Blood pressure Flashcards
What is blood pressure
force against blood vessels walls by blood in vessels in mmhg (maintains blood flow in tissues)
When is systolic BP measured
during ventricular systole (peak pressure in arteries as ejected from heart)
when is diastolic BP measured
during ventricular diastole (low pressure)
what is the artery commonly used to measure BP
brachial
what tool is used for BP
sphygmomanometer
what is pulse pressure
difference between systolic & diastolic
what is mean arterial pressure
average pressure
What are the factors affecting BP
1) Peripheral resistance
2) Cardiac output
3) Blood volume
What are the sources of peripheral resistance
- Diameter
- Length
- Blood viscosity
- Turbulence
What is peripheral resistance?
resistance to blood flow
hi PR = heart has to work harder
What is largest contributor to PR?
BV diameter
What does a decreased diameter do?
Increases BP & PR
What are the most resistance vessels?
Arterioles
explain how length is a source of PR
increased length = increased SA encountered = Increased friction = increase PR = increased BP
What is blood viscosity
thickness
what happens with increased viscosity
increased viscosity Increases PR & BP
What is blood turbulence
swirling of blood it increases PR
-could be an irregular surface or a slugger change in diameter
how does cardiac output affect BP?
veins are blood reservoirs that hold 65% of the blood at rest,
if you increase venous return you’ll increase BP
how does blood volume increase BP
increased volume = increased BP
high na intake = increased BP (b/c volume will rise)
What are the 3 forms of regulation of BP and Blood flow
1) Neural control - sympathetic
2) Local/ intrinsic control
3) Hormonal control
- ADH -ANP -RAAS
What is meant by vasomotor control (part of neural control)
The medulla oblongata sends signals to the vasomotor centre which signals the sympathetic division to release NE which will cause the contraction of smooth muscle in BV.
If you stimulate this response then it will cause vasoconstriction.
if you inhibit this it will cause vasodilation.
what is sympathetic tone
it facilitates venous return bu increasing BP in veins and maintains BP in arteries / arterioles
What is the main receptor that detects BP
Baroreceptor (detects stretch)
What is the baroreceptor initiated reflex
vasoconstriction to maintain BP to ensure blood delivery
what is the carotid sinus reflex
baroreceptors in the internal carotid A protect the blood supply to the brain
What is the aortic reflex
baroreceptors in the aortic arch protect blood supple to heart and body
explain local/ intrinsic control of BP
vasodilation is triggered by changes in the tissue environment
*THE NERVOUS SYSTEM IS NOT INVOLVED.
What are some causes of local control of BP
- increased CO2, decreased O2
- Decreased ph
- increased temp
- histmaine release
- nitric oxide
Where is nitric oxide released from?
Endothelial cells
What does nitric oxide do?
relaxes smooth muscle in tunica media by triggering ca2+ uptake into SR