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M&M Physiology > Mechanism Of Muscle Contraction > Flashcards

Mechanism Of Muscle Contraction Flashcards

1
Q

What does motor unit mean

A

Single motor neuron and the muscle fibres it innervates

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2
Q

In the muscles of fine movements what is the Muscle fibers/Neuron ratio

A

3-6

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3
Q

In the muscles of gross movements what is the Muscle fibers/Neuron ratio

A

Several hundreds (100-200)

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4
Q

What is meant by motor pool

A

Group of AHC that supply one skeletal muscle

Multiple motor unites

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5
Q

Each muscle is composed of

A

A number of muscle fibres arranged parallel to each other

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6
Q

Characters of muscle fibres

A

Cylindrical
10-100um diameter
Transverse striations

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7
Q

What’s the name of the muscle Fiber cell membrane

A

Sarcolemma

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8
Q

What’s the name of the muscle fibres cytoplasm

A

Sarcoplasm

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9
Q

The contractile elements called

A

Myofibrils

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10
Q

Each muscle fibres contain ………………. of myofibrils

A

Hundreds to thousands

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11
Q

When the muscle is fully stretched The thin filaments Covers all the sarcomere except

A

Middle of H-band

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12
Q

Thin filaments formed of

A

Actin
Regulatory proteinis :
Tropomysin
Troponin

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13
Q

Actin is formed of :

A

2 chains of a Globular actin molecules (called G-Actin molecules) twisted in a spiral manner

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14
Q

G-actin molecules has

A

An active site which the crossbridge of myosin binds with

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15
Q

Tropomyosin formation and site

A

It’s formed from two light chains twisted around each other

Found in the groove between the two actin chains

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16
Q

Function of tropomyosin

A

Inhibits the active site of G-actin

Mostly by physical covering

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17
Q

Troponin parts and function

A

TnT : bind with tropomyosin
TnC : bind with calcium ion
TnI : inhibits the interaction between actin and myosin

18
Q

Thick filaments found in

A

A-band

19
Q

Myosin parts called

A

Head
Arm
Tail

21
Q

Myosin flexible points (hinges)

A

Junction between arm and head

Junction between arm and tail

22
Q

Body of myosin filament is formed of

A

Tails of myosin molecules

23
Q

Crossbridge of myosin filament is formed of

A

Heads and arms of myosin molecules

24
Q

Head of myosin has :

A

Actin Binding site

ATPase activity site

25
Q

Longitudinal tubules are ………… to the ……………

A

Parallel - myofibrils

26
Q

Longitudinal tubules form chambers called ………… near …………..

A

Cisternae - T-tubules

27
Q

Functions of cisternae

A

Stores Calcium ions at high concentrations due to calcium pump up to 10,000 folds

28
Q

T-tubules are formed of

A

Infolds of the sarcolemma

29
Q

T-tubules penetrate the ……….. from …………

A

Muscles fibers - side to side

30
Q

T-tubules contains

A

Extracellular fluid

31
Q

T-tubules are ………. to ……….

A

Parallel - Z-line

32
Q

Function of T-tubules

A

Transmit the action potential to the interior

33
Q

What does Excitation contraction coupling and mechanism of contraction (ECCMC)

A

The process by which action potential of the muscles fibers initiates contraction

34
Q

How many steps ECCMC have

A

5

35
Q

1st step of ECCMC

A

Action potential is transmitted to the interior through T-tubules

36
Q

2nd step of ECCMC

A

Release of calcium ions from cisternae to the sarcoplasm through voltage-gated calcium channels

37
Q

3rd step of ECCMC

A

Activation of actin by calcium ions

Ca2 bind to troponin-C >
Lateral movement of troponin-tropomyosin copmlex >
Uncovering of active site of actin.

38
Q

4th step of ECCMC

A

Interaction between activated actin and cross bridge of myosin to cause contraction through walk along theory

39
Q

Steps of walk along theory

A

1- Myosin converts ATP > ADP+Pi
2- Myosin head attaches to actin active site
3- Power stroke
4- New ATP bind to the head of myosin and causes detachment
5- ATP converts again
6- Myosin head attaches to a new active site of actin

40
Q

The cycle of the walk along theory continue until

A

Z-line reaches the end of myosin filaments

41
Q

5th step of ECCMC

A

Relaxation, by active reuptake of calcium ions into Cisternae by calcium pump

42
Q

Factors resposible for gradation of muscle activity

A

Gradation of strength :
1- Number of motor units
2- Frequency of discharge in nerve fibers
3- Gradation of onset (Asynchronous activation)

55
Q

Types of tubules in the sarcoplasm

A 
Longitudinal tubules
Transverse tubules (T)

M&M Physiology (4 decks)

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