Blood and blood pressure Flashcards
what is BP?
the force or pressure exerted by blood on the walls of blood vessels.
what can happen as a result hypertension
blood vessels can become damaged, causing blot clots and ruptures (bleeding).
what can happen during hypotension
blood flow through tissue beds may become inadequate, which is particularly serious for vital organs
what is systolic (systole) BP
when the left ventricle contracts and pushes blood into the aorta. the pressure produced in the arterial system is called systolic BP, and in adults this is often 120mmHg.
what is diastolic (diastole) BP
when the heart is resting following ejection of blood. the pressure within the the veins is much lower and called the diastolic pressure, which is often 80mmHg in adults.
factors that cause BP to vary?
Time of day
- BP is lower at rest and higher during the day/activity
Age
- blood vessels lose their elasticity as we age and therefore the ability to constrict/dilate, meaning BP can be higher in older people
Smoking
- can cause the blood vessels to narrow/constrict and therefore the heart to beat faster and BP to rise
Activities;
-during activity, blood flow to tissues will have to increase to meet demand exerted on them, causing the heart to beat faster and BP to increase
Posture
- you can measure someone’s BP when lying down, then sitting and then standing
- this can detect postural hypotension, where someone’s BP drops abnormally low when standing from sitting
walls of arteries
arterial walls have a lot of elastic tissue which allows them to dilate and constrict. when the left ventricle of the heart contracts and ejects blood out into the aorta, the aorta (blood vessel) expands to accommodate for this large volume of blood at a great force and then it recoils, pushing blood forward and into the systemic (arterial) circulation; causing a heart/pulse rate.
the elastic recoil of the arteries maintains the diastolic pressure reading.
factors which determine BP
Cardiac Output;
- determined by HR X SV. an increase in CO raises both systole and diastole BP.
- an increase in SV alone increases systolic more than diastolic BP.
how blood vessel dilation & constriction affects BP readings;
vasodilation;
- causes BP to drop
vasoconstriction;
- causes BP to rise
when the lumen of a blood vessel is smaller, the force exerted by the blood is more impactful due to its small space; think of a small but fast waster slide, the water hitting off the walls
when the lumen of a blood vessel if big, the force exerted by the blood is weaker, due to its large area to flow through; think of a wide water slide, the water will stay on its ground and have no need to hit off the walls
what is auto-regulation in relation to BP?
a mechanism by which tissues control their own blood pressure in their surrounding blood vessels to protect themselves from pressure damage.
systemic (arterial) BP continually rises and falls according to levels of activity, body position, etc. however the organs are capable of adjusting BP in their own local vessels independent the whole BP system- which is called auto-regulation.
it protects tissues against the swings in systemic pressures and is vital for the kidneys which can become damaged by increased pressure in their globular capillary beds and the brain, sensitive to slight changes.
two ways bp is controlled;
short term;
- on a moment-to-moment basis which mainly involves the baroreceptor reflex, chemoreceptors and circulating hormones
long-term;
- involves regulation of blood volume by the kidneys and renin-angiostensin aldosterone system
why is pulmonary circulation lower than in systemic circulation?
there are so many capillaries in the lungs that pressure is kept low. if pulmonary capillary pressure exceeds 25mmHg, fluid is forced out of the bloodstream and into the alveoli (pulmonary oedema).
auto-regulation in the pulmonary circulation ensures blood flow through the pulmonary circulation’s vast network of capillaries is directed through well-oxygenated air sacs.
aneroid and electronic sphygmomanometers;
aneroid
- also known as manual BP devices
- less accurate and lose reliability quickly
electronic
- include a pressure sensor in the cuff which registers systolic and diastolic pressures
BP cuff points;
- a cuff too big will give an inaccurately low reading (to loose)
- a cuff too small will give an inaccurately low high reading (too tight)
- korotkoff sound 1, initial thudding- systolic reading
- kortotkoff 5- sudden silence- diastolic reading
*the BP cuff once inflated collapses the brachial artery (or whichever being used) and as it opens up; this provides us with kortokoff sounds and therefore our manual readings
arterial blood gas test/sample/ arterial sample?
an ABGT or AS is a diagnostic test that measures the acidity of ph levels of O2 and CO2 from the artery. often carried out using a syringe and a needle (or catheter), a blood sample is taken to measure blood O2 saturation and this is the only way to accurately measure someone’s O2 saturation levels.
usually taken from the radial artery but other sites can be used too.
