Physiology Midterm 2 Part 2
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During isovolumetric relaxation, ________.
- no change in volume
- ventricles are filling
- (80% of ventricular filling occurs before atria contracts)
- atrial pressure low and rising
- ventricular pressure high and decreasing
- artery pressure high
- Semilunar valves are closed
- AV valves are closed
What is occurring during ventricular ejection?
- Blood in the ventricle is under increasingly high pressure
- Semilunar valves are open
- Contraction of the ventricle occurs
- Blood is ejected into the systemic circuit
Which of the following is true of the ventricular filling phase of the cardiac cycle?
- Occurs during diastole
- 80% is filled prior to atrial contraction
- pressure is rising in ventricle & decreasing in atria
- AV valves open
The purpose of having valves in the cardiovascular system is to __
prevent backflow and keep blood going in one direction
he flattening of the action potentials of myocardial contractile cells, called the plateau phase, is due to a combination of ________ K+ permeability and ________ Ca2+ permeability.
The end of the plateau phase is due to the ________ of Ca2+ channels and ________ of K+ channels.
The importance of the plateau phase of the action potential of myocardial cells is in ____
preventing another action potential during contraction because of a long refractory period; tetanus
The depolarization of the pacemaker action potential spreads to adjacent cells through __
In which situation would the stroke volume be the greatest?
- stronger contractility
- high EDV (end diastolic volume)
- high preload
- shorter filling time
- faster venous return with with elevated HR
- positive inotropic effect from cardiac muscle with epinephrine
Manganese ions block the calcium channels in the cardiac muscle membrane. How would the presence of manganese in the extracellular fluid affect the contraction of the heart muscle?
The heart will beat less forcefully.
Drugs known as calcium channel blockers can be used to __
- decrease the force of cardiac contraction
- slow heart rate and cause vasodilation
- decreases oxygen demand on the heart
The actual sites of gas exchange within the lungs are __
The lungs are enclosed in ________ membranes
visceral & parietal pleural (double membrane)
Type II alveolar cells
- produce surfactant
- (which reduce the surface tension of water, making it easier for the lungs to re-inflate)
Air moves into the lungs because
- atmospheric pressure is high and pressure in lungs is low
- diaphragm contracts and increases lung volume
Air moves out of the lungs because
- atmospheric pressure is low and lung pressure is high
- diaphragm relaxes and decreases lung volume
Boyle's law states that gas volume is __
inversely proportional to pressure
The P-R interval represents __
the length of time for depolarization of the atria through the AV node
The P-R segment represents __
- slow conduction through the AV node and the bundle of His and finally the bundle branches
- appears isoelectric because the structures that conduct the current are too small to generate detectable voltages
The S-T segment represents __
- the electrical activity during the plateau phase of myocardial repolarization
- early phase of repolarization of the ventricles
- (any abnormalities are caused by ischemia)
Most of the oxygen transported by the blood is __
in hemoglobin in RBCs
Most of the carbon dioxide in the blood is transported as __
The most important chemical regulator of ventilation is __
An increase in the level of carbon dioxide in the blood will __
lower pH and begin negative feedback loop to breathe more
Hyperventilation would lead to a(n) ________ within the systemic arteries.
increase in pO2 and decrease in pCO2
What is a deficiency of oxygen in the tissues called?
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