Wk6- Heart Failure (incomplete) Flashcards
What is the basic function of the RAAAS System/Axis?
RAAAS System-
Works to increase cardiac output in order to increase perfusion
What do the letters in the ‘RAAAS’ Axis/System stand for?
RAAAS Axis:
R- Renin
A- Angiotensin
A- Aldosterone
A- Antidiuretic Hormone
S- Sympathetic Nervous System
The RAAAS System is triggered after ‘Decreased Perfusion’ is detected by 5 organs/cells. What are the 5?
RAAAS System- Decreased Perfusion is detected by:
1- Osmoreceptors
2- Baroreceptors
3- Kidneys
4- Liver
5- Lungs
What is the difference between an Osmoreceptor & a Baroreceptor?
Osmoreceptors= cells that evaluate osmotic pressure. This is the pressure/amount of solutes within fluid/plasma. They basically detect the thickness of the blood
Baroreceptors= Cells throughout blood vessels that sense the mechanical/physical pressure of blood flowing through
RAAAS System Q- Following detection of decreased perfusion by the Osmoreceptors, what steps occur?
- Osmoreceptors detect decreased perfusion
- Inhibit ADH (Antidiuretic Hormone)
- Decreased urination
- Increased vascular volume
- Increased pre-load
= Increased cardiac output
RAAAS System Q- Following detection of decreased perfusion by the Baroreceptors, what steps occur?
- Baroreceptors detect decreased perfusion
- Increases SNS and Decreases PSNS
- Noradrenaline release
= noradrenaline increases HR, Contraction strength & causes vasoconstriction
= Blood shifts from splanchnic veins to systemic circulation
= Increased cardiac output
RAAAS System Q- Following detection of decreased perfusion by the Kidneys, what steps occur?
- Kidneys detect decreased perfusion
- Renin is secreted
- Angiotensin I is converted into Angiotensin II (via the Angiotensin Converting Enzyme)
- Angiotensin II stimulates secretion of Aldosterone
= Increased retention of sodium and water
= Increased vasoconstriction
= Increased vascular volume
= Increased cardiac output
RAAAS System Q- Following detection of decreased perfusion by the Liver, what steps occur?
- Liver detects decreased perfusion
- Angiotensinogen is secreted
- This converted into Angiotensin I by Renin
- Angiotensin I is converted to Angiotensin II (via the Angiotensin Converting Enzyme)
- Angiotensin II stimulates secretion of Aldosterone
= Increased retention of sodium and water
= Increased vasoconstriction
= Increased vascular volume
= Increased cardiac output
RAAAS System Q- Following detection of decreased perfusion by the Lungs, what steps occur?
- Lungs detect decreased perfusion
- Angiotensin Converting Enzyme (ACE) is secreted
- ACE converts Angiotensin I to Angiotensin II
- Angiotensin II stimulates secretion of Aldosterone
= Increased retention of sodium and water
= Increased vasoconstriction
= Increased vascular volume
= Increased cardiac output
What are some conditions which can cause Heart Failure?
Heart Failure can be Caused By:
- Myocardial damage
- Valve disorders
- Arrhythmias (eg. AFib, Aflutter)
- Conduction Defects
- Reduced substrate availability
- Infiltrative or matrix disorders
- Disorders that increase demand for cardiac output
- Disorders that increase resistance to output (afterload)
- Cardiorenal syndrome
What is 1 positive effect of the RAAAS Axis/System on Heart Failure?
The changes compensate for reduced ventricular performance and help maintain hemodynamic homeostasis in the early stages of heart failure. This compensates for decreased perfusion- increasing cardiac output will then increase perfusion (in the short term)
In the long term, the RAAAS system is not sustainable and can create several negative feedback loops. What are some of these Negative Feedback Loops it creates?
RAAAS System Negative Feedback Loops:
1. Increased load on Ventricles make them dilate. So they stiffen up to increase tension which causes cell death, further heart weakening, reduced perfusion
2. Ventricular hypertrophy occurs from increased load. This diminishes their effectiveness to properly contract and reduced perfusion
3. Ventricular hypertrophy can also cause leaky valves due to distortion/change in shape of the ventricles. This decreases cardiac output and perfusion
In the long term, the RAAAS System causes increased preload & afterload which means cardiac work and effort is increased. What is the implications of this?
Increases in preload & afterload mean increased cardiac work and effort. Lots of mechanisms are working to kick the heart into gear and increase perfusion. This is tough on the heart. Results in:
1. Excess strain on the heart
2. Damaged heart muscle which can lead to cardiomyocyte necrosis & dysrhythmias
In the long term, the RAAAS System causes vasoconstriction which reduces coronary & renal perfusion. What is the implications of this?
Kidneys then hold onto sodium & water (aka sodium & water retention). This results in 2 main consequences:
(1) This causes fluid accumulation & subsequent congestion. The long term implications of fluid overload are in the next dot point
(2) Electrolyte Imbalances- For the kidneys to hold onto sodium it’s a balancing act. To retain sodium, the kidneys excrete potassium which drops serum potassium levels
What is the difference between systolic heart failure and diastolic heart failure?
Systolic Heart Failure= Heart has trouble squeezing effectively
Diastolic Heart Failure= Heart isnt relaxing properly (its tense & over constricted)
