Sunday, April 28, 2013

What are the factors affecting diastolic blood pressure?

Hi everyone!

What is diastolic blood pressure?
It is the pressure that is exerted on the walls of the various arteries around the body in between heart beats when the heart is relaxed.
It is the minimum pressure in the entire cardiac cycle.
So it basically represents amount of blood in arterial system during diastole.

What controls the amount of blood in arteriole system while your heart is filling in diastole?
The peripheral resistance arterioles! They maintain your diastolic blood pressure.

Why is it necessary to maintain diastolic blood pressure?
It is important because the coronary arteries fill up in diastole.

When arteries are dilated, diastolic blood pressure decreases.
When arteries are constricted, diastolic pressure increases.

What happens when there is a decrease in heart rate?
Because the heart rate is decreased, there is more time for the blood to run out of the arteries during diastole.
Arterial volume, therefore, drops to a lower value than before and diastolic pressure decreases as a result.

What happens when there is a decrease in stroke volume?
A decrease in stroke volume decreases the amount of blood in the arterial system, decreasing the diastolic blood pressure.

What happens in our body:
When heart rate is decreased, stroke volume increases to maintain cardiac output.
That's like two opposite things!
So what happens to diastolic blood pressure?
I have no clue. If anyone has an answer to this question please help me out.
Also, feel free to correct me if anything in this post seems to be a wrong to you.

That's all!

These are all the explanations and replies that I got, I'm publishing the nice ones :)

Explanation #1

In normal physiological states, stimuli that increase heart rate increase the blood pressure and stimuli that decrease heart rate lower the blood pressure.

However, there are two exceptions to this rule -
When atrial stretch receptors are stimulated, there is vasodilation and fall in blood pressure (production of hypotension) and an increase in heart rate (tachycardia)

And during increased intracranial pressure, blood supply to vasomotor area is compromised and the local hyprecapnia and hypoxia increase it's discharge.
This results in a rise in blood pressure to restore blood to the medulla (This is known as Cushing reflex)
The rise is blood pressure causes a reflex decrease in heart rate via arterial baroreceptors and bradycardia is produced.

Explanation #2

Your peripheral resistance in most cases will give you the answer about what happens to the diastolic blood pressure.
For example, when you exercise, your heart rate and stroke volume increases.

Then all you have to do is figure out what kind of exercise it is.

Usually, peripheral dilation will decrease your diastolic blood pressure in exercise.
This is the case in dynamic aerobic exercise.

If contraction of the skeletal muscles are physically compressing on your blood vessels, TPR rises.
This happens in static exercise like weightlifting, diastolic blood pressure will increase.

Explanation #3

When cardiac output decreases, let’s say in hemorrhage, baroreceptors will sense this and there will be a sympathetic response which releases catecholamines and activates the renin angiotensin system.

Catecholamines will act on the beta adrenergic receptors on the heart, which will increase the force of contraction, there will be an increase in stroke volume (slight) and it will increase heart rate.

The renin angiotensin system will cause an increase in peripheral resistance by vasoconstriction which will cause an increase in diastolic blood pressure.

The increase in heart rate or stroke volume doesn’t tell you much about the diastolic blood pressure.
Like it was explained in the previous explanation , it increases in exercise too!
Focus of peripheral resistance and you’ll get it right ^___^

Explanation #4

In case of hypothyroidism, bradycardia is accompanied by high diastolic blood pressure.
But the mechanisms are very unrelated and different.
Bradycardia is because decrease in the thyroid hormone (Thyroid hormone aguments intracardiac conduction and upregulation of beta receptors on the heart.)
And increased diastolic blood pressure is due to stiffer blood vessels.

