Lecture 8: Overview Of Cntrol Of Blood Pressure: Arterial Baroreflexes Flashcards
Describe postural hypotension
You sit for a long period of time and like falls down at your feet due to gravity, most of the pressure is at your feet,
If person gets up, gravity continues to pull blood down and there is not enough pressure for venous return.
Bp will decrease and not enough blood to brain so person faints.
In younger people, with good baroreceptors , these immediately increase SNA and pressure to bring that pressure difference back to normal.
Describe the valsal manoeuvre
A person inhales and restrains himself to restrain the organ
At point 1: Bp increases slightly due to increased pressure in chest
At point 2: Bp decreases and is detected by baroreceptors activating SNA so up everything that increases CO is activated.
Blood flows by pressure gradient from high to low so Bp decreases. Tis is sensed by baro. so Heart rate increases
Before point 3: pressure starts to normalise. As body has adapted to strained environment
Point 4: compensatory tachycardia. Now he stops straining, hr still slightly high as it takes time to normalise.
Baro detect difference in pressures
Once SNA stops being active heart rate returns to normal
Describe the baroreceptors control of arterial pressure
This occurs over a time scale of seconds to minutes
An increase in blood pressure is sensed by the baroreceptors. They send message to the brain which sends a message to he SNA to decrease and PNA to increase
HR and CO decrease. Contractility decreases and SV also decreases
What are nitrates?
Dilators
What is a short term regulator of blood pressure?
Baroreceptors - extrinsic neural control
What is a long term regulators of blood pressure
Kidneys - intrinsic non neural body in myogenic mechanism
What is the relationship between Bp and RAAS
Bp is inversely proportional to RAAS as RAAS increases, Bp will decrease.
More like RAAS is increased as a result of a decreased Bp
