Cardiovascular System and Cardiac Action Potential Flashcards
what is cardiovascular electrophysiology?
the study of electrical activity of the heart
what is cardiovascular mechanics?
the understanding how the contractile properties of the heart affect its function
(the forces that mediate the work)
what is cardiovascular hemodynamics?
the study of blood flow and the factors that control it?
what are the components of the cardiovascular system?
- the heart (left side and right side)
- arteries
- veins
- lungs
- capillaries
why can we consider the heart to be a dual pump system?
- left side = systemic pump that carries oxygenated blood via arteries throughout the body
- right side = pulmonary pump that carries the deoxygenated blood to the lungs
what is the significance of the capillaries?
they are the site of exchange in the body from blood to tissues back into the blood
what is the order of blood flow throughout the body?
right atrium –> tricuspid valve –> right ventricle –> pulmonary valve –> pulmonary arteries –> lungs –> pulmonary veins –> left atrium –> mitral valve –> left ventricle –> aortic valve –> aorta –> systemic circulation –> superior/inferior vena cava –> right atrium
describe how the contraction of the left heart work?
the mitral valve is controlled by the contraction of the papillary muscles contracting to pull the chordae tendinae which pull the mitral valve open
- coordination of contraction is important for opening and closing
why are valves important?
prevent backflow
what is the distribution of cardiac output to the body systems?
- 100% of blood travels through the hear and to the lungs
- after being released by left side:
- 15% to brain
- 5% to coronary
- 25% to renal
- 25% to GI
- 25% to skeletal muscle
- 5% to skin
how much is the normal cardiac output and venous return?
5L/min
- that is how much blood we have in the body
why do the kidneys get so much blood?
kidneys are important for chemical balance of the blood and help control blood pressure
how much cardiac output is there during activity?
can be as much as 18L/min cycling through the heart –> increased blood flow
where is majority of the blood located and why?
- in the veins
- because they are larger
- when you need higher output, the veins are squeezed to release blood into the heart at a faster rate for circulation
what can the heart function be characterized into?
- electrical and mechanical events
- electrical events generate by the heart trigger AP which triggers the mechanical contraction of the heart to compliment each other
what are the electrical events that occur in the heart?
- cardiac action potential
- cardiac refractory period
- conduction of the action potential
- modulation of electrical activity by the autonomic nervous system (HR)
- ECG
where are the pacemaker cells located?
SA node
what properties determine the normal electrical activity of the heart?
- automaticity
- excitability (responsiveness)
- conductivity
what is automaticity and what cells are related to it?
- the ability of the heart to spontaneously fire action potentials on its own (without stimulus from NS)
- pacemaker cells (=modified cardiac cells)
what is excitability and what is related to it?
- the ability of cardiac cells to respond to electrical activity (under normal conditions) of pacemaker cells
- refractory period
what is conductivity and what is related to it?
- the ability of the heart to conduct action potentials from its site of origin to all cardiac cells
- cardiac muscle anatomy (functional syncytium)
why is the refractory period so important for excitability?
- ensure the heart fully contracts and fully relaxes before another contraction occurs
- this prevents tetanic contraction form occurring which would keep the heart in a constant state of contraction
why is cardiac muscle anatomy so important for conductivity?
the cell anatomy is connected and coupled together so the stimulation is passed very easily between cells to contract in unison instead of delayed and unsynchronized
what are the ion concentrations and gradients extracellularly and intracelullarly?
comparison of cardiac muscle cells and their action potentials
Phases of contractile cell action potential
Phases of pacemaker cell action potential
what are “funny” channels?
- non-specific, non-selective cation channels
- tend to be open all the time
- drive automaticity and enable immediate regeneration of AP
how does the sympathetic nervous system control contraction during exercise?
increases calcium entry and increase potassium leaving which therefore increases speed of contraction during exercise
what is the functional refractory period? what are the phases? what is the purpose?
- the refractory period after the action potential first fires
- 2 main parts: effective refractory and supranormal refractory
- allows time for recovery for ion channels to be activated when the next stimulus is applied
- prevents tetanic contraction of the cardiac muscle
parts of the effective refractory period? what is significant about them?
- absolute = when another AP cannot be triggered no matter what
- relative = AP can be triggered but low likelihood
the supranormal refractory period is important because…
= “vulnerable phase” = when another AP can be triggered and is vulnerable to one prior to reaching resting voltage
why are intercalated disks important for function?
- they allow cardiac myocytes to operate at a functional syncytium
- because they have gap junctions and desmosomes to keep cells intact and connect/couple the cells to stimulate neighboring cells
what is the importance of gap junctions?
- they are located between cardiac muscle cells
- allow current to flow from the depolarized cell to a neighboring cell that has not been electrically stimulated yet
- basically allows it to contract all the cells fast and at the same time
- allows spread of AP
what are the components that make up the pacemakers of the heart?
- SA node
- AV node
- purkinje fibers
- nodes = bundle of pacemaker cells
- all cells can generate spontaneous action potentials but with different frequencies
what is the normal pacemaker of the heart?
SA node
pacemaker tissues and their rate of action potentials production?
SA node = 70-80 AP/min
AV node = 40-60 AP/min
Purkinje Fibers = 20-40 AP/min
what is overdrive suppression?
it results in the SA node serving as the normal pacemaker
what role does the autonomic nervous system have? para? sympa?
serves to modulate the rate of firing of cardiac action potentials
- para activation reduces the AP firing rate
- sympa activation increases the AP firing rate
~ antagonistic control
antagonistic control of of the heart by NS
