Renal Regulation of Blood Pressure (Nursing)

00:01 So a third but more long term mechanism for regulation of blood pressure is going to be renal regulation.

00:09 Here, baroreceptors are going to quickly adapt to a chronic or low blood pressure.

00:15 So they are going to be ineffective for long term regulation.

00:20 So long term mechanisms are going to control our blood pressure by altering the blood volume via the kidneys.

00:28 The kidneys regulate our arterial pressure by direct renal mechanisms, as well as indirect renal mechanisms like the renin-angiotensin- aldosterone mechanism.

00:41 So starting with direct renal mechanisms, these are going to alter the blood volume independent of hormones.

00:49 We get an increase in our blood pressure or blood volume, which will then cause the elimination of more urine, thus reducing that blood pressure.

01:00 Conversely, if we have a decrease in our blood pressure or blood volume, this causes the kidneys to reabsorb or conserve water and raise our blood pressure.

01:13 An indirect mechanism of renal regulation is the renin-angiotensin- aldosterone mechanism.

01:21 If we have a decreased arterial blood pressure, this causes a release of renin from the kidneys.

01:29 Renin then enters the blood and catalyzes the conversion of angiotensin found in the liver to angiotensin I.

01:38 Then angiotensin converting enzyme or ACE, especially from the lungs, is going to convert angiotensin I to angiotensin II.

01:50 Angiotensin II acts in four ways to stabilize our arterial blood pressure and our extracellular fluid levels.

01:59 First, it stimulates aldosterone secretion.

02:04 This then causes antidiuretic hormone to be released from the posterior pituitary.

02:11 This then triggers the hypothalamic thirst centers so that we are told or we think to drink more water.

02:19 Also, angiotensin II can act as a potent vasoconstrictor and directly increase the blood pressure on its own.

02:29 So for example, in direct renal regulation, a decrease in our mean arterial pressure will mean a decrease in the filtration by the kidneys.

02:41 This leads to a decrease in the amount of urine that is formed, which will then lead to an increase in blood volume.

02:48 since we reabsorb or conserve the water instead of excreting it by way of urine.

02:53 The increase in blood volume will then increase our mean arterial pressure.

03:01 However, when we look at indirect renal regulation, a decrease in the arterial pressure is going to inhibit the baroreceptors, which are going to trigger sympathetic nervous system activity.

03:15 This then causes the release of renin from the kidneys, which leads to the conversion of angiotensinogen to angiotensin II.

03:24 From there, angiotensin II is going to act on the adrenal cortex in order to release certain hormones, as well as increase the amount of antidiuretic hormone that's released by the posterior pituitary, as well as increase the thirst centers by way of the hypothalamus and also directly cause vasoconstriction in order to increase peripheral resistance.

03:50 All of these instances will then increase our mean arterial pressure.

03:57 So to summarize, the goal of blood pressure regulation is to keep our blood pressure high enough to provide for adequate tissue perfusion, but not so high that our blood vessels are damaged.

04:14 So a good example of this is if the blood pressure to the brain is too low or perfusion to the brain is inadequate, then a person can lose consciousness.

04:25 However, if the blood pressure to the brain is too high, a person could have a stroke.