Smooth muscle Flashcards
how does the synaptic input to smooth muscle differ from skeletal muscle?
- neurons are part of the autonomic NS instead of somatic NS.
- the neuron makes multiple synaptic contact through varicosities.
what are varicosities
multple synaptic contacts with a smooth muscle cell that contain the presynaptic machinery for vesicular release of transmitter
is the postsynaptic membrane of smooth muscle specilalized
little specialisation
What is multi unit smooth muscle
each muscle cell gets it own synaptic unput, but there is little intercellular EC. as a result smooth muscle cells may contract independently.
what kind of smooth muscle is found in the iris and the piloerector muscle of the skin
multi unit
what kind of smooth muscle is capable of fine control
multi unit
what is unitary or single unit smooth muscle?
a group of cells that work as a syncytium because gap junctions provide electrical and chemical communication between neighboring cells.
do gap junctions in unitary smooth muscle cause chemical or eletrical communication?
both
what gives rise to the spreading of Calcium waves
Gap junction that allow ions and small molecules to diffuse between cewlls.
what kind of smooth muscle is found within the walls of viscera
unitary smooth muscle
what is visceral smooth muscle
unitary smooth muscle
The functional size of the unit depends on the strength of intercellular coupling. For example, in the bladder, extensive coupling among cells defines large functional units, which allows the cells of the muscular wall of the bladder to contract in synchrony. On the other hand, the smooth-muscle cells of blood vessels couple to form smaller, independently functioning units that are more akin to multiunit smooth muscle.
The functional size of the unit depends on the strength of intercellular coupling. For example, in the bladder, extensive coupling among cells defines large functional units, which allows the cells of the muscular wall of the bladder to contract in synchrony. On the other hand, the smooth-muscle cells of blood vessels couple to form smaller, independently functioning units that are more akin to multiunit smooth muscle.
what is different about changes to Vm changes in smooth muscle
action potentials initiate contraction in both skeletal and cardiac muscle, diverse changes in membrane potential ( V m ) can either initiate or modulate contraction in smooth-muscle cells
You see a AP that looks like those seen in skeletal muscles, what kind of smooth muscle is probabky reponsible.
unitary smooth muscle
some in multiunit
can all smooth muscle cells generate AP?
not all
What can generate a graded response in smooth muscle
circulating and local humoral factors and mechanical stimilu such as stretching the cell.
is the AP of unitary smooth muscle longer or shorter than of skeletal
a slower upstroke and longer duration (up to ~100 ms)
what reflects the depolarizing phase of smooth muscle?
opening of L-type voltage gated calcium channels.
what channels open faster cav or Nav
Nav are faster, thats why the rate of AP in smooth muscle is slower
Why is repolarisation of smooth muscle slower?
L-type Cav exhibit prolonged opening and inactivate slowly, and delayed activasion of voltage gated K channels, n many cases, Ca 2+ -activated K + channels, which depend on significant elevation of [Ca 2+ ] i .
is hyperpolarisation slow in smooth muscle
yes
where do plateau AP take place in smooth muscle?
genitourinary tract, including the ureters, bladder, and uterus.
what does plateau in AP do?
prolonged entry of Ca 2+ , thereby elevating [Ca 2+ ] i and prolonging the contraction.
why do some smooth muscle cells have Nav channels?
not appear to be necessary for generating an action potential but rather contribute to a greater rate of depolarization and thus the activation of voltage-gated Ca 2+ channels.