1. Control of Heartbeat and Monitoring Blood Pressure

2. Learning objectives Define heart rate, stroke volume & cardiac output
List the main factors affecting blood pressure
Measure & accurately record heart rate & blood pressure, using equipment safely

3. Control of Heartbeat – a review
On your mini whiteboards, summarise what you remember about this!

4. Definitions Challenge: can you write these as numeric equations?
Heart rate: number of heartbeats per minute
Stroke volume: volume of blood (cm3) pumped by heart in 1 beat
Cardiac output: stroke volume multiplied by the heart rate gives the amount of blood (cm3) pumped by heart in 1 minute
Heart rate = # beats
minute
Stroke Volume = blood cm3
beat
Cardiac Output = blood cm3 X # beats = blood
beat minute minute

5. Cardiac Output Can be changed by a number of factors:
Cardiovascular centre in brain
Hormones e.g. adrenaline
Stretching of cardiac muscle

6. Control of Cardiac Output and Blood Pressure
Parasympathetic & sympathetic nerves
to smooth muscle of arterioles

7. What is the effect of exercise on cardiac output?
Get out your calculators!
Heart rate
(beats/min)
Stroke
Volume
(cm3/beat)
Cardiac
Output
(cm3/min)
At rest 75
During
exercise
180
120
5,625
21,600

8. Blood Pressure
Blood needs to flow through vessels at a certain pressure. If pressure is too low, exchange of nutrients and gases within the tissues will not happen efficiently.
This is why blood pressure is a vital measurement taken by doctors and nurses.
Blood pressure is measured using a sphygmomanometer and is recorded in mmHg (millimetres of mercury)

9. Blood Pressure Measured in blood vessels (artery)
Determined by cardiac output and resistance to flow of blood in vessels
Resistance to flow affected by diameter of blood vessels
Narrower vessels (vasoconstriction)
Wider vessels (vasodilation)

10. Factors affecting blood pressure
Cardiovascular centre
Diameter of blood vessels controlled by stimulation of sympathetic and parasympathetic nerves
Smoking
Nicotine causes vasoconstriction
Build up of fatty deposits in vessels
Diet
High fat diet leads to build up of fatty deposits in blood vessels
Adrenaline
Causes selective vasoconstriction & vasodilation
Increase in blood viscosity
Excess water loss (sweating/excessive urination)

11. Diastolic and Systolic Pressure Definitions
Get out your mini-whiteboards
Write down the meanings of the words ‘systolic’ and ‘diastolic’.
Compare your answers with the others on your table.

12. Recording blood pressure
Systolic blood pressure:
Maximum blood pressure
Occurs when ventricles are contracting (at the end of the cardiac cycle)
Diastolic blood pressure:
Minimum blood pressure
Occurs when ventricles are relaxed and filled with blood (at the beginning of the cardiac cycle)
We record blood pressure as: Systolic BP/Diastolic BP
e.g. 120/80 mm Hg
Diastolic pressure gives clearest indication of resistance to flow in blood vessels
Rough estimate of systolic BP is your age +100

13. Systolic and Diastolic Pressure

14. Measuring blood pressure
Sphygmomanometer

15. How to use a sphygmomanometer
1. Place the stethoscope ear pieces around your neck and wrap the cuff of your sphygmomanometer tightly around your upper arm.
2. Locate the pulse of your brachial artery by tracing your finger down your bicep down toward the crook, or inside elbow, of your arm. You should find the brachial pulse about an inch or so above this crook.
3. Put the ear pieces of the stethoscope into your ears and place the round, metal end of the stethoscope over the pulse of your brachial artery.
4. Tighten the stopcock on the sphygmomanometer bulb and squeeze the bulb of your sphygmomanometer multiple times to inflate the cuff around your upper arm. The cuff should be inflated until you've reached 180 mm of pressure. You will be able to determine how much pressure you've pumped into the sphygmomanometer cuff by reading the blood-pressure meter in front of you.
5. Release the bulb stopcock slowly and gradually. This will let the air out of the cuff, allowing you to make a blood pressure reading.
6. Note the number on the meter when you first hear your pulse through the stethoscope. Then note the number when the last pulse sound comes through the stethoscope. Record these two numbers by placing the higher number over the lower number to determine your current blood pressure.

16. Finding your pulse
Carotid artery
Radial artery

17. Challenge for Today!
Watch the demonstration of how to use the sphygmomanometer
In your book, record:
Your blood pressure three times and average the results
Your heart rate three times and average the results

18. Questions
A person’s blood pressure should be measured when they are resting and relaxed. Explain why.
People with high blood pressure sometimes have swelling in their legs and feet. Explain how this happens
Low blood pressure can cause fainting. Explain why.
Nicotine in cigarette smoke causes the muscle fibres in arteriole walls to constrict. Explain how this causes blood pressure to increase.

19. Learning objectives Define heart rate, stroke volume & cardiac output
List the main factors affecting blood pressure
Measure & accurately record heart rate & blood pressure, using equipment safely