L16 Cardiac Muscle Properties Flashcards
What are the properties of cardiac muscle?
-Excitability
-Conductivity
-Contractility
-Rhythmicity
Excitability means that cardiac muscle cells can ___________. This allows them to be synchronized by the _____ and contract as a _____.
respond to electrical signals
pacemaker cells
unit
What are the phases of AP of ventricular muscle?
Phase 0 = Rapid depolarization
Phase 1 = 1st rapid repolarization
Phase 2 = A plateau
Phase 3 = 2nd rapid repolarization
Phase 4 = Complete repolarization
The duration of contraction is ____ sec in atrial muscle and ___ sec in ventricular muscle.
0.2
0.3
The AP provides the _____ that triggers the _______, and the mechanical response is the ______ of the muscle.
signal
contraction
output
______ begins at the ___ of the plateau.
2nd rapid repolarization is completed at about the ____ of ____.
Diastole
end
middle
diastole
Excitability changes during AP passes through 3 stages such as?
- Absolute refractory period
- Relative refractory period
- Dangerous period ( supranormal period )
ARP is where the excitability of cardiac muscle is completely ____ during this period, it _____ respond to 2nd stimulus. It is _____ and occupies the whole period of ________.
lost
doesn’t
very long
systole
RRP is where the excitability of cardiac muscle cells are ______ recovered during this period, ____ stimuli is required to excite the muscle cells. It occupies the time of_____. It corresponds to the ____ phase of _____. It can be affected by _____ and ______.
partially
stronger
diastole
3rd
repolarization
heart rate
temperature
Dangerous period is where the excitability of cardiac ms is ____ at the ____ of the AP, ___ stimuli can excite the muscle.
supranormal
end
weaker
Conductivity means that cardiac ms are connected by _____ which allow ____ signals to travel quickly from cell to cell.
gap junctions
electrical
Conductivity is the ability of cardiac ms fibers to conduct the ______ that are initiated in the _____.
cardiac impulses
SA node
The parts of the His-Purkinje system include?
-His bundle ( start of the system )
-Right bundle branch
-Left bundle branch
-Purkinje fibers ( end of system )
The slowest conduction velocity is _____ . This is bcs of?
AV-node
-has few no. of intercalated discs
-allow sufficient time for reaching ventricles before they contract
The fastest conduction velocity is _____. This is bcs of?
Purkinje fibers
-to allow the 2 ventricles to contract at the same time simultaneously
Contractility is the ability of the cardiac ms to convert _____ energy into _____ work.
chemical
mechanical
Cardiac contractility is the ability of the heart muscle to ____ and pump blood. It is crucial in maintaining ______ blood circulation and supplying ____ to tissues.
contract
adequate
oxygen
A functional syncytium is a ____ of contraction comprised of a network of __________ cardiac ms.
unit
electrically connected
Excitation-contraction coupling in heart muscle is the mechanism by which _____ causes _____ of cardiac muscle to contract.
action potential
myofibril
Depolarization of myocardial cell stimulate ____ of ____ channels in sarcolemma. They diffuse ____ gradient into cell through _______ and binds to _____ & stimulates contraction.
opening
Ca2+
down
T tubules
troponin
Rhythmicity is the ability of cardiac ms to ____ in a ____ constant manner _____ nerve supply. They are ___ in origin and is initiated by ____.
contract
regular
without
myogenic
SA node
