Smooth Muscles

Question 1

troponin & T-tubules absent. in sm muscle

Answer 1

ya

Question 2

thin filaments in sm muscle

Answer 2

thin filaments are anchored to the cell membrane or to cytoplasmic structures known as dense bodies (similar to z- lines).

Question 3

what do intermediate filaments do in sm muscle?

Answer 3

non- contrac5le, form cytoskeleton
50 to 400 um in length
Smooth Muscle

Question 4

smooth muscle is uninucleate

Answer 4

ya

Question 5

major groups of sm muscle by location in humans

Answer 5

1. vasculature; 2. GI tract; 3. urinary tract; 4. respiratory; 5. reproductive (uterus); 6. ocular

Question 6

what are the categroies of sm muscles based on contraction patterns?

Answer 6

phasic and tonic

Question 7

what is phasic sm muscle?

Answer 7

sm muscle that is usually relaxed; e.g. esophagus

Question 8

what is tonic sm muscle?

Answer 8

usually contracted; relaxes to allow something to pass; e.g. sphincter

Question 9

how is sm muscle categorized with neighbouring cells?

Answer 9

unitary (single unit sm muscle); multiunit sm muscle;

Question 10

what is unitary sm muscle?

Answer 10

contains gap junctions; allows coordination of contraction of sm muscle cells as a single unit; usually makes up the walls of gi tract, bladder, e.g. visceral organs, it is called visceral sm muscle

Question 11

what is multiunit sm muscle?

Answer 11

not electrically coupled–no gap junction; e.g. iris and ciliary of the eye, in male repro tract; and uterus except just prior to labour and delivery;

Question 12

MOST smooth muscle is controlled by the ANS; -can be innervated by mul?ple neurons, capable of releasing different neurotransmitters

Answer 12

ya

Question 13

how do APs differ in sm muscles?

Answer 13

• depolarization slower: Ca2+ channels propagate the AP instead of Na+
• repolariza?on also slower: Ca2+ channels inac?vate slowly and there is a delayed ac?va?on of voltage gated K+ and in some cases Ca2+ -ac?vated K+ channels

Question 14

some sm muscle is capable of spon activity

Answer 14

ya

Question 15

Action potentials usually do not occur in multiunit smooth muscle

Answer 15

ya

Question 16

-autonomic neurons create a local depolariza?on that spreads electrotonically (graded fashion) throughout the muscle fibre triggering Ca2+ entry–the more APs in neuron–> bigger the GP in sm muscle

Answer 16

ya

Question 17

how can Cai be increased in sm muscles?

Answer 17

through voltage-gated L type channels–> CICR from the SR; through IP3 pathway; stretch activated channels;

Question 18

what are store operated channels?

Answer 18

when SR becomes depleted, store-operated channels are activated–>cause Ca to enter–> replenishes SR–>

Question 19

what are the roles of STIM1 and Orai?

Answer 19

Orai proteins make up Ca channel in cell membrane; STIM1 activates the protein to alow influx of Ca

Question 20

what is pharmacomechanical coupling?

Answer 20

drugs, excitatory neurotrans, hormones, can induce Ca release from the SR via the IP3 pathway (and Ca entry from store operated Ca channels in the plasma membrane)