Cardiovascular System and respiratory system Help!

[Frozone]

Hello everyone,
Im compiling notes for my next Sac and I am facing difficulties with a few things which are...
The 4 factors that affect heart rate
&
The relationship between HR, SV and Q and how HR,SV and Q are affected by physical activity.
Incase one doesnt know HR is Heart Rate, Sv is stroke Volume and Q is Cardiac Output.


Thanks alot!

[pi]

Well, we know that Cardiac Output (Q) = Stroke Volume (SV) x Heart Rate (HR). During exercise (ie. periods of high physical activity), both HR and SV increase, and hence Q increases too.

SV essentially increases because the heart fills up with more blood (higher end-diastolic volume) and the contractions are stronger (increased sympathetic firing). The latter of these two also causes an increase in HR.

As for factors that may affect HR, there are many such as emotional stress, physical stress, medications, vagal activity, illness, etc.

I haven't done PE, but I hope that makes some sense

[michak]

Hello everyone,
Im compiling notes for my next Sac and I am facing difficulties with a few things which are...
The 4 factors that affect heart rate
&
The relationship between HR, SV and Q and how HR,SV and Q are affected by physical activity.
Incase one doesnt know HR is Heart Rate, Sv is stroke Volume and Q is Cardiac Output.


Thanks alot!

Hey
Im assuming this is for 1/2 pe?

Heart rate is the number of beats per minute. Though you say 4 factors there are actually quite a few so I am not quite sure if you are thinking of any specific ones or not. The major factor is the intensity of the activity you are doing. The higher the intensity the more blood and oxygen your muscles will need to the faster the heart pumps so muscles can receive this oxygen (thats as much info you need to know in 1/2). Not quite sure what other factors you mean, they usually ask for stroke volume or cardiac output.

Relationship is HR x SV = Q. It is a linear relationship in which if one or both increase cardiac output will increase as it is the product of both HR and SV.

when undergoing physical activity all three of these variables will increase because the body needs more oxygen, so SV increases so more oxygen can be pumped be beat, HR increases so this extra oxygen can reach the muscles quicker and Q is the product of these two so it too will increase.

Does this make sense?

edit: beaten

[Frozone]

The speed of reply brought a tear to my eye.
Yes I am doing unit 1/2.

Thank you michak and pi, your input is very appreciated.

[MangoPengy]

Hello everyone,
Im compiling notes for my next Sac and I am facing difficulties with a few things which are...
The 4 factors that affect heart rate
&
The relationship between HR, SV and Q and how HR,SV and Q are affected by physical activity.
Incase one doesnt know HR is Heart Rate, Sv is stroke Volume and Q is Cardiac Output.


Thanks alot!

I know everyone answered this already but...

The relationship between HR, SV and Q and how HR,SV and Q are affected by physical activity.

Q(cardiac output) = HR x SV
meaning any increase in either Heart Rate or Stroke Volume, results in increase of cardiac output.

During physical activity, stroke volume increases to supply more oxygen and in order to meet the oxygen demands of the muscles. Heart Rate will increase until the demands of are met but will levels off as oxygen supply equals oxygen demand (steady state).

At this point, to in order to increase cardiac output, stroke volume increases.

Keep in mind that it is more efficient to have a lower heart rate but higher stroke volume due to there being no need to pump as frequent if a lot of blood (thus oxygen) is pumped out in one go.



Cheerios,

Hope that helps!