Mechanism Of Muscle Contraction

Question 1

What does motor unit mean

Answer 1

Single motor neuron and the muscle fibres it innervates

Question 2

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

Answer 2

3-6

Question 3

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

Answer 3

Several hundreds (100-200)

Question 4

What is meant by motor pool

Answer 4

Group of AHC that supply one skeletal muscle

Multiple motor unites

Question 5

Each muscle is composed of

Answer 5

A number of muscle fibres arranged parallel to each other

Question 6

Characters of muscle fibres

Answer 6

Cylindrical
10-100um diameter
Transverse striations

Question 7

What’s the name of the muscle Fiber cell membrane

Answer 7

Sarcolemma

Question 8

What’s the name of the muscle fibres cytoplasm

Answer 8

Sarcoplasm

Question 9

The contractile elements called

Answer 9

Myofibrils

Question 10

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

Answer 10

Hundreds to thousands

Question 11

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

Answer 11

Middle of H-band

Question 12

Thin filaments formed of

Answer 12

Actin
Regulatory proteinis :
Tropomysin
Troponin

Question 13

Actin is formed of :

Answer 13

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

Question 14

G-actin molecules has

Answer 14

An active site which the crossbridge of myosin binds with

Question 15

Tropomyosin formation and site

Answer 15

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

Found in the groove between the two actin chains

Question 16

Function of tropomyosin

Answer 16

Inhibits the active site of G-actin

Mostly by physical covering

Question 17

Troponin parts and function

Answer 17

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

Question 18

Thick filaments found in

Answer 18

A-band

Question 19

Myosin parts called

Answer 19

Head
Arm
Tail

Question 21

Myosin flexible points (hinges)

Answer 21

Junction between arm and head

Junction between arm and tail

Question 22

Body of myosin filament is formed of

Answer 22

Tails of myosin molecules

Question 23

Crossbridge of myosin filament is formed of

Answer 23

Heads and arms of myosin molecules

Question 24

Head of myosin has :

Answer 24

Actin Binding site

ATPase activity site

Question 25

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

Answer 25

Parallel - myofibrils

Question 26

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

Answer 26

Cisternae - T-tubules

Question 27

Functions of cisternae

Answer 27

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

Question 28

T-tubules are formed of

Answer 28

Infolds of the sarcolemma

Question 29

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

Answer 29

Muscles fibers - side to side

Question 30

T-tubules contains

Answer 30

Extracellular fluid

Question 31

T-tubules are .......... to ..........

Answer 31

Parallel - Z-line

Question 32

Function of T-tubules

Answer 32

Transmit the action potential to the interior

Question 33

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

Answer 33

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

Question 34

How many steps ECCMC have

Answer 34

5

Question 35

1st step of ECCMC

Answer 35

Action potential is transmitted to the interior through T-tubules

Question 36

2nd step of ECCMC

Answer 36

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

Question 37

3rd step of ECCMC

Answer 37

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

Question 38

4th step of ECCMC

Answer 38

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

Question 39

Steps of walk along theory

Answer 39

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

Question 40

The cycle of the walk along theory continue until

Answer 40

Z-line reaches the end of myosin filaments

Question 41

5th step of ECCMC

Answer 41

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

Question 42

Factors resposible for gradation of muscle activity

Answer 42

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

Question 55

Types of tubules in the sarcoplasm

Answer 55

``` Longitudinal tubules Transverse tubules (T) ```