ribe the factors that affect cardiac output (CO). Include in your description th
ID: 3478088 • Letter: R
Question
ribe the factors that affect cardiac output (CO). Include in your description the terms heart rate, 3. Desc sympathetic nervous system, parasympathetic nervous system, sontractility, and yenous return. For each factor you discuss make sure you explain the effect (does it increase or decrease CO?) and mechanism (how does it increase or decrease CO?). stroke volume 4. How are autorhythmic pacemaker cells in the conducting system of the heart different from normal contractile myocardial cells? Describe the action potential in each type of cell (which ion channels open, and when) and indicate what each type of cell does in the heart.Explanation / Answer
Ans 3. Cardiac output is generally defined as the volume of blood which can be pumped from the left ventricle of the heart in 1 minute.The cardiac output will measure between 4.5 and 5.5 L/min in an adult at rest condition.
CO=HR×SV
As increase in heart rate due to stimulation or excitation by activity,drugs,medications or other sources increase in cardiac output.
Decrease in heart rate due to electrical abnormality and decrease in cardiac output.
Cardiac output is directly proportional to heart rate.
Stroke volume is the measurement of the volume of blood being forced from the left ventricle in one cardiac contraction.
SV=EDV-ESV
EDV=end diastolic volume
ESV=end systolic volume
Exercise activates the sympathetic nervous system and increase in heart rate , stroke volume due to severe blood loss results in low venous return and therefore decreased stroke volume.sympathetic activity increases heart rate increasing cardiac output and vice versa in case of parasympathetic nervous system.
Cardiac output is the product of heart rate and stroke volume.stroke volume is the volume of blood ejected from each cardiac ventricle with each contraction. Increase in cardiac output is the principle meaning of increasing oxygen uptake during exercise.
Ans4. Authorhythmic cells of heart composed of SA node, AV node, purkynje fibres .the SA node is the one that sets the pace for the rest of the heart is the pacemaker discharging at a rate of 70/80bpm.
The excitation /conducting cells of the heart are the fibres responsible for the autorhythmicity of the heart.
Normal contractile myocardinal infractions different from authrhymic in this there is depolarisation and after that a very fast repolarisation occurs.
The action potential in ion channel , in this inward movement of ions reults in increase in concentration of sodium ion results in increase in positive charge and results depolarisation
Where potential of the cell is higher than cells resting potential.the sodium channel closes at the peak, while potassium continously leave the cell.
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