Myocyte and calcium flows

Myocyte contraction and calcium ion flow

The graphic shows the Ca2+ transport pathways in a myocyte. When an action potential arrives, voltage-dependent Ca2+channels open upon depolarization (1).

Myocyte and calcium flows

Myocyte contraction and calcium ion flow

The local rise in intracellular Ca2+ levels triggers Ca2+ release channels on the sarcoplasmic reticulum to release Ca2+, further increasing the free calcium ion concentration (2).

Myocyte and calcium flows

Myocyte contraction and calcium ion flow

Some of the calcium ions are extruded from the myocyte in exchange for sodium ions (3).

Myocyte and calcium flows

Myocyte contraction and calcium ion flow

The graphic shows the Ca2+ transport pathways in a myocyte. When an action potential arrives, voltage-dependent Ca2+channels open upon depolarization (1). The local rise in intracellular Ca2+ levels triggers Ca2+ release channels on the sarcoplasmic reticulum to release Ca2+, further increasing the free calcium ion concentration (2). Some of the calcium ions are extruded from the myocyte in exchange for sodium ions (3). Other calcium ions bind to intracellular buffers such as

mitochondria and calmodulin (4). Ca2+also binds to troponin in the contractile elements, resulting in contraction of the myocyte (5). At the end of the action potential, the Ca2+ levels in the cell are restored by various mechanisms: passive outflow via the Na+/ Ca2+ exchanger (3) and re-uptake in the sarcoplasmic reticulum via ATP-driven Ca2+ pumps (6). The Na+/K+-ATPase pump in the cell membrane restores the resting membrane potential, preparing it for a new depolarization.

1

Myocardial muscles differ from normal muscles because they

2

Actions of angiotensin II include:

3

Following acute haemorrhage, the following compensatory mechanism occurs:

4

Contraction of the myocardium depends on