• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

Card Range To Study

through

image

Play button

image

Play button

image

Progress

1/15

Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

15 Cards in this Set

  • Front
  • Back
What are the general characteristics of smooth muscle?
muscles of hollow organs.
not attached to skeleton.
innervated by ANS (extrinsic) and by nuerons in plexuses within smooth muscle tissue (intrinsic)
uninucleate
spindle shaped
smaller than skeletal
SR not as elaborate as skeletal
Does smooth muscle have T-tubules?
NOOOOOOOOOO!
What are the two types of smooth muscle?

compare them
Single-unit (visceral) - most common type, cells connected by gap junctions and respond as a unit
show spontaneous fluctuations in membrane potential that an lead to APs and contraction


Multiunit - less common, few gap junctions, cells respond individually, no spontaneous contractile activity and no APs
compare the locations of single unit vs multiunit smooth muscle
single = common = intestines, uterus, small arteries and veins

multi = iris, ciliary muscles
describe the contractile proteins in smooth muscle
contain myosin, actin, tropomyosin but NOT TROPONIN

not organized into sarcomeres
-thin filaments anchor to dense bodies, each group of thin surrounds a few thick fibers, higher thin/thick ratio then skeletal
describe the biochemistry of activation/contraction/relaxation of smooth muscle
1. stimulation --> increase in Ca inside
2. calcium binds to calmodulin
3. Ca-Cam complex activates myosin kinase
4. MK phosphorylates myosin molecules
5. Myosin-P interacts w/ actin producing contraction
6. Ca actively pumped out of cell or into SR
7. MK inactivates and stops phosphorylating myosin
8. myosin-phosphatase dephosphorylates myosin-P
9. smooth muscle relaxes
what is the Latch State?
if myosin is attached to actin it very slowly detaches. this occurs when intracellular Ca levels are intermediate and results in the maintenance of tension without energy expenditure.
how does changing the Ca sensitivity of the contractile proteins affect the contractile forces?
inhibition of phosphatase produces greater force of contraction at a given Ca level.

a decrease in the activity of the kinase reduces the force of contraction at a given Ca level.
what are the three mechanisms for Ca influx across the sarcolemma?
1. voltage-gated channels. abundant in smooth muscle, open by depolarization
2. receptor-regulated. opened by NTs or hormones, produce little or no depolarization
3. store-operated. open when SR Ca levels are low.
What are the 2 mechanisms for Ca efflux from the SR?
receptor-regulated efflux - binding of NT or hormone causes formation of 2nd messenger (IP3) which causes release of Ca from SR. Does not involve a membrane potential change.

Ca-induced Ca release -
Ca influx across the sarcolemma releases Ca from the SR, not as important as IP3.
What are the two pathways for extruding Ca from the myoplasm?
Sarcolemma Pathway - Ca Pump or Na-Ca exchanger

SR pathway - Ca pumps on SR membrane pump Ca into SR
SR contains Ca-binding proteins calreticulin in addition to calsequestrin
describe the speed of contraction in smooth muscle
contraction-relaxation cycle is very slow in smooth muscle (seconds)
-myosin has a slow attachment and detachment rate
-pumping of Ca out of myoplasm is slow
describe the energy supply in smooth muscle
Crossbridge recycling requires ATP
-no reserve such as creatine phosphate
-most ATP comes from aerobic metabolism
-ATP anaerobic when O2 is low
-sustained contraction uses less ATP than equivalent contraction in skeletal muscle (probably related to prolonged attachment of myosin)
Length-tension relationship and degree of shortening in smooth muscle
smooth muscles generate tension under greater stretch than can skeletal.
-allows hollow organs to undergo considerable stretching without loss of contractile capability of muscles surrounding them

smooth can undergo greater degree of shortening allowing volume of hollow organs to vary
what is smooth muscle tone?
a sustained low level of tension in smooth muscle due to a sufficient amount of free intracellular Ca to sustain it