Flashcards in Physiology 2 - Physiological Processes of the Heart 1 Deck (19)
At -90mV (resting potential), which way does potassium flow - in or out of the cell?
At -90mV, which way does sodium flow in or out of the cell?
What is meant by a functional syncytium?
Electrical coupling between all cells in the atria and (separately) all cells in the ventricles, allowing them to contact in synchrony
What is regarded as the intrinsic pacemaker?
Which nervous stimulations increase and decrease the rate of SAN depolarisation?
What is the result of the ventricular muscle fibre potential being held in positive figures for a while?
It is in a refractory state and therefore can't fire again until it returns to resting membrane potential
What ions maintain this plateau of ventricular muscle contraction?
See page 4
See page 4!
When do funny channels open?
When the membrane potential decreases and becomes negative
Where does the electrical signal take the longest passing through?
Where are the 10 electrodes of the 12 lead ECG positioned?
6 on the chest
4 on the limbs - 1 is an earth
What do the limb leads measure?
The sum of electrical activity of the heart and the direction that electrical activity is moving in
What is the size of the electrical signals from the heart determined by?
Direction of signal
Observed signal = ...
E x cos(theta)
(E = electrical event & theta = angle between event and ECG lead)
Which nerve parasympathetically stimulates the SAN & AVN?
In an electrocardiogram (such as the one shown on the corresponding lecture), what does the P-R interval represent?
The time it takes for an electrical signal to pass from the SAN to the ventricles
What does Q-T interval represent?
The time it takes a ventricular muscle fibre to depolarise and repolarise
What is the resting potential of a ventricular muscle fibre membrane?