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Second Year - Biomedical Sciences BS22001 > Lecture 10 - Physiology Of Smooth Muscle > Flashcards

Lecture 10 - Physiology Of Smooth Muscle Flashcards

1
Q

Where is smooth muscle mostly found

A

In the wall of hollow organs and tubes

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2
Q

What is the function of the smooth muscle within the walls and tubes of hollow organs

A

They are involved in mediating propulsive movements and exerting pressure within the blood vessels

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3
Q

What does smooth muscle control within the vessels

A

The diameter, blood flow and pressure

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4
Q

What does smooth muscle control within the lung airways

A

The diameter, airflow and air resistance

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5
Q

What does the smooth muscle control within the urinary system

A

The propulsion of urine through the ureters, bladder tone and the tone of the internal sphincter

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6
Q

What does the smooth muscle control within the gastrointestinal tract

A

the tone, motility and the opening/closing of the sphincers

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7
Q

What does smooth muscle do in the male reproductive system

A

It aids the secretion and propulsion of semen

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8
Q

What does smooth muscle do in the female reproductive tract

A

It aids propulsion within the fallopian tubes and aids child birth through the pressure exerted by the uyterus

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9
Q

What does smooth muscle do in the eye

A

It controls the pupil diameter and the lens shape

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10
Q

What muscles control pupil diameter of the eye

A

The iris muscles

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11
Q

What muscles control the lens shape of the eye

A

The ciliary muscles

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12
Q

What does smooth muscle do within the skin

A

It is involved in hair erectrion

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13
Q

What muscles cause hair erection

A

The pili muscles

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14
Q

What are the three types of filaments within smooth muscle

A

Thick myosin filaments, thin actin filaments and intermediate sized filaments

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15
Q

Within smooth muscle what do the actin filaments contain

A

Tropomyosin

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16
Q

What are the intermediate filaments involved in

A

Only involved in cytoskeletal elements but not contraction

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17
Q

What does smooth muscle respond to

A

An increase in cytosolic levels of Ca2+

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18
Q

How is smooth muscle arranged

A

In sheets

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19
Q

What does contraction occur by

A

The sliding filament mechanism

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20
Q

What is the cross bridge cycle regulated by

A

By intracellular Ca2+

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21
Q

Within smooth muscle what does Ca2+ bind to

A

Calmodulin

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22
Q

What are the differences between skeletal muscle and smooth muscle

A

Smooth muscle fibres do not form myofibrils and it also has no sarcomere pattern and no Z-line

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23
Q

What do the actin filaments in smooth muscle join to

A

The dense bodies

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24
Q

Where are dense bodies attached to

A

The inner surface of the plasma membrane

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25
Q

What proteins are the dense bodies made up of

A

Titin (the same protein that forms the Z line)

26
Q

What are the dense bodies held in place by

A

The intermediate filaments

27
Q

How many thin filaments surround each thick filament

A

10-15

28
Q

What is smooth muscle innervated by

A

The autonomic nervous system

29
Q

Are the thin filaments in smooth muscle all pulled in the same direction

A

No they are pulled in all different directions

30
Q

Where does most of the calcium required to trigger contraction in smooth muscle come from

A

The extracellular fluid

31
Q

The greater the volume of free calcium, the greater

A

The force of contraction

32
Q

How can the volume of calcium be increased

A

By binding of extracellular chemical messengers to G-protein coupled receptors

33
Q

What is an example of an extracellular chemical messenger

A

Noradrenaline

34
Q

What happens when noradrenaline binds

A

It activates phospholipase C

35
Q

What is attached to the myosin chain near the neck arean

A

The myosin light chain

36
Q

What is the function of the myosin light chain

A

The myosin light chain prevents the myosin molecule from interacting with the actin molecule while it is unphosphorylated

37
Q

What allows the interaction of actin and mysoin in smooth muscle

A

Th phosphorylation of the myosin light chain

38
Q

What phosphorylates the myosin light chain

A

The myosin light chain kinase

39
Q

What does contraction result from

A

The phosphorylation of the myosin light chain the the presence of elevated intracellular Ca2+ and ATP

40
Q

What does relaxation occur from

A

The dephosphorylation of the myosin light chain

41
Q

What dephosphorylates the myosin light chain

A

Myosin phophatase

42
Q

What type of activity does myosin phosphatase have

A

Constitutive activity

43
Q

What does it mean if a receptor has constitutive activity

A

The receptor is capable of producing a biological response in the absence of bound ligands

44
Q

What allows the Ca2+ leve;s to return to a basal concentration

A

Primary and secondary active transport

45
Q

What are the different classifications of smooth muscle

A

Phasic or tonic
Multiunit or single unit
Neurogenic or myogenic

46
Q

What are the characteristic of phasic smooth muscle

A

It contracts in bursts, the action potentials trigger a rise in intracellular Ca2+, the contraction is phasic and vigorous

47
Q

What body part are phasic contractions associated with

A

The walls of hollow organs

48
Q

What does phasic smooth muscle contain

A

Specialised, non-contractile cells that display spontaneous changes in membrane potential, independent of neural input

49
Q

Tonic smooth muscle is usually

A

Partially contracted at all times

50
Q

What is open at relatively low resting potential of tonic smooht muscle cells

A

The voltage-activated Ca2+ channels

51
Q

Ca2+ influx in tonic smooth muscle mediates a state of

A

Partial contraction or tone

52
Q

In tonic smooth muscle what does contraction vary because of

A

Factors that alter cytostolic Ca2+

53
Q

What body part is tonic smooth muscle usually associated with

A

The walls of arterioles

54
Q

Single unit muscle cells characteristics

A

The muscle fibres are electrically coupled by gap junctions, it is self-excitable but autonomic innervation modifies its activity and it can be phasic or tonic

55
Q

What is the single function unit of single unit muscle cells known as

A

A functional syncytium

56
Q

What are the two categories of myogenic activity of single unit muscle cells

A

Pacemaker potentials and slow-wave potentials

57
Q

Pacemaker potentials

A

The membrane potential gradually depolarises spontaneously to a value sufficient to reach the threshold for the generation of an action potential

58
Q

How does excitation propagate throughout the smooth muscle sheet

A

Through gap junctions to cause a self-induced contraction

59
Q

Slow-wave potentials

A

The membrane potential oscillates spontaneously between hyperpolarised and depolarised potentials but reaches the threshold for the generation of an action potential only in the presence of an external stimulus

60
Q

How does gradation of tension occur in skeletal muscle

A

Motor unit recruitment and twitch summation

61
Q

How does the gradation of tension occur in single unit smooth muscle cells

A

Through variations in the intraceullular levels of Ca2+ which regulates the number of cross bridges that are formed

62
Q

Characteristics of multiunit smooth muscle cells

A

The muscle fibres are electrically isolated for each other, excitation/contraction of the fibres occurs independently of each other, contraction is usually driven by innervation autonomic nervous system and the muscles are usually phasic

Second Year - Biomedical Sciences BS22001 (28 decks)

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