Smooth Muscles

Question 1

What are the cell characteristics of skeletal muscle?

Answer 1

Long & cylindrical, multinucleated, heavily striated

Question 2

What are the cell characteristics of cardiac muscle?

Answer 2

Branching networks, intercalated disks, single nucleus, lightly striated

Question 3

What are the cell characteristics of smooth muscle?

Answer 3

Tapered at each end, nonstriated

Question 4

What is the control of:

1. Skeletal
2. Cardiac
3. Smooth

Answer 4

1. Voluntary
2. Involuntary
3. Involuntary

Question 5

Of the muscles, which have T tubules?

Answer 5

Skeletal + Cardiac

Question 6

Of the muscles, which have the most developed SR?

Answer 6

Skeletal

Question 7

Of the muscles, which have the least developed SR?

Answer 7

Smooth

Question 8

What are the sources of calcium in the skeletal muscle?

Answer 8

SR

Question 9

What are the sources of calcium in the cardiac muscle?

Answer 9

Extracellular fluid + SR

Question 10

What are the sources of calcium in the smooth muscle?

Answer 10

Extracellular fluid + SR

Question 11

Of the muscles, which have troponin?

Answer 11

Skeletal + Cardiac

Question 12

Of the muscles, which do not have troponin?

Answer 12

Smooth

Question 13

Of the muscles, which have gap junctions?

Answer 13

Cardiac, some in smooth

Question 14

What are the neurotransmitters that are emitted from the initiation of smooth muscles?

Answer 14

Norepinephrine + Acetylcholine

Question 15

With regards to smooth muscle, what does norepinephrine do?

Answer 15

Activates a- or b-adrenergic receptors

Question 16

With regards to smooth muscle, what does acetylcholine do?

Answer 16

Activates muscarinic receptors

Question 17

Action potentials in smooth muscle open what channel?

Answer 17

Calcium

Question 18

In terms of speed, what is the difference in calcium and sodium channels?

Answer 18

Calcium channels open / close slower

Question 19

What causes a plateau in an action potential?

Answer 19

Delay opening of potassium channel

Question 20

Can smooth muscle be initiated w/o action potential?

Answer 20

Yes

Question 21

What are the steps of initiation of smooth muscle w/o action potential?

Answer 21

1. Neurotransmitter (e.g., Acetylcholine) activates muscarinic receptor
2. Leading to activation of G protein
3. Leading to activation of phospholipase C (PLC)
4. Increases production of inositol-tris-phosphate (IP3)
5. Stimulates calcium release from ER, which leads to calcium influx from extracellular fluid

Question 22

What is the relation between oxygen and smooth muscle contractibility?

Answer 22

Low oxygen = relaxed

Question 23

What is the relation between CO2 and smooth muscle contractibility?

Answer 23

High CO2 = relaxed

Question 24

What is the relation between pH and smooth muscle contractibility?

Answer 24

Low pH = relaxed

Question 25

What are the steps of smooth muscle contraction?

Answer 25

1. Calcium ions come from outside of the cell or the ER.
2. Calcium ions bind to calmodulin, which activates myosin light chain kinase (MLCK).
3. MLCK hydrolyses ATP and phosphorylates myosin light chain.
4. Phosphorylation activates myosin.
5. Myosin-actin crossbridge cycling occurs (as in skeletal muscle).
6. When calcium is pumped out of the cell, myosin light chain is dephosphorylated by myosin light chain phosphatase.
7. The myosin becomes inactive, and the muscle relaxes.