Cardiovascular System Flashcards
What is the role of the pericardium
The pericardium is a fibrous sac that protects the heart by providing lubrication during its constant movement
It helps anchor the heart against the spine
What is pulmonary circulation
Connected to the heart in ‘series’ which means that the entire blood volume has to pass through it every time it circulates the body
What is systematic circulation
Connected to the heart in ‘parallel’ which means there is a choice of which part of the body receives more or less of the available blood volume
What is the typical total blood volume for the average person
5 litres (7% body weight)
What is the typical cardiac output for the average person
5liters/min
What is driving pressure
Flow is created by the pressure difference between two points
What is Darcy’s law
Flow = pressure difference / resistance
Increased driving pressure =
Increased flow
Increased resistance =
Decreased flow
What is Poiseuille’s law
Resistance = 1 / r ⁴
Darcy’s and Poiseulle’s laws combined
Flow = pressure difference x r ⁴
Increased driving pressure + increased radius of vessel =
Increased flow
What does flow velocity of blood depend on
The cumulative radius of all vessels at a similar distance from the heart
What is large XSA and very low blood flow velocity important for in tissues
Diffusion of gases and exchange of nutrients / waste
How is cardiac muscle similar to smooth muscle
It’s involuntary
What do gap junctions allow
An electrical signal to originate from a specialised part of the heart and propagate from fibre to fibre in a structured and organised pattern
What does contraction of cardiac muscle cells depend on
Extracellular Ca2+
What is meant by cardiac muscle being highly oxidative
It is dependent on o2 supply
What is the SA node
The SA node has an intrinsic rate of approximately 100bpm and can initiate cardiac contraction in the absence of any external control (hormonal or nervous)
How can SA node cells initiate an action potential
Due to an unstable membrane potential that is continuously drifting towards the threshold
What does the rate of firing from the cells of the SA node depend on
1) initial value of the membrane potential
2) the slope of the drift towards threshold
Where is the tricuspid valve
Separates the right atrium and ventricle
When does the tricuspid valve open and close
Opens; when R atrial pressure > R ventricular pressure
Closes; when R atrial pressure < R ventricular pressure
Where is the mitral (bicuspid) valve
Separates left atrium and ventricle
When does the mitral valve open and close
Opens; when L atrial pressure > L ventricular pressure
Closes; when L atrial pressure < L ventricular pressure
Where is the pulmonary valve
Separates the right ventricle and pulmonary artery (PA)
When does the pulmonary valve open and close
Opens; when R ventricular pressure > PA pressure
Closes; when R ventricular pressure < PA pressure
Where is the aortic valve
Separates left ventricle and aorta
When does the aortic valve open and close
Opens; when L ventricular pressure > aortic pressure
Closes; when L ventricular pressure < aortic pressure
