Welcome to my new post in the health series.
You may have heard many times your Doctor saying-"Your blood pressure is increasing! It is 160/100mmHg... or saying "your blood pressure is very low its only 90/50 mmHg!......and you have no idea what is blood pressure, you only know its normal value is 120/80 and when it deviates either way from that it is bad for your health....
Today we will talk about What exactly is our blood pressure and how hypertension occurs in a simple language so that all of the steemians can understand...
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What is blood pressure?
Blood pressure is the pressure exerted by flowing blood on the wall of arteries(blood vessels).In a simple way you can understand it by comparing with the water pipes.
When water flows through the pipe it exerts some force on the wall of pipe isn't it?..that is what the blood pressure is.The amount of pressure on the wall of the pipe depend upon two things-
1-The size of lumen of pipe- Smaller is the diameter higher will be the pressure. When you open a tap having narrow lumen water will come with a greater force than in the pipe with wider lumen. JUst see the picture below, when you squeeze or press the pipe water will come with a greater force.
(credits)2-The force of the water source- The higher the force form source higher the pressure.
The case is exactly same for the blood pressure-
Fig- Blood pressure is determined by Cardiac output and the of blood vessels peripheral resistance (credits)
The blood pressure is determined by two things-
- 1---The cardiac output
like the force from source of water, the force and volume at which heart pumps the blood determines the one aspect of blood pressure. The cardiac output is nothing but the volume of blood pumped by heart in one minute. The greater amount of blood the heart pumps greater will be the blood pressure i.e pressure exerted on the arteries(blood vessels). If you like to know more about cardiac output , here is a relationship-
Cardiac output = stroke volume * Heart rate
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Stroke volume is the volume of blood pumped by heart in one beat, its value is 70ml, and heart rate is number of heart beats per minute which is about 72. If you multiply both it comes about 5 litres per minute.
When heart pumps more blood it is obvious that it will exert more pressure on the blood vessels.
- 2--- Total peripheral resistance
Just like the lumen of the water pipes, blood vessels carry blood pumped by the heart, the narrower the blood vessel the greater the force or pressure on the blood vessel and more difficult will be the flow of blood. Peripheral resistance is nothing but the resistance offered by small blood vessels(arteriloles ) to the flow of blood.
Narrower the blood vessel more will be the blood pressure(credits)
So, for the normal cardiac output blood pressure can be high due to vessels alone.
Combining the both factors(Cardiac output and the total peripheral resistance) the final equation comes like this-
Blood Pressure = Cardiac Output * Total peripheral resistance
So, increase in either of the two factors can increase your blood pressure,
What are the factors increasing cardiac output?
- Increased heart rate- In fever, anxiety, nervousness, hyperthyroidism, drugs increasing heart rate(adrenergic drugs)
- Increased blood volume- Exercise, hyperthyroidism, adrenergic drugs, some diseases of adrenal glands where blood volume is increased
What are the factors increasing peripheral vascular resistance?
- High blood cholesterol - deposited in blood vessel and narrows the blood vessels.
- Old age- blood vessels become stiff
- High sodium- it also increases stiffness of blood vessels
They say your blood pressure is 120/80 , what does this mean?
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It indicates two things, the value 120 is called systolic blood pressure, i.e. it is the pressure by blood on the blood vessels when heart contracts. and 80 is diastolic blood pressure ,i.e. it is the pressure on blood vessels when heart relaxes. During contraction heart pumps more blood so there will be more pressure on blood vessels but during relaxation heart does not pump blood which causes low value of diastolic blood pressure. That is the story behind dual value.
Systolic blood pressure is increased in normal conditions like nervousness, fever and exerscise, but diastolic blood pressure is increased only when there is pathology in the blood vessels, i.e. when blood vessels are narrowed. SO, diastolic blood pressure is more important to note.
This is all about blood pressure, Now i will show you how high choleserol increases blood pressure-
When blood cholesterol level increases, it gets deposited in on the wall of blood vessels . This results in narrowing of blood vessels.
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You can see in the picture above, the lumen of blood vessels is narrowed by atherosclerotic plaque which increases the peripheral resistance thereby increasing blood pressure.
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Images- credits are attached to the images themselves.
Contents- My Medical knowledge
Thats it for today my friends..in next post i will be talking about Diabetes and Hypertension...stay tuned, follow me at @himal..
