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Acids and bases > Lecture 1: Skeletal muscle part 1 > Flashcards

Lecture 1: Skeletal muscle part 1 Flashcards

1
Q

Are skeletal muscles striated?

A

yes

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2
Q

Are skeletal muscles under voluntary control?

A

yes

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3
Q

Shape of skeletal muscle

A

multiple peripheral cells

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4
Q

Shape of a skeletal muscle?

A

long, cylindrical cells, single

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5
Q

What are the three main types of muscle?

A

skeletal
cardiac
smooth

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6
Q

What are skeletal muscles?

A

attached to bones and is responsible for movement

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7
Q

What are cardiac muscles?

A

forms the bulk of the heart mass and its contraction ejects blood from the organ

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8
Q

Smooth

A

mainly lines hollow organs, iris, blood vessels (regulates their dimensions)

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9
Q

Are cardiac muscles under voluntary control?

A

no

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10
Q

Are cardiac muscles striated?

A

yes

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11
Q

What are the shape of cardiac muscle cells

A

branched cells with 1-3 central nuclei

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12
Q

How are cardiac muscles connected?

A

they are connected by intercalated discs

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13
Q

Where are cardiac muscles located?

A

in the heart ONLY

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14
Q

What control are smooth muscles under?

A

involuntary

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15
Q

what is the shape of a smooth muscle?

A

spindle shaped, uninucleated cells

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16
Q

Are smooth muscle cells striated?

A

no

17
Q

Where are smooth muscle cells found?

A

in the gut, respiratory system, blood vessels

18
Q

What is a motor unit?

A

a group of muscle cells which is innervated by a single motor neuron

19
Q

what are the two major groups of proteins which are responsible for muscle contractions in all 3 muscle types?

A

actins

myosins

20
Q

List in order the skeletal muscle is packaged

A

1.) skeletal muscle is attached to the bone by a tendon
it is wrapped by epimysium
2.) the skeletal muscle contains bunches of fascicles (perimysium surrounded)
3.) fascicles encase bundles of muscle fibres/cells (endomysium)
4.)muscle fibres encase myofibrils
5.) myofibrils encase filaments

21
Q

What is the structure of a muscle cell?

A

sarcolemma (plasma membrane)

sarcoplams (like cytoplasm)

t tubule (invaginations of the sarcolemma towards the centre of the myofibril; open to sarcoplasm)

22
Q

Structure of a myofibril?

A

surrounded by a sarcoplasmic reticulum (SR); stores Ca2+

triad is formed when 2 terminal cisternae and a T tubule meet

23
Q

What is the sarcomere?

A

the smallest unit of contraction

from Z to Z band

24
Q

Describe cross bridge formation, what are the 4 stages?

A

Cross bridge formation
power stroke
detachment
energization of myosin head

25
Q

What happens during cross bridge formation?

A

the energized myosin head binds to a receptor site on the actin molecule

forming a cross bridge

inorganic phosphate is released

the bond between actin and myosin become stronger

26
Q

what happens during power stroke?

A

ADP is released
the inactivated myosin head pivots
sliding the thin myofilament toward the centre of the sarcomere

27
Q

What happens during cross bridge detachment?

A

ATP binds to the myosin head
the link between the actin and myosin weakens
the myosin head detaches

28
Q

What happens during the reactivation of myosin head?

A

ATP is hydrolyzed to ADP and inorganic phosphate on the myosin heaed

the energy released during hydrolysis
reactivates the myosin head returning it to cocked position

29
Q

What is the structure of thick filaments?

A

composed of molecules of myosin mainly
has a tail and a head
the tail is oriented towards the M line

30
Q

What are thin filaments made of?

A

double stranded helical actin chain
accesory proteins which regulate them:
troponin
tropomyosin

31
Q

What is the sliding filament model?

A

the Z line is pulled to the M line
the I band and the H zone become narrower
as sarcomeres shorten
A bands do not change in length

32
Q

How does calcium regulate contraction?

A

as the sarcoplasm is depolarized
Ca2+ channels will open in the SR thus releasing ions into the sarcoplasm, increasing the Ca2+ levels

this will cause more Ca2+ to bind to troponin to enable it to change its conformation, to enable tropomyosin to expose myosin binding sites on actin

33
Q

What influences the muscle contaction?

A

the amount of Ca2+ in the cytosol

34
Q

What is the optimum length of sarcomere for max tension?

A
  1. 2 micro metres

2. 0 - 2.2 micrometres

35
Q

What happens when the length of a sarcomere is less than 2.2 micro metres?

A

the Z discs will crumple the thick filaments, less myosin head will be able to bind to actin

36
Q

What happens when the length of a sarcomere is greater than 2.2 micro metres?

A

there will be either no thin filaments that myosin heads will binds to, or decrease of binding to actin

thus overall, force generated is reduced

Acids and bases (5 decks)

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