Lecture 19/ Human circulation

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Q. How can cardiac output be increased if more O₂is required? - pump fasterand/or pump moreblood

D. Effect of size on heart rate
In general, there is an inverse relationshipbetween size and heart rate

Bigger animal (bigger heart) [!]lower HR

Partly, this may be due to the greater metabolic rate and O₂consumption per body weight of small animals.

Small humans also have higher heart rates.
Babies have heart rates of 150-180 beats/min.

Q.There's much more blood in the systemic circiut and the left ventricle contacts harder. Is more blood pumped out to the body than to the lungs? To put it another way, is CO(R) = CO(L)?
- yes, it has to beequal

E. Control of heart beat

1. Intrinsic control
As we discussed earlier, cardiac muscle will beat spontaneously and the frequency is set by the fastest cells

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a. Sinoatrial node = pacemaker
The fastest cells (the "pacemakers") are located in the sinoatrial nodein the wall of the right atrium near the superior vena cava.

b. signal spreads through gap junctions As the pacemaker cells depolarize, the signal spreads to adjacent cells by the movement of ions through gap junctions. Intercalated discsare regions with lots of gap junctions located between cardiac muscle cells.

Q. Would you predict that the cells of the two atriaare electrically coupled?
-yes, so can beat in unison

Q. Would you predict that the atria and ventricleare directly electrically coupled?
- no, because if they were to beat simultaneously, the directionality of flow would be lost.


		Q. How can cardiac output be increased if more O₂is required? - pump fasterand/or pump moreblood D. Effect of size on heart rate In general, there is an inverse relationshipbetween size and heart rate Bigger animal (bigger heart) [!]lower HR Partly, this may be due to the greater metabolic rate and O₂consumption per body weight of small animals. Small humans also have higher heart rates. Babies have heart rates of 150-180 beats/min. Q.There's much more blood in the systemic circiut and the left ventricle contacts harder. Is more blood pumped out to the body than to the lungs? To put it another way, is CO(R) = CO(L)? - yes, it has to beequal
		E. Control of heart beat 1. Intrinsic control As we discussed earlier, cardiac muscle will beat spontaneously and the frequency is set by the fastest cells		38.6
		a. Sinoatrial node = pacemaker The fastest cells (the "pacemakers") are located in the sinoatrial nodein the wall of the right atrium near the superior vena cava. b. signal spreads through gap junctions As the pacemaker cells depolarize, the signal spreads to adjacent cells by the movement of ions through gap junctions. Intercalated discsare regions with lots of gap junctions located between cardiac muscle cells. Q. Would you predict that the cells of the two atriaare electrically coupled? -yes, so can beat in unison Q. Would you predict that the atria and ventricleare directly electrically coupled? - no, because if they were to beat simultaneously, the directionality of flow would be lost.