Lecture 9 - Regulation of Cardiac Function 1

Question 1

Lusitropy?

Answer 1

relaxation of myocardium (Ca removal)

Question 2

Dromotropy?

Answer 2

conduction velocity of AV node

Question 3

Inotropic state?

Answer 3

depends on Ca2+ release from SR, balance of fluxes and affinity of troponin C for Ca

Question 4

SNS innervation of inotropic state?

Answer 4

Gs stimulates adenylate cyclase, increasing cAMP and activating PKA, leading to phosphorylation of Ca channels and ryanodine receptors, increasing opening, of channels, SR stimulation and fatser Ca kinetics -> vigorous and rapid contraction

Question 5

PNS innervation?

Answer 5

inhibits Gs, increases K+ efflux lengthening A.P.

Question 6

Force sarcomere length relationship compared to skeletal muscle?

Answer 6

no descending limb due to high passive stiffness, steeper ascending limb because of actin/myosin overlap + length dependent sensitivity of Troponin C

Question 7

Hypoxic state - reduced ATP?

Answer 7

reduced Na/K+ pump, reduced myosin head detachment, reduced sarcolemma Ca extrusion, reduced pH

Question 8

Deformation during cardiac cycle?

Answer 8

circumferential shortening + longitudinal shortening + torsion + transmural shear = radial wall thickening

Question 9

Spontaneus hypertension effect?

Answer 9

failure of myocytes to rearrange effectively -> decreased ejection