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KINESIOLOGY
WEEK 4 NOTES
-
cardiac cycle
the cardiac cycle consists of contraction and relaxation
•
•
( heart beats 70 times / min
systole ( contraction & emptying ) , diastole ( relaxation & filling )
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* contraction comes from excitation across the heart
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* relaxation is from repolarization of the cardiac musculature
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right pulmonary
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bicuspid
atria cardiac cycle
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interventricular
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* atria and ventricles have separate cycles of systole and diastole
semilunar
/
tricuspid
,
septum
•
•
the atria contract ( systole ) and blood flows into the ventricles
the atria then relax and decrease in pressure ( di stole )
YaiYara ventricle cardiac cycle
•
blood from the atria and fills the ventricles
( iso volumetric contraction )
the ventricles contract and pressure increases and the bicuspid and tricuspid valves close
•
( isovolumetric relaxation )
•
semilunar valves open and blood flows from the ventricles into the arteries and the ventricles relax
•
bicuspid and tricuspid valves open
,
blood from atria to ventricles
mid ventricular diastole
TP interval on the ECG ( interval after ventricular repolarization & before another atrial
•
•
atrial pressure
depolarization )
slightly exceeds ventricular pressure even though chambers are relaxed & Av valve is open
late ventricular diastole
•
SA node reaches threshold and tires ,
atrial
•
•
impulse spreads throughout the atria ( P wave on the ECG )
depolarization causes atrial contraction
Mr valve remains
,
atrial
pressure rises and more blood flows into the ventricle
open
end of ventricular diastole
•
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•
ends at the onset of ventricular contraction
the volume of blood = end
-
diastolic volume ( EDU )
,
average 135mL
2
ventricular excitation and onset of ventricular systole
impulse travels through the Av node & excite the ventricle
•
,
atria are contracting
•
QRS
complex induces ventricular contraction , pressure increases
•
the
delay between QRS complex and the onset of ventricular systole is required for excitation
-
contraction
ventricular pressure exceeds atrial pressure , forcing AV valves to close
•
iso volumetric ventricular contraction
isovolumetric ventricular contraction = the period of time all valves are closed before the aortic valve opens
•
ventricular chamber stays at a constant volume
•
heart sounds
ventricular ejection
aortic valve opens and blood ejects
•
amount of blood from each ventricle = stroke volume ( SU ) ,
•
approx
.
•
tub dub
•
1st sound = ventricular contraction &
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bicuspid & tricuspid valves closing
aortic pressure rises , ventricular volume decreases
•
•
end of ventricular systole
end systolic volume ( ESV )
-
•
65mL
T
-
wave , closure of the
ESV = SV ( 135 -65 = 70mL )
regulation of cardiac output
all valves are closed
ventricular
again
=
is 0 volumetric ventricular relaxation
volume of blood from each ventricle
increasing stroke volume
extrinsic & intrinsic control for stroke
volume
heart rate
•
→
the or system delivers Oz & creates a
•
•
tilling
cardiac output and its control
•
increasing heart rate or
cardiac output control
Av valve opens , diastole includes relaxation and filling
•
•
aortic valve causes disturbance on the dicrotic notch
is ovolumetric ventricular relaxation
•
ventricular relaxation +
valves close
-
ventricular repolarization + onset of ventricular diastole
•
=
pulmonary and semilunar aortic
=
difference of blood before and after contraction : EDV
•
2nd sound
CO = heart rate × stroke volume
•
parasympathetic slows heart rate
sympathetic speeds it up
pathway to eliminate waste
mechanism that assists with thermoregulation
•
Ach increases
•
permeability of SA node cells to potassium
sympathetic stimulation speeds up heart rate + depolarization of the SA node
•
•
stroke volume is determined by venous return and sympathetic activity ( influenced by intrinsic & extrinsic control )
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3
-
1-rank
•
-
starting law of the heart
the more
blood How and pressure gradient
diastolic tilting the more EDV and heart stretch
vascular physiology
•
•
blood is reconditioned so the composition remains constant
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opposition to blood HOW through a vessel
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pressure difference & resistance affect HOW rate
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How rate is
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determined by vessel radius
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resistance
pulmonary
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F = AP / R
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the vascular tree
•
consists of arteries , arterioles & smaller branches of arteries ,
capillaries
,
venules , veins
arteries are rapid transit pathways for for blood from heart
•
-
-
organs & pressure reservoir for blood when
heart is relaxed
arterial pressure has systolic pressure which is peak pressure ( 120
•
mmHg) and diastolic pressure
which is the minimum pressure ( 80 mmHg )
•
•
•
•
•
pulse pressure is the difference between systolic and diastolic
mean arterial pressure →
diastolic pressure & 's pulse pressure
arterioles are resistance vessels , vasoconstriction = narrow , vasolidation = enlargement
endothelial cells release chemical mediators ( nitric acid )
the
medullary cardiovascular control centre is in the medulla of the brain stem & is influenced by
epinephrine norepinephrine , vasopressin & angiotensin 11
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