smooth muscle

Question 1

what are the 2 types of smooth muscle

Answer 1

visceral and multi unit

Question 2

how does smooth muscle cell size compare to skeletal

Answer 2

much smaller 2-10micrometers in diameter

Question 3

cell structure of smooth muscle

Answer 3

spindle shaped with one nucleus and arranged in sheets with dense bodies, thick and thin filaments at slight diagonal from side to side giving diamond lattice organisation

Question 4

how does smooth muscle differ from skeletal in terms of troponin/tropomyosin

Answer 4

they don’t have troponin and they tropomyosin they have does not block cross bridge binding sites, rely on chemical change

Question 5

sarcoplasmic reticulum in smooth muscle

Answer 5

poorly developed

Question 6

what additional filaments do smooth muscle have and what do they do

Answer 6

intermediate filaments for supporting cell shape, hold dense bodies in place

Question 7

what happens when the thin filament slides relative to the thick filament

Answer 7

the cell shortens and expands (gets fatter)

Question 8

how is the myosin arranged in smooth muscle

Answer 8

arranged in thick filaments so cross bridges present along the entire length

Question 9

what triggers contraction in smooth muscle

Answer 9

calcium dependent phosphorylation of myosin light chains

Question 10

series of events triggering contraction

Answer 10

1. calcium binds to calmodulin
2. calmodulin activates myosin kinase
3. myosin kinase phosphorylates myosin ATPase
4. phosphorylated myosin can interact with actin
5. myosin is dephosphorylated by myosin light chain phosphatase

Question 11

how does calcium enter smooth muscle cells

Answer 11

through voltage and ligand gated channels

Question 12

how does calcium mechanism differ in smooth muscle to skeletal

Answer 12

no T tubule system
slower removal of calcium so longer contraction
graded response

Question 13

3 features of multi unit smooth muscle

Answer 13

1. neurogenic (requires nervous stimulation)
2. made of multiple discrete units that function independently
3. units must be stimulated separately by nerves to allow contraction

Question 14

5 features of single unit smooth muscle (visceral)

Answer 14

1. myogenic (no nervous stimulation needed)
2. fibres are excited and contract as one unit
3. gap junctions present
4. slow and energy efficient contraction
5. functional syncytium

Question 15

where is multi unit smooth muscle found

Answer 15

large arteries, large airways to lungs, iris

Question 16

where is single unit smooth muscle found

Answer 16

GI tract, blood vessels uterus

Question 17

2 types of single unit smooth muscle and their differences

Answer 17

phasic and tonic
phasic SM contracts in bursts, triggered by APs
tonic SM is often partially contracted at all times, no bursts of activity but varies above or below the usual tonic state (slow wave potential)

Question 18

4 factors influencing smooth muscle contractile activity

Answer 18

1. spontaneous depolarisation of cells
2. signalling molecules (neurotransmitters and hormones)
3. local changes in extracellular fluid (pH, O2)
4. stretch

Question 19

what is the stress relaxation response

Answer 19

smooth muscle can continue to develop tension when considerably stretched