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ANAT241- Module 2 > Muscle tissue- Skeletal, cardiac and smooth > Flashcards

Muscle tissue- Skeletal, cardiac and smooth Flashcards

1
Q

what are the three main types of muscle?

A

skeletal muscle
Cardiac muscle
smooth muscle

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2
Q

what are the cells of skeletal muscle?

A

long, cylindrical, multinucleated cells, the cells form obvious striations

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3
Q

what is the function of skeletal muscle?

A

volentary movement
locamotion
manipulation of the environment
facial expression
voluntary control

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4
Q

where is skeletal muscle located?

A

in skeletal muscles attached to bones or occasionally to skin

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5
Q

why do skeletal muscles look striated?

A

due to proteins and filaments involved in contraction

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6
Q

what are the layers of the skeletal muscle?

A

epimysium
Endomysium
Perimysium
Fascicles

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7
Q

what is the epimysium?

A

connective tissue sheathing the muscle

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8
Q

what is the endomysium?

A

protecting individual muscle fibers

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9
Q

what is the perimysium?

A

sheaths bundles of muscle fibers

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10
Q

what are the fascicles?

A

Bundles of muscle fibers

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11
Q

what is a muscle fiber?

A

a single muscle cell

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12
Q

what is a myofibril?

A

a fibre within a single muscle cell

can be hundreds of myofibrils in a muscle fiber

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13
Q

what is a motor neuron?

A

initiates the signal for skeletal muscle contraction

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14
Q

what is the neuromuscular junction?

A

where the motor neuron meets the skeletal muscle

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15
Q

what is a sarcolemma?

A

cell membrane of muscle fibre

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16
Q

what is a transverse T-tubule?

A

Invagination of sarcolemma into cell

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17
Q

what is the sarcoplasmic reticulum?

A

simila to endoplasmic reticulum. Store and release Ca 2+

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18
Q

what is the role of Ca2+ in skeletal muscle contraction?

A

Used to initiate contraction of the myofibril contractile units.

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19
Q

how does a muscle contract?

A

binding of thin filaments to thick filaments allows contraction to occur.

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20
Q

what makes up the thin filament?

A

Actin
Tropomyosin
Troponin

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21
Q

what is actin in thin filaments?

A

contain binding sites for thick filament

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22
Q

what is thin filament tropomyosin?

A

Protein strand that covers binding sites in relaxed state

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23
Q

what is thin filament troponin?

A

sits on tropomyosin and responds to signals for contraction

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24
Q

what is myosin?

A

Main protein of thick filament, elongated with distinctive head

25
Q

how does the sarcomere contract?

A

the head of myosin binds and “walks” along thin filament

26
Q

what causes the striations?

A

sarcomere zones

27
Q

what is a sarcomere I-band?

A

only thin filament in the sarcomere (no overlap with the thick filaments)

28
Q

what is a sacromere A-band?

A

where there is thick filament

29
Q

what is the H-zone?

A

where there is only thick filament

30
Q

what is the neuromuscular junction?

A

where the motor neuron joins with the plasma membrane of a skeletal muscle

31
Q

how is a muscle fibre action potential?

A

when acetylcholine is released which causes the membrane to be depolarised

32
Q

what releases Ca2+ into the muscle cells?

A

sarcoplasmic reticulum

33
Q

how does the Action potential spread?

A

along the sarcolemma and then into the T-tubule

34
Q

how does Ca2+ causes sarcolemma contraction?

A

binding of Ca2+ to troponin causes movemen to tropomyosin, exposing the binding sites for the myosin from the thick filament to bind to actin of the thin filament

35
Q

how does the sarcomere contract?

A

Myosin head changes shape and pulls thin filament to centre of sarcomere

ATP binds to myosin, and energy is utilized to detach myosin, reverting shape

Myosin head binds to another actin molecule further towards the Z-line

36
Q

what happens to the I-band when the sarcomere contracts?

A

The I-band decreases

37
Q

what happens to the A-band when the sarcomere contracts?

A

The A-band does not change as it is only dependednt on the length of the thick filaments

38
Q

what happens to the H-band when the sarcomere contracts?

A

The H-band decreases

39
Q

what happens to the distance between Z-lines when the sarcomere contracts?

A

decreases

40
Q

what happens within skeletal muscle during rigor mortis?

A

Ca2+ leaks from sarcoplasmic reticulum into muscles fibres following death, exposing actin binding sites

Myosin automatically binds and pulls thin filament (no ATP required)

New molecules of ATP needed for the unbinding of myosin and actin are not produced

Thus, myosin remains attached to actin and thus the contracted muscles do not relax

41
Q

what is nemaline myopathy?

A

Muscle weakness, swallowing dysfunction, impaired speech

mutations that cause changes in the thin filaments

42
Q

what are the features of cardiac muscle cells?

A

Branching, striated, generally uninucleate cells that interdigitate at specialized junctions (intercalated discs)

43
Q

what is the function of cardiac muscles?

A

As it contracts, it propels blood into the circulation; involuntary control

44
Q

where is cardiac muscle located?

A

The walls of the heart

45
Q

what forms intercalated discs?

A

Desmosomes
Fascia adherens
Gap junctions

46
Q

what is the role of desmosomes in the cardiac muscle?

A

anchor cells to each other via the cytoskeleton

47
Q

what is the role of Fascia adherens in the cardiac muscle?

A

anchor actin filaments and transmit contractile forces

48
Q

what is the role of gap junctions in the cardiac muscle?

A

transmit contraction stimulus

49
Q

what is a disease caused by desmosome dysfunction?

A

Arrhythmogenic right ventricular cardiomyopathy

50
Q

what are the cells of smooth muscle?

A

Spindle-shaped cells with central nuceli; no striations; cells arranged closely to form sheets

51
Q

what is the function of smooth muscle?

A

Propels substances or objects (food stuffs, urine, a baby) along interal passageways; involuntary control

52
Q

where is smooth muscle located?

A

Mostly in the walls of hollow organs

53
Q

how do smooth muscles contract?

A

with contractile filaments that criss-cross the cell

54
Q

how are contractile filaments anchored?

A

to the cell at focal densities in the cytoplasm and focal adhesion densities on the cell membrane

55
Q

how do smooth muscles contract?

A

works on the sliding filament theory as skeletal muscle. Thin actin molecules slide over thick myosin molecules and the smooth muscle cell takes on a globular shape.

56
Q

what are focal densities?

A

Focal densities are functionally and structurally similar to Z line

57
Q

how do actin filaments work in smooth muscle?

A

Actin filaments link to both sides of focal densities

58
Q

how do myosin filaments work in smooth muscle?

A

Myosin filaments partially overlap actin like in skeletal muscle

59
Q

how do intermediate filamets work in smooth muscle?

A

intermediate filaments provide cytoskeletal structure between densities

ANAT241- Module 2 (9 decks)

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