Muscle II

Question 1

What is the name of the structure that connects cardiomyocytes?

Answer 1

Intercalated disks

Question 2

What allows for the transfer of calcium from one cell to another?

Answer 2

Gap junctions

Question 3

T or F. Mitochondria are plentiful in cardiac muscle.

Answer 3

T

Question 4

What is the equivalent of a Z line in smooth muscle?

Answer 4

focal density

Question 5

T or F. Smooth muscle contains nebulin, titin, and myomesin.

Answer 5

F

Question 6

T or F. Smooth muscle has sarcomeres.

Answer 6

F

Question 7

What does smooth muscle have instead of a T system

Answer 7

Plasma membrane invaginations called caveolae

Question 8

What types of vesicles do smooth muscle have?

Answer 8

SR analogues w/ luminal calsequestrin

Question 9

What direction are the contraction vectors in smooth muscle?

Answer 9

All directions

Question 10

Is smooth muscle basophilic or eosionophilic? Why?

Answer 10

Basophilic - lots of RER for secretory activities (very much like fibroblasts)

Question 11

What can smooth muscle be replaced by?

Answer 11

Differentiation from pericytes

Question 12

Describe skeletal muscle EC coupling.

Answer 12

• Sarcolemma dihydropyridine receptor changes conformation with action potential, opening a ryanodine receptor in SR.
• Ca2+ passively leaves contained SR through the ryanodine receptor into the cell.
• Ca2+ binds troponin so tropomyosin reveals actin myosin interaction site
• Contraction occurs
• Ca2+ is reaccumulated by smooth ER calcium ATPase relaxation, so Ca2+ can reenter SR and bind to calsequestrin

Question 13

Which EC coupling does not require extracellular calcium, does not involve calcium induced calcium release, and has well organized and closely aligned T system and terminal cisterna in SR?

Answer 13

Skeletal muscle EC coupling

Question 14

Describe cardiac muscle EC coupling.

Answer 14

• Extracellular “trigger” Ca2+ enters cell during plateau phase of action potential which causes dihydropyridine receptors on sarcolemma to allow this influx
• Trigger Ca2+ activates ryanodine receptors
• Cytoplasmic Ca2+ increases
• Ca2+ binds troponin, tropomyosin uncovers actin/myosin interaction site, contraction
• Relaxation involves Ca/Na exchanger on sarcolemma and Ca ATPase on smooth ER

Question 15

What kinds of channels are dihydropyridine receptors and ryanodine receptors

Answer 15

Voltage-gated

Question 16

Where are RYR (ryanodine receptors) located?

Answer 16

Sarcoplasmic reticulum membrane

Question 17

Where are dihydropyridine (DHP) receptors located?

Answer 17

Sarcolemma (plasma membrane)

Question 18

Which type of EC coupling uses triad T-tubules?

Answer 18

Skeletal muscle EC coupling

Question 19

Which type of excitation-contraction coupling uses diads at the Z line?

Answer 19

Cardiac muscle EC coupling

Question 20

Which type of muscle has three different sarcolemma Ca2+ channels? What are they?

Answer 20

Smooth - stretch, voltage, and ligand gated

Question 21

Which type of muscle does not have tropomyosin or troponin?

Answer 21

Smooth muscle

Question 22

What mechanism does smooth muscle use for relaxation?

Answer 22

Ca2+ATPase on SR takes Ca2+ back out of cell

Question 23

Describe smooth muscle EC coupling.

Answer 23

Multiple pathways to get Ca2+ into cell. All increase [Ca2+]. - Ca2+ binds calmodulin (CaM). This increases production of MLCK which phosphorylates myosin light chains and allows for contraction.

Question 24

What are the three main pathways Ca2+ enters cell of smooth muscle?

Answer 24

Depolarization (voltage-gated channels), hormones/neurotramsmitters reacting with IP3 to generate Ca2+ release from SR, hormones/neurotransmitters interacting with ligand-gated Ca2+ channels