Term
| contraction velocity is inversely proportional to ____ but directly proportional to ___ and ____. |
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Definition
- afterload
- preload and contractility |
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Term
| Responses to depressed contractility: |
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Definition
Depressed force and velocity of contraction
End-systolic volume increases
End-diastolic volume increases
More favorable sarcomere lengths
Subsequent Improved force and velocity of contraction
However, radius and, thus, afterload increases. If the improved contractile function due to increased sarcomere length cannot overcome the increased afterload, further increases in radius and afterload will result.
In chronic heart failure, the beneficial effect of increased sarcomere length is reduced, because the effect of altered sarcomere length on excitation-contraction coupling is attenuated. Also diastolic stiffness increases |
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Term
| Parasympathetic effects on heart: |
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Definition
- main effect: reduce heart rate
- decrease conduction velocity in AV node
- depress contractile function (minor effect) |
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Term
| Sympathetic innervation effects on heart: |
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Definition
- increased heart rate
- increased conduction velocity
- increased contractility |
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Term
| normal rate of oxygen consumption |
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Definition
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Term
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Definition
calculation of cardiac output using the oxygen uptake/consumption method
cardiac output= (O2 consumption)/(A-V)
for oxygen, 1 vol %= 1 mL oxygen/100 mL blood |
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Term
| With the Fick Principle to get a sample of well mixed venous blood you should draw from the ___ __. |
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Definition
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