a.Generally speaking, only nerves can stimulate __ and __ i.The exception is the __ 1.why?
blood vessels and glands
cardiac muscle
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
i.SA node (upper right hand corner of atrium)
ii.Continuous with group of fibers called interatrial fibers, which run through wall of right atrium
iii.Go to AV node, causing atrium to contract
iv.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?
a.The conduction system is JUST the movement of the excitation from one component to the next and over the muscle mass
i.Its exciting the muscle mass; moving the excitation and generating a nerve impulse to excite the atria and then the ventricles
1.Once they are excited, they contract
a.When chambers are relaxed, they are not excited= __
diastole
What is the relaxation phase?
chambers are not excited
during relaxation, the chambers are fillign
Explain excitement.
a.When the chambers are excited, they are in the contraction phase, called systole
i.They are emptying when they are contracting
Explain right and left atrial contraction.
a.Right and left atrium contract together, but independent of right and left ventricle
i.Atrial mass contracts as one; likewise, the ventricular mass contracts as one
What's causing the contraction?
the conduction system
Contraction cycle steps
One
i.There is a period of time when both sets of chambers are filling in the contraction cycle
1.Time it takes for SA node to get excited
ii.As excitation passes from SA nodeà interatrial fibersà 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
False:
i.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
1.VENTRICLES CONTRACT= __ CLOSED, __ARE OPEN a.THE CLOSING OF THE __ IS THE FIRST HEART SOUND
AV VALVES
SEMILUNAR
AV VALVES
i.Excitation passes over ventricles and they __ 1.__ valves close and the __valves open a.THE CLOSING OF THE __IS THE SECOND HEART SOUND i.__ ii.They are __together, but not __together
