Continuation from Lecture 14 March..
Transition: Rest to Moderate Dynamic exercise
MAP= the extent to which it changes reflects how much CO Increased and TPR decreased
Resistance excercisese causes higher drop in MAP, since its affected by the Cardiac output.
Regulation of MAP
Exercise is causing increase in MAP, there is a reduction in baroreceptor activity, less of a signal
is being sent to the cardiovascular center (for increasing PNS).
We also have a tremendous drive coming from motor cortex that is increasing the SNS activity.
The input from SNS is able to over-ride any baroreceptor signals coming through.
That is why you are able to increase MAP, and maintain a high sympathetic nerve activity during
this because of this.
What causes the changes in HR, SV, EDV (endystolic vol) , Systolic BP? KNOW FOR
Baroreceptors you rely on them to change second-second changes in MAP.
The problem with baroreceptors that they are only good to react for a short period of time, if they
are provided with the same stimulus over an extended period of time. Then they adapt , these
are nerve cells, they like to adapt to a new setting if they are contionusly being stimulated
if there is a prolonged change in MAP, such as when people have HYPERTENSION, the
baroreceptors don’t try to bring the blood pressure down to its original value.
You started at 100mmHg, if you develop high blood pressure and the blood pressure climbs to
120mmHg. The baroreceptors get used to the new environment they reset their sensitivity , they
are trying to adjust the blood pressure to be at 120mmHg.
The operate on a changing scale, depending on what the main environment is. Slide 3
Baroreceptor can help you deal in the long run with pressure changes. Just in the SHORT
We need other ways of dealing with Blood pressure over days/weeks and months. This cannot
be done by Cardiovascular system on its own . It does not have collection of choices available
to deal with it.
You have to enlist the kidneys in order to maintain long term fluid balance and long term blood
The fluid filling the blood vessel that determines the blood pressure. The fluid vol in the body is
A HUGE player in determining MAP.
The kidney are the main player in regulating fluid balance.
If you have prolonged increase in MAP, since you have tumour in you adrenal gland so you are
overproducing EPINEPHRINE which is creating a sympathetic stimulus constricting blood
vessels, increasing cardiac output.
Then the baroreceptors over a period of time would not adapt to that blood pressure anymore.
The increase in MAP over several hours to a day or so , can cause the kidneys to increase the
amount of fluid that they are excreting. So you essentially take water out of the body and get rid
of it which will reduce blood volume, which will have impact on MAP because it effects venous
return ; reducing STROKE VOL and lowering MAP.
The kidneys help to modify blood pressure by changing the fluid vol
If you we have increase blood vol it will cause increase in blood pressure. It will cause the
kidneys to start excreting , it’s a cycle, not a starting and an ending point.
How does this feedback loop get organized?
Hormones involved are called (i) Angeiotension II and Vasopressin are both vasoconstrictor.
They will alter TPR but they also effect how kidneys handle fluid , and they will cause the body
to retain more water, by reducing how much urine gets produced. These hormones help to communicate a common goal between cardiovascular system and the
RENAL PHYSIOLOGY AND FLUID BALANCE (Chp 14, 15)
The structure of Kidney
Outer layer= Renal cortex
Fan shape layer= Renal medulla (ends up opening into these larger chambers which are fluid
chambers the Renal Pelvis)
We are moving the fluids from the outer layer of kidney down through the medulla and ultimately
the fluid is going to be accumulating in the Renal Pelvis.
The next step is go through the Urinary tract.
Kidneys are vital organs,
Kidney failure can lead to death; you can live with one kidney.
If your kidney shut down, you cannot live.
1. Fluid balance & ion homeostasis (Na & K in order to maintain the appropriate membrane
2. Waste excretion
3. Drug removal (kidneys play big role, how much of a dose of drug you need, and the
frequency of the drug you need to take. Penicillin is like that)
4. Hormone Production (Erythropoietin used to produce red blood cells via bone marrow)
5. Glucose Synthesis
Slide 5 An average size individual will have 40L of fluid (intracellular, extracellular and within the
plasma) that you need to maintain in order to keep the fluid level constant.
3L of the 40 L are plasma. Based on consumption as well as things like sweating, evaporation
causes to lose fluid.
The arm on this beaker, is representing
the kidneys and the fluid that passes from the normal body fluid vol into the kidneys. We refer
to that as glomerular filtration
The amount of fluid that is passing from the plasma into the kidney system is referred to as
glomerular filtration rate. (its approx. 20% of blood flow 180 L/Day)
The kidneys clean the blood and make sure it gets the appropriate levels of substances.
The fluid that enters the kidney’s you need to retain most of that fluid back into your regular
body reservoir. WE have a very small amount of fluid that is lost from the body by urine
production (~1.5 L/day).
The ratio between what gets reabsorbed in (taken back into regular body reservoir) compared to
what gets lost in urine. This also a regulated feature. Can vary from day to day.
The Nephron (within the kidney)= functional unit of the kidney
This is where all the fluid filtration and reabsorption occurs.
It is a nice association between vascular system and the kidney tubule n