Muscle Physiology Flashcards
From largest to smallest, what is the levels of organisation of skeletal muscle?
Skeletal muscle Muscle fascicle Muscle fiber Myofibril Sarcomere
What is the skeletal muscle surrounded by?
Epimysium
What is the muscle fascicle surrounded by?
Perimysium
What is the muscle fibre surrounded by?
Endomysium
What is the myofibril surrounded by?
Sarcoplasmic reticulum
The sarcomere is comprised of two filaments - what are they called?
Thick filaments: Myosin
Thin filaments: Actin
A sarcomere is defined by what boundary?
Z line to Z line
The centre of a sarcomere possesses which band and which line?
H band
M line
Which large band surrounds the border of the H band?
The A band
Which band surrounds the Z line?
I band
What is the Myosin II molecule made up of?
Two heavy chains and a few light chains (head region) which binds to Actin and has ATPase activity
What does the Actin filament comprise of?
Double stranded helical filamentous polymer of globular actin, with Tropomyosin reinforcing the structure. Attached to Tropomyosin is the Troponin complex (TnT, TnC, TnI). Also has a Ca2+ binding site
Where does the Troponin usually attach to on the Actin filament?
On tropomyosin
Describe what happens in Cross bridge cycling
The myosin heads attaches to the actin, and ATP binds to the myosin head. This causes dissociation of the actin-myosin complex. ATP is hydrolysed causing the myosin head to cock back and rest. A cross bridge forms the myosin head binds 12 nm along the actin. P from ATP is released, and the myosin head changes conformation resulting in the power stroke. ADP is then released and it returns to the attached state
What is the neurotransmitter at the NMJ?
Acetylcholine
