Skeletal Muscles Flashcards
Structure of the skeletal muscle
Muscle fibers, myofibril, myofilament (actin and myosin)
Muscle fibers consist of
Myofibrils
Sacromere is?
It’s in myofibrils and it’s the junction between two z-lines
Which are thin filaments and which are thick filaments?
Thin filaments are actin filaments
Thick filaments are myosin filaments
Both form sacromere
How do muscle contract?
By the sliding of thick filament (myosin) and the thin filaments (actin) along each other
Sacroplasmatic reticulum
The main storage of Ca ions
What is a traid?
Two terminal cisternae and one T-tubule
Innervation of skeletal muscle
It’s innervated by A alfa nerve fibers. This fiber makes neuromuscular synapse where ACH is the NT and N-choline is the receptor
Neuromuscular synapse is only?
Excitatory
Motor unit is
One motor neurone + muscle fiber it innervates
Function of skeletal muscle
- Contraction and posture control
- Receptive
Heat production - Protection
- Facilitate venous return
- Breath, speech, drinking…
What are the two properties of skeletal muscle?
Active properties
- Excitability
- Conduct ability
- Contract ability
passive properties
- Ability to stretch
- Elasticity
- Plasticity
Tittin filaments
Are non-contractile filaments that attach myosin to actin filaments
Hold the myosin to z-lines
Inhibitory proteins
Tropomyosin
Trponin
Ca ions role in skeletal muscle
Ca ions releases from SPR and bind to Troponin c-part which removes Tropomyosin from active site on actin filaments allows myosin head to bind to active site
What do use ATP for ?
For contraction and relaxation
Receptors in Ca release from SPR
dihydropiridine receptors : located on T-tuble, sensing the AP traveling along
Ryanodine receptors: located on SPR, change conformation
How strength of the stimuli affect muscle contraction?
A single motor unite contract according to all or non principle so it means,
Subthreshold stimulus is weak and doesn’t cause any response.
Threshold stimuli, only motor unites with highest excitability respond, but since the HE motor unites are few so force of contraction is not maximum.
Suprathreshold stimuli, the strength of the stimuli increases so force of contraction increases