Lecture 10 Flashcards
smooth muscle compared to skeletal muscle is ____ in size, and although the arrangement of fibers is different, the actin and myosin contraction is the same
smooth muscle much smaller (1-5 micrometers by 20-500)
what are the two types of smooth muscle?
multi-unit
unitary
multi-unit type of smooth muscle
separate smooth muscle fibers with independent membrane covering each fiber
Each fiber can contract independently of others in the bundle
contraction caused by single nerve innervating each fiber
Ex : iris of the eye
Unitary type of smooth muscles
fibers arranged in sheets or bundles, and sum their contraction forces
also called syncytial smooth-muscle because all fibers are connected by gap junctions
- these allow ions to flow freely from one smooth muscle cell to the next.
control of smooth muscle similarities and differences to skeletal muscle?
SIMILAR
calcium ions and ATP/ADP complexes are needed for contraction for both
DIFFERENT
dense bodies are end points of actin filaments
- through which force can be transmitted to the next cell
the myosin arrangment is thought to pull from the _____ of actin filaments between the ______. this arrangement allows _______________
center
dense bodies
contraction to occur in multiple direction across the smooth muscle
in skeletal muscle, _____ anchor at both ends, but in smooth muscle, _____ do this
Z discs
dense bodies
On average, smooth muscle requires __________ to begin contraction, then reaches full contraction in _______.
Then contraction decreases for ________.
This is _____ longer than a single contraction in skeletal muscle.
However, different smooth muscle types throughout the body are highly variable (_________per contraction)
50-100 milliseconds
.5 seconds
1 -2 seconds.
30x
0.2 to 30 seconds
The strength of smooth muscle contractions is ____ than skeletal muscle. This is thought to be a result of the amount of time the actin/myosin heads are attached in smooth muscle (much _______), which helps to determine the strength of a contraction.
Thought to be a result of __________ in smooth muscle, which slows _______ of the ATP that energizes the movement of the myosin and actin. This ____ cycling considerably.
much more
longer
decreased ATPase
degradation
slows
smooth muscle’s slow cycle allows a ________than an equal mass of skeletal muscle despite _____
greater contraction force
lower energy use
once a contraction has initiated, smooth muscle can maintain a prolonged contraction, holding its _______ position for long periods of time with _________ energy usage. this mechanism is called ______
shortened
decreased
latch mechanism
the energy for prolonged contraction is ____ the energy required for skeletal muscle
1/300 th
how much nerve signal is needed to allow this prolonged interaction in skeletal muscle?
little nerve signal needed
Smooth muscle that surrounds ________ need to provide ______ force to that organ, despite significant changes in ______ of that organ at times.
This ability is called the _____________, or conversely, the ___________, which allows the bladder to_______ in size but have the ___________ after voiding a large volume of urine
hollow organs
consistent
volume
Stress-relaxation response
reverse stress-relaxation response
shrink
same pressure
however _____ Is the initiating stimulus in smooth and skeletal, smooth also has stimuli such as _____,_____,_______,_____.
calcium
nerve stimulation
hormone stimulation
stretch of smooth muscle fibers
chemical change on the fiber’s environment
Instead of troponin as a regulatory protein, smooth muscle uses _______ (_____).
_________ either enter from the cytosol, or are released from the SR and They bind with CaM.
This complex activates ______________which phosphorylates the _______, which can then bind to actin, causing contraction.
Calmodulin (CaM)
Calcium ions
Myosin light chain kinase (MLCK)
myosin head
The SR in smooth muscle has _____ Calcium readily available than in skeletal muscle.
Calcium from the __________, and the ____________ Calcium combine to make calcium the _________ for smooth muscle contraction.
less
extracellular space
SR
limiting factor
relaxation of the smooth muscle requires the removal of ______ from the intracellular fluid.
This requires a ________ that moves calcium out of the cell, or into the SR, where present.
This allows calcium to create a threshold _____ where smooth muscle contraction occurs, and _____ which no contraction is stimulated.
calcium
calcium pump
above
below
This process of removal of calcium does not allow the ______ to ______________.
So what happens to stop the contraction?
This is what is thought to allow ________ to occur in smooth muscle
- until ____________ acts, the myosin head is engaged and “holding” tension.
myosin heads
disengage from actin via phosphorylation
Myosin Phosphatase splits the phosphate from the light chain (MLCK)
Latching
Mysoin Phosphatase
the neuromuscular junction of smooth muscle invloves _______________ control rather than _______ control.
autonomic
voluntary
the organized movement of neurotransmitter to transmit an action potential to smooth muscle is _____
not present
the neuromuscular junction of smooth muscle involves nerve fibers that branch out over ______ of smooth muscle.
the neurotransmitter is then diffused to _____ on the _____ of smooth muscle, and through ______ to the rest of the smooth muscle cells in the muscle
the surface of a sheet
receptors
surface
gap junction
what are the types of smooth muscle action potentials?
A
B
C
what are type A smooth muscle action potentials?
single spike depolarization caused by an enternal stimulus
what are type B smooth muscle action potentials?
repetitive spike depolarizations
- might be found in the gastrointestinal wall
- which are generated spontaneously
what are type C smooth muscle action potentials?
prolonged depolarization (delayed repolarization)
- in smooth muscle that requires prolonged contraction
- like the uterus
much of the smooth muscle in the body is excited by ________
muscle stretch
GI and vascular smooth muscle ______ when ______ to move boluses of food or blood along and safely distribute volume without rupturing the tract or vessel.
contract
distended
Smooth muscle reacts to stretch by _______ to keep volumes and pressures consistent.
constricting
Smooth muscle must also relax to allow more blood flow Caused by
Lack of oxygen to local tissue
Excess carbon dioxide
Increased Hydrogen Ion concentration
Increased body temperature
Decreased blood pressure
When smooth muscle contains receptors for them, ________can cause contraction or relaxation of smooth muscle.
hormones
The hormones that are active on smooth muscle include
Norepinephrine
Epinephrine
Angiotensin II
Endothelin
Vasopressin
Oxytocin
Serotonin
Histamine
