L03-The ECG Flashcards
What is an ECG?
The detection of field currents the radiate through the body from the heart.
What are the types of ECG leads?
There are 6 limb leads and 6 chest leads
They detect the direction of the electrical signal between the leads and generate a positive or negative spike depending on the direction of the electrical impulse.
How will a repolarising current appear on an ECG?
It will appear to deflect the other way as it is the opposite of the depolarising current.
i.e. a depolarising current moving towards the positive lead will cause an upwards deflection
Which part of the waveform represents atrial depolarisation?
The P wave, it is the initial hump
Which part of the waveform represents ventricular depolarisation?
The QRS wave, this is the small drop before large spike.
Which part of the waveform represents ventricular repolarisation?
The T wave, this is the positive lump following the QRS wave. Even though it is repolarisation it spreads from the epicardium to the endocardium so will be in the opposite direction to depolarisation
How can you tell the heart orientation from ECG?
Can tell orientation of the heart depending upon which lead gives the greatest deflections
What is pulse pressure?
SP-DP
How does sympathetic activity affect the RAAS?
Increases renin release to increase blood volume
What does a fall in average blood pressure cause the baroreceptor reflex to do to veins?
causes increased sympathic activity that reduces their compliance
What can vary the bloods resistance by effecting viscosity?
Haematocrit
What nerve roots is the sympathetic innervation of the SAN?
T1-T5
