Lecture 12 Flashcards
What is the circulation pathway of the blood?
Aorta, arteries, arterioles, capillaries, venues, veins, vena cava
What happens in terms of blood flow when the heart stops?
Some of the blood goes to the heart, some stay in the veins, some in blood vessels
What do you need in order for blood to move through the capillaries?
Resistance
What is higher than central venous pressure?
Arterial pressure is higher
What is compliance?
A change in volume accommodated per unit change of pressure
Is venous more complaint than the arterial side?
Yes the ratio is 19:1
Why is the venous side more complaint than the arterial side?
Because it can expand to accommodate a larger volume of pressure compared to the arterial side
Describe the arterial side?
Arteries are much muscular so are going to expand
What is the cardiac output in L?
5L per minute
What is the equation for peripheral resistance (R)?
R = (MAP-CVP)/Qr
What happens to blood flow in a cardiac arrest?
Flow becomes 0 litres per minutes - beats beforehand can keep pumping, get a trickle of blood going to the venous system
What needs to happen to the pressure in a cardiac arrest?
Need to have a change in pressure in the venous and arterial side in order to accommodate the volume of blood - will have a balance point where the volume across the system is both 0
What happens to the pressure in the arterial side compared to the venous side during a cardiac arrest?
The pressure in the arterial side increases much more than the increase in the venous side due to the property of compliance
What happens as cardiac output decreases?
Venous pressure increases
What happens as the arterial pressure falls below 0?
The veins begin to collapse
What happens to blood volume in terms of a haemorrhage?
Decrease in blood volume and decrease in cardiac output
What does vasa constriction do?
Central venous pressure stays the same but change in cardiac pressure (decreases)
What happens in vasa dilation?
Central venous pressure stays the same but CO increases
What does the vascular function curve do?
Defines Changes in central venous pressure evoked by changes in cardiac output
What is the dependent or independent variable on the vascular function curve?
Dependent = central venous pressure, independent = cardiac output
What is the expression of frank starling law on cardiac function curves?
Reflects the relationship between ventricular filling and strength of contraction
What does increase in HR and contractility do to the afterload?
Decreases
What does decrease in HR and contractility do to the afterload?
Increases afterload
What are factors that influence preload?
Increase in central venous pressure, aortic pressure, ventricular compliance, atrial contractility and decrease in heart rate
What is the Guyton model?
Coupling of the cardiac and vascular fucntion
What does circulation do?
Maintains blood flow - same flow in all vessels
What is the pulmonary system like?
A low pressure system overall
What are the terminal arteries and arterioles?
Are the main site of resistance
What is reduction in velocity of flow for?
It is protective for smaller vessels
What determines flow in a vessel?
The poiseuilles law - resistance to steady laminar flow
What are vascular intercellular connections?
Smooth muscle cell to smooth muscle cell = human myometrial resistance artery and endothelial cell to smooth muscle cell = myodenothelial junction
What is the myoendothelial junction important for?
Human resistance artery
How does smooth muscle contract?
Contraction occurs by sliding interaction of actin containing thin filaments and myosin containing thick filaments
What is a spindle?
A smooth shaped muscle cell - actin filaments are anchored to the dense band
