Cardio Flashcards
Hearts physio anatomy and pathology
Name the 2 important types of cardiac cells and there function.
Electrical cells- specialized cells which conduct electricity. They start and transmit electrical activity in the heart.
Mechanical cells- these cells contract in response to stimuli from the electrical cells.
There are 2 types of cardiac MUSCLE cells, name them
Contractile cells ( = working myocardium) and Auto-rhythmic cells (Conducting system)
Function of Contractile cells
Produce contractions and generate force.
What activates contractile cells?
Change in the membrane potential (just like skeletal muscle)
Which cardiac muscle cell makes up 99% of the heart muscle?
Contractile cells
State 2 functions of the Auto-rhythmic cells
- Initiate and distribute electrical activity
- Controls and coordinates the heart beat but does NOT contribute to contractile force.
What are cardiac muscles connected by?
Gap junctions and intercalated disc
Function of gap junctions
Allows for the electrical impulse to be transferred from one side to the other
Select the best descripton of cardiac muscle cells:
a. not striated, short, unbranched, basal nucleus
b. striated, branched, long, central nucleus
c. short, branched, striated with central nucleus
c
Role of desmosomes
Keeps the cardiac cells together ( a disruption of the desmosomes can be fatal)
What is needed for calcium to be pumped out of the cell
ATP; therefore it is an ATP dependent process
Why is the depolarization phase in cardiac muscles prolonged?
The inflow of calcium results in a prolonged depolarization phase because enough k+ will not leave until all the Ca2+ ions have entered to initiate repolarization.
In reference to the shape of the graph what occurs due to the prolonged depolarization?
A plateau is formed
What accounts for the slight fall of the plateau?
The plateau falls slightly because there is some leakage of K+ ions during the prolonged depolarization phase but most of the K+ channels remain closed.
What is the refractory period
Second stimulus will not evoke a response after the first stimulus no matter how strong
State the difference in the refractory periods of skeletal and cardiac muscle. Account for this difference.
The refractory period is short in skeletal muscles but very long in cardiac muscles because depolarization is prolonged which also results in a wider graph for cardiac muscles when compared to skeletal muscles
Cardiac muscles CANNOT sum action potentials or contractions and cannot be tetanized true or false?
True
At what membrane potential does Na+ channels begin to close in a pacemaker cell?
-40mV
Which ion enters the cell after the threshold has been reached
Captain Ca2+
What occurs after repolarization in a pacemaker cell
Slow depolarization; there is no break
Which node recovers he fastest from refractory period?
Sinoatrial Node
Where does the signal from the SA node travel to?
Atrial muscle
Which node as the slowest conduction and what is its end location
Atrioventricular node; Ventricle
Function of the Atrioventricular Bundle branches
Delays action potential from reaching the ventricles, allowing the atria to empty blood into the ventricles before they contract.
Which fibre carries signals throughout the ventricles allowing them to contract?
Purkinje fibres
Electrical activity is precisely controlled by:
a. Making sure the atria empty into the ventricles before ventricular contraction
b. Preventing simultaneous contraction of atria and ventricle
c. Ensuring ventricles are relaxed while atria contract
d. All of the above
d. All of the above
How does the fibrous skeleton facilitate order
It electrically separates atria from ventricles which prevents electrical activity from spreading from atrial muscle to ventricular muscle
Why is the SA node known as the pacemaker of the heart?
Because it has the shortest cycle of depolarization and repolarization so it fires quickly and creates the heart rate. Once it fires the impulse travels through the rest of the conducting system rendering the others unable to initiate impulses.
This is another way to facilitate order
What is the action potential per minute of the SA node, AV node and purkinje fibres respectively
70-80
40-60
20-40
List 2 reasons for the slowing of conduction flow at the AV node
- Diameter of cells at AV node is small.
- Few gap junctions
What is Vagal tone
When vagal influences dominate over sympathetic influences at rest
In parasympathetic stimulation AcH binds to muscarinic receptors on nodal membranes resulting in a conductivity increase and decrease in which ions?
Increase conductivity of K+
Decrease conductivity of Ca2+
