Lecture 11 - Excitation-contraction coupling

Question 1

chronotropy

Answer 1

pertaining to heart rate
SA node

Question 2

dromotropy

Answer 2

pertaining to conduction
AV node + Purkinje fibers
myocardium

Question 3

bathmotropy

Answer 3

pertaining to cell excitability
rhythms outside of SAN

Question 4

Inotropy

Answer 4

pertains to contractility
myocardium (specifically ventricular)

Question 5

lusitropy

Answer 5

pertain to relaxation

Question 6

during contraction _____ moves closer to each other

Answer 6

Z-disc

Question 7

describe excitation-contraction coupling in 7 steps

Answer 7

1. Na+ entry
2. depolarization
3. calcium entry across channels
4. release of calcium from the sarcoplasmic reticulum
5. calcium binds to troponin
6. tropomyosin moves
7. actin-myosin interaction causes cell contraction

Question 8

describe myocardial cell contraction in 10 steps

Answer 8

1. cell depolarizes
2. voltage change open long-lasting calcium channels
3. extracellular calcium enters cell
4. triggered calcium release from the sarcoplasmic reticulum via release channel
5. increased systolic calcium
6. calcium binds troponin and inhibition is removed
7. ATP is hydrolyzed
8. actin and myosin cross-bridge cycle
9. sarcomere tenses and shortens leading to contraction
10. calcium leaves cell and myocyte relaxes

Question 9

what is the primary regulator of contraction

Answer 9

calcium availability

Question 10

the inherent state of the actin-myosin interaction is called

Answer 10

contractility or inotropy

Question 11

T/F: a positive inotrope or related stimulus increases the strength of myocardial contraction

Answer 11

TRUE

Question 12

T/F: the sympathetic nervous system is activated by negative inotropy

Answer 12

FALSE

Question 13

T/F: the parasympathetic nervous system is activated by negative inotropy

Answer 13

TRUE

Question 14

what are examples of positive inotropic drugs

Answer 14

catecholamines, pimobendan

Question 15

what are examples of negative inotropic drugs

Answer 15

CCB, Beta-blockers, anesthetics

Question 16

summarize myocardial relaxation

Answer 16

• calcium removal or reuptake
• sodium-calcium exchanger
• two-way

Question 17

what is SERCA

Answer 17

Sarcoplasmic reticulum ATPase
- pumps calcium into the SR
- phospholamban inhibits

Question 18

summarize myocardial relaxation

Answer 18

1. beta stimulation activates cAMP
2. cAMP phosphorylates phospholamban
3. SERCA activated
4. improves calcium uptake and relaxation

Question 19

what type of cell-to-cell junction is more prone to disease

Answer 19

desmosomes

Question 20

what desmosomal protein has been found to decrease the transmittance of signals in diseases like boxer cardiomyopathy

Answer 20

striatin

Question 21

what does the heart require energy for

Answer 21

1. electrical activity
2. contraction
3. relaxation
4. cell maintenance

Question 22

what provides the most energy for the heart

Answer 22

beta-oxidation of fatty acids

Question 23

mitochondrial myopathies occur when

Answer 23

metabolic pathways of energy production are abnormal or damaged

Question 24

what determines myocardial oxygen consumption

Answer 24

1. heart rate
2. contractility
3. systolic wall tension