Physiology of the heart
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Physiology of the heart
What vital role does the cardiovascular system maintain?
continuous and controlled movement of blood through capillaries
Cardiovascular system has...
...numerous control mechanisms
What is hemodynamics?
A collection of mechanisms that influence the dynamic circulation of blood
What is essential for healthy survival?
Circulation of different volumes of blood per minute
Circulation control mechanisms must accomplish which two functions?
Vary volume and distribution of the blood circulated
The conduction system of the heart is composed of which four major structures?
1. Sinoatrial (SA) node
2. Atrioventricular (AV) node
3. AV bundle (bundle of his)
4. Subendocardial branches (Purkinje Fibers)
The SA node is responsible for which two functions?
Setting heart's pace
enters the AV node from the right atrium, its conduction
to allow complete contraction of both atrial chambers before the impulse reaches the ventricles
Action potential; slows
The P wave is created by which conduction point?
The QRS complex is created by which conduction point?
bundle of HIS
What does a heart block mean?
That the signal to the ventricles is blocked
What does the P wave represents?
Depolarization (contraction) of the atria
What does the QRS complex represents what?
The depolarization (contraction) of the ventricles and repolarization (relaxation) of the atria
What does the T wave represent?
The repolarization (relaxation) of the ventricles
What does the U wave represent?
the repolarization (relaxation) of the papillary muscle (Purkinje fibers)
How is the U wave represented on the ECG report?
as a tiny "hump" at the end of the T wave
What are some characteristics of the U wave?
Absent or small U waves are usually considered normal
U waves may be a sign of hypokalemia or too much digoxin
What is a cardiac cycle?
A complete heart beat
What does systole mean?
What does diastole mean?
a relaxation phase
What is the atrial systole?
The cycle that begins with the P wave of the ECG, which triggers atrial contraction
What are the steps of atrial systole in the cardiac cycle?
Atria contraction creates a pressure gradient that pushes blood out of atria into relaxed ventricles
Due to pressure gradients, AV valves are open and SL valves are closed
Ventricles are relaxed and filling with blood from atria
The cardiac cycle is divided into...
Isovolumetric ventricular contraction makes which heart sound?
The first; the "lub" sound
Isovolumetric ventricular relaxation makes which heart sound?
The second sound; the "dub" sound
What is the Isovolumetric ventricular contraction?
Onset of the ventricular systole that coincides with the R wave.
When does the Isovolumetric ventricular contraction occur?
Between the start of the ventricular systole and the opening of the SL valves
What occurs during the ejection phase of the cardiac cycle?
SL valves open and blood is ejected
What is rapid ejection?
Initial short phase marked by an increase in ventricular and aortic pressure and in aortic blood flow
What is reduced ejection?
decrease in ventricular volume
When does Isovolumetric ventricular relaxation begin?
At the beginning of ventricular diastole
When does Isovolumetric ventricular relaxation occur?
between closure of the SL valves and opening of the AV valves
What is passive ventricular filling?
ventricular relaxation which causes blood to rush into relaxed ventricles, which returns venous blood
What is diastasis?
Slow ventricular filling lasting approx. 0.2 second; characterized by a gradual increase in ventricular pressure and volume
What occurs when passive ventricular filling is done?
The cardiac cycle begins again
The systolic sound is...
the first heart sound from ventricles contracting and AV valves closing
The diastolic sound is...
...a short sharp sound and the SL valves closing
Blood flows because...
...a pressure gradient exists between different parts of its volume
Pressure is basically
when it reaches the capillaries
What does P
A pressure gradient with P
representing the higher pressure and P
the lower pressure
What is the arterial blood pressure represent?
The amount of blood being pumped and at what rate. The higher the volume of blood= the higher the blood pressure
What is cardiac output (CO)?
the volume of blood pumped out of the heart per minute
What determines cardiac output?
Stroke volume and heart rate
What determines stroke volume?
Volume pumped per heartbeat
CO (volume/ min) = SV (volume/ beat)x HR (beats/min)
What is Starling's law of the heart?
The more stretch the stronger the contraction. The amount of blood in the heart determines the amount of stretch placed.
What is contractility?
strength of contraction. Influenced by chemical factors
Which chemical can influence the neural system?
Which chemical can influence the endocrine system?
Contractility can also be triggered by...
stress and exercise
What is the ejection fraction (EF) ratio?
the ratio of stroke volume (SV) to end-diastolic volume (EDV)
What does the ejection fraction represent?
The amount of blood in ventricle during contraction / amount of blood in ventricle after ejection
What is the normal range for healthy adults?
at least 55%
Where is the carotid sinus reflex located?
at the beginning of the carotid artery
Where do the sensory fibers from the carotid sinus baroreceptors run?
Through the carotid sinus nerve