Skeletal Muscle Contraction Flashcards
differences between muscle types
differences between each type of muscle int eh rate of duration of contraction metabolism fatgability and ability to regulate contractile strength
what is a muscle fibre
skeletal muscle cell has a single NMJ where ACh receptors are concentrated
generation of a muscle contraction
ACh released from the pre-synaptic nerve terminal binds to nicotinic ACh receptors at the NMJThese receptors are non-selective cation channels that open in response to ACh binding, resulting in a depolarization of Em known as an end plate potential(epp). If the epp exceeds threshold for activating V-gated Na+ channels, an AP is generated. Generation of an AP initiates the sequence of events leading to contraction.ACh is rapidly inactivated by ACh-esterase
What is muscle made up
muscle run parallele to one another and is bundled by connective tissues with multi nuclei and abundance of mitchdonrida to keep up with the high energy demand of tissue
How does embronyic development work for muscle fibres
During embroynic development these muscle fibres are formed by myoblasts these together form an individual skeletal muscle
what is muscle contraction
a muscle contraction is a cycle in which myosin II head binds to actin and the cross bridges become distorted finally the mosin heads detach from actin - hydrolysis of ATP
what is the three roles of Ca2+
Ca2+ modulates contraction via regulatory protiens rather than interacting directly with the contractile proteins. act together to inhibit actin myosin interactions thus inhibiting contractile process. when Ca2+ binds to one or more proteins it release the inhibition of contraction
The two affinity Ca binding site
Troponin C has a high binding site and participate in binding troponin C to the thin filament. and a low affinity binding sites and indcues conformation change in the troponin complex.
how troponin moves to get ready for the cross bridge cycle
the binding to troponin causes I to shift allowing tropomysin to move and troponin T makes tropomyozin move away from myosin binding site on actin and into the actin groove
What is the general cross bridge cycle
ATP binding
Binds to a specific part of the myosin head
ATP hyrolsysi
First step for the mechanical engery
Cross bridge formation
Interaction of actin and myhosin
Release of Pi from myosin
Interaction of actin and myosin
ADP release
From hydolsysis of ATP
First Step
The first step is ATP binds to myosin causing the dissociation of the actin myosin complex
Second Step
Second Step - ATP is hydrolyzed causing myosin head to return to their resting conformation cuaisng ATP breakdown. this also causes the myosin head to pivot (cock)
Third Step
third step is cross bridge is formed and the myosin head binds to a new position. this stage Ca is dependent
Foruth Step
Foruth Step is P release and myosin head change conformation resulting power stroke the filament slide part each other. the hinge region oulls the actin filament towards to the tail region of the myosin filament. thick filament is stationary and thin movement moves.
Fifth Step
Fifth step is the association of ADP completes the cycle the actin myosin complex is then left in the rigid state so that they only move when ATP binds to the head
what is the sliding filament mechanism
during the sliding filament mechanism - has the thin pull z line closer together shortening scarmoere then the fibre shoten
filament movement
Binding of myosine cross bridge binds to actin molecule
Power stroke - cross bridge bends pulling thin mypfilament inward
Detachment - cross bridge deahes at the end of the power store and returns to original conformation enough calcium to allow contraction
Binding cross bridge brings to more distal actin molecule- cycle rfepeates
Rigor Mortis
during rigormortis as Ca already goes through the cross bridge but ATP cannot produce so cannot detach so thats why they are stiff
EC Coupling
increase in Ca2+ triggers muscle contraction the time during the Ca2+ remain elevated determines the duration of muscle contraction. EC Coupling is the excitation triggeres the increase in Ca2+
What is tranverse tubules
Transmission of action potential tranverse tubules which penetrate all the way through the fibre from one side to the other
what is the traid
the triad is scarcoplasmic reticulum cisterna and tranverse tubule
movement of Ca2+
The L type Ca2+ channels then these are joint and open Ca2+ release channels also open this means Ca exits the SR and go into the muscle contraction
How Ca goes out of the SR
Two channels cause Ca to go out into the extraceullar space. the pump takes out of the SR. Ca2+ in the SR by proteins calreticulin and calsequestrin.
the graph
Action potential occurs this is the latent time for the contractile response then the contraction occurs through contraction time and the relaxation time
how relaxation occurs
The contractile process is turned off when Ca2+is returned to the SR when electrical activitystops.* The SR expresses Ca2+-ATPase pumps, whichactively transport Ca2+ from the cytosol andconcentrates it in the SR.* The thin filaments then return passively to theirresting position. The muscle fibre has relaxed
