Anti-arrhythmics - Adenosine Flashcards
The cardiac electrophysiology in a pacemaker cell has only 3 phases, which ultimately lead to an action potential (as seen in the image). What is occurring at stage 4?
1 - pacemaker potential phase
2 - depolarisation phase
3 - Leaky K+ phase
4 - Ca2+ leaking into cell phase
1 - pacemaker potential phase
- similar to resting membrane potential
- around -65 mV
The cardiac electrophysiology in a pacemaker cell has only 3 phases, which ultimately lead to an action potential (as seen in the image).To move between phase 4 and 0, there is a special type of channel located on the pacemaker cells that allows Na+ to flow into the pacemaker cells, raising the action potential to -50 mV. What is the channel called?
1 - Na+ channel
2 - Na+/K+ ATPase channel
3 - hyperpolarization-activated cyclic nucleotide-gated channels (HCN)
4 - Na+/Ca2+ co-transport
3 - hyperpolarization-activated cyclic nucleotide-gated channels (HCN)
- important when cells hyperpolarise following an action potential, these channels help the pacemaker cell get close to action potential and fir again
- called the funny current
The cardiac electrophysiology in a pacemaker cell has only 3 phases, which ultimately lead to an action potential (as seen in the image). The funny current (Na+ entering the pacemaker cells) then enters phase 0. What is this phase called?
1 - pacemaker potential phase
2 - depolarisation phase
3 - Leaky K+ phase
4 - Ca2+ leaking into cell phase
2 - depolarisation phase
- Na+ enters cell through HCN
- Ca2+ enters the cell through Ca2+ channels
- pacemaker cells membrane potential becomes + (around 10mV
The cardiac electrophysiology in a pacemaker cell has only 3 phases, which ultimately lead to an action potential (as seen in the image). In phase 0 Na+ and Ca2+ enter pacemaker cells causing depolarisation (aprox 10 mV). The pacemaker cell then enters phase 3. What of the following then happens here?
1 - Ca2+ channels close
2 - Na+ channels remain open
3 - K+ channels open and K+ leaves the cell
4 - all of the above
4 - all of the above
- lots of K+ channels
- overall this causes the membrane potential to drop called repolarisation
- phase 4 begins again
In a myocyte cell the cardiac electrophysiology has 5 phases (0-4), which ultimately lead to an action potential (as seen in the image). Phase 0 is the resting phase (-90mV). What then enters the myocyte through gap junctions that raises the resting membrane potential (-90mV) to the threshold potential (-70mV)?
1 - Na+
2 - K+
3 - Ca2+
4 - Mg+
3 - Ca2+
In a myocyte cell the cardiac electrophysiology has 5 phases (0-4), which ultimately lead to an action potential (as seen in the image). Phase 0 occurs when the the membrane potential reaches -70mV. Which channels then open causing depolarisation, reaching around 20mV?
1 - Na+
2 - K+
3 - Ca2+
4 - Mg+
1 - Na+
In a myocyte cell the cardiac electrophysiology has 5 phases (0-4), which ultimately lead to an action potential (as seen in the image). Following depolarisation, we reach phase 1, called initial repolarisation. Which 2 of the following occurs here?
1 - Na+ channels close
2 - K+ channels open and K+ leaves the cell
3 - Ca2+
4 - Mg+
1 - Na+ channels close
2 - K+ channels open and K+ leaves the cell
- causes a drop in membrane potential
In a myocyte cell the cardiac electrophysiology has 5 phases (0-4), which ultimately lead to an action potential (as seen in the image). Following initial repolarisation (phase 1), to stop the myocyte going into full repolarisation, another channel opens and the membrane potential plateaus, called the plateau phase. Which channel opens to maintain this plateau phase (phase 2)?
1 - Na+ channels
2 - K+ channels
3 - Ca2+ channels
4 - Mg+ channels
3 - Ca2+
- Ca2+ flows into the cell
- membrane charge is maintained
- responsible for heart contraction
In a myocyte cell the cardiac electrophysiology has 5 phases (0-4), which ultimately lead to an action potential (as seen in the image). Following the plateau phase (phase 2) which is when the heart contracts, which of the following occurs in phase 3, called repolarisation?
1 - Ca2+ channels close
2 - K+ channels remain open
3 - Ca2+ is pumped out of the cell
4 - all of the above
4 - all of the above
- myocyte returns to resting membrane potential of around -90mV
When looking at an ECG, what does the P wave represent in relation to an an action potential?
1 - sum of depolarisation in all atrial myocytes
2 - sum of depolarisation in all ventricle myocytes
3 - sum of repolarisation in all atrial myocytes
4 - sum of repolarisation in all ventricle myocytes
1 - sum of depolarisation in all atrial myocytes
When looking at an ECG, what does the QRS wave represent in relation to an an action potential?
1 - sum of depolarisation in all atrial myocytes
2 - sum of depolarisation in all ventricle myocytes
3 - sum of repolarisation in all atrial myocytes
4 - sum of repolarisation in all ventricle myocytes
2 - sum of depolarisation in all ventricle myocytes
- atrial myocytes also repolarise here as well, but this is masked by the QRS
When looking at an ECG, what does the ST segment represent in relation to an an action potential?
1 - sum of depolarisation in all atrial myocytes
2 - sum of depolarisation in all ventricle myocytes
3 - sum of repolarisation in all atrial myocytes
4 - plateau phase
4 - plateau phase
- this is when the ventricle contract and pump blood
When looking at an ECG, what does the T wave represent in relation to an an action potential?
1 - sum of depolarisation in all atrial myocytes
2 - sum of depolarisation in all ventricle myocytes
3 - sum of repolarisation in all ventricle myocytes
4 - plateau phase
3 - sum of repolarisation in all ventricle myocytes
Which of the following is the one anti-arrhythmic medication that doesn’t come under class I - IV that we need to know?
1 - verapamil
2 - amiodarone
3 - adenosine
4 - atenolol
3 - adenosine
- is a building block of DNA, but free in the circulation it blocks conduction of the AV node
What is the mechanism of action of adenosine?
1 - antagonist of adenosine receptors in heart
2 - agonist of Gai receptors on AV node
in the heart
3 - antagonist of alpha receptors in heart
4 - antagonist of B receptors in heart
2 - agonist of Gai receptors on AV node
in the heart
-reduces cAMP activates delayed rectifier K+ channels
- hyper-polarises cardiac tissue, slowing the pacemaker potential
Adenosine is an anti-arrhythmic medication that acts as an agonist to GPCR Gai. What effect does binding with the Gai have on the cell?
1 - inhibits adenylyl cyclase
2 - inhibits cGMP
3 - activates cAMP
4 - opens Ca2+ channels
1 - inhibits adenylyl cyclase
- no AC means no cAMP, and phosphorylation
- Ca2+ channels do not open
- K+ leaves the cell
- leads to hyperpolarisation of SA node and delayed depolarisation
