Chapter 19 Deck 3 Slide 43+ Flashcards
the nodal cells do not have a stable rmp what is there rmp?
-60 millivolts
what are specific voltage-gated channels associated with nodal cells?
slow voltage-gated na+ channels, fast voltage-gated Ca2+ channels, voltage-gated K+ channels
what are the electrical events at the SA node that initiate action potential?
1) slow gated Na+ channel opens allowing Na+ to leak in. membrane potential changes from -60 to -40mV
2) fast voltage-gated Ca2+ channels open allowing Ca2+ to flow in. -40 to 0mV
3) K+ channels open allowing K+ to flow out and repolarize
uninhibited by vagal tone the heart would beat how many times per minute?
100
at rest the SA node action potentials are how far apart?
.8 seconds
what membrane protein of the SA node plays a critical role in repolarizing?
voltage-gated K channels
after threshold is reached at the sinoatrial node what membrane protein plays a critical role in depolarization?
fast voltage-gated calcium channels
in the sinoatrial node what membrane protein is critical for reaching threshold?
slow voltage-gated sodium Channels
what is the term for the inhibition of the SA node by parasympathetic activity related by the vagus nerve?
vagal tone
unlike neurons nodal cells do not have a stable rmp comma they exhibit a pacemaker potential when their?
Na+ channels open ( slow voltage-gated)
in neurons, action potential depolarization is from_____ entry, and in nodal cells depolarization is from _____ entry
Na+ entry, Ca2+ entry
how does an action potential spread through the heart?
1) SA node - AV node
2) delay at AV - AV bundle
3) AV bundle - left and right bundle branches
- bundle branches - purkinje fibers
4) spread throughout ventricles by gap junctions
action potentials are spread from pre kinji fibers throughout the Heart by what kind of Junctions?
Gap Junctions
where is the action potential delayed when it is spreading throughout the heart?
atrioventricular node
after an action potential is delayed at the atrioventricular node it then continues to the?
atrioventricular bundle then two left and right bundle branches and purkinje fibers
what are the events of cardiac muscle action potential?
1) depolarization - fast voltage-gated Na+ open
2) plateau- slow voltage-gated Ca2+ and K open
3) repolarization- voltage-gated K+ remain open
what are the changes in millivolts that occur during cardiac muscle action potential?
1) from RMP -90 to +30
2) plateau mV remain at +30
3) repolarization +30 to -90
what are special channels associated with cardiac muscle?
1) fast voltage-gated Na channel
2) slow voltage-gated Ca2 channels
3) voltage-gated K+ channels
what is an ectopic pacemaker?
a pacemaker other than the SA node
if Ave vinodh becomes default when SA node impaired how many beats per minute?
40 to 50 beats minute fast enough to sustain life
what is the rate of beats per minute that cardiac muscle alone can maintain?
20 to 40 beats per minute usually too slow to maintain life
what are some common membrane proteins that cardiac muscle cells have?
sodium potassium pumps, calcium pumps, sodium and potassium leak channels
what is the resting membrane potential of cardiac muscle cell at rest?
-90 millivolts
what is the resting memory potential nodal cells?
-60 millivolts
