Smooth Muscle Flashcards

1
Q

What are the three ways smooth muscle can be activated

A

Neurotransmitters, hormones, physical activation

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2
Q

How can a neurotransmitter stimulate a smooth muscle

A

Released from varicosities and binds to receptor
Generates action potential in smooth muscle
Activates the ryanodine receptor and released Ca from SR

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3
Q

How does a hormone stimulate smooth muscle

A

It’s released from the blood and binds to receptor
Follows camp which activated Ca on SR
A release of Ca on plasma membrane causes influx of Ca from ECF

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4
Q

How does physical activation stimulate smooth muscle

A

Physical altercation of membrane protein
Open channel which generates action potential and Ca influx

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5
Q

Why is smooth muscle lacking troponin matter

A

Caldesmon binds to actin preventing myosin to attach
Calmodulin binds to Ca and this complex binds to caldesmon which dissociates from actin

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6
Q

What is a caldesmon regulator

A

Map kinase because it phosphorylates caldesmon

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7
Q

What causes caldesmon to dissociate from the actin filament

A

When Ca is released it binds to calponin and causes confirmation change
An enzyme can also phosphorylate it and cause it to release

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8
Q

What are the steps of muscle relaxation

A

Signal stops and there is a decrease in Ca levels
Ca atpase moves Ca back into SR and ECF
Myosin phosphatase dephosphorylates myosin filament and causes it to go back to original form
Rho kinase takes myosin phosphate from inactive form to active form which activates myosin phosphatase

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9
Q

What can the myosin light chain do

A

Regulate the affinity of myosin heavy chain for the actin filament
Phosphorylated MLC induces high affinity and dephosphorylated MLC induces low affinity

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10
Q

Between tonic and physic muscles which one contracts for long periods

A

Tonic

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11
Q

Between tonic and phasic which one contracts and relaxes frequently

A

Phasic

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12
Q

Can tonic muscles contract when the myosin light chain is dephosphorylated

A

Yes but we don’t know how

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