quiz 1 chapter 9

Question 1

what are the similarities between cardiac and smooth muscle?

Answer 1

1. striated appearance
2. both rely on fast sodium channels to initiate action potential for contraction
3. contractions based on actin and myosin
4. cardiac is like type I fibers

Question 2

how is cardiac muscle different from skeletal muscle?

Answer 2

1. cardiac muscle is involuntary
2. cardiac has higher nuclei because it requires more ATP
3. cardiac is connected by intercalated discs
4. cardiac has 2 synctia
5. cardiac muscle has slow Ca channels
6. slow ca channels cause a plateau in action potential
7. contraction is 10 times longer in cardiac

Question 3

Intercalated discs fuse together to form _______ ________ allowing for rapid diffusion of ions; this allows action potential to travel from 1 cardiac monocyte to the next

Answer 3

Gap Junctions

Question 4

resting potential is between ____ and ___ mV and threshold is reached at ______mV; this continues to between ____ and ____ mV at the peak of action potential

Answer 4

• 80 to -90
• 70

+20 to +30

Question 5

the _______ is the reason why cardiac contraction is significantly longer than in skeletal muscle.

Answer 5

Plateau

Question 6

briefly describe the phases of action potential, from phase 0 to phase 4.

Answer 6

phase 0- sodium channels= rapid depolarization

phase 1- at peak, repolarization begins because sodium channels close and potassium leaves

phase 2-plateau because slow ca+ channels open and potassium decreases

phase 3- slow Ca+ channels close, potassium increases= rapid repolarization

phase 4- resting membrane potential

Question 7

the interval during the AP when a “normal”

electrical impulse cannot re-excite the already excited area is called ______ ______ _______

Answer 7

Absolute Refractory Period (ARP)

Question 8

a stronger than normal stimulus can

re-excite the area. this is called _______ _______ __________; this causes a premature contraction

Answer 8

Relative Refractory Period (RRP)

Question 9

Unlike skeletal myofibrils, cardiac myocytes
rely on extracellular_____ for contraction to occur.
-how does it get in to the sacroplasm?

Answer 9

Ca2+

• enters the sacroplasm through voltage gated calcium channels

Question 10

influx of Ca2+ activates ________` _______on the SR membrane which triggers the SR to release its Ca2

Answer 10

ryanodine receptors

Question 11

the Phonocardiogram is used to hear when heart valves _____ ; what are the 3 stages

Answer 11

close

1. A-V valves close. Vibration is low pitched and long lasting
2. aortic and pulmonary valves snap shut. the vibration is shorter
3. Not a sound often heard

Question 12

____ is the depolarization of the atria

Answer 12

P wave

Question 13

_______ is the depolarization of the ventricles

Answer 13

QRS complex

Question 14

________ is the repolarization of ventricles occurs before ventricular contraction is complete

Answer 14

T wave

Question 15

Emptying of Ventricles during Systole has 3

parts, what are they?

Answer 15

1. Period of Isovolumic(Isovolumetric) Contraction;tension has increased without a shortening of the cardiac fibers
2. Period of Ejection
   a) Rapid Ejection-70%
   b) Slow Ejection- 30%

3.Period of Isovolumic (Isovolumetric) Relaxation- ventricular relaxation

Question 16

Filling of Ventricles happens during _______.

first 1/3= rapid filling
second 1/3= blood rushes through atria and in to the ventricles
last 1/3= atria contract; last 20% of blood

Answer 16

Diastole

Question 17

___ wave caused by atrial contraction so occurs after the P wave on the ECG.

Answer 17

A

Question 18

_____ wave caused by beginning of ventricular contraction

Answer 18

C

Question 19

____ wave occurs at the end of ventricular

contraction while the A -V valves are still closed as more blood is returning to the atria from the great veins.

Answer 19

V

Question 20

The atria are called _____ _____ because the contraction of these upper chambers
only provides the last 20% to fill the ventricles.

Answer 20

primer pumps

Question 21

End-Diastolic Volume (EDV)- there is about _____mL of blood in each ventricle.

Answer 21

120

Question 22

End-Systolic Volume (ESV)— the volume of blood remaining in the ventricles after contraction (systole) is about _____ml.

Answer 22

50

Question 23

Stroke Volume (SV)—the volume of blood ejected from the ventricles during systole is
̴about \_\_\_\_ml.

Answer 23

70

Question 24

Ejection Fraction (EF)—the fraction (%) of the EDV that is ejected during systole. At rest, normally EF is about _____of EDV

Answer 24

60%

Question 25

in cardiac muscle the tension (ventricular pressure) on the muscle fibers at the onset of contraction is called _________.

Answer 25

Preload

Question 26

Cardiac muscle is highly_______ and has a high number of mitochondria

*FA (80%)+ (10%) to make ATP

Answer 26

oxidative

Question 27

maximum efficiency of the heart is considered to be _____%

20-25% of chemical energy (ATP) is converted into work energy and 75-80% to heat

Answer 27

25%

Question 28

In heart failure, work efficiency falls below

_____%

Answer 28

10%

Question 29

Intrinsic Regulation/Frank -Starling Mechanism

-the amount of blood flowing into the right atrium from the great veins is called _______

Answer 29

venous return