Muscle 8 Flashcards

1
Q

Smooth muscle is categorized by…

A
  • location
  • contraction pattern
  • communication with neighbouring cells
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2
Q

In humans, smooth muscle can be divided in which 6 major (location) groups?

A
  • vascular
  • gastrointestinal
  • urinary
  • respiratory
  • reproductive
  • ocular
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3
Q

What are the 4 contraction patterns?

A
  • a phasic smooth muscle that is usually relaxed
  • a phasic smooth muscle that cycles between contraction and relaxation
  • a tonic smooth muscle that is usually contracted
  • a tonic smooth muscle whose contraction is varied as needed
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4
Q

unitary smooth muscle (single unit)

A

contains gap junctions that allow for coordinated contraction of many cells causing muscle to contract as a single unit

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5
Q

multiunit smooth muscle

A

-not electrically coupled

iris and cilliary body of eye, in male reproductive tract and in uterus except just prior to labor and delivery

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6
Q

What can alter smooth muscle tension?

A

hormones, stretch and local factors, paracrine signals, acidity, oxygen and CO2 conc, and osmolarity

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7
Q

Paps of smooth muscle can be initiated by…

A

neural, hormonal, or mechanical stimulation

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8
Q

slow wave potentials

A

fire action potential when they reach threshold

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9
Q

pacemaker potentials

A

always depolarize to threshold

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10
Q

in some smooth muscle Vm oscillations can lead to..

A

tonic contractions in absence of APs

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11
Q

electromechanical coupling

A

contraction due to electrical signaling

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12
Q

Autonomic AP initiation

A
  • spikes or plateaus

- single unit

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13
Q

spontaneous AP

A
  • slow wave
  • pacemaker
  • single unit
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14
Q

graded potentials

A

multiunit

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15
Q

Calcium conc is increased by what three different mechanisms?

A
  • Ca2+ entry through voltage gated channels or ligand gated ion channels
  • Ca2+ release from SR
  • Ca2+ entry through voltage-independent channels
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16
Q

There is ____ SR in smooth than in skeletal and cardiac.

17
Q

IP3 pathways

A

can cause contraction with minimal depolarization and negligible extracellular Ca2+ influx

18
Q

Depletion of Ca2+ in the SR causes activation of…

A

store-operated channels

19
Q

store-operated channels

A

cause a Ca2+ influx across the cell membrane. Allows [Ca2+]i to remain elevated and replenishes SR.

20
Q

pharmacomechanical coupling

A

occurs when chemical signals change muscle tension through signal transduction pathways with little or no change in membrane potential

21
Q

stretch of smooth muscle causes..

A

an internal release of Ca2+ from the SR through the ryanodine receptor causing phosphorylation of myosin light chain leading to contraction

22
Q

myosin light chain kinase

A

phosphorylates the regulatory light chain near the myosin head which alters the conformation of the myosin head, increasing its ATPase activity and allows it to interact with actin

23
Q

In smooth muscles, cross-bridge cycling is similar but…

A

occurs more slowly

24
Q

During relaxation, the regulatory light chain must be…

A

dephosphorylated by myosin light chain phosphatase

25
latch state
when some smooth muscle can maintain force for an extended period of time with little ATP use
26
Neurotransmitters, hormones and paracrine molecules alter smooth muscle Ca2+ sensitivity by...
modulating light chain phosphatase