Physio Ch 08

Question 1

2 major types of smooth muscles

Answer 1

multi-unit smooth muscle and unitary (or single-unit) smooth muscle

Question 2

discrete, separate smooth muscle fibers

Answer 2

multi-unit smooth muscle

Question 3

major share of control is exerted by non-nervous stimuli

Answer 3

unitary smooth muscle

Question 4

Where are some locations of multi-unit smooth muscle

Answer 4

ciliary muscle of the eye, iris muscle of the eye, piloerector muscles

Question 5

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

Answer 5

unitary smooth muscle

Question 6

present in cell membrane of unitary smooth muscle wherein ions can flow freely from one muscle to the next

Answer 6

gap junctions

Question 7

also known as syncytial smooth muscle because of its syncytial interconnections among fibers

Answer 7

unitary smooth muscle

Question 8

visceral smooth muscle are found in these organs

Answer 8

GI tract, bile duct, ureter, uterus, blood vessels

Question 9

It is mainly through these bonds that the force of contraction is transmitted from one cell to the next

Answer 9

dense bodies

Question 10

serve the same role as the Z discs in skeletal muscle

Answer 10

dense bodies of smooth muscles

Question 11

sidepolar of crossbridges in smooth muscles allows it to contract how many percent of their length

Answer 11

80 percent

Question 12

major factor that determines the force of contraction in smooth muscles

Answer 12

fraction of time

Question 13

these organs maintain muscle contraction indefinitely

Answer 13

intestines, urinary bladder, gallbladder

Question 14

a typical smooth muscle reach full contraction in

Answer 14

0.5 seconds later

Question 15

reaches full contraction about 0.5 second later, and then declines in contractile force in another

Answer 15

1 to 2 seconds

Question 16

great force of smooth muscle contraction results from

Answer 16

prolonged period of attachment of the myosin cross bridges to the actin filaments

Question 17

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

Answer 17

latch mechanism

Question 18

Another important characteristic of smooth muscle, especially the visceral unitary type of smooth muscle of many hollow organs

Answer 18

stress relaxation of smooth muscle

Question 19

allow a hollow organ to maintain about the same amount of pressure inside its lumen despite long-term, large changes in volume

Answer 19

stress relaxation or reverse stress relaxation

Question 20

Factors that influence the increase of calcium ions in intracellular fluid

Answer 20

nerve stimulation, hormonal stimulation, stretch of the fiber, change in chemical environment of the fiber

Question 21

In place of troponin, smooth muscle cells contain a large amount of another regulatory protein

Answer 21

calmodulin

Question 22

calmodulin initiates contraction by?

Answer 22

activating myosin cross-bridges

Question 23

the chain present in the light chains of myosin heads, that once phosphorylated attachment-detachment of myosin head with actin filament occurs

Answer 23

regulatory chain

Question 24

calmodulin calcium complex binds with this enzyme that causes regulatory chain to be phosphorylated

Answer 24

myosin light chain kinase

Question 25

located in the cytosol of the smooth muscle cell, which splits the phosphate from the regulatory light chain

Answer 25

myosin phosphotase

Question 26

allows longterm maintenance of tone in many smooth muscle organs without much expenditure of energy

Answer 26

latch mechanism

Question 27

innervate smooth muscle located on top of a sheet of muscle fibers

Answer 27

autonomic nerve fibers

Question 28

autonomic nerve fibers forms this complex in order to secrete their transmitter subtance into the matrix through

Answer 28

diffuse junctions

Question 29

axons in smooth muscle fiber do not have branching end feet type but have this instead distributed along their axes

Answer 29

varicosities

Question 30

function in much the same way as the skeletal muscle neuromuscular junction

Answer 30

contact junction

Question 31

rapidity of contraction of these smooth muscle fibers is considerably faster than that of fibers stimulated by the diffuse junctions

Answer 31

contact junction

Question 32

most important transmitter substances secreted by the autonomic nerves innervating smooth muscle

