Ramchandra: The Cardiovascular Control System Flashcards
What is the role of the cardiovascular system?
- Maintain Blood Pressure
- Regulate Cardiac Output
- Maintain Blood Flow To Other Organ Systems
Effectively it is the means to distribute oxygenated blood around the body.
What are the two main afferent receptors?
- The Arterial Baroreceptors - Found in the Aorta and Pulmonary Trunk.
- The Cardiopulmonary Receptors - Found in large systemic veins, in pulmonary vessels, and in the walls of the right atrium and ventricles of the heart.
What are the two efferent neuron types from the brain?
- Vagal Efferents
- Sympathetic Efferents
What is the solitary tract nucleus?
The solitary tract is a compact fibre bundle that extends longitudinally through the posterolateral region of the medulla. It acts to convey afferent information from stretch receptors and chemoreceptors in the walls of the cardiovascular, respiratory and intestinal tracts.
- Lets of Efferent Fibres that are distributed to - and control - organ systems.
What factors cause the release of renin?
- Decreased Perfusion Pressure
- Increased Sympathetic Drive to the Kidney
- Decreased Salt Content in the Tubular Fluid
Renin functions as the rate-limiting step in the production of Angiotensin II
What is the function of Angiotensin II?
- Arteriole Vasoconstriction.
- Aldosterone Release - Both of which act to increase tubular reabsorption of NaCl and therefore H2O.
- Increase Sympathetic Drive - but will be deacreased if BP is high due to other causes
- Increased ADH release.
How does NaCl and H2O feedback on the RAAS system?
- Effective Circulating Blood Volume Increases.
- Perfusion of the Juxtaglomerular Apparatus Increases.
- Inhibition of Renin Release.
What causes the release of ADH?
- Angiotensin II Formation.
- Increased Osmolarity of the Blood.
ADH released from the Posterior Pituitary.
Where are the Primary Systemic Arterial Baroreceptors found?
- Carotid Sinus - carotid sinus nerve
- Aortic Arch - Aortic depressor nerve
At normal arterial pressure, what is the pattern of carotid sinus nerve impulse firing?
At the start of cardiac cycle, there is an increase in firing which gradually slows. However, the carotid sinus nerves still fire.
What happens to the carotid sinus nerve impulse as the arterial pressure is elevated?
There is an increase in the firing rate of the carotid sinus.
What happens to the carotid sinus nerve impulses as the arterial pressure decreases?
There is a decrease in the firing rate of the carotid sinus.
What is the relationship between baroreceptor nerve impulse frequency and sympathetic drive?
A decrease in the frequency of baroreceptor nerve impulse firing leads to increased sympathetic firing.
For example…
- Decreased Arterial Pressure
- Reduced Carotid Sinus Nerve Impulse Frequency
- Increased Sympathetic Firing
- Accelerated HR and Increased Contractility.
Why does hypertension lead to reduced baroreceptor reflex efficacy?
When you have high blood pressure chronically, your body reset it’s new ‘normal’ to this increased rate. this leaves the patient predisposed to maintaining a higher than normal BP.
Hypertension then means that either change in pressure…
- Doesn’t Change Sinus Activity Enough
or
- It Doesn’t Change Cardiac Output Enough.
What are the characteristics of the carotid sinus baroreceptors?
It has a…
- Threshold: Below 30 - 50 mmHg, a decrease in pressure does not alter the firing rate.
- Saturation: An increase in pressure above 150 - 180 mmHg also has no further effect on firing frequency.
- Rate Sensitivity: For a given mean pressure the rate of firing is greater for pulsatile pressure than for steady pressure. Has implications if you have left ventricular assist device which doesn’t have pulsatile heartbeats.