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FLS histology > Muscle > Flashcards

Muscle Flashcards

1
Q

What are the functions of muscle tissue?

A

Movement
Maintenance of posture
Joint stabilisation

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2
Q

What are the two main types of muscles?

A

Striated muscle
Smooth muscle

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3
Q

What are the types of striated muscle tissue?

A

Skeletal muscle - attached to bone, responsible for motor movement.
Cardiac muscle - found in the wall of the heart, and in the base of the large veins that empty into the heart.

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4
Q

What are the characteristics of skeletal muscle?

A

Attach to and move skeleton
Fibres - multinucleate cells
Have obvious striations in cells
Contractions are voluntary

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5
Q

What are the characteristics of cardiac muscle?

A

Only in the wall of the heart.
Contractions are involuntary

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6
Q

What are the characteristics of smooth muscle?

A

Lack striations
Cells are fusiform spindle shaped.
There is one central nucleus.
They are grouped into sheets perpendicular to one another.

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7
Q

What are the structures of the skeletal muscle?

A

Consists of muscle fibres which are long, cylindrical multinucleated cells.
Epimysium
Perimysium
Endomysium

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8
Q

What does epi mean?

A

Outside

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9
Q

What does endo mean?

A

Inside

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10
Q

What does peri mean?

A

Surrounding

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11
Q

What is epimysium?

A

Dense connective tissue sheath
Surrounds the whole muscle externally

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12
Q

What is perimysium?

A

Connective tissue septa
Subdivides the muscle internally into fascicles, each containing several nerve fibres.
Nerves and blood vessels penetrate.

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13
Q

What is endomysium?

A

A more delicate, looser connective tissue - surrounds individual muscle fibres.

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14
Q

What does skeletal muscle look like?

A

see image

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15
Q

What is the muscle fibre?

A

Each muscle fibre is the cell of the skeletal muscle.
It consists of myofibrils, which each have thick and thin actin and myosin myofilaments.

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16
Q

What is a sarcomere?

A

The units of contraction.
Contains actin and myosin.
Dark, transverse Z bands mark the ends of each sarcomere and anchor the thin filaments.
Titin protein binds the thick filament to the Z disc.

17
Q

What is the structure of myofibrils?

A

Myofibrils has alternating light and dark filaments.
Light filaments are actin containing I bands.
Dark filaments are myosin containing A bands along its length.

18
Q

What is the H zone?

A

In the centre of each A band.
It is lighter because it is not overlapped by thin filaments.
It is then bisected by a thin, dark M band.

19
Q

What is the sarcoplasmic reticulum?

A

The SR is smooth ER.
Invagination of the cell membrane are T-tubules which surround the myofibrils.
Two terminal cisternae of SR surround each T-tubule to form a triad.

20
Q

What do SR cisternae do?

A

Cisternae store Ca2+ and release when the muscle is stimulated to contract.

21
Q

How is there simultaneous contraction?

A

The T tubules are continuous with the sarcolemma (cell membrane) so the whole muscle contracts simultaneously.

22
Q

How does muscle contraction occur?

A

The depolarisation of the T tubule membrane triggers the release of Ca2+ from terminal cisternae.
This initiates muscle contraction by binding to the troponin-tropomyosin complex.
This causes horizontal sliding of thin filaments on thick filaments, which shortens the muscle.

23
Q

How does muscle relaxation occur?

A

Results from the decrease of cytosolic free Ca2+ concentration.

24
Q

What is cardiac muscle?

A

Branched and striated.
It consists of individual cylindrical cells, each containing one or more central nuclei, and linked by adherens and gap junctions.

25
Q

Where are the nuclei in skeletal muscle?

A

Peripheral in the cell

26
Q

What are intercalated discs?

A

Adjacent cardiac cells are joined to each other by intercalated discs.
These are highly specialised adhesion junctions containing fascia adherens, gap junctions and desmosomes.
Found only in cardiac muscle.

27
Q

How does contraction occur in cardiac muscle?

A

Purkinje fibres exhibit a spontaneous rhythmic contraction.
They generate and rapidly transmit action potentials to various parts of the myocardium.
It is regulated by the autonomic nervous system.

28
Q

How are cisternae arranged in cardiac muscle?

A

Terminal cisternae are much smaller than in skeletal muscle.
One terminal cisterna and T tubules form diads located at the level of the Z line, with one in each sarcomere.

29
Q

What is the structure of smooth muscle?

A

Dense bodies are the main unit of contraction.
Thin filaments attach to dense bodies using a-actinin, located at the cell membrane and deep in the cytoplasm.
Dense bodies at the membrane are also attachment sites for intermediate filaments and adhesive junctions between cells.

30
Q

What are the contractions of smooth muscle?

A

Contractions are involuntary, slow, sustained and resistant to fatigue.
Does not always require a nervous signal - can be stimulated by stretching or hormones.

31
Q

Where is smooth muscle found?

A

The walls of hollow organs - digestive organs.
Also found in the respiratory, urinary and reproductive tracts, and are a major component of blood vessels.

32
Q

How is smooth muscle adapted?

A

The arrangement of the cytoskeleton and contractile apparatus allows the multicellular tissue to contract as a unit, which provides better efficiency and force.

33
Q

How does contraction occur in smooth muscle?

A

Actin-myosin binding occurs with myosin phosphorylation by myosin light chain kinase (MLCK).
This is triggered when calmodulin binds Ca2+.

34
Q

How is skeletal muscle repaired?

A

There is a sparse population of satellite cells.
Limited regeneration capcity.
After injury, inactive reserve myoblasts become activated, proliferate and fuse to form new skeletal muscle.

35
Q

How is cardiac muscle repaired?

A

Lacks satellite cells.
Shows very little regenerative capacity.
Damaged heart muscle is replaced by fibroblasts and growth of connective tissue, this causes scarring.

36
Q

How is smooth muscle repaired?

A

Has similar mononucleated cells.
Has active regenerative capacity.
After injury, smooth muscle cells undergo mitosis and replace the damaged tissue.

FLS histology (6 decks)

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