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Physiology of Cells and Systems (Year 2) > Lecture 6 (Respiration) > Flashcards

Lecture 6 (Respiration) Flashcards

1
Q

What do each of these receptors do? (3)
Gq
Gs
Gi

A

Gq receptors linked to contraction
Gs linked to relaxation
Gi oppose relaxation process

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2
Q

Describe the process of smooth muscle contraction? (5)

A
  • Increase in intracellular calcium
    -Binds to calmodulin
    -You have activated calcium calmodulin which activates MLCK
    -MLCK phosphorylates myosin chain which causes contraction
    -Smooth muscle remain contracted while MLCK is phosphorylated
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3
Q

How do you reverse smooth muscle contraction?

A

MLCP relaxes smooth muscle
(doesn’t reverse with less calcium)

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4
Q

What are the 3 classes of Gq receptor? (3)

A

M3 Muscarinic receptors
H1 Histamine receptors
BK bradykinin receptors (g protein coupled)

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5
Q

What are the 3 classes of Gq receptor? (3)

A

M3 Muscarinic receptors
H1 Histamine receptors
BK bradykinin receptors (g protein coupled)

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6
Q

What happens when agonist binds to receptor (Gq)? (3)

A

-Agonist binds to receptor, activates G protein
-Leads to stimulated phospholipase C
-Which breaks down PIP2 into DAG and IP3

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7
Q

What are the short term effects after agonist binds to receptor (Gq)? (5)

A

Short term effects ->
-Muscle contraction, IP3 will act on IP3 receptors leads to release of calcium
-From the source calcium binding to calmodulin
-Activation of MLCK and contraction of the muscle
-We reduce the airway diameter
-Increases resistance of airflow makes it harder to breathe
(More effort required for breathing)

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8
Q

What are the long term effects after agonist binds to receptor (Gq)? (2)

A

Long term effects ->
-DAG stimulates protein kinase C
-Protein kinase C has longer term effects on muscle cell which leads to remodelling of airway smooth muscle

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9
Q

What happens when agonist binds to receptor (Gs)? (8)

A

-Stimulation of adenylate cyclase
-Camp is then formed
-This activates protein kinase A which has various effect on cell
-One of the effects is stimulation of potassium channels
-Potassium efflux into cell, hyperpolarized membrane, makes membrane potential away from voltage calcium channels opening
-Inhibits MLCK, activation of MLCP
-Diameter increases
-Decreases in resistance to airflow, so easier to breathe

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10
Q

What are the long term effects of agonist binding to Gs?

A

-Inhibit remodeling growth, of muscle cells

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11
Q

Explain the control of airway smooth muscle via Gi? (4)

A

-Activation of Gi receptors leads to inhibition of Adenylate Cyclase

-Knock on effect of this is to counteract the stimulatory effect of Gs activation

-Opposes the relaxation of the smooth muscle

-Also inhibits the BK potassium channel

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12
Q

What receptors act through Gi pathway?

A

M2 Muscarinic receptors

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13
Q

Where do you find M2 receptors?

A

On post ganglionic nerve fibers

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14
Q

What receptors are found on blood vessels?

A

M3

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15
Q

What receptors are found on smooth muscle cells?

A

M3 (some may have M2)

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16
Q

What receptors are found on epithelial cells? (2)

A

We have M1 and M3 on epithelial cells, stimulation of these is due to mucus secretion

17
Q

What happens when M3 receptors are activated? (4)

A

M3 receptors on smooth muscle
Are activated

-Stimulates phospholipase 3
-IP3 causes calcium release
-MLCK activation
-Phosphorylation of MLC causes contraction

18
Q

Describe auto-inhibition for hypersensitivity inn airways? (3)

A

Auto-inhibition (negative feedback mechanism) –

-Ach is released at nerve terminal, some of it will interact with the M2 receptors on post–ganglionic nerve
-Activation of these receptors inhibits/reduces further release of Ach
-Negative feedback mechanism to prevent overstimulation/contraction of smooth muscle

Detects feedback in hypersensitivity of the airways

19
Q

What does B2 agonist do? (4)

A

-Acts on receptor which stimulates adenylate cyclase
-Camp production had genomic effect, reduces inflammation and proliferation, inhibits MLCK, stimulates BK potassium channels (hyperpolarize membrane)

-Increases activity of sodium calcium exchanges (you remove calcium form the cytoplasm)
-Helps lower calcium levels so you have less muscle contraction

20
Q

What is Noradrenergic/noncholinergic (NANC) signalling?

