Short Term Control Of Blood Pressure 2 Flashcards
What are the effects of the Valsalva manoeuvre on the cardiovascular system?
It increases thoracic pressure, impacting blood pressure and heart rate.
How does the Valsalva manoeuvre affect blood pressure during its phases?
Phase one involves increased thoracic pressure leading to increased blood pressure, while phase two makes it harder for blood to return to the heart.
Define phase one of the Valsalva manoeuvre.
It is the initial phase where thoracic pressure increases, transmitting pressure through the heart and aorta, resulting in elevated blood pressure.
What is the significance of phase two in the Valsalva manoeuvre?
Phase two involves increased thoracic pressure, making it more challenging for blood to return to the heart.
Describe the respiratory pump and its role in the Valsalva manoeuvre.
The respiratory pump involves the movement of the diaphragm during inspiration, creating negative thoracic pressure that aids in pushing blood from veins back to the heart, facilitating blood return.
Describe the process of how decreased venous return affects stroke volume and cardiac output.
Decreased venous return leads to reduced preload, resulting in less efficient excitation-contraction coupling, fewer cross bridges forming, reduced force of contraction, and ultimately a decrease in stroke volume and cardiac output.
Define the role of baroreceptors in regulating mean arterial pressure.
Baroreceptors in the aortic arch and carotid sinus detect changes in mean arterial pressure and signal the medullary cardiovascular center to adjust sympathetic tone, heart rate, contractility, and vascular resistance.
How does the body respond to low mean arterial pressure?
In response to low mean arterial pressure, the body increases sympathetic tone, leading to the release of noradrenaline, which binds to beta-1 receptors on the sinoatrial node, resulting in increased heart rate, contractility, and vasoconstriction.
Describe the impact of arteriolar constriction on total peripheral resistance.
Arteriolar constriction increases total peripheral resistance, which helps to maintain or elevate blood pressure by regulating the flow of blood through the systemic circulation.
What effect does vasoconstriction have on venous return?
Vasoconstriction, particularly in veins and venules, helps push more blood back to the heart, increasing end diastolic volume and aiding in maintaining cardiac output.
Explain the relationship between decreased preload and excitation-contraction coupling efficiency.
Reduced preload leads to less efficient excitation-contraction coupling, resulting in fewer cross bridges forming and a reduced force of contraction, ultimately impacting stroke volume and cardiac output.
Describe the phases involved in the response to the Valsalva manoeuvre.
Phase three involves a decrease in blood pressure due to decreased thoracic pressure transmitted to the heart. Phase four sees a massive increase in blood pressure as blood returns to the heart.
What causes the rebound increase in blood pressure after stopping the Valsalva manoeuvre?
The rebound increase is mainly due to the accumulation of blood in veins and venules during the manoeuvre, which then floods back to the heart upon cessation.
How does the baroreflex respond to the increase in blood pressure post-Valsalva manoeuvre?
The baroreflex increases vagal tone, leading to the release of acetylcholine from the vagus nerve, which slows down the sinoatrial node, decreasing heart rate and cardiac output.
Define the clinical significance of using the Valsalva manoeuvre.
The Valsalva manoeuvre can be used as a test of autonomic function and to assess the baroreceptor reflex, which may be reduced in older individuals due to decreased arterial elasticity.
