Physiology 2 - Physiological Processes of the Heart 1 Flashcards
At -90mV (resting potential), which way does potassium flow - in or out of the cell?
Out
At -90mV, which way does sodium flow in or out of the cell?
In
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?
SAN
Which nervous stimulations increase and decrease the rate of SAN depolarisation?
Sympathetic increases
Parasympathetic decreases
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?
Ca2+
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?
AVN
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?
Current
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?
Vagus nerve
