Cellular and Molecular Events in the CVS Flashcards Preview

ESA 2- Cardiovascular System > Cellular and Molecular Events in the CVS > Flashcards

Flashcards in Cellular and Molecular Events in the CVS Deck (79)
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1

Does Na/K-ATPase set the RMP?

No

2

What happens to RMP if the sodium pump is blocked?

It only changes by 5-7mV

3

What is the RMP set by?

Due to K permeability of the cell membrane at rest

4

What state are K channels in at rest?

Open

5

What channels do cardiac myocytes possess?

Inward rectifier K channels

6

How permeable to other ions are cardiac myocytes?

Only a small permeability

7

What can be said of cardiac myocytes?

They are electrically active

8

What is meant by cardiac myocytes being electrically active?

They fire action potentials

9

What do action potentials trigger?

An increase in cytosolic [Ca]

10

What is a rise in calcium required for?

To allow actin and myosin interaction

11

What does actin and myosin interaction generate?

Tension (contraction)

12

How do action potentials in heart cells differ from those in nerves and skeletal muscle?

They are much longer

13

What are the stages in the ventricular (cardiac) action potential?

Opening of voltage gated Na channels causes a rapid depolarisation, from RMP to +30mV as Na enters the cell 
Transient outward K current causes a return towards a lower membrane potential, reaching +10mV
Membrane potential lowers to about -10mV because of opening of voltage gated Ca channels
Ca channels inactivate and voltage gated K channels open, causing return to RMP

14

What is rapid depolarisation due to opening of Na channels called?

The upstroke

15

What might happen after the initial depolarisation that contributes to a lower membrane potential?

Might get some reversal of Na/Ca transport

16

What may also happen when the voltage gated Ca channels are open?

May be some K channels open, allowing efflux of K

17

What do cardiac myocytes possess lots of different types of?

K channels

18

Draw the ventricular action potential

Answer…

19

Why do cardiac myocytes have lots of different types of K channels?

Because they each behave in a different way, and contribute differently to the electrical properties of the cell

20

What is the SA nodes set membrane potential?

Doesn’t really have one

21

Why does the SA node not really have a set membrane potential?

Because the whole time, there is a long, slow depolarisation

22

What is the SA nodes long, slow depolarisation called?

The pacemaker potential

23

What causes the pacemaker potential?

Influx of Na

24

What happens as Na channels open?

Na ions go in to cause a little bit of depolarisation, but become inactivated in accommodation due to long depolarisation

25

What is the result of the Na channels becoming inactivated by the long depolarisation?

The upstroke cannot rely on Na channels, it also needs voltage gated Ca channels

26

What is the initial slope to threshold of the SA node action potential known as?

The funny current

27

When is the SA node action potential activated?

When it reaches membrane potentials that are more negative than -50mV

28

What is the result on the SA node action potential when the membrane potential reaches a more negative level?

The more it activates

29

What channels does the funny current use?

HCN

30

How are HCN channels activated?

Hyperpolarisation