L6 - Respiration III - Control of Airway Smooth Muscle

Question 1

Contraction of smooth muscle

Answer 1

• intracellular calcium levels increase.
• Calcium binds to calmodulin - Ca+/Calmodulin
  complex is activated.
• Ca+/Calmodulin complex stimulates MLCK by
  phosphorylation.
• MLCK phosphorylates the MLC causing
  contraction.
• MLC phosphatase dephosphorylates MLC leading
  to relaxation.

Question 2

What receptors are linked to contraction?

Answer 2

Gq - Receptors

Question 3

What receptors are linked to relaxation?

Answer 3

Gs - Receptors

Question 4

What receptors inhibit the relaxation process?

Answer 4

Gi Receptors

Question 5

What receptors act through the Gq pathway?

Answer 5

M3 - Muscarinic Receptors
H1 - Histamine Receptors
Bk - Bradykinin Recepors

Question 6

What receptors act through the Gs pathway?

Answer 6

B2 adrenergic receptors
VIP Receptors

Question 7

What drug acts as an agonist on Gs Receptors?

Answer 7

Salbutamol

Question 8

What happens when the Gs pathway is activated?

Answer 8

Adenylate cyclase is stimulated leading to the formation of cAMP which causes downstream efffects that cause the activation of protein kinase A.

Question 9

What is a downstream effect of the Gs pathway stimulation?

Answer 9

Stimulation of potassium channels, hyperpolarising the membrane.

Question 10

what does the activation of Gi receptors cause?

Answer 10

Inhibition of adenylate cyclase.
Opposes the relaxation of smooth muscle.
Also inhibits the Bradykinin Potassium channel

Question 11

Where are the M1-3 receptors located for parasympathetic control?

Answer 11

• M2 - Postganglionic Nerve
• M2 and M3 - Airway smooth muscle
• M1 and M3 - Epithelial Cells

Question 12

What receptor is muscle contraction controlled by?

Answer 12

M3

Question 13

Activation of M3 receptors

Answer 13

Causes muscle contraction - Ach is released at the nerve terminal, some of which will interact with M2 receptors - inhibiting Ach and preventing overstimulation.

Question 14

What receptor is responsible for parasympathetic contol?

Answer 14

B2 adrenoreceptor

Question 15

How does a B2 agonist (eg. Salbutamol) work?

Answer 15

• Acts on the receptor stimulating adenylate cyclase and the prodcution of cAMP reducing inflammation.
• Also reduces MLCK and stimulating the potasssium channel, hyperpolarising the membrane and reducing calcium influx.
• All leading to relaxation.

Question 16

What are the 2 types of asthma?

Answer 16

Atopic (extrisic)
- Associated with allergies, linked to elevated levels of serum IgE
Non- Atopic (intrinsic)
- Induced by various factors such as excersise, cold air, inhaled irritants, stress and drugs.

Question 17

What are the 2 types of asthma?

Answer 17

Atopic (extrisic)
- Associated with allergies, linked to elevated levels of serum IgE
Non- Atopic (intrinsic)
- Induced by various factors such as excersise, cold air, inhaled irritants, stress and drugs.

Question 18

What type of activity increase in asthma associated with?

Answer 18

Parasympathetic increase
- manifests as an increase in basal tone and increased muscle constriction

Question 19

What is the change in M2 function linked toin the case of antigen challenge?

Answer 19

Eosinonopils

Question 20

Where are eosinophils and where are they mainly located?

Answer 20

A variety of white blood cells that cluster around nerve endings.

Question 21

What do activated eosinophils release?

Answer 21

Major basic protein (MBP) which inhtibit M2 receptors.

Question 22

What can be used to treat asthma?

Answer 22

Anticholinergics - Block the effects of ACh
- Competitive inhibitors of M1-3
receptors.
- Help reverse the effect of
brochoconsriction

Question 23

What is a short-lasting anticholinergic?

Answer 23

Ipratropium - used with short lasting B2 adrenoreceptor agonists as an add on therapy.

Question 24

What is a long lasting anticholinergic?

Answer 24

Tiotropium - Used in combination with long lasting