Blood pressure and its regulation Flashcards
What is arterial blood pressure defined as?
Pressure exerted by blood flow on blood vessel walls
What is arterial BP equation?
Arterial BP = Cardiac Output (CO) x Total Peripheral Resistance (TPR)
What does TPR tell us about?
TPR tells us about the resistance/radius of arteries and arterioles
e.g., More constricted the vessels the more blood flow exerts pressure,
as such blood flow exerts less pressure through more dilated vessels
Why is BP important?
This means measuring BP can tell us about:
Heart rate
Stroke volume,
Whether vessels are constricted/dilated
Blood flow to our tissues
Ultimately, informing you about whether tissues and organs
are receiving appropriate O2 transport
What is considered normal BP?
120/80 mmHg
What does the 120 mmHg mean in BP?
Blood pressure in the brachial artery during ejection of the left
ventricle = Systolic blood pressure (SBP)
What does the 80 mmHg mean in BP?
Blood pressure in the brachial artery during relaxation and filling
of left ventricle, non-ejecting phase of heart
= Diastole blood pressure (DBP)
What BP is too high and what can this lead to?
Chronic BP >140/90 mmHg becomes a risk factor for
cardiovascular disease e.g., myocardial infarction, heart failure
What BP is too low and what can this lead to?
Difficult to be absolute, but SBP <80 and/or DBP <60 would
be a concern – poor blood flow and O2 transport
An exercising student lifts heavy weights at gym
Their BP increases to 160/95 mmHg from a resting value of 118/83 mmHg, why?
Muscles need more O2
Increase blood flow by increasing CO through increasing HR and SV
Heart working faster + stronger contraction (Sym NS)
Increasing BP
An individual suffers haemorrhage in a road-traffic accident
Their blood pressure is 85/70 mmHg, why?
Blood volume is reduced, hypovolemia, less CO due to reduced SV
Decreased BP
A 65-year-old visits their GP for the first time in over 20 years, with symptoms
of low mood, the GP takes their BP several times with an average reading of
162/97 mmHg
Probable chronic high BP, hypertension
Why? Likely increased TPR, blood vessels are excessively vasoconstricted
Increased BP
What does a BP too low cause?
Low drive for convection transport, insufficient O2 transport
What does a BP too high cause?
Risk for cardiovascular disease
What systems increase or respond to low BP?
Sympathetic Nervous System
Renin-Angiotensin-Aldosterone System (RAAS)
Anti-diuretic hormone (ADH or called Vasopressin)