Summary
The force of blood against vessel walls, recorded as systolic over diastolic pressure.
In depth
Normal is about 120/80 mmHg. Hypertension increases risk of stroke and heart disease. Controlled by cardiac output, resistance, blood volume, baroreceptors and hormones.
Baroreceptors in the carotid sinus and aortic arch provide rapid feedback. Long-term control is renal. Hypertension is silent but damaging.
Common mistake: normal blood pressure is not a single number but a range.
Blood pressure is written as systolic over diastolic, with pulse pressure the difference. It is measured with a sphygmomanometer and stethoscope (Korotkoff sounds) or automatic cuffs. Mean arterial pressure is about diastolic plus one third of pulse pressure. Short-term control is by baroreceptors in the carotid sinus and aortic arch, which signal the medulla to adjust heart rate and vessel tone. Long-term control uses the kidney and RAAS to adjust blood volume.
High blood pressure (over 130/80 mmHg by current US guidelines, 140/90 by others) is called the silent killer since it usually has no symptoms and damages heart, brain, kidneys and eyes. Management includes reducing salt, weight loss, exercise and drugs (ACE inhibitors, beta-blockers, diuretics, calcium channel blockers). Low pressure causes fainting.
Example: standing up quickly triggers a baroreceptor reflex to maintain brain blood flow.
Frequently asked questions
What is Blood Pressure?
The force of blood against vessel walls, recorded as systolic over diastolic pressure.
Which area of biology covers Blood Pressure, and how advanced is it?
Blood Pressure is one of the 51 topics in Human Physiology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Renal Autoregulation, Frank-Starling Law, Renin-Angiotensin-Aldosterone System.
Can you give an example of Blood Pressure?
Salt reduction and exercise lower blood pressure.
What should I learn before Blood Pressure?
Work through the Beginner topics in Human Physiology first, such as Homeostasis, Tissues and Organs, Skeletal System, then return to Blood Pressure. Intermediate topics assume the Beginner vocabulary.
What topics are related to Blood Pressure?
The closest topics to Blood Pressure are Renal Autoregulation, Frank-Starling Law, Renin-Angiotensin-Aldosterone System, Cardiovascular Disease Mechanisms. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Blood Pressure?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Blood Pressure. To practise the whole of Human Physiology, use the Human Physiology quiz.
How is Blood Pressure different from Renal Autoregulation?
Blood Pressure: The force of blood against vessel walls, recorded as systolic over diastolic pressure. Renal Autoregulation: Kidneys adjust arteriole resistance to keep glomerular filtration steady despite blood pressure changes. Read both side by side and note what each one explains.
What is a common mistake about Blood Pressure?
Normal blood pressure is not a single number but a range.
How should I study Blood Pressure step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Renal Autoregulation and explain the difference aloud. Finally, take the Human Physiology quiz and come back to this page for any question you miss.