Regulation of heart activity

Question 1

What are long/short QT syndromes associated with in ventricular myocytes?

a) Dysfunctional depolarisation mechanism
b) Dysfunctional repolarisation mechanism
c) Dysfunctional diastolic mechanisms
d) Dysfunctional systolic mechanisms

Answer 1

b

Question 2

What mechanical change occurs during the QT period in ventricular cardiomyocytes?

Answer 2

Systole

Question 3

What are the 3 methods to defibrillate the heart?

Answer 3

Physical blow to the heart to depolarise and allow SAN rhythm to be re-established
Electrical stimulus to depolarise and allow AVN to take control
KCL infusion, allows AVN to take control

Question 4

What characteristics are present on an ECG of ventricular fibrillation?

Answer 4

No QRS complex

P waves unrecognisable

Question 5

What do inotropic effects modify?

a) electrical conduction and nerves to affect HR
b) force and speed of contraction
c) conduction rate in AVN to alter pulse rate

Answer 5

b

Question 6

What do chronotropic effects modify?

a) electrical conduction and nerves to affect HR
b) force and speed of contraction
c) conduction rate in AVN to alter pulse rate

Answer 6

a

Question 7

What do dromotropic effects modify?

a) electrical conduction and nerves to affect HR
b) force and speed of contraction
c) conduction rate in AVN to alter pulse rate

Answer 7

c

Question 8

What are the inotropic, chronotropic and dromotropic responses to sympathomimetics on cardiac muscle?

Answer 8

Positive inotropic - increase contractility
Positive chronotropic - increase HR
Positive dromotropic - increase conduction speed and rate of pulse

Question 9

What are the inotropic, chronotropic and dromotropic responses to parasympathomimetics on cardiac muscle?

Answer 9

Negative inotropic - decrease contractility
Negative chronotropic - decrease HR
Negative dromotropic - decrees conduction speed and rate of pulse

Question 10

What neurotransmitter is used in sympathetic responses?

Answer 10

Noradrenaline

Question 11

What neurotransmitter is used in parasympathetic responses?

Answer 11

Acetylcholine

Question 12

How does the sympathetic NS increase HR/contractility?

Answer 12

Stimulate B adrenoreceptors - G coupled receptors - adenyl cyclase activation - phospholamban phosphorylated - SERCA activated - increases in Ca2+ gradient - positive ion/chronotropic effect - increase in contractility

Question 13

How does the parasympathetic NS decrease HR/contractility?

Answer 13

Stimulate M2 cholinoreceptors - G coupled receptors - adenyl cyclase inhibited - phospholamban dephospho rylation - SERCA inhibited - decease in Ca2+ concentration gradient - negative ion/chronotropic effect - decrease in contractility

Question 14

What are cardiac glycosides?

Answer 14

Compounds that increase the output force of the heart (positive inotropic) and decrease the HR (negative chronotropic) by suppressing Na+/K+ ATPase pump

Question 15

How do cardiac glycosides increase contractility and decrease HR?

Answer 15

Inhibit Na+/K+ ATPase pump
Increase of Na+ in the cell
Activation of the NA+ Ca2+ exchanger (reversed mode)
Increase of Ca2+ in the cell
More Ca2+ released from SR - increase contraction and SV (positive inotropic)
Increased load on SERCA - increased refractory period - decreased HR

Question 16

What is hyponatremia and hypernatremia?

Answer 16

Low / high extracellular Na+

Question 17

What is Na+ responsible for?

Answer 17

Maintenance of osmolarity

Question 18

What occurs during hyponatremia? (ino, chrono and dromo effects)

Answer 18

Water moves into cell and cardiomyocytes swell
Na+/Ca2+ exchanger activated (reversed mode)
Ca2+ increases in the cell
Positive ino, chrono and dromo effects

Question 19

What occurs during hypernatremia?

Answer 19

Water moves out of cell and cardiomyocytes shrink
Na+/Ca2+ exchanger activated (direct mode)
Reduced Ca2+ in the cell
Negative ino, chrono and dromo effects

Question 20

What is hypokalaemia and hyperkalaemia?

Answer 20

Low/high extracellular K+

Question 21

What is K+ responsible for?

Answer 21

Maintaining resting potential

Question 22

What occurs during hypokalaemia?

Answer 22

Cardiomyocytes hyperpolarise
K+ voltage gates ion channels open
Na+ voltage gated ion channels open
Up-regulation of sinus rhythm
Positive ino,chrono and dromo effects

Question 23

What occurs during hyperkalaemia?

Answer 23

Cardiomyocytes depolarise
Driving force through K+ voltage gated ion channels decreases
Na+ voltage gated ion channels inactivated
Suppression of sinus rhythm
Negative ino, chromo and dromo effects

Question 24

What is Ca2+ responsible for?

Answer 24

Contraction

Question 25

What occurs during hypocalcaemia?

Answer 25

Cardiomyocytes hyperpolarise

Negative ino, chrono and drono effects

Question 26

What occurs during hypercalcaemia?

Answer 26

Cardiomyocytes depolarise

Positive ino, chrono dan drono effects

Question 27

What is the action of cardiac glycosides?

Answer 27

Increase SV and decrease HR

Question 28

Which ionic conditions cause negative ino, chromo and dromo effects?

Answer 28

Hypernatremia, hyperkalaemia, hypocalcaemia

Question 29

Which ionic conditions cause positive ino, chromo and dromo effects?

Answer 29

Hyponatremia, hypokalaemia, hypercalcaemia