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Physiology > Cardiovascular Physiology Smooth Muscle > Flashcards

Cardiovascular Physiology Smooth Muscle Flashcards

(54 cards)

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1
Q

where is smooth muscle found

A

around hollow organs such as blood vessels, airways, GI tract, uterus and fallopian tubes, ureters and bladder

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2
Q

what is smooth muscle important in

A

ocular function, piloerection

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3
Q

what can contraction of smooth muscle cause

A

propulsion or resistance

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4
Q

is stimulus for smooth muscle intrinsic or extrinsic

A

can be either

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5
Q

what is smooth muscle regulated by

A

autonomic neurons, hormones, and autocrine/paracrine signals

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6
Q

describe the smooth muscle cell

A

smaller cells with single central nucleus

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7
Q

describe the contraction of smooth muscle compared to skeletal muscle

A

-contractions are slower to develop
-contractions last significantly longer
-maximum force generation greater
-primarily oxidative metabolism

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8
Q

what is the shape of smooth muscle cells

A

elongated and tapered

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9
Q

does smooth muscle contain T tubules or SR

A

lacks T tubules and only has rudimentary SR

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10
Q

describe the duration of twitches between all 3 types of muscle

A

skeletal muscle is shortest and smooth muscle is the longest

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11
Q

what are the 2 types of smooth muscle

A

-multi unit
- single unit (unitary, visceral)

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12
Q

describe multi unit smooth muscle

A

-no gap junctions
-each cell responds independently
- muscle behaves as multiple units
-control exerted mainly by nerve signals
- cells function independently
- no tone

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13
Q

describe single unit smooth muscle

A

-cells connected by gap junctions
-functional syncytium
-control by variety of stimuli
- pacemaker cells
-cells organize into sheets or bundles
-may have tone

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14
Q

what are examples of multi unit smooth muscle

A

-piloerector muscle
-iris
- ciliary muscles

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15
Q

what are examples of single unit smooth muscle

A

gut
bladder
uterus

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16
Q

what is an example of a multi unit and single unit smooth muscle cell

A

blood vessels

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17
Q

what are the contractile elements of smooth muscle

A

actin and myosin

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18
Q

describe actin in smooth muscle

A

higher levels and longer than in skeletal/cardiac myocytes
- arranged diagonally to long axis of cell

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19
Q

what does alpha actinin attach to

A

actin to dense bodies instead of Z line

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20
Q

describe myosin in smooth muscle

A

-fewer myosin fibers than skeletal/cardiac myocytes
- myosin filaments interspersed with actin

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21
Q

what does calcium bind to in smooth muscle

A

calmodulin

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22
Q

what are the two actin binding proteins and what do each do

Study These Flashcards
A
  • calponin: inhibits myosin ATPase
  • caldesmon: inhibits myosin/actin bond
23
Q

what needs to be removed from calcium in smooth muscle before contraction can occur

Study These Flashcards
A

calponin and caldesmon

24
Q

is smooth muscle organized into sarcomeres

25
what are the requirements for contraction in smooth muscle
-calcium -ATP -myosin light chain phosphorylation
26
what is myosin light chain phosphorylation required for
myosin head to interact with actin
27
what does myosin light chain kinase do
adds phosphate and begins contraction
28
what does myosin light chain phosphatase do
removes phosphate and stops contraction
29
what can smooth muscle contraction be stimulated by
-stretch -ligands (NTs, hormones, paracrines, autocrines) -intrinsic activity (pacemaker cells)
30
where does calcium come from in smooth muscle
mostly extracellular and some intracellular
31
are action potentials required for contraction
no or depolarization
32
are smooth muscle cells tonic or phasic
tonic, they are normally contracted and can alter their force of contraction
33
what is cross bridge cycling in smooth muscle controlled by
a calcium regulated enzyme that phosphorylates myosin
34
what are the steps of contraction in smooth muscle
- inactive calmodulin -> actin calcium calmodulin -inactive myosin light chain kinase -> active myosin light chain kinase -phosphorylation by myosin light chain kinase which forces cross bridge toward thin filament - cross bridge cycling - myosin light chain phosphatase dephosphorylates and stops contraction
35
what are the two sources of calcium in smooth muscle
-the SR - extracellular calcium entering the cell through plasma membrane calcium channels
36
how is the calcium removed in smooth muscle
-to SR via calcium ATPase - to ECF via calcium ATPase and sodium/calcium exchanger
37
how do you vary the force of contraction in smooth muscle
alter the amount of calcium
38
what is the latch state
tension is maintained in the smooth muscle although calcium levels and ATP usage in the cytosol are low
39
what is the mechanism for how the latch state occurs
-binding of acetylcholine to muscarininc receptors - increased influx of calcium into the cell - activation of calmodulin dependent myosin light chain kinase - phosphorylation of myosin - increased myosin ATPase activity and binding of myosin to actin -contraction -dephosphorylation of myosin by myosin light chain phosphatase -relaxation or sustained contraction due to the latch bridge and other mechanisms
40
which muscle cells can be activated or inhibited
smooth muscle and cardiac muscle
41
do smooth muscle neurons form synapses
no
42
what do smooth muscle axons contain
varicosities
43
where is the NT in smooth muscle released into
interstitial fluid
44
how does the NT distribute to receptors on smooth muscle cell surfaces
via simple diffusion
45
do hormones change membrane potential in smooth muscle
may or may not
46
what is the difference between multiunit and single unit smooth muscle
mutli unit smooth muscle - each cell has its own activation in single unit smooth muscle - theres only one signal to all cells
47
what local factors cause smooth muscle activation
paracrine signals, acidity, O2, and CO2 levels, osmolarity and the ion composition of the ECF
48
what does response to local factors do
alters smooth muscle contraction in response to changes in the muscles immediate internal environment, independent of long distance signals from nerves and hormones
49
what local factor causes smooth muscle relaxation
nitric oxide
50
what does stretching do locally to smooth muscle
cause response by contracting by opening mechanosensitive ion channels leading to membrane depolarization
51
describe pacemaker potentials in smooth muscle
-resting membrane not stable, slow depolarization to threshold -mechanism unknown
52
where are smooth muscle pacemaker cells found
in GI tract
53
what is the only type of muscle that has tone
single unit smooth muscle
54
which muscle type is unaffected by hormones
skeletal

Physiology (41 decks)

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