Smooth muscle and enteric nervous system Flashcards

1
Q

What are the two types of muscle in the GIT

A

Smooth involuntary

Skeletal voluntary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where is the smooth muscle located?

A

Most regions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where is the skeletal muscle located?

A

Pharynx, top third of oesophagus, external anal sphincter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the functions of GIT?

A

Digestion
Absorption
Secretion
Motility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is motility in the GIT supported by?

A

Intestinal smooth muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the two types of smooth muscle?

A

Phasic

Tonic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is phasic smooth muscle?

A

rapid contraction and relaxation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Where is phasic smooth muscle located?

A

body of oesophagus, stomach antrum, small and large intestines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is tonic smooth muscle?

A

sustained contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where is tonic smooth muscle located?

A

Sphincters (lower oseophageal, ileocaecal, internal anal) , orad (upper stomach)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the basic rate of smooth muscle determined by?

A

Pacemaker activity- an intrinsic property of the interstital cells of CAJAL/ICC.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens when ICC is depolarised?

A

ICC is electrically coupled to the smooth muscle cells through gap junctions. This allows the spread of slow waves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Stimulation of electrical activity by…

A

Mechanical- stretch

Pharmacological- ACh, parasympathetics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Inhibition of electrical activity by…

A

Noradrenaline

Sympathetics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does stimulation of electrical activity lead to?

A

oscillating potential increases above the threshold membrane potential. Depolarisation occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does inhibition of electrical activity lead to?

A

hyperpolarisation. High depolarisation to reach threshold potential

17
Q

What is the role of threshold for electrical contraction?

A

Whenever this threshold is breathed, contractile activity occurs. If the threshold is breathed at a greater level, there is greater contractile activity

18
Q

Why is there lag between electrical activity and contractile activity?

A

It takes some time between depolarisation and contraction

19
Q

Where does the Ca2+ come from?

A

membrane depolarisation lead to the opening of Voltage Operated Calcium Channel (VOCC)

20
Q

Where does the Ca2+ come from?

A

membrane depolarisation lead to the opening of Voltage Operated Calcium Channel (VOCC)
PLC pathway- muscarinic ACh receptor

21
Q

What happens in smooth muscle contraction?

A

Ca2+ binds to calmodulin
This activates myosin light chain kinase MLCK
MLCK phosporylates myosin to myosin phosphate
Allows binding to actin

22
Q

How does smooth muscle relaxation occur?

A

Myosin light chain phosphatase MLCP dephosphorylates myosin phosphate
Phosphorylation of MLCK prevents binding of calmodulin

23
Q

How is the phosphorylation of MLCK regulated?

A
PKA pathway
i.e. VIP/B adrenergic induces adenyl cyclase
induces cAMP
induces PKA
phosphorylation of MLCK
24
Q

Innervation of the GIT

A

Intrinsic- enteric

Extrinsic- autonomic- parasympathetic and sympathetic

25
What neurones does the intrinsic innervation contain?
Motor: activatory, inhibitory Sensory Interneurones
26
Activation of the myenteric plexus leads to...
increased tonic contraction increased intensity of rhythmic contraction increased rate of contraction which increases velocity of conduction
27
Activation of submucosal plexus leads to...
increased secretory activity | modulated intestinal absorption