SFOS 12

Excitation-contraction Coupling

Matching stimulation with mechanical work
What is the fundamental contracting unit in the heart?

Cardiac myocyte
What is the function of intercalated disks?
- Attach two cells in a fiber
- Provide gap junctions
Syncytium

Electrically coupled cell group
Describe the mechanism of Ca release from SR
- Ica channels open during Phase 2 plateau
- Influx of trigger Ca
- Causes calcium release channels in SR to open
- Ca induced Ca release
What molecule effects the contractile state? How?
- Catecholamines (isoproterenol or norepinephrine)
- Increase available Ca levels
Preload
- Wall tension prior to contraction
- Increases with increased EDV as per law of la place
- Approx. by end diastolic pressure
Frank-Starling relationship
- Relationship between EDV and cardiac performance
- Increased venous return --> increased cardiac output
Afterload
- Force against which the cardiac muscle is working in systole
- High afterload degrades ventricular performance
- Approx. by systolic pressure
Variables of cardiac performance
- Contractile state
- Preload
- Afterload
- Heart rate

Author

zf2010

80011

Card Set

SFOS 12

Description

SFOS 12

Updated

2011-04-16T19:57:06Z