cardiac physiology Flashcards
primary function of the cardiovascular system
Pump blood
Deliver oxygen and nutrients
Remove CO2 and byproducts of cellular metabolism
secondary function of cardiovascular systems
Maintain heat temperature
Deliver white blood cells for defense and hormones
Cardiac output
5- 6 L per minute
volume of blood ejected out of left ventricle into systemic vasculature per minute
CO= HR x SV
cardiac index
CO/body surface area
stroke volume
amount of blood pumped from ventricles with each contraction/ beat
55-100ml
rate pressure product RPP
an index of myocardial O2 consumption; reflecting cardiac fitness
RPP= HR X systolic bp/1000
Regulation of stroke volume
myocardial cell length
Myocardial cell contractility influenced by intrinsic myocardial stretch
Frank Starling mechanism
preload
blood Returning to heart or end diastolic volume
effect of stretch prior to contraction
Extrinsic activity of sympathoadrenal system
afterload
blood ejected out of heart is influenced by the pressure generated in ventricle compared to pressure in systemic vasculature
intrinsic heart rate regulation
SA and AV nodes
Sympathetic- increase heart rate via SA
parasympathetic- slows heart rate via SA
extrinsic heart rate regulation
Neural influences
Peripheral
Cortical
sympathetic nerve endings
Beta adrenergic receptors in myocardial wall
1- vasodilates coronary arteries
2- increase heart rate rate via catecholamines
3- cardio accelerator center in medulla
Parasympathetic influence
1- vasoconstricts coronary arteries
2-decrease the heart rate through the action of acetylcholine via vagus nerve
3-cardio inhibitory in medulla
HR chronotrophic effects
+ chronotrophic effects if HR is high
- chronotrophic effects if HR is low
contractility- ionotrophic effects
+ iontrophic effects if contractility is high
- iontrophic effects if contractility is low
What has a positive influence on stroke volume?
Preload
Sympathetic outflow to heart
Circulating epinephrine
Circulating norepinephrine
What has a negative influence on stroke volume
Afterload
Parasympathetic outflow to the heart
What has a positive influence on heart rate?
preload
Sympathetic outflow
Circulating epinephrine and norepinephrine
what has a negative influence on heart rate
Parasympathetic outflow
Coronary blood flow
squeezed during systole, but perfuse myocardium during diastole
regulated by autonomic nervous system
Diastolic pressure is primary determinant of coronary pressure
Ejection fraction
good indicator of cardiac function
Ratio of volume of blood ejected out of ventricles relative to volume of blood by ventricles
60-70% is normal
venous return
effected by two factors
Total blood volume
Pressure within venous vasculature
blood flow patterns change at the result of
sympathetic nervous system action
blood flow to muscles during exercise release of norepinephrine
vasoconstrict blood to digestive organs, kidneys, thus redirecting to skeletal muscle
determinants of myocardium metabolic rate is
rate pressure product= HR X systolic BP / 1000
aging and cardiovascular system
L Ventricle wall thickness increases
increase vascular thickness
Maximum oxygen uptake and cardiac output reduce
cardiac muscle
Striated
Involuntary
Branched
Single nucleated
Intercalated discs
troponin and tropomyosin
Calcium from ECF and ER
Self exciting tissues
EC coupling
Venous capacity
Capacity of the veins
increase in CVP
The pressure in the thoracic veins SVC and IVC
EDV
Max blood in ventricles before a contraction
ESV
Maximum amount of blood in ventricle after contraction
MAP
mean arterial pressure
Pressure in the aorta during one cardiac cycle
Influences blood delivered to the organs
Hematocrit normal value
45%
Red blood cell count normal value
5×10 ^12 cells/L
Hemoglobin normal value
15 g/dL
White blood cell count, normal value
5×10 ^9 cells/L
platelets, normal value
250×10 ^9 cells/L
plasma proteins, normal value
7 g/dL
Na normal value
140 mEq/L
Cl normal value
100 mEq/L
K normal value
3.5-5 mEq/L
Parasympathetic preganglion fibers release
Acetylcholine
sympathetic preganglion fibers release
Acetylcholine
parasympathetic post ganglionic receptors
Nicotinic cholinergic
Sympathetic post ganglionic receptors
nicotinic cholinergic
Parasympathetic post ganglionic fibers release
acetylcholine
Sympathetic postganglionic fibers release
Epinephrine
Acetylcholine binds to
Muscarinic cholinergic receptors on the effector organ
epinephrine binds to
adrenergic receptors on the effector cardiac muscle
