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Crrab 1 > Cardiac muscle characteristics > Flashcards

Cardiac muscle characteristics Flashcards

1
Q

What are three causes of parasympathetics innervation on the heart?

A
  1. Slows HR (prolongs depolarization time)
    - neg chronotropic effect
  2. Slows rate of spontaneous depolarization of membrane
  3. Initial hyper-polarization of resting membrane potential is decreased
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2
Q

What is released from the sympathetics onto the heart?

A

Norepinephrine

- increases diastolic inward currents I(f) through HCN channels

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3
Q

What is the net effect of sympathetics innervation on the heart?

A

Speeds HR by shortens time to depolarize

- also increases rate of spontaneous depolarization of membrane

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4
Q

What is preload?

A

Passive resting tension placed on cardiac muscle cells before contraction
- a function of volume and pressure at the end of diastole

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5
Q

What causes increased preload?

A

Hypervolemia
Regurgitation
Heart Failure

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6
Q

What is afterload?

A

Active tension placed on cardiac muscle cells during contraction
- a function of resistance the left ventricle must over come to circulate blood

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7
Q

What causes increased afterload?

A

HTN

Vasoconstriction

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8
Q

What are the 3 differences between striated and cardiac muscle action potentials?

A
  1. Self- generating
  2. conducted directly from cell to cell
  3. Long duration (long refractory period)
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9
Q

Which ions are higher outside the cell and inside the cell?

A

Sodium and calcium

Potassium

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10
Q

What form of ion passage is most used?

A

Ion channels

- membranes permeability is the net status of the ion channels (high perm to Na means many ion channels open)

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11
Q

What are the 3 states of both the inactivation gates and activation gates? Which are open and closed when?

A
  1. Closed- Activation gate in the close; Inactive gate is not
  2. Active- Both gates are open and out of the way
  3. Inactive- Activation gate is open; Inactivation gate is closed
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12
Q

Do activation gates response quickly or slowly to depolarization?

A

quickly

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13
Q

Do inactivation gates respond quickly or slowly to depolarization?

A

Slowly

- Limits time channel can remain open

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14
Q

What are the 2 types of cardiac muscle cells?

A
  1. Myocardial contractile cells (similar AP’s to other cells)
  2. Myocardial autorhhythmic or pacemaker cells
    - generate APs spontaneously cause of Unstable membrane
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15
Q

Which reponse slow or fast is pacemaker and contractile cells respectively?

A

Slow and fast

- think Pace yourself for slow

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16
Q

What does rectifier mean?

A

Allows for flow of ions in only one direction

- ex. inward rectifier only lets K+ into the cell during repolarization

17
Q

How many phases does the myocardial pacemaker cells have and what are they?

A

Three

  1. Ca(l)- long lasting Ca channels; causes depolarization after Ca(t)’s have opened
  2. Ca(t)- causes slow upward swing that leads into Ca(l)’s depolarization
  3. I(f)
18
Q

Which phases are missing in pacemaker cells?

A

1 and 2

19
Q

Which period are cells fast response AP’s found in most of the time?

A

Absolute refractory period

- thus cannot be stimulated to contract again and this fights against tetanic contractions

20
Q

what is a intercalated disk?

A

Specialized adheren juction structions that connects ends of two adjacent cells

21
Q

What makes up an intercalated disk?

A
  1. Gap junctions - connexin is protein that forms these channels that permit passage of ions between cells= (Increased efficiency of spread of AP’s)
  2. Fasica adherens - anchors actin
  3. Macula adherens (desmosomes) - joins intermediate filaments
22
Q

What is the purpose of the desmosomes and fascia adherens?

A

Ensure the transmission of force from one muscle cell to the next

23
Q

What is the purpose of gap juctions?

A

Facilitate the transmission of electrical impulse from cell to cell

  • the more GP’s means faster AP transmitted to the next cell
  • this idea is how the AV nodes slows the 100BPM coming from the SA node
24
Q

What is an electrocardiogram?

A

Record of how the voltage between 2 points on the body surface changes with time as a result of the electrical events of the cardiac cycle.

25
Q

What is needed to increase/decrease the automaticity of the intrincic rate and where do they synapse?

A

Sympathetic and para NS

- on the SA node

26
Q

How doe parasympathetic fibers interact with the SA node and what is its cause?

A

Via vagus and Acetylcholine

  • Increases perm of resting membrane K+
  • Leads to more negative resting membrane and thus increases threshold potential
  • Decreases diastolic I(f) current thru HCN channels

Crrab 1 (27 decks)

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