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Human Physiology > Human Phys 2.9 > Flashcards

Human Phys 2.9 Flashcards

1
Q

What do smooth muscles lack?

A

Striations

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2
Q

Do smooth muscles have actin and myosin?

A

Yes, but they are not arranged in sarcomeres

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3
Q

Motility

A

To propel chyme down the GI tract (Phasic)

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4
Q

Tension

A

To maintain appropriate vascular diameter in blood vessels (tonic)

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5
Q

What are the types of smooth muscles?

A

Unitary/visceral/single unit

Multi unit

Combination

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6
Q

What are single unit smooth muscles linked by?

A

Gap junctions

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7
Q

What are single unit smooth muscles present in?

A

GI tract

Bladder

Uterus

Ureter

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8
Q

What are single unit smooth muscles characterized by?

A

Spontaneous pacemaker activity (slow waves) (Phasic contractions)

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9
Q

Are multi unit smooth muscles linked by gap junctions?

A

No

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10
Q

What are multiunit smooth muscles present in?

A

Iris

Ciliary muscles of the lens

Vas deferens

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11
Q

What are characteristics in multiunit smooth muscles?

A

Each muscle fiber behaves as a separate motor unit

Little or no coupling between cells

Densely innervated by the ANS

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12
Q

What type of contractions do multiunit smooth muscles do?

A

Tonic

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13
Q

What is a combination of both types of smooth muscles present in?

A

Vascular smooth muscle

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14
Q

What do smooth muscles not contain?

A

Troponin complex

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15
Q

What are dense bodies in smooth muscles?

A

Behave like Z disc in the skeletal muscles

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16
Q

Have much of there length can smooth muscles contract?

A

80% (skeletal can do 30%)

17
Q

What is the myosin ATPase activity in the smooth muscles compared to the skeletal muscles?

A

1/10 compared to 1/300 is required ti maintain the same tension

18
Q

Why is myosin cross bridge much slower in smooth muscles compared to skeletal muscles?

A

Because less energy is used

19
Q

What does smooth muscle require more time for?

A

To contract and relax (slow onset of contraction)

20
Q

What is the maximum force of contraction in smooth muscle compared to skeletal muscle?

A

Much higher (4-6 kg/cm2)

21
Q

How can smooth muscles maintain prolonged tonic contractions, for hours using minimal energy?

A

Via the latch mechanism

22
Q

Stress relaxation and reverse stress relaxation

A

Allows hollow organs to maintain constant luminal pressure despite large changes in volume

23
Q

What is poorly developed in the smooth muscle?

A

Sarcoplasmic reticulum

24
Q

What is used in smooth muscles instead of troponin?

A

Calmodulin

25
Q

What is smooth muscle cell contraction initiated by?

A

Extracellular calcium

26
Q

What is the correct temporal order of events for the smooth muscle?

A

MLC phosphorylation

Contraction

MLC dephosphorylation

Relaxation

27
Q

Actin and myosin filaments in smooth muscles are structured how?

A

Overlap, with the actin filaments anchored at dense bodies

Human Physiology (41 decks)

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