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

Question 1

what does smooth muscle tissue form in almost every organ

Answer 1

sheets, bundles, or sheaths around other tissues

Question 2

smooth muscles general function

Answer 2

coordinate the movement of substances through internal passageways

Question 3

role of smooth muscle in the integumentary system

Answer 3

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

Question 4

cardiovascular system

Answer 4

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

Question 5

respiratory system

Answer 5

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

Question 6

digestive system

Answer 6

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,

Question 7

urinary system

Answer 7

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

Question 8

reproductive system

Answer 8

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

Question 9

shape and typical dimensions of smooth muscle cells

Answer 9

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

Question 10

does smooth muscle fiber have T tubules

Answer 10

no
sarcoplasmic reticulum forms a loose network throughout the sarcoplasm

Question 11

nonstriated muscle

Answer 11

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

Question 12

thick filament arrangement of smooth muscle

Answer 12

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

Question 13

thin filaments arrangments

Answer 13

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

Question 14

what are dense bodies

Answer 14

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

Question 15

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

Answer 15

dense bodies and intermediate filaments anchor the thin filaments

Question 16

significance of dense bodies not being arranged in straight line

Answer 16

when contraction occurs, muscle cell twists like corkscrew

Question 17

how are adjacent smooth muscle cells bound together

Answer 17

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

Question 18

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

Answer 18

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

Question 19

trigger for smooth muscle contraction

Answer 19

appearance of free calcium ions in the cytoplasm

Question 20

upon stimualtion,

Answer 20

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

Question 21

net result of events after stimulation

Answer 21

rise in calcium ion conc throughout the cell

Question 22

calcium ions activity once in the sarcoplasm

Answer 22

interact with calmodulin (calcium-binding protein)

Question 23

what does calmodulin acitvate

Answer 23

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

Question 24

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

Answer 24

thick and thin filaments are sacttered and not organised into sarcomeres

Question 25

plasticity

Answer 25

ability to function over a wide range of lengths

Question 26

smooth muscles can contraxt over a range of lengths —- times greater than skeletal muscles

Answer 26

4

Question 27

example of importance of plasticity

Answer 27

digestive organs e.g the stomach

Question 28

two categories of smooth muscle cells

Answer 28

multiunit
visceral

Question 29

how are multiunit smooth muscle cells innervated

Answer 29

in motor units comparable to those of skeletal muscles
but each smooth muscle cell may be connected to more than one motor neuron

Question 30

what do many visceral smooth muscle cells lack

Answer 30

direct contact with any motor neuron

Question 31

what does nural activity in multiunit smooth muscle cells produce and what does this resemble

Answer 31

produces AP that travels over sarcolemma
resembles skeletal and cardiac muscle cells

Question 32

how are visceral smooth muscle cells arranged

Answer 32

sheets or layers

Question 33

within the layers of the visceral smooth muscle cells, how are adjacent muscle cells connected

Answer 33

gap junctions

Question 34

result of gap junctions

Answer 34

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

Question 35

smooth muscle cells can also contract or relax in response to

Answer 35

chemicals, hormones, conc of oxygen or CO2, extreme stretching or irritation

Question 36

electormagnetic coupling

Answer 36

stretching the muscle can produce depolarisation

Question 37

smooth muscle tone

Answer 37

multiunit and visceral smooth muscle tissue have normal background level of smooth muscle tone