Lecture 15 Flashcards
Tricuspid vs Mitral valve
Tricuspid is on the right side, mitral on the left
Cardiac muscle features
Striated, uninucleated, branched fibres attached by intercalated discs
Fick’s Principle equation (find VO2)
VO2= Q x a-vO2diff
Cardiac output equation (Q)
Q= HR x SV
a-vO2diff equation
a-vO2= CaO2-CvO2
CaO2 equation
CaO2= (Hb x SaO2 x 1.34) + (PaO2 x 0.003)
What is the Q to VO2 ratio?
6:1
For every 1L increase in VO2, Q increases by 6L
How many bpm would the heart be if only controlled intrinsically?
100bpm (only SA node affecting HR)
Intrinsic order of heart contraction
- SA node -> contracts atria
- AV node
- Bundle of His
- Purkinje Fibers -> contracts ventricles
3 extrinsic factors affecting HR
- PSNS
-Vagus nerve sends Ach to SA node, slowing HR - SNS
-SNS send NE to SA node, increasing HR - Endocrine
-Adrenal medulla sends Epi & NE to increase ventricular contraction
What do beta blockers do
Block Epi/NE receptors, slowing HR
What is the rise in HR during exercise attributed to
At low intensity, the decrease of PSNS input to SA node increases HR, at higher intensities, an increase in SNS input to SA node increases HR
What is the average stroke volume in healthy individuals?
70mL/beat
Stroke volume equation
SV= EDV-ESV
Ejection fraction formula and average EF
EF= SV/EDV
Average EV is ~65%
