Term
| What is the ectopic focus? |
|
Definition
| The region of spontaneous firing other than the SA node |
|
|
Term
| If the SA node is damaged, what may take over governance of heart rhythm? |
|
Definition
|
|
Term
|
Definition
|
|
Term
| Will a nodal rhythm (ectopic focus in the AV node) raise or slow heartbeat? |
|
Definition
|
|
Term
| What is the difference between the membrane potential of skeletal muscles and those of the SA node? |
|
Definition
| They dont have a stable resting membrane potential |
|
|
Term
|
Definition
| The gradual depolarisation of the resting membrane potential of cells of the the SA node |
|
|
Term
| At what voltage the resting membrane potential of the SA node begin at? |
|
Definition
|
|
Term
| What is the threshold for the membrane potential of the SA node at which voltage-regulated fast calcium-sodium channels open |
|
Definition
|
|
Term
| What happens when the membrane potential of the SA node reaches its threshold of -40mV? |
|
Definition
| Voltage-regulated fast calcium-sodium channels open, and both Ca2+ and Na+ flow in from ECF - makes rising phase (polarisation) of action potential |
|
|
Term
| What happens at the peak of the membrane potential of the SA node? |
|
Definition
| K+ channels open and K+ leaves cell |
|
|
Term
| What happens to the membrane potential of the SA node as K+ leaves the cell? |
|
Definition
| It enters a repolarising phase |
|
|
Term
| Each depolarisation of SA node sets off what? |
|
Definition
|
|
Term
| Why do signals slow in the AV node? |
|
Definition
| Cardiocytes are thinner and fewer gap junctions |
|
|
Term
| Do electrical signals quicken or slow down in the AV node? |
|
Definition
|
|
Term
| Why is it beneficial that signals in the AV node are slowed down? |
|
Definition
| It allows ventricles time to fill with blood before they begin to contract |
|
|
Term
| Signals reach where in the heart first, before they reach the rest of the myocardium? |
|
Definition
|
|
Term
| Ventricle systole begins where? |
|
Definition
| At the apex, then travels upwards |
|
|
Term
| Ventricular cardiocytes are arranged in what formation? |
|
Definition
| Spiral - so ventricles twist slightly as they contract |
|
|
Term
| Why do the ventricles twist slightly as they contract? |
|
Definition
| The ventricular cardiocytes are arranged in a spiral formation |
|
|
Term
| What is the difference between the membrane potential of cardiocytes and that of the SA node? |
|
Definition
| Cardiocytes have a stable resting potential |
|
|
Term
| Stimulus open what type of gates in cardiocytes? |
|
Definition
| Voltage-regulated sodium gates - Na+ inflow - depolarisation of cell to threshold |
|
|
Term
| Cardiocytes contract as long as the ion potential is in what? |
|
Definition
|
|
Term
| Is the plateau in potential more pronounced in ventricular or atrial cardiocytes? |
|
Definition
|
|
Term
| What happens at the end of the plateau of the membrane potential of cardiocytes? |
|
Definition
Ca2+ channels close and K+ channels open
K+ diffuses rapidly - Ca2+ back into ECF - membrane voltage drops rapidly muscle tension declines |
|
|
