Heart As A Pump Flashcards
Pulmonary circuit (pumps blood to the lungs)
Right Atrium & Ventricle side
Systemic circuit (pumps blood to the body)
Left Atrium and Ventricle side
Separates the 2 chambers of the heart
Fibrous Skeleton
What are the 2 functions of the fibrous skeleton?
1) anchor the heart down
2) electrically insulates
Why is it important for the atria and ventricles to be covered by an insulating fibrous skeleton?
Makes it so the atria and ventricles don’t contract at the same time. This is only possible if there is something to insulate the 2 wave contractions
What are the 3 major types of cardiac mm?
1) atria mm
2) ventricle mm
3) specialized excitatory and conductive mm fibers
Characteristics of Cardia mm
- striated (due to actin and myosin filaments)
- mm fibers are shorter and branch more
Electrical impulses propagate freely between cells in every direction, so that the myocardium functions as a single contractile unit
Synctium
3 junctions that are special for cardiac mm and allow it to act as a synctium
- intercalated discs
- gap junctions
- desmosome junctions
It separates individual cardiac mm cells from one another. At each disc, they form “communicating” gap junctions
Intercalated discs
What is the function of gap junctions?
Electrical junctions: they allow for rapid electrical diffusion of ions
Function of desmosome
Mechanical Junctions : resist mechanical stress because they are strongly adhesive
These are localized patches that hold 2 cells together.
Desmosomes
These are attached to intermediate filaments of keratin in the cytoplasm
Desmosomes
It is the mechanism by which an action potential of any kind causes the myofibrils of a mm to contract
Excitation-contraction Coupling
Does cardiac mm use t-tubules or caveolae?
T-tubules
Once there is full Ca++ buildup in the cell, does the Ca++ interact with calmodulin or troponin?
Troponin
What channels are prominent in the AP of Cardiac mm?
- fast opening sodium channels (for spike)
- slow calcium channels (for plateau)
Aside from presence of the slow opening of Ca++ channels, what is another reason that plateau is possible?
Immediately after the onset of AP the permeability of the cardiac mm membrane.
Decreases a lot for K+
Specialized fibers of the heart aid the conduction of the signal, not contraction.
Purkinje fibers
Velocity of the AP varies in the Atrium and Ventricles but this aid to conduct the speed of the potential thru the heart.
Purkinjie Fibers
The interval of time during which a normal cardiac impulse cannot re-excite an already excited mm
Refractory Period
Immediately follows the AP and is at the end of the refractory period
Relative Refractory Period
It is a period during which the mm os even more difficult to excite and only very very strong excitatory signals will effect it
Relative Refractory Period
Very very strong signals which can affect the relative refractory period cause what?
Early “premature” contraction
The beginning of one heart beat to the beginning of the rest
The cardiac cycle
Phase of relaxation
Diastole
Phase of contraction
Systole
How are spontaneous mm AP generated in cardiac mm?
By the Sinoatrial node
Another reason why the atria contract together before the ventricles contract together
SA Node (Sinus node/ sinoatrial node)
Why are the atrias considered primer pumps?
Great veins dump all the blood in the atria. About 80% of the blood flows directly thru the atria into the ventricles before it even begins contracting
Pressure changes in the atria are denoted by which waves?
A-wave
C-wave
V-wave
A-wave is caused by?
Atrial contraction
C-wave is caused by?
Ventricular contraction and bulging of the valve
V-wave os caused by?
Build up of blood returning to atrial from veins
Why are the ventricles considered to be the pumps?
The atrias are not absolutely not necessary since blood flows right from the atria into the vetricles
The filling of ventricles occurs during….?
Diastole
The filling of the ventricular pumps occurs in 3 stages…
- period of rapid filling
- slower filling
- atria contracts (atrial systole)
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