ek bio 1001 #684

[KiroMD]

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Hey guys,

I was wondering if anyone could help me out with this one.

The question refers to a chart in passage 703.

I'm not sure why it's not B... I don't get why it's D.

Here's the question:

In comparing various medium-sized animals, it can be determined that:

b) an active fish increases cardiac output by increasing the heart rate

d) a swimming fish increases the ejection volume by increasing the cardiac output

(a and c are useless).

Here's the relevant part of the chart:

For Medium Fish

cardiac ejection volume:
@ rest: .59 ml
very active: 1.15 ml
Heart Rate
@rest: 35
very active 61
Blood flow
@ rest 19
very active 65

thank you guys in advance

 

[IntelInside]

Hey guys,

I was wondering if anyone could help me out with this one.

The question refers to a chart in passage 703.

I'm not sure why it's not B... I don't get why it's D.

Here's the question:

In comparing various medium-sized animals, it can be determined that:

b) an active fish increases cardiac output by increasing the heart rate

d) a swimming fish increases the ejection volume by increasing the cardiac output

(a and c are useless).

Here's the relevant part of the chart:

For Medium Fish

cardiac ejection volume:
@ rest: .59 ml
very active: 1.15 ml
Heart Rate
@rest: 35
very active 61
Blood flow
@ rest 19
very active 65

thank you guys in advance

I am going with B because increasing cardiac output doesnt necessarily increase ejection volume

 

[KiroMD]

I am going with B because increasing cardiac output doesnt necessarily increase ejection volume

the right answer is D though, lol

 

[jphwki82]

Hey guys,

I was wondering if anyone could help me out with this one.

The question refers to a chart in passage 703.

I'm not sure why it's not B... I don't get why it's D.

Here's the question:

In comparing various medium-sized animals, it can be determined that:

b) an active fish increases cardiac output by increasing the heart rate

d) a swimming fish increases the ejection volume by increasing the cardiac output

(a and c are useless).

Here's the relevant part of the chart:

For Medium Fish

cardiac ejection volume:
@ rest: .59 ml
very active: 1.15 ml
Heart Rate
@rest: 35
very active 61
Blood flow
@ rest 19
very active 65

thank you guys in advance

The equation for Cardiac Output is CO = Stroke Volume X Heart Rate. Increasing Heart Rate does not necessarily mean that Cardiac Output will increase. It depends on the circumstances. If you were to increase the sympathetic response via NE, then you would increase Heart Rate & Stroke Volume. Increasing Heart Rate alone (SV held constant) decreases diastolic filling time, and the heart would be ejecting less blood. In this situation, Cardiac Output would decrease because there is no compensation for the decreased filling time. The sympathetic response utilizes SV to compensate for this decreased diastolic filling time for the heart via increasing the Stroke Volume. More over, since you are dealing with a animal that is swimming or moving, there will be a sympathetic response. Thus, the contractility of the heart will increase in response to the circulating NE. Stroke Volume & Heart Rate will increase and etc. www.cvphysiology.com will go over starling's law of the heart in great detail for you, and will clear up any other questions you may have as well. So, Stroke Volume (D) would be the better answer to account for increased Cardiac Output. Hope this cleared up any confusion. There is a lot more that goes into this mechanism, and the above website will be extremely helpful in understanding this.

 

[CodeBlu]

Mmmmm cardiovascular phys. My favourite.

I think the simplest way to put this is that...

Cardiac Output = Mean Arterial Pressure x Total Peripheral Resistance

Also, that CO = Heart Rate x Stroke Volume...

You should note that Stroke Volume = End Diastolic Volume - End Systolic Volume

Knowing all of this, the more blood in the heart, the more that the walls of the heart stretch. The muscle fibers in the heart stretch, and this is known as the Frank-Starling law of the heart, it means a more forceful contraction occurs to pump the blood out of the heart.

Set, Heart Rate x Stroke Volume = MAP x TPR

Now, this holds true because these are both equal to Cardiac Output right?

So Stroke Volume = MAP x TPR / Heart Rate

We've got an inverse proportion here my friends, increase heart rate, means you decrease the stroke volume which is equal to EDV - ESV. Less blood leaving the heart during systole. There are a few other factors that could come into play, like the metabolic theory bla bla bla. Ejection volume is actually EDV - ESV / EDV.

But the relationship still holds true. The more blood you have entering the ventricles during diastole, the more blood will be subsequently ejected into the aorta etc.

But I do recommend you look up the Frank-Starling Law of the heart, it is pretty cool. This is not to be confused with the Starling forces which are the oncotic and osmotic pressures across a capillary bed. Look those up too. Fascinating stuff!


Good luck!

 

[Swagster]

Mmmmm cardiovascular phys. My favourite.

I think the simplest way to put this is that...

Cardiac Output = Mean Arterial Pressure x Total Peripheral Resistance

Also, that CO = Heart Rate x Stroke Volume...

You should note that Stroke Volume = End Diastolic Volume - End Systolic Volume

Knowing all of this, the more blood in the heart, the more that the walls of the heart stretch. The muscle fibers in the heart stretch, and this is known as the Frank-Starling law of the heart, it means a more forceful contraction occurs to pump the blood out of the heart.

Set, Heart Rate x Stroke Volume = MAP x TPR

Now, this holds true because these are both equal to Cardiac Output right?

So Stroke Volume = MAP x TPR / Heart Rate

We've got an inverse proportion here my friends, increase heart rate, means you decrease the stroke volume which is equal to EDV - ESV. Less blood leaving the heart during systole. There are a few other factors that could come into play, like the metabolic theory bla bla bla. Ejection volume is actually EDV - ESV / EDV.

But the relationship still holds true. The more blood you have entering the ventricles during diastole, the more blood will be subsequently ejected into the aorta etc.

But I do recommend you look up the Frank-Starling Law of the heart, it is pretty cool. This is not to be confused with the Starling forces which are the oncotic and osmotic pressures across a capillary bed. Look those up too. Fascinating stuff!


Good luck!

Great explanation. I wish you wrote the explanations for EK books.

If you didn't go through the concept, couldn't you also get the right answer from the numbers they present. It seems like they are looking for the answer to involve and increase in blood volume correlating to increased cardiac output because they give you the ml numbers.

 

[UTA2012]

Without even looking at the chart, I take this question this way. An "active fish" is a fish who swims but is not currently swimming, so when we exercise like say for an active marathon runner our heart rate actually decreases over time, so it does not make sense for a physically active fish's heart rate to increase unless they are "very active" at that moment.
The "swimming" fish or a person who is currently engaging in physical exercise is definitely going to increase their cardiac output along with EV.

I hope this helped.