Blood Pressure Flashcards
Describe the path of oxygenated and deoxygenated blood through the body.
- > From the heart through the arteries (large, thick-walled, muscular and elastic) and arterioles (small, less connective tissue, pre-capillary sphincters). Arterioles will decrease their orifice and that will reduce the blood pressure.
- > To the capillaries (small, thin-walled (one cell thick), endothelial, no muscle. Allows carbon dioxide to diffuse back into the capillaries. Inside the capillaries there are no muscles, it is just a pipe for flow through. Gaseous exchange occurs.
- > Returns to the heart vis the venules (small, thin-walled, smooth muscles, vales to prevent back-flow) and the veins (large, thin-walled, smooth muscles, valve, under control of the SNS)
What is the vasomotor centre (VMC)?
A portion of the medulla oblongata together with the cardiovascular centre and respiratory centre, that regulates blood pressure and other homeostatic processes.
Compare vasoconstriction and vasodilation.
Vasoconstriction: increased contraction -> increased resistance and blood flow
Vasodilation: decreased contraction -> decreased resistance and increased flow
What is systolic and diastolic blood pressure?
Systolic blood pressure: pressure exerted on arterial walls during ventricular systole (contraction). pressure from the left ventricle. Around 120mm of mercury pressure is healthy.
Diastolic blood pressure - pressure exerted on the arterial walls during ventricular diastole (relaxation). The blood distends the walls of the arteries as the blood passes through. Puts pressure on the blood passing through. Around 80 is healthy
What are the major determinants of blood pressure?
- Peripheral resistance in the arterioles - higher resistance = high BP
- Cardiac output - HR and stroke volume
- Blood volume - lo volume -> low BP
- Blood viscosity - number of cells in the body, like fluidity
- High viscosity (thicker) - high BP
- Elasticity of arterial walls - low elasticity
Describe the relationship between cardiac output and systolic/diastolic blood pressure.
Decrease in BP results in an increase in HR to maintain BP levels. An initial decrease in BP will cause the body to increase the heart rate to maintain blood pressure levels to maximise the profusion of arterial blood to this tissue.
What is the role of the baroreceptor reflex in relation to cardiac output?
The baroreceptor reflex is one of the body’s homeostatic mechanisms that helps to maintain blood pressure at nearly constant levels. It supplies feedback for short-term regulation of HR and peripheral resistance. It can increase or decrease the rate of the heart, it can increase stroke volume, increase sensitivity of the heart, increase contractability
- Located in the walls of carotid sinus and in the aortic arch
- The main baroreceptor is located in the neck, sends signal to the medulla, telling it what the situation is in relation to blood pressure
- Immediate solution to a change in blood pressure
- Cardiac output is the amount of blood pumped out by each ventricle in 1 minute
- Cardiac output = stroke volume x heart rate
Explain the renin-angiotensin system (RAS).
- Renin - enzyme
- Angiotensin - hormone
Both of these work together to adjust fluid levels in your veins to control BP. If you have more volume in your arteries, then it makes the blood flow easier and keeps up your blood pressure because there is more of it
Long term regulation of BP via the renal function
Angiotensin is ready to do something, when blood pressure is low, kidney produces renin, as the angiotensin is floating around, renin joins it. Renin can change something chemically without changing itself (enzyme). Enzyme in the lung that can convert angiotensin I into angiotensin II which is more powerful and does most of the work. Decreases the size of the arterioles and that directly increases our blood pressure and also goes to the adrenal cortex and that produces aldosterone. We retain water, don’t let anything go and we can reabsorb it
How do we measure BP?
Using a Hg sphygmomanometer and stethoscope.
- Place stethoscope over brachial artery just below cuff
- Inflate cuff around arm to occlude brachial artery. Bring the pressure up to about 160
- Deflate cuff gradually while listening for Korotkoff sounds and not mmHg for manometer
- What you can hear is the turbulent flow of the blood, the backwash going through
- First sounds -> systolic pressure
- Last sounds -> diastolic pressure
The limitations of this method are that the sounds can be difficult to hear, it requires skills and training and it decreases the reliability of the measurement, over time and between users
Nowadays we have automatic sphygmomanometers. It is recommended to take a few measurements and average them.
List some blood pressures measures and how they are calculated.
Systolic BP - from the left ventricle, 95-140 mmHg
Diastolic BP - from arteries and vessels pushing back, 60-85 mmHg.
Average BP - SBP/DBP
Pulse pressure (PP) - PP = SBP - DBP
Mean arterial pressure - MAP = DBP - PP/3
Compare blood volume and pulse amplitude.
Blood volume is the amount of blood going into an area. Slow, tonic changes in blood volume.
Pulse amplitude is a phasic measure. Rapid, pulse-to-pulse amplitude changes in blood volume
Could peripheral vasoconstriction (PVC) be an index of the OR?
No. The constriction occurs about 4 beats post-stimulus and the constriction, but there is an intensity effect on change trial. If it was an OR measure, we would expect it to go down.
Explain the relationship between blood pressure and sexual response.
Blood volume increases in genital areas during sexual arousal. Useful for studying aspects of sexual dysfunction and behaviour
Explain the relationship between blood pressure and stress.
When stress increases, so does blood pressure. These effects are greater in systolic blood pressure than diastolic blood pressure. These effects are also larger in hypertensives.
Explain the relationship between blood pressure and personality.
Type A men are more competitive, impatient and hostile achievers. They are more likely to suffer coronary heart disease. Show larger cardiovascular responses to stressors, reflecting hostility and aggression. This exaggerated response pattern may lead to hypertension and cardiovascular problems
