Physiology 2 - Physiological Processes of the Heart 1 Flashcards Preview

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Flashcards in Physiology 2 - Physiological Processes of the Heart 1 Deck (19)
1

At -90mV (resting potential), which way does potassium flow - in or out of the cell?

Out

2

At -90mV, which way does sodium flow in or out of the cell?

In

3

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

4

What is regarded as the intrinsic pacemaker?

SAN

5

Which nervous stimulations increase and decrease the rate of SAN depolarisation?

Sympathetic increases
Parasympathetic decreases

6

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

7

What ions maintain this plateau of ventricular muscle contraction?

Ca2+

8

See page 4

See page 4!

9

When do funny channels open?

When the membrane potential decreases and becomes negative

10

Where does the electrical signal take the longest passing through?

AVN

11

Where are the 10 electrodes of the 12 lead ECG positioned?

6 on the chest
4 on the limbs - 1 is an earth

12

What do the limb leads measure?

The sum of electrical activity of the heart and the direction that electrical activity is moving in

13

What is the size of the electrical signals from the heart determined by?

Current
Direction of signal

14

Observed signal = ...

E x cos(theta)
(E = electrical event & theta = angle between event and ECG lead)

15

Which nerve parasympathetically stimulates the SAN & AVN?

Vagus nerve

16

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

17

What does Q-T interval represent?

The time it takes a ventricular muscle fibre to depolarise and repolarise

18

What is the resting potential of a ventricular muscle fibre membrane?

-90mV

19

What is the predominant autonomic tone?

Parasympathetic

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