Cardio Formulas and Cardiology Flashcards
Velocity of blood flow
v = volume of blood flow/cross sectional area
Blood flow is also the
Ohm’s law
Blood flow formula
Flow rate = P1 - P2/Resistance
Tendnecy for turbulent flow =
Reynolds number = (velocity of blood flow x diameter x density) / viscosity
Re = vdp/n
cm/sec, cm
Greatest in proximal aorta and pulmonary artery
Resistance of the entire peripheral circulation =
TPR = 100mmHg (Pa - Pv)/ 100ml/sec (CO or blood flow)
Total pulmonary vascular resistance =
TPVR = (16 - 2)/100
(Pulmo artery pressure - left atrial pressure)/ 100 (CO, blood flow)
Total pulmo vascular resistance = 0.14 PRU
Conductace =
Conductance = 1/ resistance
Conduntance of vessel
inc in proportion to fourth power of diameter
C inc in proportion to fourth power of diameter
The great inc in conductance when diameter inc is exemplified by
Poiseuille’s law
Velocities of all concentric rings of flowing blood x areas of the ring
Poiseuille’s law
Poiseuille’s law =
Rate of Flow = pie(pressure difference between ends of vessels)radius raised to the 4th power / 8(viscosity)(length=1)
The greatest role of all factors in determining rate of blood flow
Diameter
2/3 of total systemic resistance to blood flow comes fr
arterioles
Arterioles regulate blood flow by
Turning off blood flow (arterioloconstriction) and inc flow by 256fold by arteriolodilation
The flow through artery, arteriole, cap, venule and vein are arranged in
Series
Rtotal = R1 + R2 + R3
Blood flow to organs are arranged in
Parallel
1/Rtotal = 1/R1 + 1/R2
Total conductance = C1 + C2
Amputation of limb or removal of kidney reduces total vascular conductance and total blood flow (CO) inc total peripheral vasc resistance
Viscosity of blood is
3x as great as water
Vascular distensibility =
Vascular distensibility = inc in volume / inc in pressure x original volume
fractional inc in volume for each millimeter of mercury rise in pressure
Vascular compliance =
VC = inc in volume/inc in pressure
Compliance = distensibility x volume
So a highly distensible vessel may have far less complaince than a vessel with large volume
Pulse pressure =
pulse pressure = stroke volume/arterial compliance
Damping =
Damping = resistance x compliance
MAP is not just average of systolic and diastolic pressure bec
Bec greater fraction of cardiac cycle is spent in diastole
60 Diastolic
40 Systolic
MAP =
Averahe arterial pressure with respect to time
MAP = (SBP + 2DBP)/3
Diastolic pressure + 1/3 of pulse pressure
Four primary forces determining fluid movement in capillary membrane:
Starling forces
1 Capillary pressure
2 Interstitial fluid pressure
3 Capillary plasma colloid osmotic pressure
4 Interstitial fluid colloid osmotic pressure
Net Filtration Pressure =
NFP = (Pc-Pif)-(Plasmacoll+Ifcolloid)
Filtration=
Filtration= capillary filtration coeff x NFP
Plasma colloid osmotic pressure is 28 mmHg; 19 by proteins and 9 by Na, potassium and cations. Extra osmotic pressure is called
Donnan effect
Physiologic properties of the heart:
All or none principle
No fatigue, no tetany
Duration of cardiac muscle contraction is a function of the duration of the action potential
Is the principle that the strength by which a nerve or muscle fiber responds to a stimulus is not dependent on the strength of the stimulus
All-or-none Law
If the stimulus is any strength above threshold, the nerve or muscle fiber will give a complete response or otherwise no response at all
All-or-none law
Increase in contractility
Positive inotropic effect
Decrease in contractility
Negative inotropic effect
Ability to initiate its own beat
Ability to generate spontaneous action potential
Automaticity
Regularity of such pacemaking activity
Rhythmicity
Fibers of SA node connect with surrounding atrial muscles
Conductivity
Conduction velocity in atrial muscle
0.3-0.5 m/sec
Ability of the heart to initiate an action potential in response to an inward depolarizing current
Excitability
Smallest branches of the arteries
Arterioles
The site of highest resistance in the cardiovascular system
Alpha 1 and beta 2 adrenergic
Arterioles
Arteriole SNS receptors
Alpha 1 and beta 2 adrenergic
Contains the highest proportion of blood in the cardiovascular system
Largest total unstressed blood volume
Thin walled
Low pressure
Alpha 1 adrenergic
Veins
Gas and nutrients exchange in the cardiovascular system
Largest total cross sectional and surface area
Capillaries
A collapsed larger lumen
Thin wall
No Internal elastic lamina
Tunica media has large quantity of collagen (few smooth muscles and less elastic fibers) that is the reason they are easily compressed
Tunica adventitia is thicker than tunica media in large veins
Presence of valves to prevent back flow
Medium sized vein
Thick wall
Arteries retain their patency
Internal elastic lamina is present only in arteries
Tunica media is thicker than adventitia
Medium sized artery
Inotropic drugs
Dopamine
Dobutamine
Pacemaker of heart
Located near:
SA Node
Sulcus terminalis and SVC as it enters the right atrium
Formed bt the left and right brachiocephalic/innominate vein
SVC
Level at which the SVC is formed
1st right costal cartilage
Send blood from the heart
High pressure
Narrow lumen diameter
Thick walled
Wall layers:
T. Adventiria
T. Media
T. Intima
Large amounts of muscle and elastic fibers
No valves
Arteries
Change in HR
Chronotropic
Change in conduction velocity
Dromotropic
Send blood to the heart
Low pressure
Wide lumen diameter
Thin walled
Wall layers:
T. Adventitia
T. Media
T. Intima
Small amounts of muscle and elastic fibers
With valves
Veins
Thick walled
Extensive elastic tissue and muscles
Artery
Material exchange with tissues
Low pressure
Extremely narrow lumen diameter
Extremely thin walled
Wall layers:
T. Intima
No muscle and elastic fibers
No valves
Capillaries
Receives blood from left ventricle
Aorta
Transport under high pressure, strong vascular walls
Arteries
Control conduits, last branch of arterial system, strong muscular walls that can strongly constrict or dilate
Arteriole
Exchange substances through pores
Capillaries
Collect blood from capillaries
Venules
Low pressure, transport blood back to the heart, controllable reservoir of extra blood
Veins
Means blood flows crosswise in the vessel and along the vessel
Forms whorls in the blood called
Turbulence
Eddy currents
Normal blood flow is
Laminar