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Practical 4 - Cardiovascular.
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Practical 4 - Cardiovascular.
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Practical 4 - CardiovascularCompare time from ECG component to heart sound for the two heart sounds? - ANS-R
wave to S1 is shorter than T wave to S2
Effect of skeletal muscle contraction on ECG? - ANS-- Shorter RR interval, reflects
increased heart rate
- More noise on trace, indicates increased electrical activity of myocardial autorhythmic
cells providing interference
Electrical and mechanical events associated with PR segment? - ANS-- Electrical
conduct spreads to AV node and AV bundle
- Atrial contraction occurs
Electrical and mechanical events associated with ST segment? - ANS-- Ventricles are
about to repolarise
- Ventricular contraction occurs, and then relaxation begins
Electrical event associated with P wave? - ANS-Atrial depolarisation
Electrical event associated with T wave? - ANS-Ventricular repolarisation
Electrical event immediately before P wave? - ANS-SA node generates autorhythmic
AP which spreads across both atria
Electrical events associated with QRS complex? - ANS-Ventricular depolarisation and
atrial repolarisation (mostly obscured)
How and why does blood pressure vary throughout the body due to gravity? - ANS-- In
lower body parts, gravity increases hydrostatic pressure of blood, resulting in elevated
measurements of blood pressure
- Blood pressure is conventionally measured in upper arm because roughly same level
as heart
How can arterial blood pressure be measured directly? - ANS-Measuring instrument or
its attached catheter (cannula) must be in direct contact with blood in artery
How can arterial blood pressure be measured indirectly in a manual way? - ANS--
Called manual auscultatory method
, - Pressure applied to tissues around artery to affect blood flow within
- Stethoscope placed over bifurcation of brachial artery to listen to Korotkoff sounds
- First Korotkoff sound is sharp, tapping sounds, indicates systolic pressure
- Fifth Korotkoff sound is no sound, indicates diastolic pressure
How can arterial blood pressure be measured indirectly in an automatic way? -
ANS-Automatic sphygmomanometer
How can heart sounds be listened to and recorded? - ANS-Electronic stethoscope or
phonendoscope
How can instantaneous changes in blood pressure and heart rate be monitored? -
ANS-- Finapres recording device
- Uses infrared beam to measure changes in arterial BP
- Changes in arterial pressure affect transmural pressure (difference in pressure
between two sides of separator) in artery of finger
- Alters colour of skin, which is detected by sensor
- Cuff pressure is automatically adjusted to maintain transmural pressure of 0, so cuff
pressure is equal to arterial pressure
How does exaggerated breathing affect average, maximum and minimum heart rate? -
ANS-- Increases average heart rate
- Significantly increases maximum heart rate
- Slightly decreases minimum heart rate
How does heart rate change during inspiration? - ANS-1. Diaphragm contracts to
expand thoracic cavity
2. Drop in pressure that increases venous return through the respiratory pump
3. Increased EDV sensed by low-pressure baroreceptors in large veins and ventricular
walls
4. Triggers sympathetic activity to increase HR to pump the more rapidly returning blood
out of the heart
5. Inspiration also inhibits Vagal activity on the SA node, increasing HR
How does skeletal muscle activity increase heart rate? - ANS-1. Increased venous
return through skeletal muscle pump
2. Increased EDV sensed by low-pressure baroreceptors in large veins and ventricular
walls
3. Triggers sympathetic activity to increase HR to pump the more rapidly returning blood
out of the heart
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