C15 - Skeletal muscle

Question 1

what are the 3 types of muscle

Answer 1

skeletal
Non-skeletal
Cardiac

Question 2

What is muscle tissue made of

Answer 2

cells are known as muscle fibres

Question 3

what are muscle fibres bundled into

Answer 3

Fascicle

Question 4

what is the tissue fluid that surrounds the fascicle

Answer 4

perimysium

Question 5

What is a bundle of fascicles known as

Answer 5

muscle

Question 6

what is a muscle surrounded by

Answer 6

connective tissue called the epimysium

Question 7

what are other names for skeletal muscles

Answer 7

striped
striated
Voluntary muscle

Question 8

what are other names for non-skeletal muscle

Answer 8

Unstriped
Non-striated
Smooth
Involuntary muscle

Question 9

What does ultrastructure mean

Answer 9

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

Question 10

what is another name for ultrastructure

Answer 10

Fine structure

Question 11

Describe the ultra structure of a muscle fibre

Answer 11

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

Question 12

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

Answer 12

the sarcolema

Question 13

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

Answer 13

sacroplasmic reticulum

Question 14

what is the name of the muscle fibre cytoplasm

Answer 14

sarcoplasm

Question 15

what is a myofibril

Answer 15

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

Question 16

what is a myofillament

Answer 16

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

Question 17

where are myofibrils found withi

Answer 17

muscle fibres

Question 18

what are myofibrils made of

Answer 18

they are made proteins
actin
troponin
tropomyosin

organised in long thin structures to form the myofillaments

Question 19

Thick myofillament are made of what

Answer 19

primarily myosin

Question 20

thin myofillaments are made primarily of what

Answer 20

largely actin

Question 21

LEARN ULTRA STRUCTURE OF MYOFIBRIL

Answer 21

LEARN ULTRA STRUCTURE OF MYOFIBRIL

Question 22

What is the role of the sarcolemma

Answer 22

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.

Question 23

Sliding filament theory of muscle contraction

Answer 23

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

Question 24

Part 2

Answer 24

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.

Question 25

Describe the sliding filament theory

Answer 25

the sliding filament theory describes the molecular mechanism of muscle contraction

Question 26

Sliding filament theory explaination

Answer 26

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

Question 27

Define the sliding filament theory

Answer 27

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.

Question 28

summary of sliding filament theory

Answer 28

``` 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 ```

Question 29

what are the two types of muscle fibres

Answer 29

Fast twitch | Slow twitch

Question 30

what is the use of slow twitch

Answer 30

Endurance e.g. long distance running

Question 31

what is the use of fast twitch

Answer 31

Bursts of activity such as jumping or sprinting

Question 32

What is the physiology of slow twitch muscle fibres

Answer 32

contract for longer time contract slowly fatigue slowly

Question 33

what is the physiology of fast twitch muscle fibres

Answer 33

contract then relax rapidly contract quickly fatigue rapidly

Question 34

describe the myofibrils of slow twitch muscles

Answer 34

many mitochonria producing high ATP concentration low density of myofibrils

Question 35

describe the myofibrils of fast twitch muscles

Answer 35

few mitochondria high density of myofibrils

Question 36

Describe respiration of slow twitch muscles

Answer 36

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

Question 37

Describe respiration of fast twitch muscles

Answer 37

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

Question 38

what is the colour of a slow twitch muscle fibre

Answer 38

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

Question 39

what is the colour of a fast twitch muscle fibre

Answer 39

Light in colour because little blood and low myoglobin concentration

Question 40

how does oxygen availability impact ATP production

Answer 40

less ATP is made by oxidative phosphorylation in the mitochondria

Question 41

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

Answer 41

Creatine phosphate store to make ATP in the sarcoplasm

Question 42

Describe the creatine phosphate store making ATP

Answer 42

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

Question 43

Define muscle fatigue

Answer 43

decline in ability of a muscle to generate force

Question 44

what are the 2 types of fatigue

Answer 44

neural fatigue Metabolic fatigue Cramp

Question 45

Define a cramp

Answer 45

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

Question 46

how does lactate cause fatigue

Answer 46

reduces stimulation of calcium ions, allows potassium ions to enhance muscle contraction but prevents chlorine ions from inhibiting it.

Question 47

what is hitting the wall

Answer 47

when long distance athletes use up all their glycogen stores

Question 48

How can hitting the wall be avoided

Answer 48

Eating food with a high glycaemic index Endurance training Carbohydrate loading