Heller Ch. 2 Flashcards
What is the RMP of calcium?
+100mV (more in interstitial fluid)
What is the RMP of sodium?
+70mV (more in interstitial fluid)
What is the RMP of potassium?
-90mV (more in intracellular fluid)
What does movement of ions across a membrane cause?
A charged membrane…cations move out leaving behind negative proteins
Phase 0 of Fast Response Action Potentials?
Sodium permeability rapidly goes UP–>
a sudden DEpolarization
Phase 1 of FRAP?
Sodium permeability rapidly goes DOWN and
Potassium permeability goes DOWN–>
a slight REpolarization
Phase 2 of FRAP?
Calcium permeability goes UP
Sodium permeability slightly UP and
Potassium permeability stays LOW–>
a PLATEAU
Phase 3 of FRAP?
Potassium permeability goes UP
Calcium permeability goes DOWN and
Sodium permeability goes DOWN–>
a REpolarization (Phase 4)
Pacemaker potential cells (Slow-Response Action Potential)?
Unstable membranes
Net movement in SRAP cells before AP?
Potassium goes DOWN while
Calcium (major) and Sodium (minor) go UP–>
an eventual DEpolarization (action potential)
How is conduction velocity modified?
Connexin proteins in gap junctions
Parasympathetic actions through the vagus nerve (ACh):
An initial hyperpolarization of the RMP
Slows the rate of spontaneous depolarization of the RMP
How does ACh achieve parasympathetic effects?
ACh interacts with muscarinic receptors–>activates Gi
Increases potassium permeability (K[ACh] channels)
Suppresses adenylate cyclase–>decreased cAMP–>reduces inward-going pacemaker current by sodium (i[f] current)
Sympathetic actions (NE):
Increases inward currents carried by both sodium (i[f] current) and calcium during the diastolic interval–>increases rate of diastolic depolarization
How does NE achieve sympathetic effects?
NE interacts with beta1-adrenergic receptors–> activates Gs
Increases adenylate cyclase–> increases cAMP–> increases open-state probability of the pacemaker sodium current channel (i[f] current)
