Lecture 10

Question 1

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

Answer 1

smooth muscle much smaller (1-5 micrometers by 20-500)

Question 2

what are the two types of smooth muscle?

Answer 2

multi-unit
unitary

Question 3

multi-unit type of smooth muscle

Answer 3

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

Question 4

Unitary type of smooth muscles

Answer 4

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.

Question 5

control of smooth muscle similarities and differences to skeletal muscle?

Answer 5

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

Question 6

the myosin arrangment is thought to pull from the _____ of actin filaments between the ______. this arrangement allows _______________

Answer 6

center
dense bodies

contraction to occur in multiple direction across the smooth muscle

Question 7

in skeletal muscle, _____ anchor at both ends, but in smooth muscle, _____ do this

Answer 7

Z discs
dense bodies

Question 8

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)

Answer 8

50-100 milliseconds
.5 seconds

1 -2 seconds.
30x

0.2 to 30 seconds

Question 9

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.

Answer 9

much more
longer

decreased ATPase
degradation
slows

Question 10

smooth muscle’s slow cycle allows a ________than an equal mass of skeletal muscle despite _____

Answer 10

greater contraction force
lower energy use

Question 11

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 ______

Answer 11

shortened
decreased

latch mechanism

Question 12

the energy for prolonged contraction is ____ the energy required for skeletal muscle

Answer 12

1/300 th

Question 13

how much nerve signal is needed to allow this prolonged interaction in skeletal muscle?

Answer 13

little nerve signal needed

Question 14

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

Answer 14

hollow organs
consistent
volume

Stress-relaxation response
reverse stress-relaxation response
shrink
same pressure

Question 15

however _____ Is the initiating stimulus in smooth and skeletal, smooth also has stimuli such as _____,_____,_______,_____.

Answer 15

calcium

nerve stimulation
hormone stimulation
stretch of smooth muscle fibers
chemical change on the fiber’s environment

Question 16

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.

Answer 16

Calmodulin (CaM)
Calcium ions
Myosin light chain kinase (MLCK)
myosin head

Question 17

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.

Answer 17

less
extracellular space
SR
limiting factor

Question 18

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.

Answer 18

calcium
calcium pump
above
below

Question 19

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.

Answer 19

myosin heads
disengage from actin via phosphorylation

Myosin Phosphatase splits the phosphate from the light chain (MLCK)
Latching
Mysoin Phosphatase

Question 20

the neuromuscular junction of smooth muscle invloves _______________ control rather than _______ control.

Answer 20

autonomic
voluntary

Question 21

the organized movement of neurotransmitter to transmit an action potential to smooth muscle is _____

Answer 21

not present

Question 22

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

Answer 22

the surface of a sheet
receptors
surface
gap junction

Question 23

what are the types of smooth muscle action potentials?

Answer 23

A
B
C

Question 24

what are type A smooth muscle action potentials?

Answer 24

single spike depolarization caused by an enternal stimulus

Question 25

what are type B smooth muscle action potentials?

Answer 25

repetitive spike depolarizations
- might be found in the gastrointestinal wall
- which are generated spontaneously

Question 26

what are type C smooth muscle action potentials?

Answer 26

prolonged depolarization (delayed repolarization)
- in smooth muscle that requires prolonged contraction
- like the uterus

Question 27

much of the smooth muscle in the body is excited by ________

Answer 27

muscle stretch

Question 28

GI and vascular smooth muscle ______ when ______ to move boluses of food or blood along and safely distribute volume without rupturing the tract or vessel.

Answer 28

contract
distended

Question 29

Smooth muscle reacts to stretch by _______ to keep volumes and pressures consistent.

Answer 29

constricting

Question 30

Smooth muscle must also relax to allow more blood flow Caused by

Answer 30

Lack of oxygen to local tissue
Excess carbon dioxide
Increased Hydrogen Ion concentration
Increased body temperature
Decreased blood pressure

Question 31

When smooth muscle contains receptors for them, ________can cause contraction or relaxation of smooth muscle.

Answer 31

hormones

Question 32

The hormones that are active on smooth muscle include

Answer 32

Norepinephrine
Epinephrine
Angiotensin II
Endothelin
Vasopressin
Oxytocin
Serotonin
Histamine