Heart - Conduction System - Stock Image

Signature Collection
  • S
  • M
  • L
  • XL
  • XXL
  • XXXL
Standard license only
You need XX iStock Credits to download this photo
You need 1 iStock Credit to download this photo
Already have credits or subscription? Sign in

You've got XX/XX downloads / remaining.

Having troubles with the download? Start downloading

You can return to re-download this image at any time before your subscription term ends.

You have 0 subscription downloads left

It looks like you're out of subscription downloads for the but you've still got XX iStock credits in your account.
It looks like you're out of subscription downloads for the .
You can still download this image with iStock credits.

Unable to download file

We're unable to process your download at this time. Please try again later. If the problem persists, contact us.
Description
1. The cardiac cycle begins at the SA (sinoatrial) node located in the sulcus terminalis between the superior vena cava and the right atrium.
2. From this pacemaker, a wave of negativity (excitation) spreads over both atria and initiates atrial contraction, thereby increasing atrial blood pressure.
3. When atrial pressure exceeds ventricular pressure, both atrioventricular (AV) valves open and blood rushes into both ventricles. Soon the impulse reaches the AV node and is passed along the AV bundle (shown in green) to the two ventricles, causing them to contract.
4. When ventricular pressure exceeds atrial pressure, the AV valves close, and this can be heard with a stethoscope as the first of the two heart sounds of the heartbeat.
5. Continued ventricular contraction forces the pulmonary and aortic valves to open, and blood rushes simultaneously into the pulmonary artery and the aorta.
6. When the pressure in these vessels exceeds ventricular pressure, blood tends to rush back into the ventricles, but it gets trapped in the sinuses behind the semilunar cusps. This closes both the pulmonary and aortic valves, resulting in the second of the two heart sounds.
Not a member?Join