week 3: 10.10 smooth muscle tissue contracts to move substances within internal passageways Flashcards

1
Q

what does smooth muscle tissue form in almost every organ

A

sheets, bundles, or sheaths around other tissues

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2
Q

smooth muscles general function

A

coordinate the movement of substances through internal passageways

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3
Q

role of smooth muscle in the integumentary system

A

smooth muscles around blood vessels regulate the flow of blood to the superficial dermis, smooth muscles of the arrector pili elevate hairs

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4
Q

cardiovascular system

A

smooth muscles around blood vessels control blood flow through vital organs and help regulate blood pressure

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5
Q

respiratory system

A

smooth muscles contract or relax to alter the diameters of the respiratory passageways and change their resistance to airflow

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6
Q

digestive system

A

extensive layers of smooth muscle in walls of digestive tract play essential role in moving materials along the tract,
smooth muscles in walls of gall bladder contracts to eject bile into digestive tract,

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7
Q

urinary system

A

smooth muscle tissue in walls of small blood vessels alter rate of filtration in kidneys,
layers of smooth muscle in walls of uterus transport urine to urinary bladder,
contraction of smooth muscle in wall of urinary bladder forces urine out of the body

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8
Q

reproductive system

A

males: layers of smooth muscle help move sperm along reproductive tract, cause ejection of glandular secretions from accessory glands into the reproductive tract
females: layers of smooth muscle help move oocytes along reproductive tract,
contractions of smooth muscle is walls of uterus expel fetus in delivery

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9
Q

shape and typical dimensions of smooth muscle cells

A

relatively long and slender
5-10μm diameter
30-200 μm length
spindle shaped
single centrally located nucleus

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10
Q

does smooth muscle fiber have T tubules

A

no
sarcoplasmic reticulum forms a loose network throughout the sarcoplasm

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11
Q

nonstriated muscle

A

smooth muscle cells lack myofibrils and sarcomeres
as a result has no striations

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12
Q

thick filament arrangement of smooth muscle

A

thick filaments scattered throughout the sarcoplasm of a smooth muscle cell
smooth muscle cells have more myosin heads per thick filament

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13
Q

thin filaments arrangments

A

thin filaments are attached to dense bodies
some of the dense bodies are firmly attached to the sarcolemma

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14
Q

what are dense bodies

A

structures distributed throughout the sarcoplasm in a network of intermediate filaments composed of desmin (protein)

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15
Q

when sliding occurs between thick and thin filaments, cell shortens, why

A

dense bodies and intermediate filaments anchor the thin filaments

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16
Q

significance of dense bodies not being arranged in straight line

A

when contraction occurs, muscle cell twists like corkscrew

17
Q

how are adjacent smooth muscle cells bound together

A

at dense bodies
transmitting the contractile forces from cell to cell throughout the tissue

18
Q

althoug smooth muscle cells are surrounded by connecitce tissue, collagen fibers never

A

unite to form tendons or aponeuroses as thy do in skeletal muscles

19
Q

trigger for smooth muscle contraction

A

appearance of free calcium ions in the cytoplasm

20
Q

upon stimualtion,

A

surge of calcium ions enters the cell from the extracellular fluid and SR releases additional calcium ions

21
Q

net result of events after stimulation

A

rise in calcium ion conc throughout the cell

22
Q

calcium ions activity once in the sarcoplasm

A

interact with calmodulin (calcium-binding protein)

23
Q

what does calmodulin acitvate

A

myosin light chain kinase enzyme
enables myosin heads to attach to actin

24
Q

why are tension development and resting length of smooth muscle not related

A

thick and thin filaments are sacttered and not organised into sarcomeres

25
plasticity
ability to function over a wide range of lengths
26
smooth muscles can contraxt over a range of lengths ---- times greater than skeletal muscles
4
27
example of importance of plasticity
digestive organs e.g the stomach
28
two categories of smooth muscle cells
multiunit visceral
29
how are multiunit smooth muscle cells innervated
in motor units comparable to those of skeletal muscles but each smooth muscle cell may be connected to more than one motor neuron
30
what do many visceral smooth muscle cells lack
direct contact with any motor neuron
31
what does nural activity in multiunit smooth muscle cells produce and what does this resemble
produces AP that travels over sarcolemma resembles skeletal and cardiac muscle cells
32
how are visceral smooth muscle cells arranged
sheets or layers
33
within the layers of the visceral smooth muscle cells, how are adjacent muscle cells connected
gap junctions
34
result of gap junctions
when one muscle cell contracts, electrical impulse can travel to adjacent smooth muscle cells contraction spreads in a wave that involves every smooth muscle cell in the layer
35
smooth muscle cells can also contract or relax in response to
chemicals, hormones, conc of oxygen or CO2, extreme stretching or irritation
36
electormagnetic coupling
stretching the muscle can produce depolarisation
37
smooth muscle tone
multiunit and visceral smooth muscle tissue have normal background level of smooth muscle tone