Blood pressure: definition, contol and factors affecting it

What does it mean?

It is the amount of force on arteries walls when the blood circulates around the body.

What does arterial BP mean?

It is the pressure exerted by blood on arteries walls, it is expressed in millimeteres of mercury. There are two types of arterial blood pressure: systolic and diastolic.

1- systolic BP: it is the maximum blood pressure value when the ventricles contracted.

2- disatolic BP : it is the blood pressure minimum value that achieved at the moment before ventricles contraction.

Factors affecting blood pressure:

1- Age.

2- environment.

3- life style.

4- diet.

5 – genetic factors.

6 – activity level.

7- stress.

8 – circadian rythem.

Cardian rhythm definition:

It is a daily cyclic fluctuation in physiologic processes like hormone levels and nervous system activity.

Blood system control:

There are many factors control BP. We can divid it to :

1- Nervous system control : sympathetic and parasympathetic nerves.

2 – Hormonal control : adrenaline, noradrenaline and catecholamines.

3 – Renal control.

4 – Renin angiotensin aldesterone system ( RAAS).

How does nervous system control blood pressure?

1 – Sympathetic nerves :

when pressure become low , baroreceptors send signals to the sympathetic nerves. Sympathetic nerves activate adreanline, noradrenaline and catacholamines in our bodies. These homones increases heart rate and vasoconstriction contrations that leads to increase pressure.

2 – Para sympathetic nerves:

when pressure become high , baroreceptors send signals to the para sympathetic nerves. para sympathetic nerves activate acetylcholine secrection in the body. This homone slow heart rate and decrese vascular contrations that leads to low high pressure.

Angiotensin effect on blood pressure:

1 – It stimulates thirst.

2- It stimulates central nervous system.

3 – It stimulates pituitary gland to secret antidiuretic hormone (ADH) that leads to water retention and increase BP.

4 – It has an effect on vaso constrictions thet increase peripheral resistance that leads to increase BP.

5 – It stimulates aldesterone secretion that leads to salt and water retention.

6 – It has an effect on kidneys, it increase BP because it retain salt and water.

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