L16 Cardiac Muscle Properties

Question 1

What are the properties of cardiac muscle?

Answer 1

-Excitability
-Conductivity
-Contractility
-Rhythmicity

Question 2

Excitability means that cardiac muscle cells can ___________. This allows them to be synchronized by the _____ and contract as a _____.

Answer 2

respond to electrical signals
pacemaker cells
unit

Question 3

What are the phases of AP of ventricular muscle?

Answer 3

Phase 0 = Rapid depolarization
Phase 1 = 1st rapid repolarization
Phase 2 = A plateau
Phase 3 = 2nd rapid repolarization
Phase 4 = Complete repolarization

Question 4

The duration of contraction is ____ sec in atrial muscle and ___ sec in ventricular muscle.

Answer 4

0.2
0.3

Question 5

The AP provides the _____ that triggers the _______, and the mechanical response is the ______ of the muscle.

Answer 5

signal
contraction
output

Question 6

______ begins at the ___ of the plateau.
2nd rapid repolarization is completed at about the ____ of ____.

Answer 6

Diastole
end
middle
diastole

Question 7

Excitability changes during AP passes through 3 stages such as?

Answer 7

1. Absolute refractory period
2. Relative refractory period
3. Dangerous period ( supranormal period )

Question 8

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 ________.

Answer 8

lost
doesn’t
very long
systole

Question 9

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 ______.

Answer 9

partially
stronger
diastole
3rd
repolarization
heart rate
temperature

Question 10

Dangerous period is where the excitability of cardiac ms is ____ at the ____ of the AP, ___ stimuli can excite the muscle.

Answer 10

supranormal
end
weaker

Question 11

Conductivity means that cardiac ms are connected by _____ which allow ____ signals to travel quickly from cell to cell.

Answer 11

gap junctions
electrical

Question 12

Conductivity is the ability of cardiac ms fibers to conduct the ______ that are initiated in the _____.

Answer 12

cardiac impulses
SA node

Question 13

The parts of the His-Purkinje system include?

Answer 13

-His bundle ( start of the system )
-Right bundle branch
-Left bundle branch
-Purkinje fibers ( end of system )

Question 14

The slowest conduction velocity is _____ . This is bcs of?

Answer 14

AV-node

-has few no. of intercalated discs
-allow sufficient time for reaching ventricles before they contract

Question 15

The fastest conduction velocity is _____. This is bcs of?

Answer 15

Purkinje fibers

-to allow the 2 ventricles to contract at the same time simultaneously

Question 16

Contractility is the ability of the cardiac ms to convert _____ energy into _____ work.

Answer 16

chemical
mechanical

Question 17

Cardiac contractility is the ability of the heart muscle to ____ and pump blood. It is crucial in maintaining ______ blood circulation and supplying ____ to tissues.

Answer 17

contract
adequate
oxygen

Question 18

A functional syncytium is a ____ of contraction comprised of a network of __________ cardiac ms.

Answer 18

unit
electrically connected

Question 19

Excitation-contraction coupling in heart muscle is the mechanism by which _____ causes _____ of cardiac muscle to contract.

Answer 19

action potential
myofibril

Question 20

Depolarization of myocardial cell stimulate ____ of ____ channels in sarcolemma. They diffuse ____ gradient into cell through _______ and binds to _____ & stimulates contraction.

Answer 20

opening
Ca2+
down
T tubules
troponin

Question 21

Rhythmicity is the ability of cardiac ms to ____ in a ____ constant manner _____ nerve supply. They are ___ in origin and is initiated by ____.

Answer 21

contract
regular
without
myogenic
SA node