Kia ora team, my name's Ben and let's have a look at the sympathetic response to hypotension. So if we have falling blood volume and falling blood pressure, our sympathetic nervous system, which is our fight, flight, part of our autonomic nervous system is going to kick in. So let's have a look at which receptors are in which organs and what their effect is and how we can save our blood pressure. So to begin with let's have a look at at our alpha-1 receptors. So if we've got falling blood pressure, hypotension, then we have alpha-1 receptors in the smooth muscle of our blood vessels around our skin, abdominal organs, our digestive tract, and our kidneys.
So our sympathetic response is going to cause vasoconstriction of those blood vessels. So if we do that, that vasoconstriction is going to increase the total peripheral resistance. So basically squeeze the pipes and that's going to increase our blood pressure.
Then we have beta 1 receptors. So think beta 1, 1 heart. And we have them on our SA node, on our AV node, and then the myocardium. So myomuscle, cardi, heart.
And what the beta 1 receptors are going to do, our beta 1 receptors on our SA node are going to have a chronotropic response. and increased heart rate so our SA node will send more action potentials out to tell the heart to contract. Our beta 1 receptors on the AV node, atrioventricular node, they're going to increase the electrical conduction speed which is a dromotropic effect because normally we delay the impulse from the SA node when it gets to the AV node with a sympathetic response we're going to increase the conduction velocity through the AV node so we can generate that contraction quicker. And then finally we've got our beta-1 receptors in the myocardium, the heart muscle, and they're going to increase the contractility of that heart muscle.
So it's going to squeeze harder. So that's an enotropic effect. SA node, AV node, that's all going to increase the heart rate.
and the inotropic effect of beta-1 on the myocardium, because of squeezing harder, that's going to increase our stroke volume. So each squeeze, we're going to get more blood out of the heart. So this is going to help our blood pressure.
We also have beta-1 receptors in our kidney, in our juxtaglomerular cells, juxta, beside, glomerular, which is the start of the nephron, the filter in the kidney. And these beta-1 receptors cause our juxtaglomerular cells to release renin. And renin is the start of our RAF system, and that helps to increase our blood pressure by reabsorbing fluid from our kidneys. And that is how our sympathetic nervous system helps to preserve our blood pressure and responds to hypotension. Happy studying, Jane!