smooth muscle

Question 1

what are the three categories of smooth muscle

Answer 1

location, contraction pattern, and communication with neighboring cells.

Question 2

where is smooth muscle found in the body?

Answer 2

vascular (blood vessels), gastrointestinal (digestive tract), urinary (bladder and ureters), respiratory (airways), reproductive (uterus and reproductive structures), and ocular (eye).

Question 3

what are the contraction patterns found in smooth muscle?

Answer 3

can be phasic (alternating between contraction and relaxation) or tonic (continuously contracted)

Question 4

visceral smooth muscle (single unit) is electrically connected by

Answer 4

gap junction, allowing coordinated contraction

Question 5

multi-unit smooth muscle cells function

Answer 5

independently and are electrically linked allowing fine control of contractions

Question 6

single unit smooth muscle is found in the walls of

Answer 6

internal organs and contracts as a coordinated unit due to gap junctions. the force of contraction is determined by the amount of Ca2+ entering the cell.

Question 7

multi unit smooth muscle is found in the

Answer 7

iris, ciliary muscle of the eye, part of the male reproductive tract, and the uterus (except just before labor). these cells are stimulated independently and allow fine control of muscle contractions.

Question 8

during the final stages of prganancy, the uterus transitions from multi-unit to

Answer 8

single-unit smooth muscle enhancing coordinated contractions for labor

Question 9

smooth muscle force is created by

Answer 9

actin-myosin crossbridge interaction and initiated by increased cytosolic Ca2+ concentrations, similar to skeletal muscle.

Question 10

smooth muscles operate over a range of lengths,

Answer 10

unlike skeletal muscles which operate over a narrow range

Question 11

smooth muscles within an organ can run in

Answer 11

multiple directions, allowing for complex movements and changes in organ shape

Question 12

smooth muscles contract and relax

Answer 12

more slowly than skeletal or cardiac muscles

Question 13

smooth muscles use less energy to generate and maintain force, reluying more on

Answer 13

glycolysis and having fewer mitochondria

Question 14

smooth muscle cells are small, spindle-shaped and have a single

Answer 14

nucleus, unlike the large, multi-nucleated fibers of skeletal muscles

Question 15

smooth muscle contractile fibers are not arranged in

Answer 15

sarcomeres, lacking the banding patterns seen in striated muscle

Question 16

contraction in smooth muscle can be initiated by electrical or chemical signals, unlike

Answer 16

skeletal muscle which requires an action potential

Question 17

what is the smooth muscle controlled by? what is the skeletal muscle controlled by?

Answer 17

smooth muscle = autonomic nervous system. skeletal muscle = somatic motor division

Question 18

what does the smooth muscle lack?

Answer 18

lacks specialized receptor regions, receptors are distributed over the cell surface and neurotransmitters diffuse across the surface

Question 19

where does the Ca2+ for smooth muscle come from? how about the skeletal muscle?

Answer 19

smooth muscles come from both the extracellular fluid, and the sarcoplasmic reticulum; skeletal muscle comes from solely from the sarcoplasmic reticulum.

Question 20

in smooth muscle, the calcium signal initiates a cascade ending in myosin light chain phosphorylation and myosin ATPase activation

Answer 20

in skeletal muscle, calcium binds to troponin to initiate contraction

Question 21

smooth muscle and skeletal muscle both contain

Answer 21

actin and myosin that interact through crossbridges

Question 22

both muscle types (smooth and skeletal) have sarcoplasmic reticulum that stores and releases

Answer 22

Ca2+

Question 23

structural elements differ between

Answer 23

smooth and skeletal muscle

Question 24

actin is more abundant in what muscle

Answer 24

in smooth muscle than in striated muscle, with an action to myosin ratio of 10-15 in smooth

Question 25

smooth muscle actin is associated with what and lacks what?

Answer 25

associated with tropomyosin, but lack troponin unlike skeletal muscle

Question 26

smooth muscle contains less myosin than?

Answer 26

than skeletal muscle, with myosin filaments surrounded by actin filaments in a 12-15 to 1 ratio

Question 27

myosin filaments in smooth muscle are

Answer 27

longer and have myosin heads covering the entire surface, allowing for greater stretch while maintaining tension (needed for bladder)

Question 28

smooth muscle cells have an extensive cytoskeleton with intermediate filaments

Answer 28

and protein dense bodies, which anchor actin filaments

Question 29

cytoskeleton fibers link dense bodies to the cell membrane, stabilizing actin, and protein fibers in the….

Answer 29

extracellular matrix connect smooth muscle cells, transferring force between them

Question 30

what varies by type in smooth muscles?

Answer 30

the amount of sarcoplasmic reticulum (SR)

Question 31

smooth muscle (SR) is less organized than in skeletal muscle,

Answer 31

forming a network of tubules extending from just under the cell membrane into the cell’s interior

Question 32

smooth muscle lacks

Answer 32

t-tubules, but the SR is closely associated with membrane invaginations called caveolae, which are involved in cell signaling

Question 33

dense bodies in smooth muscle anchor

Answer 33

actin and are analogous to Z disks in a sarcomere

Question 34

smooth muscle myosin differs from skeletal muscle in two ways:

Answer 34

it has a slower ATPase activity and it is regulated by phosphorylation of myosin light chain

Question 35

actin in smooth muscle is associated with calmodulin and myosin light chain kinase, where as skeletal muscle

Answer 35

it is associated with troponin and tropomyosin

Question 36

smooth muscle contraction is more complex than skeletal muscle contraction as it

Answer 36

can occur with or without an action potential

Question 37

smooth muscle can

Answer 37

hyper polarize (decreasing contraction likelihood) or depolarize without firing action potentials

Question 38

contraction in smooth muscle can be triggered by

Answer 38

an action potential, a sub threshold graded potential, or without any change in membrane potential

Question 39

what is the resting membrane potentials in smooth muscle

Answer 39

varies between -40mV and -80mV

Question 40

cells with cyclic depolarization and repolarization exhibit

Answer 40

slow wave potentials, if depolarization reaches the threshold, action potentials fire, leading to muscle contraction

Question 41

pacemaker potentials are

Answer 41

regular depolarization that always reach the threshold and fire action potentials, creating rhythmic contractions. these are found in some cardiac and smooth muscles

Question 42

what do both slow wave and pacemaker potentials result from?

Answer 42

ion channels in the cell membrane that spontaneously open and close

Question 43

slow wave potentials are

Answer 43

oscillating membrane potentials that do not always reach the threshold to trigger action potentials but can modulate the excitability of the smooth muscle.