Lec 11- Smooth and Cardiac Muscle

Question 1

Calmodulin

Answer 1

An intracellular Ca2+ binding protein that, on activation by Ca2+, induces a change in in structure and function of another intracellular protein; especially important in smooth-muscle excitation-contraction coupling.

Question 2

Myosin Phosphatase

Answer 2

An enzyme that is responsible for removing the phosphate group (dephosphorylating) from the regulatory chains near the myosin head group.
Stop contraction in the smooth muscle cells.

Question 3

Single-unit smooth muscle

Answer 3

Most smooth muscle. Found in the walls of hollow organs or viscera.
When excited, contract as a single unit. Contain gap junctions.

Question 4

Multiunit smooth muscle

Answer 4

Consists of multiple discrete units that function independently of one another and must be separately stimulated by nerves to undergo action potentials and contract.
Found: 1. walls of large blood vessels
2. small airways to the lungs
3. muscle of eye that adjusts lens to near and far vision
4. iris
5. base of hair follicles (goosebumps)

Question 5

Slow wave potential

Answer 5

Are spontaneous, gradually alternating depolarizing and hyperpolarizing swings in potential brought about by known mechanisms.
Occur only in smooth muscle of the digestive tract.

Question 6

Latch state

Answer 6

enables smooth muscle to maintain tension with comparatively less ATP consumption because each cross-bridge cycle uses up one molecule of ATP.

Question 7

Syncitium

Answer 7

Interconnected muscle cells that funciton electrically and mechanically as a unit.
Seen in single-unit smooth muscle cells.
Have gap junctions.

Question 8

Pacemaker potential

Answer 8

the membrane potential of specialized muscle cells gradually depolarizes on its own because of shifts in passive ionic fluxes accompanying automatic changes in channel permeability.

Question 9

Intercalated disk

Answer 9

Joins cardiac muscle cells (end to end) through branching fibers.

Question 10

Desmosome

Answer 10

A type of adhering junction that mechanically holds cells together.

Question 11

Gap junction

Answer 11

Areas of low electrical resistance that allow AP’s to spread from one cardiac cell to adjacent cells

Question 12

Pacemaker cells

Answer 12

Initiate and conduct AP’s responsible for contraction

Question 13

NO (nitric oxide)

Answer 13

brings about local arteriolar vasodilation by causing relaxation of arteriolar smooth muscle in the vicinity.

Question 14

Contractile cells

Answer 14

99% of cardiac muscle cells, do the mechanical work of pumping. Normally do not initiate their own AP’s

Question 15

Plateau phase

Answer 15

maintained by Ca2+ coming in slow

Question 16

MLCK (myosin light chain kinase)

Answer 16

Activated by Ca2+-calmodulin complex.
Phosphorylates and activates myosin.
Myosin forms crossbridges with actin.

Question 17

Regulatory light chains

Answer 17

ASK

Question 18

Dense bodies

Answer 18

smooth muscles have this; contains the same protien constituent found in Z lines
(smooth muscles do not have Z lines)

Question 19

Myogenic

Answer 19

Nerve independent contractile activity initiated by the muscle itself.
Found only in single unit smooth muscle.