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WEEK 21:
The Systemic Arterial Blood Pressure:
| Question | Answer |
|---|---|
| decrease in aortic elasticity leads to | increase in systolic blood pressure (because aorta not able to cushion blood flow so it increases in systolic) |
| elastic aorta takes up kinetic energy from | blood during systole and dampens the rise in pressure |
| inelastic aorta can cause what | systolic hypertension in the elderly |
| formula for pulse pressure | systolic pressure - diastolic pressure |
| hard arteries lead to what | reduce baroreceptor response |
| SVR formula | (MAP- CVP)/ CO |
| when is systolic and diastolic pressures measured instead of MAP | in normal clinical practice systolic and diastolic pressures are measured not MAP - that measurement is only measured when SVR needs to be calculated |
| what is usually measured | systolic and diastolic pressures |
| when is MAP measured | when SVR needs to be calculated |
| AP formula | (CO X SVR) + CVP |
| increase in HR does what to MAP | increase |
| resistance vessels are innervated by | SNS nerve terminals which cause vasoconstriction when active |
| explain the whole concept bro | when BP falls the heart relies on constricting the vessels rather than the heart pumping harder (CO) |
| cardiovascular systems used to monitor/ maintain arterial pressure | baroreceptor reflex (fast activating and helps compensate for short term pressure changes), and slow activating system (manipulates MAP through changes in circulating blood volume by modifying renal function) |
| baroreceptor reflex | fast activating and helps compensate for short term pressure changes |
| how does slow activating system work | manipulates mean arterial pressure through changes in circulating blood volume by modifying renal function |
| baroceptors are found where | medulla |
| types of baroreceptors | 2 - high pressure and low pressure |
| high pressure baroreceptors are found in | carotid sinus and aortic arch |
| low pressure baroreceptors are found in | cardiopulmonary receptors |
| which type of baroreceptor are mainly used to detect changes in MAP | carotid and aortic baroreceptors (high pressure) |
| how do the high pressure baroreceptors (carotid and aortic arch) work | around found in elastic tissues where they monitor pressure indirectly by responding to arterial wall stretch. |
| information from carotid sinus travels to the brain how | glossopharyngeal nerve CNIX |
| information from the aortic arch travels to via | travels back on CN X - vagus nerve |
| as MAP increases what happens | nerve endings are stretched leading to graded potential (the higher the pressure the higher frequency) |
| to enable a more nuanced response, stretch sensitivity | varies from one nerve ending to the next allowing for responsiveness over a wide pressure range |
| range of aortic baroreceptors | operate over a range of 100-300mmHg meaning they are usually inactive under resting conditions |
| preload | load applied to a myocyte and establishes muscle length before contraction begins (filling and lengthening) |
| in LV, preload equates with | volume of blood entering chamber during diastole (EDV) which is dependent on EDP |
| arterial pressure | product of CO and SVR (MAP = CO X SVR) and control centres adjust both parameters simultaneously |
| cardioinhibitory centre | depresses HR (acts via parasympathetic fibres traveling in vagus nerve that target SAN and AVN) |
| cardioacceleratory and vasomotor centres | increase HR by manipulating SAN and AVN excitability and increase eg myocardial contractility and act via sympathetic nerves |
| vasometer centre function | controls resistance vessels, veins and adrenal glands |
| CVP | pressure in vena cava just before blood enters heart |
| on standing (blood rush down due to gravity) what happens | high venous compliance veins expand, increasing venous pressure and volume in lower limb which decreases volume of blood in thorax hence pressure |
| systemic arterial blood pressure | pressure exerted by blood against walls of systemic arteries |
| systolic pressure | highest arterial pressure during ventricular systole |
| diastolic pressure | lowest arterial pressure during ventricular relaxation |
| pulse pressure is | difference between systolic and diastolic pressure |
| what affects pulse pressure | stroke volume and arterial compliance |
| MAP | mean arterial pressure - average arterial pressure driving blood into tissues |
| heart spends longer in what cardiac stage | diastole |
| sphygmomanometry mechanism | measuring BP using cuff (cuff occludes brachial artery and as cuff pressure falls blood flow resumes) |
| korotkoff sounds are caused by | turbulent blood flow |
| influences on BP | aortic distensibility (ability to stretch) |
| why is aortic distensibility important | if arteries stiffen (ageing) the aorta cannot expand so systolic pressure increases (as blood is forced into stiff vessel) so diastolic pressure falls (as recoil reduced) leading to increase pulse pressure |
| where is aortic distensibility seen mostly | the ELDERLY |
| increased peripheral resistance leads to | arteriolar constriction which increases diastolic pressure as blood drains from arteries more slowly |
| systolic BP affected by | stroke volume and aortic compliance |
| diastolic BP affected by | peripheral resistance |
| what happens during standing up | decrease in all (venous return, SV, CO, MAP, baroceptor response etc) so medulla respond by increase sympathetic activity and decreasing parasympathetic activity to increase these things back to normal |
Created by:
kablooey
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