small spindle shaped cells, 2-10 Micrometers in diameter, 20-600 micrometers in length
do smooth mm have banding pattern?
No
Sarcoplasmic reticulum of smooth mm
Not well developed
does smooth mm have transverse tubules?
No
thick and thin filaments of smooth mm are made of
actin, myosin, tropomysin + calmodulin
ratio of thick and thin filaments of smooth mm
10:1
Dense bodies on Smooth mm
similar to Z-lines of skeletal mm
Dense bands of smooth mm
attach actin to membrane
link dense bands to dense bodies and cytoskeleton network
intermediate filaments
attachments b/t cells
intermediate junction
low resistance electrical pathways b/w cells
gap junctions
from autonomic nervous system
innervation of smooth mm
twitches of smooth mm are ___ than skeletal mm (phasic)
slower
smooth mm does not _____
fatigue
dephosphorylates myosin so that it detaches from actin
phosphatase
major sources of calcium for contraction (4)
voltage-gated Ca channels
receptor mediated
stretch-activated
store-operated
T or F, Smooth mm has a neuromuscular junction
False
synapse b/w autonomic nerves and smooth mm is called
neuroeffector junction
Allows smooth mm to contract in concert with other cells
gap junctions (single unit smooth mm or unitary smooth mm)
Length-tension relationship of smooth mm is ____ then skeletal
broader (allows for variations in organ volume)
tension of smooth mm as compared to skeletal mm is _____,
Velocity of smooth mm as compared to skeletal mm is _____,
Reasons for this are (3 B)
the same,
10 to 100 times slower
(B) ATPase for myosin is slower,
Ca comes from extracellular sources,
cross bridge cycle depends on the degree of phosphorylation of the myosin (greater % phosphorylated myosin=faster velocity of contraction
depolarization causes the generation of an action potential. The tension generated is due to the entry of Ca through the voltage-gated Ca channels
Stimulus -induced action potentials
oscillations in the resting membrane potential bring the membrane to threshold and generate an action potential. The tension generated is due to the entry of Ca through the voltage-gated Ca channels.
Slow wave/ pacemaker depolarization
There are changes in the membrane potential with no action potentials. the tension in the mm is dependent on the membrane potential.
Graded potentials
Contraction w/out changes in membrane potential. Receptor activation leads to increase inositol triphosphate (IP3) and release of Ca from SR
Pharmacomechanical coupling
Agents that produce pharmacomechanical coupling (3)
