BIOA02 – LEC 3
• The Neuromuscular Junction
The innovation of muscle cells to trigger muscle contract.
ACETYLCHOLINE is released and it binds to the nicotinic receptor. The channel
opens up and Na+ flows in. This causes an action potential in the muscle cell which triggers the
• Fasciline are where muscle cells are grouped together and sorounded by a connective tissue.
• What are contractile elements?
• TTubules is where the action potential travels down.
• Actin thick filament.
• Myosin – thin filament.
• These 2 are bound together and repeated in the myofibril.
• THE SARCOMERE
• The blue lines regulator proteins
• No overlap – light
• These filaments silde across one another to generate muscle contractions.
The THIN ACTIN
Each filament has 2 strands of actin
Myosin also has the same binding sites.
They will slide among one another and generate.
TROPOMYOSIN is a protein that blocks the binding of Myosin on the Actin
TROPONIN – It’s a regulatory protein and it binds to the actin/tropomyosin/Ca+
THE THICK MYOSIN
The subunit have a actin binding site and AN ATPASE SITE
The myosin molecules binf at their tails such that the heads extend in the opposite direction.
ATP ▯ADP + Pi
The Thick filaments have hundreds of MYOSIN molecules in it. ***THE MYSOIN HEAD
The head has low and high energy states.
LOW – HEAD LEFT
HIGH – HEAD RIGHT
The binding is called crossbridges.
The actin molecule and myosin come together and attack (HIGH TO LOW) this generates muscle power.
Regulation of Muscle Contraction
1. Acetylcholine release at the neuromuscular
junction → muscle action potential (AP: ).
2. AP spreads along the
T-tubule sarcolemma (muscle cell
plasma membrane) and
down the Ttubules.
3. The AP triggers C