1.9 Flashcards
characterisctics of Striated muscle
- each muscle fiber behaves as a single unit
- multinucleated
- myofibrils are surrounded by Sarcoplasmic Reticulum and invaginated by T (Transverse) Tubules
myofibrils are divided to
repeating units of- Sarcomeres, which are the basic contractile unit
Sarcomeres are composed of
Thick and Thin filaments
Thick filaments contain
Myosin
structure of Myosin
1x heavy chain
2x light chains
Thin filaments contains 3 proteins:
- Actin
- Tropomyosin
- Troponin
Describe what is Tropomyosin:
Runs along the Actin filament
It blocks the Myosin-binding site on Actin
we have to remove Tropomyosin in order for contraction to occcur
Describe what is Troponin:
composed of 3 proteins:
- Troponin T (attaches the Troponin to tropomyosin)
- Troponin I (inhibits the intercation of actin-myosin)
- Troponin C (binds Ca++)
what is the name for continued cross-bridge cycling?
Tetanus
The force of contraction depends on
Length of the sarcomer
why do Passive tension arises when the muscle is stretched to long?
bcs of the elasticity of the muscle
what creates the active tension?
the voluntary movement of the muscle
Isometric?
muscle length is not changing
tension increases
antigravity muscles
Isotonic?
tension remains the same
muscle shortens
what doe we call it when both length and load varies during contraction?
Auxotonic
Describe slow twitch muscle fiber
type I red oxidative high mito low glycogen
Describe type IIa muscle fiber
red oxidative highest amount of mitochondria very little glycogen fast twitch
Describe type IIb muscle fiber
fatigable white glycolitic many glycogen less mito fast twitch
Types of motor units
S: slow twitch
FF: like chicken breast. Fast twitch, Fatigable
FR: Fast and Resistable, like chicken leg
what is the Ca sensor on the smooth muscle cell?
Calmodulin
twitch duration in smooth muscle cell
200 ms-sustained
Define the NMJ
chemical synaps in which ACh is release by a-motor neuron into the synaptic cleft
***only ACh!!
Define the End Plate Potential
when the membrane of the skeletal muscle depolarize from -90 mV to -50 mV
* -50 mV is the EPP
How many vesicles are necessary to reach the threshold?
from -90 to -50 mV
about 100 each MEPP (Miniature End Plate Potential= ACh in one vesicle) depolarize the membrane about 0.4 mV
what can alter NMJ function?
Botulinium
Curare
Neostigmine
Hemicholinium
How does Botulinium alter NMJ function?
blocks ACh release from the axon
How does Curare alter NMJ function?
blocks NAChR
How does Neostigmine alter NMJ function?
inhibits ACh Esterase
prolongs ACh effect on the NMJ
what does Atropin do?
blocks muscarinic ACh R
How does Hemicholinium alter NMJ function?
blocks choline reuptake by the Na/choline symporter
