CV System Flashcards
What is diastole
Relaxation phase during which the ventricles fill with blood
AV value opens
Aortic and pulmonic valves closed
What is systole
Contraction phase during which the ventricles expel blood
AV valves closed
Aortic and pulmonic valves open
Intrinsic control of the heart is made up of what parts
Autorhythmaticity
SA node
AV node
Purkinje fibers
What happens in autorhythmaticity
This is the ability to initiate impulse for contraction at regular intervals
SA node is
The pacemaker of cardiac contraction
AV node does what
Delays impulse by 1/10 second allowing atria to contract before ventricles
What do Purkinje fibers do
Rapidly spreads impulse to contract throughout ventricles
What does ECG measure
Records the electrical activity of the heart
What is the ECG measurement broken up into
P wave
QRS complex
T wave
What is the P wave
Atrial depolarisation
What is the QRS complex
Ventricular depolarisation and atrial repolarisation
What is the T wave
Ventricular repolarsation
ECG abnormailites may indicate what
Coronary heart disease
What can indicate myocardial ischemia on an ECG
ST segment depression
When does intraventicular pressure rise during PQRST
What causes this pressure increase
From R to S
Ventricles contracting
When does intraventricular pressure fall during PQRST
What causes this pressure decrease
T wave
Ventricles relaxing
When does the AV valves close
When do the semilunar valves close
When ventricles contract
When blood has just left the heart
During Diastole:
Pressure is…
Blood is…
Pressure in ventricles is low
Ventricles filling with blood from atria
AV valves open when ventricular pressure < atrial pressure
During Systole:
Pressure is….
Blood is…
Pressure in ventricle rises
Blood ejected in pulmonary and systemic circulation
Semilunar valves open when ventricular pressure > aortic pressure
How many heart sounds are there
When are they
2 sounds
1st: Closing of AV valves
2nd: Closing of aortic and pulmonary valves
What is cardiac output equation
Q = HR x SV
Heart rate is controlled both
Intrinsically
Extrinsically
Stroke volume is controlled by
End Diastolic volume (EDV)
Afterload
Contractility
How is heart rate extrinsically controlled
Parasympathetic nervous system
Sympathetic nervous system
Parasympathetic tone
Onset of exericse
How does the parasympathetic nervous system control heart rate
Via the vagus nerve
Slows HR by inhibiting SA AND AV node
How does the sympathetic nervous system control heart rate
Via cardiac accelerator nerves
Increases HR by stimulating SA and AV node
Low resting heart rate is due to
Parasympathetic tone
What is the reason for an increase in HR on the onset of exercise
Initial increase due to parasympathetic withdrawal - up to 100 beats/per
Later increase is due to increased SNS stimulation
End diastolic volume is
The volume of blood in the ventricles at the end of diastole (preload)
Aortic blood pressure is
The pressure the heart must pump against to eject blood (afterload)
Mean arterial pressure
Contractility refers to
Is enhanced by
Strength of the ventricular contraction
Circulating epinephrine and norepinephrine
Direct sympathetic stimulation of heart
Regulation of stroke volume via end diastolic volume is dependent on
Frank starling mechanism
Venous return
What is frank starlings mechanism
Greater EDV results in a more forceful contraction due to stretch of ventricles
Venous return is increased by
Venoconstriction via SNS
Skeletal muscle pump
Respiratory pump
The skeletal pump is
What prevents back flow
Rhythmic skeletal muscle contractions force blood in the extremities towards the heart
One way valves in veins
The respiratory pump is
Changes in thoracic pressure pull blood toward heart
As stroke volume increases so does
End diastolic volume
When is the increase in stroke volume/end diastolic volume due to increased venous return
100ml SV
200ml EDV
Intercept
What is afterload
The tension developed in the wall of the left ventricle during ejection
What does a high afterload result in
Why
Decrease stroke volume
Because it requires greater force generation by myocardium to eject blood into the aorta
Afterload is represented by a decrease in ______
Stroke
What results in a higher stroke volume
Increased contractility
Circulating epinephrine and norepinephrine
DIrect sympathetic stimulation of the heart
An increase in EDV and Contractility and a decrease in Afterload results in
Higher Cardiac output and SV
HR remains the same
Q = HR x SV
What are the factors that influence arterial blood pressure
Determinants of mean arterial pressure
Short term regulation
Long term regulation
What are the determinants of MAP
Cardiac output
Total vascular resistance
ABP = Q x TPR
Short term regulation of arterial blood pressure involves
Sympathetic nervous system to heart and vasculature
Baroreceptors in aorta and carotid arteries
Baroreceptors detect changes in
Blood pressure
Baroreceptors cause ________ when blood pressure increases
Decreased SNS
BP normalises
Baroreceptors cause ________ when blood pressure decreases
Increased SNS
BP normalises
Long term regulation of arterial blood pressure is due to
The kidneys
Via control of blood volume
What regulates total peripheral resistance
Vasodilation
Vasoconstriction
Vasodilation causes
It can be initiated by
Decreased resistance
Decreased Blood pressure
Nitric oxide
Vasoconstriction causes
Increased resistance
Increased BP
