What is high blood pressure (hypertension)?

marie4u

i want complete information on what is high blood pressure or hypertension?

Reply 1

hslt

It pretty much is exactly what is says on the tin, what exactly do you want to know?

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Reply 2

seaholme

In an easy-to-understand way, imagine that you have a tap that sprays water out. If the system is at a low pressure you get a sort of gentle trickling effect, but if it is at a high pressure then you'll get a powerful stream of water coming out of the tap. Your heart is a pump and all your blood vessels are the system. Within that system there is a resting pressure. Hypertension is where that resting pressure is too high. Your heart has to work a lot harder to pump blood out against a system that's so high pressured and it adjusts its physiology to some extent to do so.

As for why resting pressure becomes too high, the most common reason is to do with the system itself. Water pushed through a tiny hole is going to come out at a higher pressure than water pushed through a wide bit of hose, and it's the same with blood. If blood vessels become narrower then pressure rises. Blood vessels also have some elasticity to them which reduces pressure because they can sag out slightly as the pressure gets higher. If they lose this, pressure gets higher.

Over our lifetimes, damage to our blood vessels happens to everyone, and to some people more than others because certain factors increase the amount of damage - smoking, diabetes, dietary factors such as cholestrol, alcohol consumption - and as they become damaged and the elasticity falls and the vessels get narrower, blood pressure goes up.

It's a complicated system, there are a lot of ways in which pressure goes up and down. For instance in old age, despite thinking that actually damage is cumulative and so it should be the HIGHEST blood pressure, we actually drop our blood pressure. So you can see it's complicated. Issues with the pump, with blockages, with reflexes that help us maintain sufficient blood pressure, with the areas perfused by the blood such as the liver, kidneys and so on... many many things! But in terms of issues with the classic sort of hypertension you see in middle age, that's the most common scenario.

Hypertension is dangerous for various reasons, largely because it increases your risk of strokes, it seems to be a negative factor on survival in multiple conditions and has profound effects on your physiology as it adapts to the higher pressure. For instance you can have hypertrophy of the muscle of the wall of the heart, which seems quite logical except that it reduces the amount of space inside the chambers of the heart for blood and means that the resting pressure actually increases as well. This is also complicated :P

(edited 10 years ago)

Reply 3

ThePoster

If this is to do with Biology AS, you'll want to research the process of atherosclerosis. It is basically something that can narrow the artery, by build up of atheroma, causing hypertension and increasing risk of heart attack.

Remember, only the arteries have very high pressure, not veins I believe.

Reply 4

Mushi_master

Original post by ThePoster

You may want to look back into this - it isn't atherosclerosis that causes hypertension.

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Reply 5

ThePoster

Original post by Mushi_master

You may want to look back into this - it isn't atherosclerosis that causes hypertension.

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It is a cause, and the main one you have to know if doing AS bio with edexcel. Where am I going wrong?

Reply 6

shiggydiggy

Original post by ThePoster

It is a cause, and the main one you have to know if doing AS bio with edexcel. Where am I going wrong?

They are different processes. However, it is suggested that hypertension can cause structural defects within the arterial system which allow for the development of atherosclerosis. But atherosclerosis doesn't cause hypertension.

Reply 7

ThePoster

Original post by shiggydiggy

I'm certain it does, but isn't the only cause. It's a feedback loop, hypertension can increase risk of damage to arterial walls, which causes the inflammatory response leading to atherosclerosis. This narrows the lumen, increasing the pressure within the artery. And so on.

Reply 8

Mushi_master

Original post by ThePoster

This certainly isn't how this is taught at medical school. Atherosclerosis may be related closely to hypertension, in that the high pressure vessels lead to damage to the vascular endothelium and inducing inflammatory changes. Isolated lesions of atheroma aren't going to have a particularly significant effect on peripheral vascular resistance (which is what you're talking about), in that it isn't likely to be a cause of systemic hypertension. It is certainly not a leading cause of hypertension. If you can show me some papers that state otherwise then I'd be happily corrected.

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Reply 9

ThePoster

Original post by Mushi_master

Ah, I'm just regurgitating information given to me at sub-degree level, I'm happy to accept it was wrong or over-simplistic. It's a bit gutting to know that, though.

Reply 10

hslt

Original post by ThePoster

Blood pressure = total peripheral resistance x cardiac output

So to raise blood pressure you can increase resistance - the main site of resistance though, is in the arterioles, not the great arteries (where atherosclerosis predominates).

So even though you can narrow the lumens of the arteries, and cause decreased flow, this has minimal impact on the blood pressure because the great arteries contribute little to the overall resistance of the system.

The classic scenario where atherosclerosis does cause hypertension is if it affects the renal arteries though, because of the effects this has on the kidney's role in blood pressure control.

That is my understanding of BP physiology and its relationship to atherosclerosis, hope it helps.