BIO310H5 Lecture Notes - Lecture 11: Mitral Valve, Fetal Hemoglobin, Umbilical Cord

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11 Aug 2016
Pacemaker Potential
- Not a resting potential
- Funny channels  hyperpolarization  change in membrane potential  opening of Ca
channels (T-type)  Depolarization
- Repolarization: closing of Ca channel and opening of K channels  or hyperpolarization
Pacemaker and Contractile  located in the heart
Cardiac Pacemaker cells
- Control Heart Rate
- SA and AV node  ANS
- PNS  decreases Heart Rate
oEffects K conductivity  decreased Ca conductivity
oNegatively effects T-type Ca (close) and open K channels
Hyperpolarization  increases distance between 2 action potentials
- SNS  increases Heart Rate
oIncreased Na and Ca conductivity
oNE (norepinephrine) or E ( Epinephrine)  phosphorylate funny channels  easily
NE/E on Cardiomyocytes
- SNS  controls HR (heart rate) and contractions
- NE/E  bind to G protein  activate P. Kinase  phosphorylation of Ca channels of L-type
- Immediate excitation b/c of gap junction: Actin and Myosin
Excitation Transmission
- AV – Latent pacemaker
oRight atrium
oAP (action potential)  ventricle
oExcitation of Atria reaches through AV node thorough the bundle of his 
capillary muscle ( open and close valves)
If the bundle of his removed: Atria will contract but both ventricles would
not contract
- SA – more frequent AP  if removed AV takes over
oAP occurs in form of ions  transmitted to myocytes
oRight and left contract  Ap travels through all cells
ogeneral excitation (Atria contracts in ms ) but not the ventricles
- Always follows a relaxation period
- Heart cannot contact atria and ventricles at the same time  Av node makes sure that
the atria contracts first
Transmission of Contraction
- Electrical transmission
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