Answer 32

ACH, norepinephrine

Question 33

normal resting state of smooth muscle

Answer 33

negative fifty to negative sixty

Question 34

action potential of this smooth muscle do not normally occur the same way as skeletal muscles

Answer 34

multi-unit smooth muscle

Question 35

action potentials of visceral smooth muscle occur in one of two forms

Answer 35

spike potentials, action potential with plateus

Question 36

spike potential duration

Answer 36

10 to 50 milliseconds

Question 37

its importance account for the prolonged contraction that occurs in some types of smooth muscles

Answer 37

plateau

Question 38

flow of these cations to the interior of smooth muscle fiber is mainly responsible for the action potential

Answer 38

calcium ions

Question 39

a local property of the smooth muscle fibers that make up the muscle mass

Answer 39

slow wave rhythm

Question 40

caused by waxing and waning of the pumping of positive ions outward through the muscle fiber membrane

Answer 40

slow wave rhythm

Question 41

when strong enough, can initiate action potentials

Answer 41

slow wave rhythm

Question 42

approximate threshold for eliciting action potentials in most visceral smooth muscle

Answer 42

negative 60 to about negative 35 millivolts

Question 43

repetitive sequences of action potentials elicit rhythmical contraction of the smooth muscle mass

Answer 43

pacemaker waves

Question 44

when stretched sufficiently, spontaneous action potentials generate

Answer 44

unitary smooth muscle

Question 45

Excitation of visceral smooth muscle by muscle stretch is a result from

Answer 45

normal slow wave potentials; decrease in overall negativity of the membrane potential caused by the stretch itself

Question 46

how many fibers must depolarize simultaneously before action potential ensues in multi-unit smooth muscle

Answer 46

30 to 40 smooth muscle fibers

Question 47

local depolarization of multi unit smooth muscle caused by the nerve transmitter substance

Answer 47

junctional potential

Question 48

2 types of non nervous and non action potential stimulants

Answer 48

local tissue chemical factors, hormones

Question 49

cause vasodilation

Answer 49

Adenosine, lactic acid, increased potassium ions, diminished calcium ion concentration, and increased body temperature

Question 50

hormones affecting smooth muscle contraction in some degree

Answer 50

norepinephrine, epinephrine, acetylcholine, angiotensin, endothelin, vasopressin, oxytocin, serotonin, and histamine

Question 51

hormone causes contraction of a smooth muscle when the muscle cell membrane contains

Answer 51

hormone gated excitatory receptors

Question 52

time required for this diffusion of calcium ions into the cell occur averages 200 to 300 milliseconds before contraction begins

Answer 52

latent period

Question 53

latent period is greater by how many times in smooth muscle compared to skeletal

Answer 53

50 times

Question 54

Small invaginations of the cell membrane in smooth muscle

Answer 54

caveolae

Question 55

rudimentary analog of the transverse tubule system of skeletal muscle

Answer 55

caveolae

Question 56

When the extracellular fluid calcium ion concentration falls down into this number, smooth muscle contraction ceases

Answer 56

1/3 to 1/10 normal

Question 57

removes calcium and pumps back into ECF or sarcoplasmic reticulum

Answer 57

calcium pump

Question 58

Smooth muscle of each organ is distinctive from that of most other organs in several ways

Answer 58

1. physical dimension 2. organization into bundles or sheets 3. response to different types of stimuli 4. characteristics of innervation 5. function

Question 59

Major differences of smooth and skeletal muscles

Answer 59

1. physical organization 2. excitation-contraction coupling 3. control of the contractile process by calcium ions 4. duration of contraction 5. amount of energy required for contraction

Question 60

Control factors that influence smooth muscle contraction in response to local tissue chemical factors

Answer 60

1. Lack of oxygen in the local tissues causes smooth muscle relaxation and, therefore, vasodilatation 2. Excess carbon dioxide causes vasodilation 3. Increased hydrogen ion concentration causes vasodilation