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Physiology and Pharmacology > Smooth muscle physiology > Flashcards

Smooth muscle physiology Flashcards

1
Q

What would be the main components of the histology of smooth muscle?

A

Unstriated
Involuntary
Automonic innervation

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2
Q

How would you describe the structure of smooth muscle?

A

Individual muscle fibres are relatively small, spindle shaped, and possess a nucleus

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3
Q

What function does smooth muscle in the vasculature system have?

A

Controls diameter, regulates flow and pressure

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4
Q

What function does smooth muscle in the airways have?

A

Controls diameter, regulates flow and resistance

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5
Q

What function does smooth muscle in the urinary system have?

A

Propulsion of urine into ureters, bladder tone, tone of internal sphincter of bladder

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6
Q

What function does smooth muscle in the gastrointestinal tract have?

A

Controls tone, motility, opening/closing of sphincters

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7
Q

What function does smooth muscle in the male reproducitve tract have?

A

Secretion, propulsion of semen

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8
Q

What function does smooth muscle in the female reproductive tract have?

A

Propulsion (Fallopian tubes), partiuition (uterus)

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9
Q

What function does smooth muscle in the skin have?

A

Pill erection

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10
Q

What types of smooth muscle are there?

A

Tonic and phasic

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11
Q

What is the tonic type of smooth muscle based on their function. Give some examples?

A

Function ‘individually’ - Electrical isolatioon of cells allow fine motor control

Example: Iris and vas deferens

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12
Q

What is the phasic type of smooth muscle based on their function. Give some examples?

A

Function as a syncytium- Gap junctions permit coordinated contraction

Example: Stomach, urinary bladder and bronchioles

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13
Q

What are varicosities?

A

Synaptic contacts - in tonic smooth muscle fibres

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14
Q

What is the contractile machinery of smooth muscle. What do they rely on?

A

Sliding filament mechanism of genereated during actin-myosin cross-bridge formation to facilitate contraction

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15
Q

What is cross bridge formation and sliding filament in smooth muscle driven by?

A

A rise in [Ca+]i which binds to calmodulin

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16
Q

What does the Ca2+ -calmodulin complex activate?

A

Myosin light chain kinase (MLCK)

17
Q

Where is the myosin light chain phosphorylated? And what occurs here?

A

The myosin head

Phosphorylation of myosin head ‘cocks’ it and increases its ATPase activity readying it to interact with actin to form a cross-bridge

18
Q

To what length of [Ca2+] evokes maximal contraction?

A

1um

19
Q

Elevated [Ca2+]i results from what?

A

Ca2+ release from the SR and Ca2+ influx across the plasma membrane

20
Q

What are the factors that affect striated muscle cross-bridge formation?

A
  • Increased intracellular [Ca2+]

- Stretch (Frank-starling relationship) law of heart (more stretched-more calcium uptake)

21
Q

What are the factors that affect smooth muscle cross-brudge formation?

A
  • Increased intracellular [Ca2+]
  • Phosphorylation of myosin light chain kinase
  • Inhibition of myosin light chain phosphatase
22
Q

In smooth muscle cells, an increase in intracellular calcium conc. is sensed by what. What does this activate and phosphorylate. Then state what this allow, leads to and cause?

A 
Sensed- CaM
Activates- MLCK
Phosphorylates- Myosin
Allows- Actin-myosin
Leads to- Crossbridge cycling
Causes- Contraction
23
Q

In striated muscle cells, an increase in intracellular calcium conc. is sensed by what. What does this move and expose binding sites to. Then state what this allow, leads to and cause?

A 
Sensed- Troponin
Moves- tropomyosin
Exposes- Binding sites on actin
Allows-Actin-myosin interaction
Leads to- Cross bridge cycling
Causes- contraction
24
Q

What is calmodulin?

A

A multifunctional Ca2+ binding protein present in the cytoplasm of all eukaryotic cells

25
Q

What does relaxation involve?

A

A drop in [Ca2+]i to pre-excitation concentrations

26
Q

How is [Ca2+]i returned to its pre-excitation concentrations?

A

Membrane bound Ca2+ ATPase and Na+-Ca2+ exchangers expel calcium from the cell and calcium is sequestered into stores by Marco(endocrone)plasmic reticulum calcium ATPase (SERCA)

27
Q

How does dephosphorylation occur in relaxation of smooth muscle?

A

Myosin light chain phosphatase (MLCP)

28
Q

What nervous system is the smooth muscle innervated into?

A

Autonomic nervous system

29
Q

Describe the innervation of arterial smooth muscle

A

Sympathetic innervation with noradrenaline

30
Q

What are the anchor points in the sliding filament?

A

Plasma membrane- actin myosin filaments in between dense bodies

31
Q

What is pharmacomechanical coupling?

A

Refers the process by which an agent causes a change in smooth muscle tone without a change in membrane potential

32
Q

Pharmacomechanical coupling involces the production of intracellular second messengers that either contract, or relax, the muscle. What are the important second messengers?

A
  • Inositol triphosphate (IP3) causing contraction

- Cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP), both causing relaxation

33
Q

What is electromechanical coupling?

A

Refers primarily to the opening of plasma membrane voltage-activated L-type Ca2+ channels in response to depolarisation with, or without, action potential generation

34
Q

What is peristalsis?

A

Propulsive mmovements

35
Q

What is arterial tone?

A

Exerts pressure

36
Q

In pharmacochemical coupling, what activates the G-protein coupled receptor?

A

Transmitter or hormone activates GPCR

37
Q

Myosin light chain phosphatase plays what role in pharmacochemical coupling?

A

Inhibitor

38
Q

What will electromechanical coupling receptors respond to?

A
  • Stretching in mechanosensitive stretch receptor allowing movement of ions into the cell
  • Gap junction propagating a current
  • Receptor-operated calcium channel- adrenergic or muscarinic

Physiology and Pharmacology (22 decks)

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