Cardiovascular regulation Flashcards
What do increased activity of baroreceptors cause?
Heart and blood vessels reduce cardiac output
What factors cause increased systemic vascular resistance?
Increased RBC’s, increased blood viscosity, total blood vessel length, decreased blood vessel radius and increased systemic resistance, cause increased mean arterial blood pressure
What is the primary objective of cardiovascular regulation?
To maintain a stable MAP, to ensure adequate blood flow to vital organs
Where do you find non-encapsulated nerve endings?
Carotid sinus and aortic arch
What are mechanoreceptors sensitive to?
Stretch
What does increased arterial pressure do to baroreceptors?
Increases distending pressure on arterial wall to stretch which excites baroreceptors
Where do baroreceptor afferents project?
Glossopharyngeal and vagus nerves
What do increases in afferent input lead to?
Increased parasympathetic and decreased sympathetic stimulation of the heart
If baroreceptors detect a decrease in blood pressure what happens?
Increased sympathetic stimulation, increased secretion of epinephrine and noradrenaline, increased heart stroke volume and CO.
Vasoconstriction causes increased systemic vascular resistance
What is orthostasis?
Effect of gravity on the distribution of venous blood, more venous volume, reduction in pressure, EDV, pulse pressure and MAP
How does CV centre respond to orthostasis?
Less vagal outflow to the heart more outflow in cardiac and vasomotor nerves, increased heart rate and contractility, increase TPR and MAP
What are arterial baroreceptors responsible for?
Buffering of blood pressure
What has the responsibility of regulating blood pressure long term?
Cardiopulmonary pressure receptors and hormonal influences
What receptors respond to much lower pressures than baroreceptors?
Atria and pulmonary arteries
What is the primary role of cardiopulmonary stretch receptors?
Regulate blood volume, primary determinant of cardiac output so determines arterial pressure
If venous blood pressure decreases what is this reflected by?
Less atrial pressure and less stimulation of cardiopulmonary stretch receptors causing:
Increase of ADH from hypothalamus, increasing reabsorption of fluid from renal tubules and production of concentrated urine
Reflex that constricts the afferent renal arterioles reducing the rate of glomerular filtration
- reduces fluid loss in urine and increases blood volume
What other effect does ADH have?
Vasoconstrictor, in the gut and spleen, increases TPR so the fall in atrial pressure triggers compensatory responses to restore mean arterial pressure
When both baroreceptors and cardiopulmonary stretch receptors are denervated what happens?
Leads to marked increase in mean arterial pressure
What do chemoreceptors do?
Monitor chemical composition of arterial blood sensitive to oxygen, hydrogen ions
How do chemoreceptors affect breathing
Increased rate and depth of breathing, increase in tidal volume - lung inflation reflex - small vasodilation.
Increase in cardiac output and TPR producing increase in mean arterial pressure
What is the most important determinant of arterial pressure in long term?
Blood volume
The greater the renal arterial perfusion pressure the greater the rate of…?
Glomerular filtration and urine production
The relationship between renal arterial perfusion pressure and glomerular filtration is amplified by?
Renin-angiotensin-aldosterone system
What is a fall in blood volume or renal blood flow detected by?
Juxtaglomerular cells in the kidney which release enzyme renin
What chain of events does renin trigger?
Angiotensinogen released by liver, angiotensin 1 and 2 released and aldosterone, more sodium retention in renal tubular cells which increases blood volume
What are the end results of the renin-angiotensin-aldosterone system?
Vasoconstriction mediated by angiotensin 2 raises TPR
Increased reabsorption of sodium from renal tubules results in an increase in water reabsorption down the resulting osmotic gradient, raising blood volume and cardiac output, elevates MAP
Adrenaline causing an increase in cardiac output is mediated by which receptors?
B-adrenoceptors
Noradrenaline causing vasoconstriction via which receptors to raise TPR?
A-adrenoreceptors
What does atrial natriuretic peptide do?
Released in response to high cardiac filling pressures, reducing MAP by causing vasodilation and promotes Na+ excretion in kidneys
