Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
WEEK 20:
Cardiac Function:
| Question | Answer |
|---|---|
| formula for cardiac output | cardiac output (L/min) = stroke volume (L/beat) x heart rate (bpm) |
| cardiac output at rest | 5L/min = 70mL/beat x 70bpm |
| cardiac output during exercise | 22L/min = 110ml/beat x 200bpm |
| cardiac output depends on (2) | factors affecting heart rate and factors affecting stroke volume |
| how to measure heart rate (3) | pulse oximeter, counting pulses in major arteries (radial, brachial, femoral), and analysis of ECG |
| pulse oximeter | measures automatically beat by beat but can be affected by physical factors eg cold peripheries and does not show character of pulse or regularity/ irregularity |
| peripheral pulses | count number of pulses in 60 secs which allows you to estimate character of pulse and regularity/ irregularity |
| normal heart rate range | 60-100bpm |
| ECG as a mean of measuring heart rate | often detect most common arrhythmias, count number of QRS complexes/R waves in 10secs (so x6 to get HR) |
| heart rate influenced by (4) | SNS, PNS, hormones and extra/intracellular ions (alter membrane potential) |
| factors affecting heart rate | intrinsic rate (SAN and AVN conduction) |
| stroke volume determined by interaction of (3) | preload (volume of blood in ventricles before systole), cardiac contractility (how efficient myocardium is at contracting), and after load (pressure needed for ventricles to contract and open valves) |
| stroke volume | difference between end diastole volume (EDV) and end systolic volume (ESV) |
| slide 8** factors affecting stroke volume** | posture, intrathoracic pressure (breathing in/out), filling time, atrial contractility |
| Frank Starling Curve | force of contraction of cardiac muscle fibres is proportional to degree of stretch (increased stretch EDV means increased force of contraction therefore increased contractility) |
| cardiac contractility and stroke volume increases and depends on | amount of force generated by cardiac muscles which depends on degree of stretch (eg increases if SNS activity increases) |
| cardiac contractility and stroke volume decreases and depends on | hypoxia, acidosis, heart failure, and reduced SNS |
| increased aortic pressure means | increased afterload (pressure needed to contract ventricle) increases which will reduce stroke volume at constant preload |
| velocity of ventricular contraction at fixed length is greatest when | afterload is low (as needs less pressure and therefore effort to contract) |
| slide 13-16 relationship between stroke volume, pressure and volume graph** | LV pressure mmHg on Y axis and LV volume ml on X axis |
| explain the stroke volume graph** | |
| increased EDV (preload)/ increased cardiac contractility leads to | increased stroke volume |
| increased aortic pressure (afterload) leads to | decrease in stroke volume |
Created by:
kablooey
Popular Medical sets