Muscle 8

Question 1

Smooth muscle is categorized by…

Answer 1

• location
• contraction pattern
• communication with neighbouring cells

Question 2

In humans, smooth muscle can be divided in which 6 major (location) groups?

Answer 2

• vascular
• gastrointestinal
• urinary
• respiratory
• reproductive
• ocular

Question 3

What are the 4 contraction patterns?

Answer 3

• a phasic smooth muscle that is usually relaxed
• a phasic smooth muscle that cycles between contraction and relaxation
• a tonic smooth muscle that is usually contracted
• a tonic smooth muscle whose contraction is varied as needed

Question 4

unitary smooth muscle (single unit)

Answer 4

contains gap junctions that allow for coordinated contraction of many cells causing muscle to contract as a single unit

Question 5

multiunit smooth muscle

Answer 5

-not electrically coupled

iris and cilliary body of eye, in male reproductive tract and in uterus except just prior to labor and delivery

Question 6

What can alter smooth muscle tension?

Answer 6

hormones, stretch and local factors, paracrine signals, acidity, oxygen and CO2 conc, and osmolarity

Question 7

Paps of smooth muscle can be initiated by…

Answer 7

neural, hormonal, or mechanical stimulation

Question 8

slow wave potentials

Answer 8

fire action potential when they reach threshold

Question 9

pacemaker potentials

Answer 9

always depolarize to threshold

Question 10

in some smooth muscle Vm oscillations can lead to..

Answer 10

tonic contractions in absence of APs

Question 11

electromechanical coupling

Answer 11

contraction due to electrical signaling

Question 12

Autonomic AP initiation

Answer 12

• spikes or plateaus

- single unit

Question 13

spontaneous AP

Answer 13

• slow wave
• pacemaker
• single unit

Question 14

graded potentials

Answer 14

multiunit

Question 15

Calcium conc is increased by what three different mechanisms?

Answer 15

• Ca2+ entry through voltage gated channels or ligand gated ion channels
• Ca2+ release from SR
• Ca2+ entry through voltage-independent channels

Question 16

There is ____ SR in smooth than in skeletal and cardiac.

Answer 16

less

Question 17

IP3 pathways

Answer 17

can cause contraction with minimal depolarization and negligible extracellular Ca2+ influx

Question 18

Depletion of Ca2+ in the SR causes activation of…

Answer 18

store-operated channels

Question 19

store-operated channels

Answer 19

cause a Ca2+ influx across the cell membrane. Allows [Ca2+]i to remain elevated and replenishes SR.

Question 20

pharmacomechanical coupling

Answer 20

occurs when chemical signals change muscle tension through signal transduction pathways with little or no change in membrane potential

Question 21

stretch of smooth muscle causes..

Answer 21

an internal release of Ca2+ from the SR through the ryanodine receptor causing phosphorylation of myosin light chain leading to contraction

Question 22

myosin light chain kinase

Answer 22

phosphorylates the regulatory light chain near the myosin head which alters the conformation of the myosin head, increasing its ATPase activity and allows it to interact with actin

Question 23

In smooth muscles, cross-bridge cycling is similar but…

Answer 23

occurs more slowly

Question 24

During relaxation, the regulatory light chain must be…

Answer 24

dephosphorylated by myosin light chain phosphatase

Question 25

latch state

Answer 25

when some smooth muscle can maintain force for an extended period of time with little ATP use

Question 26

Neurotransmitters, hormones and paracrine molecules alter smooth muscle Ca2+ sensitivity by…

Answer 26

modulating light chain phosphatase