Card Set Information
BIO 220 Test Two
Generally speaking, only nerves can stimulate __ and __
The exception is the __
blood vessels and glands
The cells have been modified to do what neurons doa. Can excite, not only themselves, but the rest of the muscle mass I the heart
What can the atrial mass do?
can become excited independent of the ventricular mass, and vice versa
Components of the conduction system
SA node (upper right hand corner of atrium)
Continuous with group of fibers called interatrial fibers, which run through wall of right atrium
Go to AV node, causing atrium to contract
During contraction, the excitement runs down the Bundles of His and up the Purkinje fibers, causing the ventricles to contract
What is the conduction system JUST?
The conduction system is JUST the movement of the excitation from one component to the next and over the muscle mass
Its exciting the muscle mass; moving the excitation and generating a nerve impulse to excite the atria and then the ventricles
Once they are excited, they contract
When chambers are relaxed, they are not excited=
What is the relaxation phase?
chambers are not excited
during relaxation, the chambers are fillign
When the chambers are excited, they are in the contraction phase, called systole
They are emptying when they are contracting
Explain right and left atrial contraction.
Right and left atrium contract together, but independent of right and left ventricle
Atrial mass contracts as one; likewise, the ventricular mass contracts as one
What's causing the contraction?
the conduction system
Contraction cycle steps
There is a period of time when both sets of chambers are filling in the contraction cycle
Time it takes for SA node to get excited
As excitation passes from SA node
AV node, the whole atrial mass will contract
When does most ventricular filling occur?
70% of ventricular filling occurs when both sets of chambers are at diastole (relaxed
True or False:
Chambers frequently get devoid of blood
Chambers never get devoid of blood, but most occurs when both sets are relaxed; the other 30% occurs when blood is squeezed out of atria during contraction
At point where atria relax and ventricles contract, what occurs?
the AV valves close
VENTRICLES CONTRACT= __ CLOSED, __ARE OPEN
THE CLOSING OF THE __ IS THE FIRST HEART SOUND
Excitation passes over ventricles and they __
__ valves close and the __valves open
THE CLOSING OF THE __IS THE SECOND HEART SOUND
They are __together, but not __together
6) Open (1stsound)