Muscle II Flashcards
What is the name of the structure that connects cardiomyocytes?
Intercalated disks
What allows for the transfer of calcium from one cell to another?
Gap junctions
T or F. Mitochondria are plentiful in cardiac muscle.
T
What is the equivalent of a Z line in smooth muscle?
focal density
T or F. Smooth muscle contains nebulin, titin, and myomesin.
F
T or F. Smooth muscle has sarcomeres.
F
What does smooth muscle have instead of a T system
Plasma membrane invaginations called caveolae
What types of vesicles do smooth muscle have?
SR analogues w/ luminal calsequestrin
What direction are the contraction vectors in smooth muscle?
All directions
Is smooth muscle basophilic or eosionophilic? Why?
Basophilic - lots of RER for secretory activities (very much like fibroblasts)
What can smooth muscle be replaced by?
Differentiation from pericytes
Describe skeletal muscle EC coupling.
- 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
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?
Skeletal muscle EC coupling
Describe cardiac muscle EC coupling.
- 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
What kinds of channels are dihydropyridine receptors and ryanodine receptors
Voltage-gated
Where are RYR (ryanodine receptors) located?
Sarcoplasmic reticulum membrane
Where are dihydropyridine (DHP) receptors located?
Sarcolemma (plasma membrane)
Which type of EC coupling uses triad T-tubules?
Skeletal muscle EC coupling
Which type of excitation-contraction coupling uses diads at the Z line?
Cardiac muscle EC coupling
Which type of muscle has three different sarcolemma Ca2+ channels? What are they?
Smooth - stretch, voltage, and ligand gated
Which type of muscle does not have tropomyosin or troponin?
Smooth muscle
What mechanism does smooth muscle use for relaxation?
Ca2+ATPase on SR takes Ca2+ back out of cell
Describe smooth muscle EC coupling.
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.
What are the three main pathways Ca2+ enters cell of smooth muscle?
Depolarization (voltage-gated channels), hormones/neurotramsmitters reacting with IP3 to generate Ca2+ release from SR, hormones/neurotransmitters interacting with ligand-gated Ca2+ channels
