PSL301: Cardio 3 Flashcards
Heart is stimulated by the…
sympathetic cardioacceletatory center
Heart is inhibited by the…
parasympathetic cardioinhibitory center
Where is the sympathetic cardioacceletatory center located?
Medulla oblongata
Where is the parasympathetic cardioinhibitory center located?
Medulla oblongata
How does the parasympathetic cardioinhibitory center connect to the heart?
Interneuron to dorsal motor nucleus of vagus -> Vagus nerve -> heart
How does the sympathetic cardioacceletatory center connect to the heart?
Interneuron to tharacic spinal cord (sympathetic trunk) -> PS fibres to sympathetic trunk ganglion -> interneurons to heart
Which neuron activates the PSm pathway?
ACh binding to muscarinic receptors on autorhythmic cells
Which neuron activates the Sm pathway?
NE binding to B1-receptors on autorhythmic cells
Autonomic NTs alter…
heart rate
Catecholamines modulate…
cardiac contraction
Phospholamban
Integral membrane protein that regulates the Ca2+ pump in cardiac muscle and skeletal muscle cells
The cAMP system activated by NE/E {P}…
- Voltage gated Ca channels
2. Phospholamban
What does the {P} of phospholamban result in?
Stimulate Ca-ATPase on SR
What does the {P} of voltage gated Ca channels result in?
More Ca from ECF can come into the cell
How do catecholamines affect cardiac contraction?
- Increase Ca stores in SR
- > more Ca released
- > more forceful contraction - Faster removal of Ca from cytosl
- > shorter duration of contraction
Increase of Ca from ECF will result in…
- More Ca in SR
2. More Ca released when it’s time to contract
What does ECG measure?
Summed electrical activity of all cells
Recorded from surface of body
The ____ Triangle places electrodes on the right arm, left arm, left leg.
Einthoven’s
What is the purpose of Einthoven’s Triangle?
Places the heart in the middle
Einthoven’s law
Lead II - Lead I = Lead III
What does a lead consist of?
2 electrodes: 1 + and 1 -
The waves of the ECG
P QRS T
How many beats can be seen in 1 second?
Almost 2 full waves / beats
P wave = activity at…
Atria
QRS = activity at…
ventricle
T = …
ventricle diastole signal
When does atria systole happen on the ECG?
Somewhere during the QRS
What intervals is the ECG divided into?
PR interval (beginning of P -> beginning of Q)
QT interval (beginning of Q -> end of T)
PR segment
End of P -> beginning of Q
QRS complex
Beginning of Q -> end of S
ST segment
End of S -> beginning of T
Major difference between ECG & myocardial contractile cell AP
Since myocardial contractile cell AP is measured from a single cell, the voltage change is much greater than the ECG (110 mV vs. 1 mV)
Mechanical pumping events of the cardiac cycle
- Late diastole
- Atrial systole
- Isovolumic ventricular contraction
- Ventricular ejection
- Isovolumic ventricular relaxation
What lasts longer, systole / diastole?
Diastole
What is the standard diagram used to combine ECG, pressure, heart sounds, and left ventricular volume?
Wiggers diagram
What does Wiggers’ diagram comprise of?
- ECG graph
- Pressure (atria, ventricles, aorta)
- Heart sounds
- Left ventricular volume
ventricular diastole occurs at where on the ECG graph?
after T wave
Atrial systole occurs at where on the ECG graph?
Middle of P -> Q
Ventricular systole occurs where on the ECG graph?
Q -> end of T
When is volume highest in left ventricle? What is this called?
After arterial systole
End Diastole Volume (EDV)
When is volume lowest in left ventricle? What is this called?
After ventricular systole
End Systole Volume (ESV)
Max volume of ventricle
135 mL
On average, how much blood does ventricle pump per beat?
70 mL
Pressure changes in the atria are mostly due to…
Activity in the ventricle
What is the increase in pressure during ventricular systole?
110 mmHg
Dicrotic notch
Slight increase in pressure in the aorta when aortic valves close
What causes atrial pressure to drop?
Opening of AV valves
Questions to ask when analysing ECG
- HR normal (60-100 bpm)?
- Regular rhythm?
- All waves normal and present (PQRST)?
- P followed by QRS?
- PR segment at constant length?
What does the ECG look like for 3rd degree block?
- normal P
- S dips lower than usual
- P doesn’t always trigger QRS
What does the ECG look like for atrial fibrillation?
- no P
- irregular QRS
What does the ECG look like for ventricular fibrillation look like?
- no P
- no QRS
What does the ECG look like for 2nd degree heart block look like?
- normal P
- normal QRS
- P doesn’t always trigger QRS
Where does the problem lie when someone has 2nd degree heart block?
AV node (not every signal goes through)
Heart block
Impulse generated in SA node does not generate response in ventricles
Ventricles follow a slower pacemaker
When is defibrillation used?
ventricular fibrillation
Purpose of defibrillator?
Reset all electrical activity in the heart so SA node can take the lead properly
How to treat heart block?
Artificial pacemaker
Components of ECG
- Waves
- Segments
- Intervals
Information from ECG
- HR
- Heart rhythm
- Conduction velocity
- Condition of myocardium
Heart rate too fast
Tachycardia
Heart rate too slow
Bradycardia
Tachycardia
heart rate too fast
Bradycardia
heart rate too slow
What acts as the pacemaker for the ventricles during 3rd degree heart block?
Purkinje fibres
What is unusual QRS activity typically caused by?
When repairing damage to the heart, it is hard to get it back to normal. Bad repair job.
What is atrial fibrillation usually caused by?
- problems with SA node
- problems with atria
- AV node
