1

Physiology & Medicine / Topic Deletion Request

« on: 06/04/2015 18:51:33 »

I'd like to delete that topic as I haven't received more replies concerning my questions.
But Dr. Chris,
Thanks a lot for your reply, I really appreciate it. You have clarified some points for me.  []

2

Physiology & Medicine / Re: Concerning the Trans-pulmonary pressure.

« on: 01/04/2015 21:31:36 »

cheryl j, Thanks a lot for your help, your second diagram was very useful. I got it! []
evan_au & alancalverd, Thanks for your replies.

3

Physiology & Medicine / Concerning the Trans-pulmonary pressure.

« on: 31/03/2015 17:44:35 »

I've read that: "Trans-pulmonary pressure is the difference between the intra-alveolar pressure and the intra-pleural pressure in the lungs."

I'll be very grateful if anyone could please explain that in more details.
(Note: I've read about the intra-alveolar and the intra-pleural pressures, but I still can't understand how the trans-pulmonary pressure can be the difference between them.)

4

Physiology & Medicine / Re: A question concerning the Cardiovascular system ( Frank-Starling law )

« on: 08/03/2015 12:50:27 »

Colin2B,
Sorry for my late reply.
I'd like to thank you a lot for your replies and efforts to help.

I've also found some good answers, I hope others can also benefit from it.
http://www.thescienceforum.com/biology/48523-question-concerning-cardiovascular-system-frank-starling-law.html
(Sorry for cross-posting. I really needed a fast reply, and you were the first to help. Thanks.)

5

Physiology & Medicine / Re: A question concerning the Cardiovascular system ( Frank-Starling law )

« on: 24/02/2015 20:20:29 »

Colin2B,
I'm so glad to receive your reply.

- First of all, thanks a lot, you have clarified it a bit for me.

- Concerning:

Hadn't come across this graph before.

I've modified the topic and made my questions in bold.

- Concerning my first and second questions: ( i.e. the difference between the passive and active tensions)
I've understood from some articles and videos in addition to your reply that:
The passive tension is the tension produced when the muscle is being stretched ( i.e. the desire of the muscle to oppose the stretching, if it's being stretched by an external force ), while the active tension is the tension produced when the muscle is being contracted ( i.e. the movement of actin along myosin filaments, which produces a tension or pressure opposing the contraction, depending on the initial length of the muscle fiber). If that is right, Hence when the passive tension = the active one, they will balance or cancel each other, as both tensions oppose each other, as you have mentioned before. I hope that that's right, isn't it?

- And concerning my third question: I think you had already answered it perfectly. ( i.e. the 2 curves never meet each other -which means that they never become equal as illustrated in the graph- except at Cardiac standstill.

6

Physiology & Medicine / A question concerning the Cardiovascular system ( Frank-Starling law )

« on: 23/02/2015 19:22:29 »

Hi all!

My question is related to "Frank-Starling law", which can be illustrated by the following graph:

( image link: s6.postimg.org/9usp2x12p/Lenth_tension.jpg )

I've read that:
- When the heart is over stretched, it will not be able to contract, there will be cardiac standstill. This occurs at the point of meeting of the 2 curves of active and passive tension, this doesn't occur except at time of death.
- the previously mentioned point happens when passive tension = active tension, where the heart can not contract. ( i.e. death )

My Questions:
- Can you clarify the difference between active and passive tensions ?
- Why when the passive tension = active tension, the heart will not contract ?
- What does the "the point of meeting of the 2 curves" mean ?

Finally:
Thanks in advance for any help which I'd greatly appreciate.
I hope I've explained my question well.