Tissu Musculaire 1: Generalities and Skeletal starter pack Flashcards
What are the three main groups of muscle type and their characteristics?
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
Actin vs Myosin:
Actin is the thin passive filament
Myosin is the thick filament that pulls actins together
What are sacromes?
Mitochondria of muscle
What is sacrolemme?
The membrane of the muscles
What is a rhabdomyocyte?
Cellule musculaire striée squelettique
What is a myoblast?
The initial progenitor muscle cell
What is Hyperplasie?
From Myoblaste (in the embryo)
A lot of multiplication that leads to Fusion →
We get Myotubes
Where do we find the nuclei in myofibers?
At the periphery
What are Satellite Cells:
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
Why does squelettique muscle appear striated?
Due to the alignment of bandes A I and Z disques in myofibrilles
What are the main differences between Type 1 and Type 2 fibers?
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
What are Intermediate Fibers?
gym bro fibers
Can adapt depending on the muscle (short term and long term)
Describe the structure of the myofibrille and where do we find this?
- We find it in Muscle Squelettique
- 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
Where does actin connect to?
La ligne Zd
What connects two Z lignes together?
filaments intermédiaires de desmine
What is bande I?
It is the space between two sacromeres
From end of one A to start of otehr A
What is the molecule used as energy in muscle contraction (squelettique)?
ATP -> release of myosin head and dislocation -> relaxation of muscle
What is système T?
réseau de canalicules transversaux
qui entoure la myofibrille au niveau
de chaque jonction A-I
forment des triades avec les citernes
terminales
What is triade?
tubules transverses entre 2 citernes terminales
(page 32)
What is citerne terminale?
Formed by sacrotubules at the A-I junctions
What is the role of tubules and triade?
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
What does calcium release do to myosin?
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
