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Biology Year 2 > C15 - Skeletal muscle > Flashcards

C15 - Skeletal muscle Flashcards

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1
Q

what are the 3 types of muscle

A

skeletal
Non-skeletal
Cardiac

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2
Q

What is muscle tissue made of

A

cells are known as muscle fibres

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3
Q

what are muscle fibres bundled into

A

Fascicle

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4
Q

what is the tissue fluid that surrounds the fascicle

A

perimysium

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5
Q

What is a bundle of fascicles known as

A

muscle

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6
Q

what is a muscle surrounded by

A

connective tissue called the epimysium

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7
Q

what are other names for skeletal muscles

A

striped
striated
Voluntary muscle

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8
Q

what are other names for non-skeletal muscle

A

Unstriped
Non-striated
Smooth
Involuntary muscle

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9
Q

What does ultrastructure mean

A

The detailed structure of a cell as seen in the electron microscope.

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10
Q

what is another name for ultrastructure

A

Fine structure

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11
Q

Describe the ultra structure of a muscle fibre

A

long thin cell

formed by fusion of several cells in the embryo and so it has many nuclei

and can be described as
Coenocytic
or
syncytium

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12
Q

what is the name of the cell membrane of a muscle fibre

A

the sarcolema

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13
Q

what is the name of the endoplasmic reticulum of a muscle fibre

A

sacroplasmic reticulum

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14
Q

what is the name of the muscle fibre cytoplasm

A

sarcoplasm

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15
Q

what is a myofibril

A

long thin structure in a muscle fibre made largely of the proteins actin and myosin

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16
Q

what is a myofillament

A

thin filaments of mainly actin and thick filaments of mainly myosin in myofibrils that interact to produce muscle contraction

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17
Q

where are myofibrils found withi

A

muscle fibres

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18
Q

what are myofibrils made of

A

they are made proteins
actin
troponin
tropomyosin

organised in long thin structures to form the myofillaments

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19
Q

Thick myofillament are made of what

A

primarily myosin

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20
Q

thin myofillaments are made primarily of what

A

largely actin

21
Q

LEARN ULTRA STRUCTURE OF MYOFIBRIL

A

LEARN ULTRA STRUCTURE OF MYOFIBRIL

22
Q

What is the role of the sarcolemma

A

invaginatinates making tubules across the myofibrils (known as transverse tubules)

The T tubules cross the myofibril and transmit a nervous impulse through the muscle fibre very quickly and all the myofibril

all the myofibrils can contract at the same time

the sarcoplasmic reticulum makes a network around the myofibrils and dilates next ot the T tubules to make a terminal cisterna.

23
Q

Sliding filament theory of muscle contraction

A

Thin filaments are made of primarily actin but contain 3 different proteins which all have different roles

Actin molecules are globular protein
G actin joined in a long chain
2 chains twist around each other forming a fibrous strand known as F ACTIN

Tropomyosin is a protein that warpas around F actin lying in a grove between the 2 chains

Toponin is a globular protei located at intervals along the thin filament

24
Q

Part 2

A

The thick filaments are made of any myosin molecules
Each has a globular head with ATPase activity projecting from a fibrous tail.

The globular heads of adjacent myosin molecules are 6nm apart

Muscles contract when the thin actin filaments slide between the thick myosin filaments the lengths of actin and myosin molecules do not change but:

The sarcomerers shorten so the myofibrils shorten and so the whole muscle fibre shortens.

The A band remains the same length because it is defined by the length of the myosin filaments

The I band shortens

The H zone shortens andmay get so small it cannot be seen.

25
Q

Describe the sliding filament theory

A

the sliding filament theory describes the molecular mechanism of muscle contraction

26
Q

Sliding filament theory explaination

A

The action potential of the nervous impulse crosses the neuromuscular junction

The wave of depolarization passes along the sarcolemma and T tubules so that it penetrates all through the muscle fibre

Calcium channels in the sarcoplasmic reticulum open and Calcium ions diffuse into the myofibrils

Calcium ions bind to troponin molecules which changes its shape

This moves tropomyosin molecules, exposing myosin binding sites on the F actin

Myosin heads make cross bridges to the actin by binding to these binding sites

ADP and a phosphate ion attached to the head are released changing the angle of the myosin head back to its relaxed shape and the myosin molecule rotates pulling actin past the myosin (power stroke)

another ATO molecule binds to the myosin head and this breaks the crossbridge to the actin

hydrolysis of the ATP makes energy available and extends the myosin head again ready to bind to actin

The sequence repeats until calcium ions, which exposed the myosin binding site on the actin are all pumped back into the sarcoplasmic reticulum

27
Q

Define the sliding filament theory

A

it is the theory of muscle contractions which theory of muscle contraction in which thin, actin filaments slide between thick myosin filaments in response to a nervous impulse mediated by the T system.

28
Q

summary of sliding filament theory

A 
1/ Myosin head extends
2/Myosin binds to actin
3/ADP and Pi released
4/Power stroke
5/ATP binds to myosin head
6/Myosin unbinds from actin
29
Q

what are the two types of muscle fibres

A

Fast twitch

Slow twitch

30
Q

what is the use of slow twitch

A

Endurance e.g. long distance running

31
Q

what is the use of fast twitch

A

Bursts of activity such as jumping or sprinting

32
Q

What is the physiology of slow twitch muscle fibres

A

contract for longer time
contract slowly
fatigue slowly

33
Q

what is the physiology of fast twitch muscle fibres

A

contract then relax rapidly
contract quickly
fatigue rapidly

34
Q

describe the myofibrils of slow twitch muscles

A

many mitochonria producing high ATP concentration

low density of myofibrils

35
Q

describe the myofibrils of fast twitch muscles

A

few mitochondria

high density of myofibrils

36
Q

Describe respiration of slow twitch muscles

A

Aerobic respiration

High density of capillaries to deliver oxygen

Little glycogen as blood brings glucose

High concentration of myoglobin, so oxygen available even at low oxygen partial pressure

Little lactate made bc little anaerobic respiration any made is slowly removed

37
Q

Describe respiration of fast twitch muscles

A

Anaerobic respiration

Low density of capillaries as little oxygen needed

high glycogen store to generate glucose for glycolysis

low concentration of myoglobin as no need for oxygen store

lactate removed quickly by oxidation to pyruvate or reversion to glucose

38
Q

what is the colour of a slow twitch muscle fibre

A

dark in colour because of rich blood supply and high myoglobin concentration

39
Q

what is the colour of a fast twitch muscle fibre

A

Light in colour because little blood and low myoglobin concentration

40
Q

how does oxygen availability impact ATP production

A

less ATP is made by oxidative phosphorylation in the mitochondria

41
Q

in limited oxygen condition what does the body rely on to produce ATP

A

Creatine phosphate store to make ATP in the sarcoplasm

42
Q

Describe the creatine phosphate store making ATP

A

Transfers a phosphate group to ADP to maintain ATP levels in cell

43
Q

Define muscle fatigue

A

decline in ability of a muscle to generate force

44
Q

what are the 2 types of fatigue

A

neural fatigue
Metabolic fatigue
Cramp

45
Q

Define a cramp

A

severe involunatary muscle contraction that can occur in striated or non-striated muscle.

46
Q

how does lactate cause fatigue

A

reduces stimulation of calcium ions,

allows potassium ions to enhance muscle contraction but prevents chlorine ions from inhibiting it.

47
Q

what is hitting the wall

A

when long distance athletes use up all their glycogen stores

48
Q

How can hitting the wall be avoided

A

Eating food with a high glycaemic index

Endurance training

Carbohydrate loading

Biology Year 2 (37 decks)

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