Lecture 22 Flashcards
What is blood pressure?
We are referring to systemic arterial pressure. Pressure in your large arteries. [Be careful when you use the term blood pressure.] For a whole circuit the mean pressure is 7mmHg - however mean arterial pressure is 100mmHg.
What is the importance of blood pressure?
BP is a risk factor for cardiovascular diseases - one modifiable risk factor that makes the biggest effect on our outcome of life (DALY). Major problem with high BP is being at risk of stroke.
Describe what happens when you increase BP?
For every 10mmHg increase in BP there is doubling in the incidence of CVD. The higher the BP the more likely you are to have CVD. Healthy young female’s tend to have lower BP and lower CVD risk.
What are the main features of BP?
Systolic - 120mmHg.
Diastolic - 90mmHg.
MAP - 100mHg.
Does tend to increase with age.
Describe the effect of lifestyle on BP?
Lifestyle has a big effect on BP - good diet, exercise, relaxation time (meditation) and not a lot of stress in their life.
Describe Mean Arterial Pressure?
MAP = Minimum diastolic pressure + 1/3 of the pulse pressure (which is peak systolic pressure - minimum diastolic pressure) MAP = Pd + 1/3 PP MAP = Pd + 1/3 (Ps - Pd).
What is special about 100mmHg?
At most mammals, the MAP is around 100mmHg. The exception are the long neck mammals e.g. giraffe. This is the pressure that is required to ensure that down at the capillary level there is sufficient movement of fluid (by filtration) out of the capillary at the arteriole end out at the venous end. Enough diffusion down at the cellular level i.e. oxygen.
What determines MAP?
MAP = CO x TPR.
Mean Arterial Pressure = Cardiac Output x Total Peripheral Resistance.
There are lots of things that affect CO and TPR. Nerves cause short-term control of BP. Where as long-term BP control is about controlling blood volume.
What are the main determinants of aortic pulse pressure (Ps-Pd)?
Ps = SV and how quickly it is ejected form the heart and aortic compliance. Pd = Aortic complicate and diastolic run off (HR and TPR).
Describe aortic pulse pressure?
When your heart contracts the blood goes straight into the aorta, but not all the blood goes through, however your aorta stretches and contains some of the blood during the systolic phase. Once the aortic valve shuts, the blood stored is then recoiled out during diastole. If you have stiff vessels in your aorta, the pressure will go high initially but then through diastole it will be lower (high systolic but low diastolic).
What are the major factors determining pulse pressure?
Compliance of the aorta (how stretchy your vessels are and the amount of volume that can be stored in the aorta).
Describe compliance of blood vessels?
When there is low compliance there is same volume, however bigger change in pressure. In the compliant aorta there is lots of blood being stored. Compliance decreases as you get older.
Describe the determinant stroke volume?
The bigger the SV the bigger increase in pressure. Anything that increases the SV will effect the systolic pressure (why when you exercise you get an increase in systolic pressure).
What is the biggest determinant of diastolic pressure?
Total Peripheral Resistance; there will be less run-off if you increase TPR. During exercise TPR decreases; more rapid run off; decrease in Pd and increase in Pp (pulse pressure).
Describe the effect of CVD on pulse pressure?
With arteriosclerosis there is a decrease in compliance so there is an increase in systolic pressure.
