Term
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Definition
| pressure in an artery when the ventricles are contracting |
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Term
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Definition
| pressure in the artery when the ventricles are relaxing |
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Term
| Why is diastolic blood pressure not zero? |
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Definition
Peripheral resistance in the arteries, arterioles
Expand - systole
Snap back - diastole |
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Term
| Why does the force of the heartbeat fall almost to zero in veins and venules? |
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Definition
Blood returns to the heart because of some pressure in veins from heartbeat
gravity
muscles near veins |
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Term
| Measurement of blood pressure |
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Definition
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Term
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Definition
| constriction and dilation of arterioles; opening and shutting of precapillary sphincters |
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Term
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Definition
an electrical signal in a nerve cell or a muscle cell is self-sustaining wave of membrane depolarization
results from the movement of ions across the plasma membrane |
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Term
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Definition
| an inherent activity of the heart because the heart has its own pacemaker but is modified by outside influences |
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Term
| sinoatrial node (SA node) |
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Definition
the heart's natural pacemaker
can initiate atrial systole
The electrical signal initiated is an action potential just like in nerve cells |
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Term
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Definition
allow electrical current to pass from one myocardial cell to another
located in intercalated disks |
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Term
| atrioventricular node (AV node) |
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Definition
| passageway for contractional signals into ventricles |
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Term
| How does slowing depolarization to threshold slow down heart rate? |
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Definition
| Nerves releas acetylcholine (neurotransmitter) to the cells of the SA node, resulting tin the opening of K+ channels and the efflux of K+ from the cells. this lowers the resting potential of the cells. |
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Term
| How can heart rate be accelerated by speeding depolarization to threshold? |
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Definition
Nerves release norepinephrine to the cells of the Sa node, which increases Ca2+ and Na+ influx
Nervous signals can also increase venous return of blood to the heart by venous constriction, and can strengthen ventricular contractions by allowing more Ca2+ into the ventricular cells. |
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Term
| Assume a blood cell is in the right ventricle of the heart. Arrange the following list of structures in the order the blood cell would visit them in one trip around the body: right atrium, aorta, liver capillaries, pulmonary artery, venule (in liver), lung capillaries, inferior vena cava, left ventricle |
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Definition
| Pulmonary artery, lung capillaries, left ventricle, aorta, liver capillaries, venule, inferior vena cava, right atrium |
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Term
| What are two differences between veins and arteries? |
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Definition
| Veins carry blood away from the heart and do not have valves |
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Term
| When you check a person's pulse, you must touch an artery, not a vein. Why? |
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Definition
| The blood flowing in an artery moves by the force of the heartbeat. By the time the blood reaches a vein, that force has dissipated, and the blood moves largely because of squeezing by the skeletal muscles and by gravity. |
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Term
| What is special about the functioning of the cells of the SA node (the pacemaker), in contrast to the other cells of the heart? |
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Definition
| The cells of the SA node initiate an electrical signal that causes the myocardial cells to contract |
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Term
| What sort of gated ion channel (voltage-gated, mechanically-gated, or ligand-gated) would you expect to find in the SA node? |
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Definition
| Since the SA node initiates an electrical signal, you would expect to find voltage-gated channels |
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Term
| Why must the signal from the SA node be delayed at the AV node before it is passed to the ventricles? |
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Definition
| The signal from the SA node, being an electrical signal, moves very fast; the delay at the AV node gives time for the ventricles to fill with blood before the signal for ventricular contraction is passed along |
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Term
| How does the size of the conducting cells in the AV node contribute to the slowing of this signal? |
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Definition
| The cells have a narrow diameter. The speed of conduction of an action potential (electrical signal) decreases with decreasing diameter of the conducting cell. |
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Term
| What are two ways arterioles contribute to the regulation of circulation? |
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Definition
Arterioles can contract and dilate, thus restricting or increasing the blood supply to a capillary bed.
Arterioles have precapillary sphincters that can open and close, according to the tissue's need for oxygen. |
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Term
| Why is diastolic blood pressure not equal to zero? |
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Definition
| During systole, arteries do not empty completely; the arterioles receiving the blood will offer resistance to blood flow, a phenomenon called peripheral resistance. This resistance maintains some positive pressure in the arteries even during diastole. |
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