Anatomical Basis Of The Cardiac Cycle Flashcards
Contraction =
Systole
Relaxation =
Diastole
Why does contraction takes place?
Due to the intrinsic conducting system
What is the conducting system made up of?
Specialised cardiac muscle cells
What is the extrinsic conducting system controlled by?
Nerves
What does the extrinsic conducting system control?
Heart rate, contraction and force
What two nodal tissues does the intrinsic conducting system consist of?
Sinoatrial node and the atrioventricular node
Describe the SA node
The pacemaker of the heart, is a cluster of cells situated on the posterior wall of the right atrium
What sets the rhythm of the heartbeat?
Automatic depolarisation
Where is the SA node found?
Close to the superior vena cava
How is the SA node modified?
By autonomic input
What is autonomic input?
Sympathetic increasing heart rate and parasympathetic decreasing heart rate
Describe a pacemaker
A group of cells or a body part (such as the sinus node of the heart) that serves to establish and maintain a rhythmic activity
What does bifurcate mean?
To cause a divide into branches or parts
Where do the impulses pass along after the AV node?
Through the insulating Annulus fibrosus
What is the annulus fibrosus?
Cardiac/fibrous skeleton
After the annulus fibrosus where do the impulses go?
Down the interventricular septum of the heart where it bifurcates into the right and left bundle branches
What do the right and left bundle branches comprise?
Narrow slow-conducting fibres (modified cardiac muscle cells) which terminate
Where do the cardiac muscle cells terminate?
At an extensive network of fibres in the subendocardium called purkinje fibres
Describe purkinje fibres
Fast conducting fibres that spread the impulse throughout the ventricular myocardium
What do the purkinje fibres cause when spreading an impulse through the ventricular myocardium?
Cause an upward wave of contraction
Where is the moderator band found?
In the right ventricle
What does the moderator band provide?
A shortcut for electrical impulses of the right bundle branch from the interventricular septum to the anterior papillary muscle of the right ventricle