A

Noradrenergic/NonCholinergic (NANC) nervous system present in airways but importance in humans is unestablished and controversial

21
Q

What are the two pathways of NANC signalling? (2)

A

– excitatory or eNANC - bronchoconstriction
transmitters: Substance P/Neurokinin A (SP/NKA)

  • inhibitory or iNANC - bronchorelaxation (dilation)
    transmitters: Vasointestinal Peptide (VIP)
    Nitric Oxide
    Neuropeptide Y (NPY)
22
Q

What is Athsma?

A

“a common chronic disorder of the airways that is complex and characterised by variable and recurring symptoms, airflow obstruction, bronchial hyper-responsiveness, and an underlying inflammation.”

23
Q

What are the two types of asthma? (2)

A

Atopic (extrinsic)
Non-Atopic (intrinsic)

24
Q

What is Atopic (extrinsic) asthma?

A

Atopic (extrinsic) – Associated with allergies. Linked to elevated levels of serum IgE and positive skin-prick test.

Presentation of allergen leads to activation of mast cells. Release of inflammatory mediators including histamine.
Can lead to activation of other inflammatory cells such eosinophils.

25
Q

What is Non-Atopic (intrinsic) asthma?

A

Non-Atopic (intrinsic) – No positive skin-prick test and normal serum IgE levels.

Induced by a variety of factors such as exercise, cold air, inhaled irritants, stress, drugs.  May be linked to localized increase in IgE production.
26
Q

What does asthma being associated top parasympathtic activity mean?

A

Manifests as an increase in basal tone and increased muscle constriction in response to irritant

27
Q

What does increased parasympathetic activity mean? (6)

A

-Hyper-responsiveness of the muscle
-Ach released and acts of cells in epithelial layer
-Stimulates muscle production and fluid secretion
-Decreases the lumen of the airway which affects resistance of flow
-M3 receptors on the airway smooth muscle, ACH binds to them which leads to muscle contraction
-Long term remodelling of airway smooth cells to become thicker
-Activates eosinophils, macrophages and lymphocytes which leads to an increase in inflammation

28
Q

What receptor is affected in parasympathetic activity in airway?

A

(No change in function of M1 or M3 receptors but)

Decrease in neuronal M2 function

29
Q

How does decrease in M2 activity lead to asthma symptoms? (8)

A

-You inhibit negative feedback which means more ACH is released
-More ach in system which makes system more hyper-responsive

-Link between eosinophils and M2 receptors
-Eosinophils cluster around the nerve fiber

-Activates eosinophils release MB
-MBP is an antagonist of M2 receptors

-MBP bind to M2 receptor which inhibits negative feedback mechanism
-Activates hyperresponsivity of airways and leads to constriction of airways and asthma symptoms

30
Q

What lowers M2 activity? (4)

A

-Antigen challenge (eosinophils, MBP etc..)
-Insulin
-Virus
-Vitamin A Deficiency

31
Q

What do Anticholinergics do? (5)

A

-Block the effects of endogenous Ach.
-Short lasting or long lasting.
-Competitive inhibitors of M1, M2 and M3 receptors.
-Dissociate more slowly from M3 receptors compared to M2.
-Exert effect to help reverse bronchoconstriction, mucus secretion and airway remodeling.

32
Q

What do anticholinergics treat?

A

Asthma

33
Q

What are the short and long lasting treatments for asthma? (2)

A

Short lasting:
Ipratropium – used in combination with short acting β2-adrenorecptor agonists as an add on therapy.

Long lasting:
Tiotropium – used in combination with long acting β2-adrenoreceptor agonists and
Inhaled corticosteroids.
Inhaled once daily with actions mainly via M1 and M3 receptors.

Physiology of Cells and Systems (Year 2) (21 decks)

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