Lecture 15 Cardiac Output, Blood Flow, Blood Pressure Flashcards
DRILL INTO YOUR HEAD (26 cards)
How do we measure cardiac output? (formula)
Stroke volume
x
Heart/ Cardiac rate
How is homeostatic change in CO accomplished?
Varying heart rate or stroke volume or BOTH
Why will the heart continue to beat as long as myocardial cells are alive even when there are ZERO neural influences?
Because it contains the SA node which act as a natural pacemaker
What is the process of the sympathetic effect for regulating cardiac rate?
Norepinephrine from sympathetic fibers and epinephrine from the adrenal medulla binds to adrenergic beta receptors and alters permeability of HCN and Ca2+ channels within pacemaker cells which increase ion flow through channels and induce faster rate of diastolic depolarization
What is the process for the parasympathetic effect for regulating cardiac rate?
Acetylcholine released by parasympathetic nerve endings within the vagus nerve binds to muscarinic cholinergic receptors which influence K+ and Ca2+ channels in pacemaker cells
What are the two separate effects of parasympathetic regulation of cardiac rate?
- Increases K+ permeability which hyperpolarizes cells and makes pacemaker potentials beginning at more negative value
- Ca2+ permeability is decreased which slows pacemaker cell depolarization rate
What variables determine stroke volume?
- End diastolic volume (EDV)
- Total peripheral voume (TPR)
- Contractility
True or False: EDV is directly proportional to SV
Trueeeeee
What is known as preload?
What is known as afterload?
EDV: preload (affects degree of ventricular myocardial stretch before contraction) (remember the frank stirling law!!!)
TPR: afterload (impedes ejection of blood from ventricle)
True or False: TPR is inversely proportional to SV
Trueee
What is the Frank- Starling Law of the heart?
When EDV increases, myocardial stretch also increases. When MS increases, contractility of ventricles also increases. When contractility increases, stroke volume also increases
How is the heart able to compensate for an increase in TPR?
They are inversely related, and more blood remains in the ventricle and EDV is greater for the next cycle.
Ventricle is stretched to a greater degree in the next cycle and contracts more strongly to eject more blood which results in more SV the next cycle
Basically balancing it out
What is venous return?
The return of blood to the heart via veins and ultimately determines SV
What does venous return depend on?
Total blood volume and venous pressure
What are capacitance vessels?
What are resistance vessels?
Veins
Arteries
Where is venous pressure highest and lowest?
Highest: venules
Lowest: junction of vena cava with right atrium
What are some ways venous return is aided?
- Smooth muscle contraction in venous walls
- Skeletal muscle pump which squeezes veins during muscle contraction
- Pressure difference between thoracic and abdominal cavities
- Valves
The sum of all vascular resistances within systemic circulation is called _______
Total peripheral resistance (TPR)
What is blood pressure and its measurement?
The pressure of blood against blood vessel walls (mmHg)
What are the aortic pressures reached during ventricular systole and diastole?
120mmHg HIGH (systolic pressure) and 80mmHg LOW (diastolic pressure)
What do we use sphygmomanometers for?
to indirectly or auscultatorily measure blood pressure
What are Korotkoff sounds and what do they determine?
They are vibrations in the vessel used to determine systolic and diastolic BP
True or False: the 1st Korotkoff sound is the systolic pressure, and the 2nd Korotkoff sound is the diastolic pressure
FALSE: the last Korotkoff sound is the diastolic pressure
How do you find pulse pressure?
Systolic pressure - Diastolic pressure
