Cardiac Muscle Structure & Function Flashcards Preview

CVPR - CV Unit 1 > Cardiac Muscle Structure & Function > Flashcards

Flashcards in Cardiac Muscle Structure & Function Deck (10):
1

Troponin - 3 subunits

TN-C: Calcium-binding troponin subunit

TN-I: Inhibitory subunit; contains N-terminal extension that is highly regulated by PKA phosphorylation,

TN-T: Tropomyosin-binding subunit

2

Properties of cardiac muscle cells

Striated
Mono-nucleated
Coupled via gap junctions & intercalated discs
Not under direct neural control
Rich in mitochondria

3

How is Ca2+ removed from the active myocyte?

70% via SR Ca2+ ATPase (SERCA)

30% via Na+-Ca2+ exchanger (NCX)

4

3 molecular factors underlying the length-tension relationship

1. Extent of overlap - peak tension development occurs at sarcomere lengths of ~2.2uM

2. Changes in Ca2+ sensitivity - at longer lengths, more of the cross-bridges become activated by the same change in intracellular Ca2+

3. Increased Ca2+ release - due to stretch-sensitive ion channels in the cell membrane

5

Cardiac Index

CO normalized to body size

6

What determines CO?

CO = HR x SV

HR can increase by a larger % than SV and so can produce larger changes in CO

SV is determined by pre-load, afterload, and contractility

7

Stroke Volume - Definition

SV = EDV - ESV

8

Ejection Fraction - Definition

EF = (EDV-ESV) / EDV

EF = SV / EDV

9

Stroke Work - Definition

Energy expended per beat (J), corresponds to the area inside the PV loop diagram

10

Pulse Pressure - Definition

PP = peak systolic pressure - end diastolic pressure