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BIPN 105 > Uterus muscle > Flashcards

Uterus muscle Flashcards

1
Q

Are Smooth muscle cells smaller or bigger than SKM cells?

A

Smaller

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2
Q

How many nuclei do smooth muscle cells have?

A

one

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3
Q

What are the myofilaments in smooth muscle cells?

A
  • actin
  • myosin
  • no sarcomeres
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4
Q

How are myofilaments distributed in smooth muscle cells?

A

“random distribution”-> not striated (smooth)

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5
Q

What is the process of depolarization in smooth muscle cells?

A

LTCC –> Ca2+ influx (Ca2+ plateau lasts 10s-100s of msec)

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6
Q

Is the AP caused by Na+ influx for smooth muscle cells?

A

no

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7
Q

What is in charge of Repolarization in smooth muscle cells?

A

K+ channels(multiple types)

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8
Q

Is smooth muscle myogenic or neurogenic?

A

myogenic (muscle) - can trigger its own APs/contractions

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9
Q

What causes the “Slow Wave Depolarization” at rest?

A

mostly from Ca2+ influx through T-type Ca2+ channels

  • Vm drifts up towards threshold-> fires APs
  • Acts as a pacemake-> smooth muscle is myogenic
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10
Q

How do APs spread in smooth muscle cells?

A
  • No T-tubules (bc no sarcomeres)
  • AP spreads from cell to cell through gap junctions (cell are electrically connected)
  • Group of smooth muscle cells act as a “single unit”- wave depolarization starts at one location and then spreads through all the connected cells
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11
Q

What occurs during Contraction?

A

A. Prolonged Ca2+ entry/ Slow Ca2+ removal - >long duration contractions
B. Slow myosin-actin interaction-> slow increase in tension; low ATP use (doesn’t fatigue)

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12
Q

What are the two sources of Ca2+ in smooth muscle cells?

A
  1. Sarcoplasmic reticulum

2. LTCC

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13
Q

What is the main source of Ca2+?

A

extracellular Ca2+ from LTCC

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14
Q

What are the steps for Triggering of Contraction in smooth muscle cells?

A

Ca2+ enters cell by LTCC and SR releases Ca2+ as well -> 4 Ca2+ come together and form CAM (calmodulin) -> stimulates MLCK (myosin light chain kinase) -> phosphorylates inactive myosin -> contraction

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15
Q

What are the steps for Relaxation in smooth muscle cells?

A

Voltage-dependent K+ channels activate during depolarization-> K+ begins to leave the cell-> Ca2+ activate K+ channels that are Ca2+ dependent-> both inhibit LTCC–> Na+ Ca2+ exchanger pumping 3 Na+ into cell and 1 Ca2+ out –> SERCA pumping Ca2+ back into SR –> MLCP (myosin light chain phosphatase inactivating myosin -> relaxation

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16
Q

What NT is parasympathetic?

A

ACh

17
Q

What is the receptor for ACh for smooth muscle cells?

A

Muscarinic cholinergic

18
Q

Which muscarinic cholinergic receptor activates the Gq pathway?

A

m3AChR

19
Q

What happens when the Gq pathway is activated?

A

Contraction

20
Q

What NT is sympathetic?

A

Norepinephrine (NE)

21
Q

Which hormone is sympathetic?

A

Epinephrine (E) - from adrenal medulla

22
Q

What type of receptors does NE and E bind to on smooth muscle cells?

A

Adrenergic

23
Q

What type of receptor can both NE and E bind to on smooth muscle cells?

A

alpha 1

24
Q

Which pathway is activated by alpha 1? What does it trigger?

A

Gq pathway- contraction (blood vessels, uterus)

25
Q

What type of receptor can only E bind to on smooth muscle cells?

A

Beta 2

26
Q

Which pathway is activated by beta-2 receptors? What does it trigger?

A

Gs pathway- relaxation (blood vessels, uterus, bronchioles)

27
Q

What are the steps for Gq pathway?

A

G alpha q subunit stimulates PLC -> PLC acts on PIP2 and breaks it down to two molecules -> IP3 and DAG-> IP3 binds to IP3-R on SR to release more Ca2+ into cytosol-> DAG activates PKC-> PKC inhibits K+ channels and stimulates LTCC-> contraction

28
Q

What is the steps for Gs pathway?

A

G alpha s subunit activates and stimulates AC (adenylate cyclase) -> AC converts ATP to cAMP-> cAMP activates PKA -> stimulates K+ channels and MLCP and inhibits MLCK -> relaxation

BIPN 105 (6 decks)

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