Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

PA10315 > Smooth muscle > Flashcards

Smooth muscle Flashcards

1
Q

Where is smooth muscle found?

A

In hollow organs in the body and blood vessels.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Give examples of where smooth muscle is found.

A

The intestine, uterus, airways, hairs in the skin and eyes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where is smooth muscle found in arteries and veins?

A

Between the connective tissue and elastin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the typical diameter of a smooth muscle cell?

A

2-10um.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the typical length of a smooth muscle cell?

A

50-400um.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is absent in smooth muscle compared to skeletal muscle?

A

There is no troponin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are some of the properties of smooth muscle?

A

It is involuntary, there are dense bodies instead of Z discs, it has a smooth appearance (without striations), there is slow myosin ATPase compared to skeletal and there is a less well developed sarcoplasmic reticulum compared to skeletal muscle.
Thin filaments anchored to either the plasma membrane or dense bodies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the two sources of calcium in smooth muscle contraction?

A

Internal calcium stores in the sarcoplasmic reticulum and voltage gated calcium ion channels in the plasma membrane.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What starts the contraction in smooth muscle?

A

Calmodulin binds to calcium.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is cross-bridge activation?

A

Phosphorylation of myosin to allow it to undergo cross-bridge cycling. This is controlled by a Ca+ -regulated enzyme.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the key steps in cross-bridge activation?

A

Ca2+ binds to calmodulin (present in cytosol). This complex binds to myosin light-chain kinase and activates the enzyme. The active enzyme (kinase) then uses ATP to phosphorylate the myosin light chains in the globular head of myosin. This allows the myosin to bind to actin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What factors influence smooth muscle contraction?

A

Spontaneous electrical activity of the muscle cell, neurotransmitter release from autonomic neurons, circulating hormones, local environment changes in the fluid surrounding the cells and mechanical stretch.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why is smooth muscle shortening much slower than in skeletal muscle?

A

Smooth muscle has a low rate of ATPase activity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why does smooth muscle not undergo fatigue during prolonged periods of activity?

A

Slow rate of energy usage due to the low rate of ATPase activity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the two uses of ATP in smooth muscle?

A

Hydrolyzing one ATP to transfer a phosphate onto a myosin light chain to start cross-bridge cycling and then one ATP is used per cycle to provide the energy for force generation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is a varicosity

A

A swollen region at the end of a branch from the axon of a postganglionic autonomic neuron.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What do varicosities contain?

A

Many vesicles filled with neurotransmitter - some of which are released when an action potential passes the varicosity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How can a number of smooth muscle cells be influenced by neurotransmitters from a single neuron?

A

The varicosities from a single axon may be located on multiple muscle cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How can a single muscle cell be influenced by neurotransmitters from more than one neuron?

A

A single muscle cell may be located may be located near to varicosities from sympathetic and parasympathetic neurones.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the two types of acetylcholine receptors?

A

Nicotinic and muscarinic.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Where are the two types of acetylcholine receptors found?

A

Nicotinic in the skeletal muscle neuromuscular junction and muscarinic in the smooth muscle.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What do alpha-adrenergic receptors do?

A

Mediate constriction in most vascular smooth muscle.

23
Q

What do beta-adrenergic receptors do?

A

Mediate dilation of vascular smooth muscle and lung airway smooth muscle. (bronchodilation)

24
Q

What do muscarinic receptors (M3) do in the bronchial smooth muscle?

A

Mediate bronchoconstriction.

25
Q

What do beta-adrenergic receptors do in the bronchial smooth muscle?

A

They mediate smooth muscle relaxation and bronchodilation.

26
Q

What is the volume of an empty stomach?

A

50ml.

27
Q

What smooth muscles relax before the arrival of food to increase the volume of the stomach?

A

The muscles in the fundus and body.

28
Q

What is the maximum volume of the stomach?

A

1.5 litres.

29
Q

What is receptive relaxation?

A

Relaxation of the smooth muscles of the stomach (fundus and body) when food is swallowed - mediated by parasympathetic nerves in the enteric nerve plexuses.

30
Q

What neurotransmitters mediate receptive relaxation?

A

Nitrous oxide and serotonin.

31
Q

What are peristaltic waves?

A

Waves produced in the stomach in response to arriving food.

32
Q

Where do peristaltic waves begin and what path do they follow?

A

They begin in the body of the stomach and produces only a ripple as it proceeds towards the antrum.

33
Q

What happens as the wave approaches the larger mass of wall muscle surrounding the antrum?

A

A more powerful contraction is produced which mixes the luminal contents and closes the pyloric sphincter.

34
Q

What is the pyloric sphincter?

A

A ring of smooth muscle and connective tissue between between the antrum and duodenum.

35
Q

What happens to the pyloric sphincter muscles as a peristaltic wave arrives?

A

It contracts.

36
Q

What is retropulsion?

A

Backward motion of chyme.

37
Q

What does retropulsion do?

A

It generates strong shear forces that help to disperse the food particles and improve mixing of the chyme.

38
Q

How is stomach contents stopped from entering the esophagus.

A

The lower esophageal sphincter prevents the retrograde movement of the stomach contents into the esophagus.

39
Q

How are gastric peristaltic waves created?

A

Pacemaker cells in the longitudinal smooth muscle layer.

40
Q

What is the basic electrical rhythm of the stomach?

A

Spontaneous depolarisation-repolarisation cycles. These are slow waves.

41
Q

Where are slow waves conducted?

A

They are conducted through gap junctions along the stomach’s longitudinal muscle layer and also induce similar slow waves in the overlying circular muscle layer.

42
Q

Why are neural or hormonal inputs needed for slow waves to be conducted?

A

Without these inputs, the depolarisations are too small to cause significant contractions.

43
Q

How is the membrane further depolarised for the gastric peristaltic waves?

A

Excitatory neurotransmitters and hormones act upon the smooth muscle.

44
Q

What is single-unit smooth muscle?

A

Smooth muscle that responds to stimulation as a single unit because gap junctions join muscle fibres, allowing electrical activity to pass from cell to cell.
fibres aggregated into sheets/bundles

45
Q

How are the fibres arranged in single-unit smooth muscle?

A

They are aggregated into sheets or bundles.

46
Q

What are examples of single unit smooth muscles?

A

The intestine, bladder and small diameter blood vessels.

47
Q

What are multi-unit smooth muscle cells?

A

They have no or jew gap junctions and each cell responds independently and the muscle behaves as multiple units.

48
Q

What are some features of multi-unit smooth muscle?

A

They are not activated by stretch, they resemble striated muscle where there is no electrical coupling which allows fine control and gradual responses.
APs do not occur often

49
Q

What are some examples of multi-unit smooth muscle?

A

Large arteries, large airways in lungs and pilomotor muscles.

50
Q

shape of smooth muscle cells

A

spindle shaped

51
Q

how does the organisation of actin and myosin in smooth muscle compare to skeletal

A

less organised in smooth

52
Q

single unit smooth muscle example

A

intestine, bladder

53
Q

multi unit smooth muscle example

A

large arteries, large airways in lungs

PA10315 (47 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions