Tissu Musculaire 1: Generalities and Skeletal starter pack

Question 1

What are the three main groups of muscle type and their characteristics?

Answer 1

Muscle Squelettique:
* Striated and Elongated cells
* Multiple Nuclei in the Sarcolemma
Muscle Lisse:
* Short Juxtaposed Cells
* No Striation
* Central Single Nuclei
Muscle Cardiac:
* Short striated cells
* Central Nuclei

Question 2

Actin vs Myosin:

Answer 2

Actin is the thin passive filament
Myosin is the thick filament that pulls actins together

Question 3

What are sacromes?

Answer 3

Mitochondria of muscle

Question 3

What is sacrolemme?

Answer 3

The membrane of the muscles

Question 4

What is a rhabdomyocyte?

Answer 4

Cellule musculaire striée squelettique

Question 5

What is a myoblast?

Answer 5

The initial progenitor muscle cell

Question 6

What is Hyperplasie?

Answer 6

From Myoblaste (in the embryo)

A lot of multiplication that leads to Fusion →

We get Myotubes

Question 7

Where do we find the nuclei in myofibers?

Answer 7

At the periphery

Question 8

What are Satellite Cells:

Answer 8

Au cours de la formation des cellules musculaires, certains myoblastes ne fusionnent pas mais restent en dormance accolés à la surface (sous la lame basale) de la cellule nouvellement formée. Ce sont les cellules satellites: elles jouent le rôle de cellules-souche pour la réparation locale des fibres musculaires during a blessure

In healthy adult muscle tissue, satellite cells are usually quiescent, meaning they are not actively undergoing cell division2. However, they can be activated in response to muscle injury, which causes them to proliferate and differentiate

Question 9

Why does squelettique muscle appear striated?

Answer 9

Due to the alignment of bandes A I and Z disques in myofibrilles

Question 10

What are the main differences between Type 1 and Type 2 fibers?

Answer 10

Type I fibers (lentes)

We see Type I fibers first

Aerobie mode, mitochondries et myoglobine abondantes, forte teneur en O2

They undergo contractions soutenues, permanentes : muscles anti-gravifiques:

Muscles that help us stand

Type II fibers (rapide):

mode anaérobie à partir du glycogène, moins de myoglobine et de mitochondries

contractions rapides ,sporadiques courtes: muscles oculaires

peu résistantes à la fatigue,

bon potentiel de croissance

Question 11

What are Intermediate Fibers?

Answer 11

gym bro fibers
Can adapt depending on the muscle (short term and long term)

Question 12

Describe the structure of the myofibrille and where do we find this?

Answer 12

1. We find it in Muscle Squelettique
2. Dark A zone that is separated in two from the clearer H zone
   The H zone is separated into two by the Ligne Mediane (M)
   Two Zone A are separated by ligne Z

Question 13

Where does actin connect to?

Answer 13

La ligne Zd

Question 14

What connects two Z lignes together?

Answer 14

filaments intermédiaires de desmine

Question 15

What is bande I?

Answer 15

It is the space between two sacromeres
From end of one A to start of otehr A

Question 16

What is the molecule used as energy in muscle contraction (squelettique)?

Answer 16

ATP -> release of myosin head and dislocation -> relaxation of muscle

Question 17

What is système T?

Answer 17

réseau de canalicules transversaux
qui entoure la myofibrille au niveau
de chaque jonction A-I
forment des triades avec les citernes
terminales

Question 18

What is triade?

Answer 18

tubules transverses entre 2 citernes terminales

(page 32)

Question 19

What is citerne terminale?

Answer 19

Formed by sacrotubules at the A-I junctions

Question 20

What is the role of tubules and triade?

Answer 20

The Tubule will go on the surface to form a pore:

Some membrane potential travelling across will be detected by the tubules and by the voltage sensitive receptors which will lead to Ca++ release and thus → movement; contraction

Ca++ acts on the filaments

Question 21

What does calcium release do to myosin?

Answer 21

Activates its head (with ATP of course)

Here’s how it works:

When a muscle cell is stimulated, calcium ions are released2.
These calcium ions bind to a protein called troponin-C14.
This binding causes a conformational change in another protein called tropomyosin, which is wrapped around actin filaments14.
Normally, tropomyosin blocks the binding sites on actin where myosin heads attach. But when calcium binds to troponin-C, tropomyosin moves away from these binding sites14.
With the binding sites exposed, myosin heads can now attach to actin, forming what’s known as a cross-bridge34.
This cross-bridge formation allows myosin to pull on actin, causing the muscle to contract3