# Help with a few random questions



## terrible one (Apr 30, 2012)

I am having some difficulty understanding a few concepts and was wondering if someone would be able to help me understand them a little better.


Driving pressure in relation to hemodynamics

Diffusion gradients related to myocardial myoctye and pacemaker cell function

Autoregulation of blood flow involving cell metabolism and energy homeostasis


I've read the chapters related to these topics and can understand their basic defintion and principles involved, however, I am having trouble putting them together with each other. Anyone with a better understanding that could help? Or even point to the information online would be greatly appreciated.

Thanks


----------



## terrible one (May 1, 2012)

Anyone?


----------



## Anjel (May 1, 2012)

Sorry....,you lost me at driving.


----------



## DrankTheKoolaid (May 1, 2012)

*re*

If your into listening to podcasts look for Biology with Doc C.  He has patho[hys, biology, advanced pathophysiology and A&P podcasts


----------



## terrible one (May 1, 2012)

I'll check it out thanks


----------



## Melclin (May 1, 2012)

I think your issue here is that the questions you're asking are like more complex versions of, "I'm having trouble understanding how the heart pumps, like with the arteries and veins".

Its not really a clear question, so its pretty hard to answer. Could you be a bit more precise?

Have you got Guytons physiology? That'd be the first place I'd turn to.


----------



## terrible one (May 1, 2012)

Understand...I'll see what I can do...

Autoregulation is essentially the ability of an organ to maintain a constant pressure despite changes in perfusion pressure. The way this is accomplished is by the vessels near the target organ and their ability to self regulate by dilating via vasoactive agents. That's what I got so far. Now how does metabolism and energy homeostasis relate to the vessels ability to autoregulate? As far as gluconeogenosis, glycolysis?

Hemodynamics, or the movement of blood is controlled like any other fluid according to Ohm's law (F=∆P /R). Flow = the difference in the pressure gradients / resistance. Now how does perfussion or driving pressure relate to this?

Diffusion gradients are controlled by specialized proteins that maintain an ionic concentration gradient between the inside and outside of the myocyte. The phases of depolarization stimulated by an action potential allow for changes in the concentration gradients between sodium, potassium, and calcium. I understand the phases but wanted to make sure I was on the right track with this one?

I'm not sure if that helps?


----------



## TheGodfather (May 2, 2012)

terrible one said:


> Understand...I'll see what I can do...
> 
> *Autoregulation is essentially the ability of an organ to maintain a constant pressure despite changes in perfusion pressure. The way this is accomplished is by the vessels near the target organ and their ability to self regulate by dilating via vasoactive agents.* That's what I got so far. Now how does metabolism and energy homeostasis relate to the vessels ability to autoregulate? As far as gluconeogenosis, glycolysis?



I'm really not understanding what you are asking here... 

For that reason, I'm going to look past the portion in red and focus more on the bolded portion...

Are you familiar with the nitty gritty physiology of baroreceptors? These are pressure-sensitive receptors located in the walls of the bifurcation of the carotid arteries as well as in the aortic arch (other low pressure baroreceptors can be found elsewhere, but don't worry about that right now).... physiologic autoregulation of blood pressure, although also regulated in other mechanisms (e.g., in the kidneys), occurs here on a second-to-second basis.. 

*ARTERIAL PRESSURE TOO HIGH: *baroreceptors send barrages of nerve impulses to the medulla of the      brain; here, these impulses inhibit the vasomotor center, which in      turn decreases the number of impulses transmitted from the vasomotor      center through the sympathetic NS to the heart and blood vessels.
 Lack of these impulses       causes diminished pumping activity by the heart and also dilation of the       peripheral blood vessels, allowing blood to flow through the vessels       (both decreasing arterial pressure toward "normal"). 
*ARTERIAL PRESSURE TOO LOW:* relaxes the stretch receptors, allowing the vasomotor center to become      more active than usual, thereby causing vasoconstriction and increased      heart pumping (both raising arterial pressure toward "normal"). 


back on the the "red" text: obviously if the specific cells that are responsible for these functions are not properly supplied with all components of aerobic metabolism, and thus ATP, they will begin to malfunction. HOPEFULLY, the other blood pressure regulating mediators are still being supplied properly, allowing there to still be compensation.... otherwise it will fail... Of note, it will also eventually fail if the underlying pathology is not corrected as well.



terrible one said:


> Hemodynamics, or the movement of blood is controlled like any other fluid according to Ohm's law (F=∆P /R). Flow = the difference in the pressure gradients / resistance. Now how does perfussion or driving pressure relate to this?



The definition of hemodynamics is not defined as "the movement of blood", but rather "the study of forces involved in the movement of blood" -- not a huge error, but just making that clear..

The concept of Ohm's law, related to the circulatory system, is very simple:

Since we know that Flow = Pressure Gradient / Vascular Resistance, think of it this way....

Lets first remove the vascular resistance from the equation:

pretend below is your arterial vessel and the direction of flow is from right to left... for forward flow, the "pressure gradient" (noted in torr for sake of example) must be present. If there was not a higher pressure on one end than the other (noted as 2x higher on the right than on the left), then the blood would not be "forced" to move ahead and, instead, would just be stagnant..

<---------------------------------------------FLOW
____________________________________________________

(<--Body)~~50torr~~~~~~~~~~~~~~~~~~100torr~~(LV-->)
____________________________________________________

Now onto resistance, aka vascular resistance: obviously the smaller the internal diameter of the vessel, the less potential the blood contained in that vessel has to move forward--> more impedance to flow.




terrible one said:


> Diffusion gradients are controlled by specialized proteins that maintain an ionic concentration gradient between the inside and outside of the myocyte. The phases of depolarization stimulated by an action potential allow for changes in the concentration gradients between sodium, potassium, and calcium. I understand the phases but wanted to make sure I was on the right track with this one?
> 
> I'm not sure if that helps?



instead of me telling you this one, do yourself a favor and watch Dr. Najeeb's lecture on Action Potential... It will clear any confusion you might be having..

http://www.youtube.com/user/DoctorNajeeb




hopefully that was what you were looking for! good luck!


----------



## terrible one (May 2, 2012)

TheGodfather said:


> Are you familiar with the nitty gritty physiology of baroreceptors? These are pressure-sensitive receptors located in the walls of the bifurcation of the carotid arteries as well as in the aortic arch (other low pressure baroreceptors can be found elsewhere, but don't worry about that right now).... physiologic autoregulation of blood pressure, although also regulated in other mechanisms (e.g., in the kidneys), occurs here on a second-to-second basis..




It was my understanding that the barorecptors are more of a systemic control over short term blood pressure regulation? 
The autoregulation in question I was refering to was a local response in which the target organ regulate its own blood flow. This is mediated by vasoconstrictor and vasodilation agents (epi/norepi, angiotensin II, ADH, glucose, etc...)   




TheGodfather said:


> The definition of hemodynamics is not defined as "the movement of blood", but rather "the study of forces involved in the movement of blood" -- not a huge error, but just making that clear..



thanks, long night.



TheGodfather said:


> The concept of Ohm's law, related to the circulatory system, is very simple:
> 
> Since we know that Flow = Pressure Gradient / Vascular Resistance, think of it this way....
> 
> ...



that helps, thank you




TheGodfather said:


> instead of me telling you this one, do yourself a favor and watch Dr. Najeeb's lecture on Action Potential... It will clear any confusion you might be having..
> 
> http://www.youtube.com/user/DoctorNajeeb
> 
> ...



I appreciate it, thank you


----------

