18.4-18.6 Cardiac Muscle

Question 1

Striated, short, branched, fat, and interconnected
Cardiac muscle cells

Answer 1

Cardiomyocytes

Question 2

Contain numerous large mitochondria, which resist fatigue
One central nucleus
Rest of volume composed of sarcomeres

Answer 2

Cardiac muscle cells

Question 3

Wider, but less numerous in cardiac muscle cells

Answer 3

T tubules

Question 4

Simpler in cardiac muscle rather than in skeletal muscle

Answer 4

Sarcoplasmic reticulum

Question 5

Connecting junctions between cardiac cells

Answer 5

Intercalated discs

Question 6

Allow ions to pass from cell to cell
Electrically couple adjacent cells
Allows heart to be a functional syncytium

Answer 6

Gap junctions

Question 7

Holds cell together
Prevents cells from separating
Velcrow like

Answer 7

Desmosomes

Question 8

1. Muscle contraction is preceded by depolarizing action potential
2. Depolarization wave travels down T tubules
3. Excitation-contraction coupling occurs

Answer 8

Similarities between skeletal and cardiac muscles

Question 9

Cardiac muscle type; Responsible for contraction
Bulk of heart and are responsible for pumping action

Answer 9

Contractile cells

Question 10

Cardiac muscle type; Autorhythmic cells
Non Contractile cells that spontaneously depolarize and initiate depolarization of entire heart
No nervous system support (self-excitable)

Answer 10

Pacemaker cells

Question 11

Network of pacemaker cells; Initiate and distribute impulses to coordinate depolarization and contraction of heart
Electrical events precede mechanical events
5 parts

Answer 11

Intrinsic cardiac conduction system

Question 12

“Pacemaker” of the heart

Answer 12

Sinoatrial node (SA node)

Question 13

Rhythm of the SA node and determines heart rate

Answer 13

Sinus rhythm

Question 14

Device that can detect electrical currents generated by the heart

Answer 14

Electrocardiograph

Question 15

A graphic recording of electrical activity of the heart

Answer 15

EKG

Question 16

Depolarization of SA node and atria
First wave

Answer 16

P wave

Question 17

Ventricular depolarization and atrial repolarization

Answer 17

QRS Complex

Question 18

Ventricular repolarization

Answer 18

T wave

Question 19

Beginning of atrial excitation to beginning of ventricular excitation

Answer 19

P-R interval

Question 20

Entire ventricular myocardium depolarized
Flat line on EKG

Answer 20

S-T segment

Question 21

Beginning of ventricular depolarization through ventricular repolarization

Answer 21

Q-T interval

Question 22

Depolarization and repolarization

Answer 22

Electrical events

Question 23

Contraction of heart

Answer 23

Systole

Question 24

Relaxation of heart

Answer 24

Diastole

Question 25

Cardiomyocytes in an area contract as a unit

Answer 25

Functional syncytium

Question 26

Does cardiac muscle use extracellular Ca2+?

Answer 26

Yes

Question 27

True or false. Tetanic (sustained) contractions cannot occur in cardiac muscles

Answer 27

True

Question 28

True or false. Cardiac muscle relies more on oxygen than skeletal muscle?

Answer 28

True - More mitochondria

Question 29

Unstable resting membrane potential in cardiac muscle cells Never a flat line; upward trend from trough to threshold Na+ open, K+ close

Answer 29

Pacemaker potential

Question 30

Pacemaker potential Depolarization Repolarization

Answer 30

Cardiac AP

Question 31

Action potential begins when pacemaker potential reaches threhold; Ca2+ influx through channels

Answer 31

Depolarization

Question 32

Ca2+ channels inactivating and K+ channels opening K+ efflux, brining membrane potential back to original voltage

Answer 32

Repolarization

Question 33

Where impulses pause in conduction system Part 2

Answer 33

AV node

Question 34

Connects atria to ventricles

Answer 34

AV bundle

Question 35

Irregular heart rhythms

Answer 35

Arrhythmias (Murmurs)

Question 36

Rapid, irregular heart beat Heart useless for pumping blood

Answer 36

Fibrillation

Question 37

Defective AV node AP "blocked"

Answer 37

Heart block

Question 38

Increase rate and force of heartbeat "Accelerator" Fight or flight

Answer 38

Sympathetic nervous system

Question 39

Slows heart rate down

Answer 39

Parasympathetic nervous system

Question 40

Depolarization due to Na+ influx through fast voltage-gated Na+ channels

Answer 40

Depolarization of contractile muscle cells

Question 41

Due to Ca2+ influx through slow Ca2+ channels Keeps cell depolarized because K+ channels are closed

Answer 41

Plateau phase of contractile muscle cells

Question 42

Due to Ca2+ inactivating

Answer 42

Repolarization of contractile muscle cells

Question 43

True or false. Are action potentials and contraction longer in cardiac muscle?

Answer 43

True

Question 44

Longer contraction ensures efficient blood ______

Answer 44

Ejection

Question 45

First stage of cardiac cycle; 80% of blood passively flows from atria through open AV valves into ventricles AV = open SL = closed Fills ventricles with blood

Answer 45

Ventricular filling

Question 46

Second stage of cardiac cycle; Atria relax and ventricles contract; Rising ventricular pressure causes closing of AV valves Blood flows into pulmonary trunk and aorta AV = closed SL = open

Answer 46

Ventricular systole

Question 47

Following T wave; Ventricles relax and atria fill with blood AV = open SL = closed

Answer 47

Early diastole (Isovolumetric relaxation)

Question 48

Volume of blood in each ventricle at end of each ventricular diastole

Answer 48

End diastolic volume (EDV)

Question 49

Volume of blood remaining in each ventricle after systole

Answer 49

End systolic volume (ESV)

Question 50

*cardiac cycle page*