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Dig > L14: Smooth Muscle > Flashcards

L14: Smooth Muscle Flashcards

1
Q

Which process in the gastro-intestinal tract requires innervation

A

Secretion

Motility

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2
Q

Why do we need need motility in the gut

A

To move food in the gut for absorption and expelling it out through anus

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3
Q

What are the 2 layers of smooth muscles in the GIT

A

Longitudinal

Smooth

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4
Q

What are the two ways that smooth muscle can act in

A

Phasic manner

Tonic manner

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5
Q

What is meant by the phasic manic

A

Contracting and relaxing quickly

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6
Q

What is the tonic manner

A

Sustained contraction

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7
Q

Give an example of a structure that acts with tonic manner

A

Sphincters

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8
Q

What are the pace making cells of the smooth muscle called

A

Interstitial cells of CAJAL

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9
Q

How are interstitial cells of CAJAL coupled to other smooth muscle cells

A

Electrically coupled by GAP junctions

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10
Q

What stimulates depolarisation in smooth muscles

A

Stretch
Acetycholine
Parasympathetics

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11
Q

What is depolarisation

A

Excitation that causes contraction of the smooth muscle

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12
Q

What is hyperpolarisation

A

Low membrane potential

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13
Q

What is hypepolarization stimulated by

A

Noradrenaline

Sympathetics

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14
Q

What does hyperpolarization cause

A

Relaxation of smooth muscle

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15
Q

What has to me met before for depolarisation to occur

A

Electrical threshold

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16
Q

What major ion causes smooth muscle contraction

A

Calcium

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17
Q

How does calcium cause smooth muscle contraction

A

1) calcium influx occurs
2) calcium binds to calmodulin to activate inactive myosin light chain kinase into active form
3) active myosin light chain kinase (enzyme) phosphorylates myosin to myosin-P
4) myosin-P interacted with actin to give contraction by using ATP

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18
Q

How does relaxation happen after the activity of active myosin light chain kinase

A

Myosin light chain phosphatase dephosphorylates myosin-P to myosin

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19
Q

Where does calcium come from for contraction

A

Voltage operated calcium channels

Acetycholine mediated signals which gives IP3

20
Q

Where is calcium stores

A

Inside the smooth endoplasmic reticulum bound to calcesquestrin

21
Q

When in calcium stored

A

After contraction

22
Q

Why is calcium stored

A

To make the contraction efficient

23
Q

Apart from myosin light chain phosphatase what are the other ways of initiating relaxation

A

Phosphorylating myosin light chain kinase

24
Q

How is the myosin light chain kinase phosphorylated for relaxation of the smooth muscle

A

1) VIP initiates adenyl cyclase
2) adenyl cyclase gives CAMP
3) CAMP activated protein kinase A to its active form
4) protein kinase A phosphorylated myosin light chain kinase

25
Q

What nervous system innervated the extrinsic system

A

Parasympathetic

Sympathetic

26
Q

What nervous system innervates the intrinsic system

A

Enteric

27
Q

Overall what nervous system is the parasympathetic, sympathetic and enteric nervous system part of

A

Autonomic nervous system

28
Q

What are the two plexus of the enteric nervous system

A

Submucosal plexus

Myenteric plexus

29
Q

What two layers is the submucosal plexus located between

A

Mucosa

Circular muscle

30
Q

What two layers is the myenteric plexus located between

A

Circular muscle

Longitudinal muscle

31
Q

What does activation of the submucosal plexus lead to

A

Increased secretory activity

Modulates intestinal absorption

32
Q

What does activation of the myenteric plexus lead to

A

Increased tonic contraction

Increased intensity of rhythmic contraction

33
Q

What are the types of motor neurones in the enteric nervous system

A

Excitatory

Inhibitory

34
Q

What are the types of sensory neurones In the enteric nervous system

A

Mechano-reception

Chemo-reception

35
Q

What do mechanoreceptors-receptors detect in the enteric nervous system

A

Pressure

36
Q

What do chemo receptors detect in the enteric nervous system

A

Chemicals such as acid

37
Q

What activity does the parasympathetic nervous system cause in GIT

A

Depolarisation that causes contraction

38
Q

What activity does the sympathetic nervous system cause in the GIT

A

Hyper-polarisation that causes relaxation

39
Q

What main cranial nerve parasympathetically innervated the oesophagus to proximal 1/3rd colon

A

Vagus nerve (CN10)

40
Q

What main cranial nerve parasympathetically innervates distal 2/3rd of colon to anus

A

Pelvic nerves (S1-S3)

41
Q

What is hirschprung disease

A

Congenital lack of neuronal ganglionic cells in the ENS

42
Q

What is Chagas’ disease

A

Infectious disease of a parasite resulting in reduction of ganglionic cells in the ENS

43
Q

What is achalasia

A

Loss of myenteric plexus in the lower gastro-oesophageal region

44
Q

Where does hirschprung disease start and extend to

A

Start at anus

Extends to colon

45
Q

What can hirschprung disease result in

A

Megacolon

Dig (20 decks)

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