Explanation #5

In case of aortic regurgitation, diastolic pressure decreases because of the retrograde flow from the aorta to the left ventricle.
This is not related to heart rate or stroke volume or peripheral resistance :)

Explanation #6

Effect of excessive sodium in ECF.
Excess sodium enters smooth muscle cells of peripheral resistance arterioles.
Sodium opens up calcium channels causing vasoconstriction of smooth muscle cells.
Increased total peripheral resistance increases diastolic blood pressure.
(Excessive sodium is seen in Conn’s syndrome)

Thank you so much everyone for helping me out on this =D
You all are awesome! <3
 Lemme know if there are any more, I'll keep updating xoxo


  1. ↑Stroke Volume = ↑ Pulse pressure
    ↓Compliance of the arterial (Aorta) = ↑ Pulse pressure

    ↑Stroke Volume = ↑ Systolic pressure
    ↓Compliance of the arterial (Aorta) = ↑ Systolic pressure

    ↑Stroke Volume = ↓ Diastolic pressure (TPR)
    ↓Compliance of the arterial (Aorta) = ↓ Diastolic pressure (TPR)

    ↓Compliance of the arterioles = ↑ Diastolic pressure (TPR)
    ↑ Compliance of the arterioles = ↓ Diastolic pressure (TPR)

    ↑ Cardiac Output = ↑ Compliance of the arterioles = ↓ Diastolic pressure (TPR)
    ↓ Cardiac Output = ↓Compliance of the arterioles = ↑ Diastolic pressure (TPR)

    ↑Mean Arterial pressure = ↓Compliance of the arterioles = ↑ Diastolic pressure (TPR)
    ↓ Mean Arterial pressure = ↓ Cardiac output

    ↑Blood Flow (volume) = ↑Pressure
    ↓ Radius (compliance) Vessel = ↑Pressure= ↑ Resistance

    ↑Venous pressure = ↓Compliance of the Vein (venoconstriction) = ↑ Venous blood volume (leg Pooling) = ↑ Venous Blockage

  2. Thanks for sharing this.It helped me a lot. It is great of you to take time and help me.

    1. You're most welcome. Time best invested if it helped and made someone's life easy :)

  3. I have a doubt regarding explanation 1
    When the bp increases the arterial stretch receptors r stimulated which inhibits the vastconstrictor arean stimulates the vagal parasympathetic system as a result of which there is vasodilatation n decrease in the heart activity resp.
    BT the exp1 says there will be vasodilatation (agreed) BT then how does the heart increases (there is stimulation of the vagus nerve)?

    1. Heart rate increases through reflex tachycardia.

      Wikipedia: The body has several feedback mechanisms to maintain adequate blood flow and blood pressure. If blood pressure decreases, the heart beats faster in an attempt to raise it. This is called reflex tachycardia. This can happen in response to a decrease in blood volume (through dehydration or bleeding), or an unexpected change in blood flow. The most common cause of the latter is orthostatic hypotension (also called postural hypotension). Fever, hyperventilation, diarrhea and severe infections can also cause tachycardia, primarily due to increase in metabolic demands.

      An increase in sympathetic nervous system stimulation causes the heart rate to increase, both by the direct action of sympathetic nerve fibers on the heart and by causing the endocrine system to release hormones such as epinephrine (adrenaline), which have a similar effect.

  4. Part of this is incorrect. A decrease in SV does NOT produce a decrease in diastolic pressure. A decrease in stroke volume decreases systolic pressure because there is less blood being pumped into your non-compliant arteries, but it has no effect on diastolic pressure, because it remains unchanged during ventricular systole. This is why a decrease in stroke volume decreases pulse pressure (if a decrease in pulse pressure decreased both systolic and diastolic pressure, there would be no change in pulse pressure). Refer to BRS for more details.

  5. Hello, I want to add somethings here..
    when there is,
    *increase total preripheral resistance>decrease stroke volume(as increase end systoloc volume)> decrease pulse pressure>increase diastolic pressure.*
    and,for U all,
    # pulse pressure & systolic pressure is dorectly propotional to stroke volume
    # diastolic pressure is the index of total peripheral resistence.


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