PJ Response of Intestinal Smooth Muscle Flashcards Preview

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Flashcards in PJ Response of Intestinal Smooth Muscle Deck (14):
1

Learning Outcomes

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  1. Handle living tissue in a manner which maintains and supports its activitiy in vitro
  2. Show that acetylcholine has a stimulatory effect on gut smooth muscle which is concentration-related
  3. Demonstrate that atropine competitively blocks (antagonises) the effects of acetylcholine at muscarinic receptors
  4. Demonstrate that adrenaline inhibits (relaxes) intestinal smooth muscle
  5. Explain that acetylcholine and adrenaline bind to specific receptors on the cell membrane of the smooth muscle
  6. Show that muscle contraction can be produced by depolarisation of the membrane
  7. Plot a log concentration effect curve
  8. Understand the bases of the following terms
    1. Dose- (or conc) response curve
    2. sigmoid curve
    3. plateau
    4. agonist
    5. competitive agonist

 

 

2

Name the neurotransmitters associated with the autonomic nervous system

1.Acetylcholine

2.Noradrenaline

3

Name a hormone that modifies smooth muscle activity

Adrenaline

4

Name a solution that depolarises muscle 

High K+ solution

5

How should the tissue be prepared?

•Keep the tissue immersed

  in physiological saline

•Avoid over-stretching or

  squeezing the gut

•Transfer the tissue to the

  warmed bath quickly

•Ensure that the bath is

  continuously bubbled

  with O2

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6

Expt. 1 Dose-response relationship for ACh

  1. ACh is associated with which division of the ANS?

  2. ACh is an agonist for which type of receptors?

  3. Which of these have a contractile effect?

  1. Parasympathetic
  2. Muscarinic &

    Nicotinic

  3. Muscarinic

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7

Cumulative Concentration-Effect Curve

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The shape of this curve can be linked to receptor site occupancy

(plateu as all Rs are occupied)

8

Expt. 2 Adrenaline

  1. What are the 2 types of adrenoceptors & what is the result of their activation?
  2. Your piece of intestine has mostly β-receptor - what will this mean?

  1. α - contraction & β - relaxation

  2. adrenaline will be predominately inhibitory, see graph attached

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Expt. 3 Atropine & a high K+ solution

  1. What is atropine?

Add atropine before ACh to show a reduction in response.

2. Then add a high K+ solution. Note what happens. Why are the responses different?

  1. A competitive antagonist/inhibitor of ACh at smooth muscle muscarinic receptors

  2. K+ will depolarise the smooth muscle

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10

Why does the smooth muscle of isolated intestine exhibit spontaneous, rhytmic contractions in the organ bath?

Might be due to the action of intrinsic nerve plexuses, or the inherent rhythmicity in the smooth muscle cells themselves

11

ParaS and Symp axons supply the gut

  1. What doe the Symp nerves release?
  2. What do the paraS nerves release?

  1. the catecholamine noradrenaline
  2. acetylcholine

12

Where is adrenaline released from?

What effects does it have?

Adrenal medulla gland into circulation

Both excitatory (a) and inhibitory (b) on smooth muscle

 

13

Where is noradrenaline released from?

Sympathetic nerve terminals

has mainly a-receptor efects

14

What is Atropine? What are it's actions?

competitive blocker (antagonist) of acetylcholine at smooth muscle muscarinic receptors

(NOT at ganglia or skeletal muscle)

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