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GEM > 1.12 GI Smooth Muscle + Blood Flow > Flashcards

1.12 GI Smooth Muscle + Blood Flow Flashcards

1
Q

Peristalsis in the GI tract is an example of what smooth muscle structural type?

A

single unit (unitary)

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2
Q

What differentiates smooth muscle form skeletal muscle in the ways that it can receive signals to contract?

A

smooth muscle can be signaled via circulating hormones in the bloodstream (skeletal cannot)

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3
Q

smooth muscle contractile activity type with rapid short contract and relax pattern?

A

phasic

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4
Q

what is phasic contraction used for?

A

period, strong for mixing, propulsion, and emptying organs

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5
Q

what is tonic smooth muscle used for?

A

continuous tension or tone to regulate lumen size (ex. blood vessels)

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6
Q

What smooth muscle activity type with sustained stead-state contraction over long durations with min energy spent?

A

tonic

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7
Q

electric properties of phasic smooth muscle?

A

slow waves

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8
Q

electric properties of tonic muscle?

A

sustained to keep contracted

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9
Q

what is the natural state of tonic activity?

A

normally contracted (ex. Lower esophageal sphincter)

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10
Q

What are the (4) key sources of calcium into cell for muscle contraction?

A

Extracellular
(1) Voltage-gated L-type channels
(4) Store-operated Ca²⁺ channels (SOCC) - warning low

Intracellular
(2) Calcium-induced calcium release (CICR) from SR
(3) IP3-mediated release from SR

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11
Q

What activates the L-type ca channel for smooth muscle contraction?

A

ICC (Interstitial cell of Cajal) chloride channels triggered via Ach or SubP from enteric motor neuron

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12
Q

what activates the SK3 channel then L-type ca channel for smooth muscle relaxation?

A

PDGFR a+ cell via NO or VIP from enteric motor neuron

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13
Q

Where are NT released in smooth muscle?

A

autonomic varicosities (not NMJ)

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14
Q

what does increased intracell calcium activate to initiate contraction?

A

MLCK - myosin light chain kinase

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15
Q

What has to happen to myosin heads for it to bind to actin and muscle to contract?

A

phosphorylated

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16
Q

Once calcium is in the cell what does it need to bind to first in smooth muscle to activate the MLCK?

A

calmodulin to make CAM complex

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17
Q

How does phosphorylated (ML20) myosin interact with thin actin filaments?

A

cross bridges

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18
Q

what is the Latch State?

A

Mechanism of low energy sustained smooth muscle contraction to use less energy (ATP)

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19
Q

What do you need to remove calcium or relax smooth muscle? (4)

A

sarcolemma membrane transporters
(1) Plasma membrane Ca²⁺-ATPase (PMCA)
(2) Na⁺/Ca²⁺ exchanger
(4) CRAC channels

intracellular
(3) SERCA pump

20
Q

which channel is NOT ATP dependent to remove calcium from the cell?

A

Na+/Ca2+ exchanger

21
Q

how is the CAM complex dissociated?

A

decreased intracell calcium

22
Q

what is activated to remove phosphate from the ML20?

A

MLCP myosin light chain phosphatase

23
Q

hypocalcemia clinical presentations? (<2.12 mmol/L)

A

decreased contractility = dysphagia, pain in abdomen since motility is reduced

24
Q

what is essential in skeletal muscle to expose the binding sites on actin?

A

troponin to activate tropomyosin

25
Q

does smooth muscle have a defines motor end plate?

A

nope

26
Q

what are the (3) regulatory pathways to control relax/contract in MLCP?

A

PKG, PKC, ROCK

27
Q

what reg pathways promote relaxation via the MLCP?

A

PKG

28
Q

what reg pathways promote contraction via the MLCP?

A

ROCK and PKC

29
Q

Where is PKG working?

A

LES and pyloric sphincters + relax peristalsis

30
Q

where is PKC working?

A

contraction, mixing, segmentation, secretion regulation

31
Q

ROCK where is it working?

A

bloods vessels & tonic contraction at sphincters

32
Q

What is NO activating to convert GTP to cGMP ?

A

guanylyl cyclase (GC)

33
Q

what does cGMP activate to increase the dephopshorylation of MLC20 for smooth muscle relaxation?

A

PKG

34
Q

What kind of receptor and activation triggers PKC to initiate smooth muscle contraction?

A

GPCR then indirect activation of PK

35
Q

What does PKC activate by phosphorylation?

A

CPI-17

36
Q

What does the phosphorylated CPI-17 do?

A

MLCP inhibition to increase the phosphorylation of MLC for smooth muscle contraction

37
Q

How is RhoA activated?

A

indirect activation via GPCR

38
Q

what does Rho-kinase do once phosphorylated?

A

MYPT1 inhibitory sites activated of MLCP to increase myosin light chain phosphorylation for contraction

39
Q

What hormones are implicated in constriction of GI circulation?

A

Catecholamines:
Angiotensin II (ANG-II)
Arginine vasopressin (AVP/ADH)

40
Q

What hormones are implicated in GI vasodilation?

A

Gastrin, CCK, Secretin

41
Q

What are catecholamines implicated in?

A

STRESS response

42
Q

What are ANG-II implicated in?

A

response to low BP

43
Q

What are AVP/ADH implicated in?

A

shock response

44
Q

What is gastrin implicated in?

A

gastric mucosa for digestion/secretion

45
Q

What is CCK implicated in?

A

intestinal circulation for nutrient absorption and enzymes delivery in digestion

46
Q

What is secretin implicated in?

A

pancreas and small intestine for bicarb secretion and digestive enzyme delivery

GEM (28 decks)

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