smooth muscle

Question 1

single unit

Answer 1

hundreds to thousands of smooth muscle fibers that contracts together as a single unit

Question 2

single unit features

Answer 2

fibers arranged in sheets/bundles

Question 3

cell membranes are adhered to multiple points and joined by gap junctions. true/false

Answer 3

true

Question 4

what excites single unit smooth muscle?

Answer 4

nerve signals, hormones, chemical factors, action potentials, ion flow

Question 5

where are single unit smooth muscle located?

Answer 5

walls of viscera, ureters, uterus, urinary bladder, blood vessels

Question 6

what characterizes multi unit smooth muscle?

Answer 6

discrete fibers separated by glycoprotein + collagen

Question 7

what excites multi unit smooth muscle?

Answer 7

nerve signals

Question 8

where is multi unit smooth muscle located?

Answer 8

ciliary muscles of the lens, iris muscles of the eye, erector pili muscles, bronchial muscles, ductus deferens, large arteries

Question 9

multi unit smooth muscle

Answer 9

separate smooth muscle fibers that operate independently

Question 10

what are the other names for single unit smooth muscle?

Answer 10

unitary/visceral/syncytial smooth muscle

Question 11

dense bodies

Answer 11

bind to a large # of actin filaments and act like a z-disc

Question 12

“side polar” cross bridges

Answer 12

efficient shortening that allows myosin to pull actin filaments in many different directions

Question 13

latent period

Answer 13

time required for diffusion of calcium into cell + activation of enzymes to trigger muscle contraction

Question 14

how long is the latent period in smooth muscle?

Answer 14

200-300 milliseconds

Question 15

smooth muscle characteristics

Answer 15

small, thin, short, single/central nucleus, spindle shaped, no striations

Question 16

what regulates contraction in smooth muscle?

Answer 16

calmodulin

Question 17

what must happen to regulatory chains?

Answer 17

they must be phosphorylated

Question 18

what are caveolae?

Answer 18

small invaginations of the cell membrane (resemble rudimentary t-tubules)

Question 19

where are caveolae located?

Answer 19

in the SR

Question 20

where does calcium for smooth muscle contraction come from?

Answer 20

extracellular fluid (ECF)

Question 21

what innervates smooth muscle?

Answer 21

the ANS

Question 22

smooth muscle resting membrane potential

Answer 22

-50 to -60 mV

Question 23

varicosities

Answer 23

contain vesicles filled with neurotransmitters

Question 24

diffuse junctions

Answer 24

autonomic nerve fibers that branch diffusely on top of a sheet of muscle fibers

Question 25

contact junctions

Answer 25

varicosities that are close to the cell membrane that have rapid contraction

Question 26

spike potentials

Answer 26

similar to skeletal muscle AP. drastic increase in mV

Question 27

what causes spike potentials?

Answer 27

electrical stimulation, action of hormones, transmitter substances from nerve fibers, stretch, spontaneous generation

Question 28

plateau potentials

Answer 28

repolarization is delayed allowing for prolonged contraction

Question 29

slow wave action potentials

Answer 29

create rhythmical phases when the cells are self excitatory

Question 30

where are slow wave APs used?

Answer 30

GI tract

Question 31

pacemaker waves

Answer 31

repetitive sequences of APs that cause rhythmical contractions of smooth muscle

Question 32

where are pacemaker waves contractions used?

Answer 32

specific GI organs. stomach (3/min) + duodenum (12/min)

Question 33

what causes depolarization of smooth muscle?

Answer 33

influx of calcium by voltage gated Ca+ channels

Question 34

does smooth muscle have a long or short latent period?

Answer 34

long

Question 35

what is needed to relax smooth muscle?

Answer 35

dephosphorylation of myosin

Question 36

parasympathetic postganglionic neurons

Answer 36

release ACH which binds to muscarinic receptors

Question 37

what does parasympathetic ACH cause contraction of?

Answer 37

smooth muscle of GI tract, bronchi, iris sphincter, ciliary muscles, and some veins

Question 38

what do sympathetic postganglionic neurons release?

Answer 38

norephinephrine which activates adrenergic receptors

Question 39

what do sympathetic postganglionic receptors innervate?

Answer 39

sweat glands that release ACH

Question 40

activation of alpha-1 recpetors causes?

Answer 40

smooth muscle to contract

Question 41

activation of beta-2 receptors causes?

Answer 41

smooth muscle to relax

Question 42

where are alpha-1 receptors found?

Answer 42

blood vessels for skin and GI

Question 43

where are beta-2 receptors found?

Answer 43

cardiac muscle, skeletal muscles, bronchial muscles

Question 44

junction potential

Answer 44

local depolarization occurs across the membrane to allow an influx of calcium for muscle contraction

Question 45

why do junction potentials occur?

Answer 45

bc muscle fibers are too small to generate an AP

Question 46

muscle stretch

Answer 46

smooth muscle is stretch generating spontaneous APs to contract smooth muscle

Question 47

what cells are the pacemakers for GI smooth muscle?

Answer 47

interstitial cells of cajel

Question 48

what causes small blood vessels to contract/relax?

Answer 48

chemicals released by the tissues they supply

Question 49

vasodilation of small blood vessels

Answer 49

lack of oxygen. excess carbon dioxide. increased H+. increase in tissue temp. decrease in BP. lactic acid, adenosine, potassium ions, nitric oxide

Question 50

vasoconstriction in small blood vessels

Answer 50

increased blood pressure

Question 51

hormone gated excitatory receptors

Answer 51

open sodium or calcium channels

Question 52

hormone gated inhibitory receptros

Answer 52

close sodium or calcium channels

Question 53

slow cycling of myosin cross bridges

Answer 53

myosin attach to actin, release actin and reattachment is MUCH SLOWER

Question 54

low energy requirement for smooth muscle contraction

Answer 54

conserves energy in intestines, urinary bladder, gall bladder, etc

Question 55

total contraction time for smooth muscle

Answer 55

1-3 seconds

Question 56

why is maximum force of contraction in smooth muscle greater than skeletal muscle?

Answer 56

because of prolonged periods of attachment of the myosin cross bridges to the actin filaments

Question 57

latch mechanism

Answer 57

ability of smooth muscle to maintain prolonged tonic contraction for hours with little energy use

Question 58

stress-relaxation of smooth muscle

Answer 58

ability to return to original force of contraction after muscle has been elongated/shortened