Cardiac Ion Channels (Exam IV) Flashcards Preview

A&P I (Fall 2022) > Cardiac Ion Channels (Exam IV) > Flashcards

Flashcards in Cardiac Ion Channels (Exam IV) Deck (11)
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1
Q

What does the i stand for in describing ion channels?

A

i = current

2
Q

What is the iKI channel?
What is its gating mechanism?
What three things define its purpose?

A
  • K⁺ (Inward Rectifying Channel)
  • Voltage-Gated
    Purpose:
    1. ↑ pK⁺ during Phase 4
    2. Phase 0-2 closure = ↑ plateau & preserved K⁺
    3. Contributes to diastolic depolarization
3
Q

What is the iNa channel?
What is this channel’s gating mechanism?
What phase is this channel open?
What does inactivation of this channel contribute to?

A
  • Fast Na⁺ Channel
  • Voltage-Gated
  • Phase 0
  • Inactivation contributes to phase I.
4
Q

What is the iTO channel?
What is this channel’s gating mechanism?
When does this gate open & what phase of the cardiac action potential does it contribute towards?

A
  • K⁺ Transient Outward channel
  • Voltage-Gated
  • Opens at very end of Phase 0 thus contributing to Phase 1.
5
Q

What is the iCa channel?
What is this channel’s gating mechanism?
When does this channel open & close?

A
  • L-type Ca⁺⁺ Channel
  • VG & Ligand
  • Opening causes phase 2, closing contributes to phase 3
6
Q

Which channels are enhanced by β-adrenergic & sympathetic stimulation?

A
  • iCa channel
  • if channel
7
Q

What is the iK channel?
What is this channel’s gating mechanism?
What does this channel contribute to the cardiac action potential?
What enhances this channel’s function?

A
  • K⁺ Delayed Rectifier Channel
  • Voltage-Gated
  • Phase 3 enhancement
  • ↑ Intracellular Ca⁺⁺
8
Q

What is the iKATP channel?
What is this channel’s gating mechanism?
When does this channel open? Why?

A
  • K⁺ ATP sensitive channel
  • Ligand Gated (ATP)
  • Opens in response to ↓ ATP = ↑pK⁺ = - Vᵣₘ.
  • Protective mechanism for myocardial ischemia.
9
Q

What is the iKACh channel?
What is this channel’s gating mechanism?
What three effects are achieved by activation of this channel?

A
  • K⁺ ACh-activated channel
  • Ligand-gated
    1. Shortens Phase 2
    2. ↓ Diastolic Depolarization (thus ↓ HR)
    3. Hyperpolarizes Vᵣₘ
10
Q

What is the if channel?
Why the “f”?
What is this channel’s gating mechanism?

A
  • HCN (Hyperpolarization Cyclic Nucleotide channel)
  • “f” is for funny; funny because it opens in response to hyperpolarization.
  • Voltage-Gated & Ligand-Gated
11
Q

What ions conduct through the if channel?
What enhances this channel’s activity?
What suppresses this channel’s activity?

A
  • Na⁺ (primary), K⁺, Ca⁺⁺
  • β-agonism = enhancement
  • Vagal (PSNS) activity = inhibition