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a. Generally speaking, only nerves can stimulate __ and __
i. The exception is the __
- 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= __
What is the relaxation phase?
- chambers are not excited
- during relaxation, the chambers are fillign
- 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
- 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
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
- 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
ii. They are __together, but not __together
- SEMILUNAR VALVE
- 1) Diastole
- 2) Diastole
- 3) open
- 4) closed
- 5) Systole
- 6) Open (1stsound)
- 7) Closed
- 8) diastole
- 9) Systole
- 10) Closed
- 11) open
- 12) diastole
- 13) open
- 14) closed