CFB L3 Flashcards
Define blood pressure
The force exerted by blood on walls of blood vessels.
Definition of blood pressure reflects large arteries
In patients, measured in brachial artery
- aorta
-brachial arteries
State the units of BP
mm Hg (millimitres mercury)
What does a BP of 120 mm Hg tell us?
This is the force the blood exerts on wall of vessel. Also, this force can cause a column mercury to rise by 120 mm
What is systolic pressure?
Highest pressure in arteries when the heart contracts, heart beats + blood flows into it
Normal: 120 mm Hg
What is diastolic pressure?
Lowest pressure in arteries
When heart is relaxing between heart beats / contractions
Normal: 80 mm Hg
Define pulse pressure
Also known as arterial pulse
Difference beteween systolic pressure + diastolic pressure.
Felt as pulsation by palpating eleastic arteries
Occurs during systole, ventricles contract, blood ejeceted into arteries, they then expand.
Pulse pressure directly proportion to stroke volume,
High pulse pressure = high stroke volume
Why is Mean Arterial Pressure taken ?
Alternative value to pulse pressure (arterial pulse)
MAP
Blood ressure in aorta / arteries fluctuates with each heart beat
Pulse pressure fluctuates
What is MAP?
Avg of systolic and diastolic pressure
Avg BP in arteries during 1 cardiac cycle ( 1 heart beat)
How do you calculate MAP?
(2x diastolic) + (1 x systolic) / 3
What is a healthy MAP ?
70 - 110 mm Hg
<60 mm Hg - organ hypoxia, organ ischemia
What happens if MAP is too low?
<60 mm Hg - organ hypoxia, organ ischemia, NO FILTRATION IN KIDNEYS
How is blood pressure regulated?
- Neural control
- Hormonal control
- Local factors
These factors control heart rate, blood volume, stroke volume
This allows consistent control of blood pressure
NHL
(NHS took an L)
Where is neural control of blood pressure regulated?
Cadiovascular centre
(bundle of neurones in medulla oblongata)
State the location of the cardiovascular centre
Medulla oblongata
State the function of the cardiovascular centre
Control heart rate
Control ventricular contractility
Control blood vessel diamater
State the four centres in the cardiovascular centre
There are 4 groups of neurones the CV centre:
Cardiostimulatory centre - stimulates heart function
Cardioinhibitory centre - inhibits heart function
Vasodilator centre - reduces diameter of blood vessels
Vasocontrictor centre - expands diameter of blood vessels
What are the inputs of the CV centre?
Inputs = impulses towards CV centre
INputs from higher brain centres:
-Cerebral cortex
-Limbic system
-Hypothalamis
Input from sensory receptors:
-Barroreceptors
-Chemoreceptors
-Proprioreceptors
- Barroreceptors - detect changes in BP
- Chemorecepors - detect changes in O2 + CO2 levels of blood (blood acidity)
- Proprioceptors - detect changes in muscle + joint movement
State sympathetic efferents from the CV centre
- Electrical signals sent via cardiac accelearotr nerves to heart to increase heart rate and increase ventricular contractility
- Electrical signals sent via vasomotor nerves to blood vessels, vasoconstriction of blood vessels