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Cardiovascular System Module > Lecture 13 Part 2 > Flashcards

Lecture 13 Part 2 Flashcards

1
Q

What can contractile stimulation of smooth muscle occur by?

A

Receptor stimulation, mechanical perturbation and electrical excitation

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2
Q

What can receptor stimulation occur by?

A

Neuronal (noradrenaline), hormonal (Adrenaline, angiotensin 2) and Paracrine (adenosine, histamine)

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3
Q

What is mechanical perturbation?

A

Stretch, intraluminal pressure

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4
Q

What is electrical excitation?

A

Action potential generation (uncommon in vascular smooth muscle)

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5
Q

What is the role for ca2+ in smooth muscle contraction?

A

Free ca2+ regulates contraction of membrane permeabilised smooth muscle

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6
Q

What are the mechanisms to increase cytosolic ca2+?

A

Ca2+ release from intracellular organelles from the SR and ca2+ entry into the cell through plasma lemma channels

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7
Q

How is ca2+ released from the SR?

A

IP3 induced ca2+ release from the SR mediated by IP3 and CICR release mediated from RYR receptors

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8
Q

What is the contractile mechanism in the cardiac muscles?

A

Increase in cytosolic ca2+,
Binding of ca2+ to calmodulin,
Calmodulin complex is formed,
Activates myosin light chain kinase (MLCK)
Causes phosphorylation of MYCL20
Activates contractions

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9
Q

How can you cause relaxation in smooth muscle?

A

You have a light chain phosphatase which can dephosphorylate the MLC20 subunit which causes relaxation

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10
Q

What does a global increase in ca2+ lead to?

A

Leads to a change in vascular diameters which leads to vasoconstriction

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11
Q

What can be used to measure pressurised arteries to measure ca2+?

A

Laser scanning confocal microscopy

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12
Q

What is a phenylephrine induced tonic contraction?

A

Upon contractile stimulation another form of ca2+ dynamics occurs individual cell dynamics

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13
Q

What would happen if all of the cells had the same increase?

A

Get an increase, decrease cause of contraction

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14
Q

What is change in ca2+ proportional to?

A

Intensity of the stimuli

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15
Q

What are smooth muscles cells ca2+ not?

A

They are not unidirectional

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16
Q

What are smooth muscle cells ca2+ waves?

A

They are asynchronous

17
Q

What is good about asynchronous ca2+ waves?

A

They are more likely to be advantageous for maintaining constant tone

18
Q

What are ca2+ changes in arterial smooth muscle like?

A

They are dynamic and spatially regulated

19
Q

What can ca2+ sparks regulate?

A

The electrical excitability of vascular smooth muscle cells

20
Q

What does a spontaneous transient inward current =

A

Depolarisation

21
Q

What does a spontaneous transient outward current =

A

Hyperpolarisation

22
Q

What do ca2+ sparks generally act as?

A

A brake for tone development, they are more frequent when tone is present

23
Q

What is important for SR?

A

Its location it’s important, it needs to be close to the mitochondria and filaments, as well as caveolae

24
Q

Does physical disruption of plasma lemma caveolae alter ca2+ dynamics?

A

Yes, cholesterol sequestion using methyl B cyclodextrin can distrupt the calveolae

25
Q

What does extrinsic treatment reduce?

A

Reduces calveolae in vascular smooth muscle cells

26
Q

What does dextrin treatment also reduce?

A

The number of ca2+ waves in vascular smooth muscle cells

27
Q

What happens after disruption of caveolae?

A

Reduced frequency and amplitude of ca2+ sparks in smooth muscle cells

28
Q

What does release of ca2+ from RYR receptors trigger?

A

STOCs and STICs and they need myogenic or agonist stimulated tone present for ca2+ sparks

29
Q

Where do ca2+ waves originate?

A

At one end of the smooth muscle cell - the propagate by peripheral and central localisation of the SR

30
Q

When do ca2+ waves occur?

A

During myogenic or agonist stimulated tone

31
Q

What is ca2+ sensitisation like in vascular smooth muscle cells?

A

Greater force of contraction in response to noradrenaline compared with KCL but with same ca2+

32
Q

What is noradrenaline induced vasoconstriction?

A

Alpha 1 receptor stimulation, ca2+ release from SR by IP3 receptors, PKC inhibition of MYLCP via CPI-17

Cardiovascular System Module (18 decks)

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