Cardiovascular system Flashcards
What is the function of cardiovascular system?
To maintain an adaptable supply of blood to the tissue.
What is hemodynamics?
The study of the blood flow. It is determined by resistance and pressure difference
What is Darcy’s Law?
F (flow)= Pressure difference / resistance difference
What determines resistance?
Length of vessel, radius of vessels, fluid viscosity.
What is the equation of resistance?
R = rLn / pi x r^4
What is systole?
Contraction
Why could blood pressure increase with age?
The systole blood pressure can increases because of artery stiffness or blocked artery.
How would you calculate the Mean Arterial pressure?
Diastolic Pressure + 1/3 pulse pressure.
What is pulse pressure?
The difference between systole and diastole pressure.
Describe the conduction pathway of the heart
SA node down the right atria to the AV node. A delay to allow atrial contraction and blood to go into ventricle. Down the bundle of His and then at the apex branches into the Purkinje fibres. This causes ventricular contraction.
Describe the cardiac cycle
1) Atrial systole
2) Atrial diastole
3) Ventricular systole
4) Ventricular diastole
5) Blood fills ventricles from atrias passively
What isometric ventricular contraction?
Change in pressure without change in volume. Occurs in early ventricular systole.
What is ECG?
Electrocardiogram. Detects electrical responses of the heart. Shown as the graph seen in hospital.
What order does the ECG waves go?
P-wave, QRS complex, T wave.
What is the P wave?
Atrial contraction
What is the QRS complex
Shows the contraction of ventricles. The atrial relaxation is masked and causes a sharp peek instead of wave.
What is the T-wave?
Ventricular relaxation and masks atria contraction
What is QT- interval?
The time from initiation of ventricular contraction to the end of ventricular relaxation.
What is the equation of cardiac output?
Cardiac Output = Heart rate x stoke volume.
What is stroke volume ?
Volume of blood ejection by each ventricle per beat.
What is repolarisation?
When relaxing occurs
What is depolarisation?
When contraction occurs
What does innervate mean?
To supply nerves to.
Give the three ways the heart can be innervated
1) As a result of blood volume
2) Autonomic Innervation (Parasympathetic and Sympathetic nerves)
3) Sympathetic via adrenal gland (secreting hormones such as adrenaline and noradrenaline)
Does noradrenaline increase heart rate?
Yes
Does acetlycholine increase heart rate?
No, slows down
Does adrenaline increase heart rate?
Yes
What is the vagus nerve?
A parasympathetic nerve which innervates the heart and decreases heart rate.
What is a chronotropic effect?
Those that change the heart rate. Positive chronotropes increase heart rate and negative decrease heart rate.
What is used more in resting heart rate, Parasympathetic or sympathetic?
Parasympathetic, sympathetic only a little
What is the average heart range for an adult?
60-100 Bpm
Give the equation for stroke volume?
End diastolic Volume - End systolic Volume
What factors affect stroke volume?
Preload, contractility and afterload.
What is Preload?
Venous return and Filling time.
What is venous return determines by?
Posture (standing decreased venous return), muscle pump and respiratory pump moves blood into the atria.
What is Starlings Law?
The energy of contraction is proportional to the initial length of the cardiac muscle fibre
What is Tachycardia?
Fast heart rate (>100)
What is Bradycardia
Slow heart rate (<60)