Review PSIO 420 CARDIO
Lecture 28: Heart anatomy
• Beats 100,00 times a day
• 60,000 miles of blood vessels
• Heart develops autorhythmicity after gestation.
Cardiac cells: Cardiac muscle
• 25% mitochondrial density - Therefore the heart is continually generating ATP so that it
does not have to use anaerobic respiration. This would be bad. Cardiac muscle is a
aerobic muscle. Compare to skeleton muscle which only has 2% Mitochondria.
• Intercalated disks allow for the heart as a whole to function as one big pump per
• Gap junctions - allow for a rapid dispersal of action potentials that generate a
• Desmosomes - Physical connection between fibers.
Conduction system of HEART:
SA node (Cardiac myocytes)
• Sets autorythmicity of heart
• Important in generating HR
• Affected by autonomic nervous system
Sympathetic nervous system increases HR, Contractility with an increase in
Norepinephrine and epinephrine.
Parasympathetic nervous system affects depolarization, by releasing
Acetylcholine which reduces Camp and ultimately reduces HR - example of rest
AV node (atrioventricular)
• Slows conduction of electrical signals before the spreading the signals to the ventricles.
Allows for maximal filling of the ventricles.
Bundle of His • Electrical conduit between atria and ventricles
Right and left bundle branches
• Signal spreads rapidly through to the perkinjie fibers (end)
Draw pacemaker potentials and action potentials in autorhythmic fibers of SA node. (funny
current, resting membrane potential =intracellular voltage)
Influence of Total cross sectional area of the vascular system:
Aorta - velocity fast, 2.5 diameter (not largest diameter)
Arteries - bulk flow (responsible vessels), Fairly elastic (expansion), Expand during
systole, and recoil during diastole - aids in blood flow
Arterioles - These are the resistance vessels, responsible for redistribution of blood,
hence they contain smooth muscle which can be vasodialated ( very important for
exercise) or vasoconstricted (NE/E, increase in resistance to flow) depending on what
the situation is.
Capillaries - Diffusion cite, small, thin, slowest velocity of blood flow, and largest cross
Veins - Very low pressure, at rest they are the blood reservoir (about 60% of blood).
They also contain some one way valves which stop the blood from moving down with the
pull of gravity. Makes blood move to the heart. Without one way valves we have varicose
veins. Flow = Change in pressure/ resistance or
Cardiac output (L/min) = mean arterial pressure (mmHg)/ Systemic vascular resistance
* This is the sum of all the blood flow resistance in the network
Parallel arrangement of organ blood flow:
Tissue is connected in parallel, except the hepatic portal vein.
Arterioles all contain stopcock which allows for the redistribution of blood during exercise
and rest. These stop cocks represent different arterial resistance to blood flow which is
regulated by the sympathetic and parasympathetic nervous system.
Lecture 29: Cardiac performance (stroke volume)
Stroke volume: changes with exercise, Maximal HR does not change with - stays around age
The about of blood ejected from the heart per heart beat (L/beat)
Resting CO = 5L/min
Resting HR - 60-80 Beats/min
Resting SV untrained - 60-80 ml/beat
Maximal exercise for UT - 100-120 ml/beat
Maximal exercise for T - up to 180 ml/beat
SV= End diastolic volume - Ends systolic volume
= Amount of blood left in ventricle after diastole - the amount of blood left in ventricle after
1. Systolic (systole) - time when heart is contracting (generating pressure, emptying) 1/3
2. Diastolic (diastole) - time when heart is relaxing ( filling with blood) 2/3 time of Cardiac
cycle Factors affecting SV:
Preload - venous return - how much blood is returned to the heart after diastole
Afterload - affects ESV - Mean arterial pressure affects this, The higher the blood
pressure the harder the heart has to work to push the blood out of the ventricle. This can
also be the resistance from the arterioles/arteries. Therefore the afterload is the
pressure needed to push the blood out of the left ventricle.
contractility - degree of forcefulness which doesn't affect EDV or preload, however it
affects the End systolic volume. More force more blood leaves the left ventricle, the
smaller the End systolic volume the greater the SV. Mechanism - Sympathetic nervous
system release of NE. NE binds to B-adrenergic receptors, which increases Calcium
release which increases the crossbridge formation increasing contractility - only affects
Factors affecting EDV: Stretching of myocardium
-Stretch of myocardium is associated with
an increase in the filling which is an increasem
in EDV. L
increase in blood volume - increase
EDV and Preload
Body position - Prolonged standing decreases
EDV - blood pools in legs (vein reservoir).
Ventricular EDV (ml)
Laying down prone position causes the EDV to
increase. When we go from prone to standing our EDV
decreases and we get a fainting response.
Respiratory pump - increased ventilation will cause blood to be sucked back to the heart
which increases the venous return.
Venous tone - Venoconstriction (mediated by SNS)- contraction of the veins so that
there is a push of blood back to the heart. Increases with trained individuals more
venous tone. Muscle pump - pumping action of skeletal muscles causes blood to be pumped back to
the heart. Happens when we contract our muscles - exercise.
Time of filling - (HR) decrease in HR increase in EDV, increase in HR decrease in EDV.
The relationship between CO and HR and how it relates to SV: Graph
RELATIONSHIP: With Increases in HR, there is less filling time therefore the stroke
volume decreases. This is with exercise and a "denervated" heart -No PNS or SNS
Relationship between SV (ml/beat), EDV (ml) and Aortic Pressure( mmHg):Graph
HR (beats/min) resting HR: 60 - 80 beats/min - below 60 bradycardia, above 100 tachycardia.
Maximal HR 220-age
Maximal HR for trained is lower than heart rate of untrained an maximal VO2
Increase metabolic work, increase HR relationship
Rest SV: 60-80 ml/beats
Maximal untrained 100-120 ml/beat
Maximal trained up to 180 ml/beat
Maximal SV reached at 50% of VO2 max.
Resting: 0.3 L/min, 300ml/min, 5ml/kg*min
Maximal trained athlete, heavy person - 6-7 L/min absolute
Maximal trained althetes only - 60-85ml/kg*min relative
Maximal untrained maybe - 45ml/kg*min, 4-5 L/min
rest 0 W
Maximal trained 800Watts
Maximal untrained 300-500 Watts
Maximal 100% for both trained and untrained.
Q(L/min) = VO2L/min/(CaO2 - CvO2)/100
Q = SV(mL/min) x HR (beats/min)
RELATIONSHIP: between VO2 and extr