Describe how muscle cells contract

An action potential depolarises the sarcoma and depolarisation travels down the T-tubules to the sarcoplasmic reticulum, which releases Ca2+ (calcium ions) to the sarcoplasm. Ca2+ cause tropomyosin to change shape so that the binding site of actin is exposed. Myosin head binds to actin forming an actin-myosin cross bridge. Ca2+ promotes the hydrolysis of ATP which releases energy that causes the myosin head to bend, pulling the actin filament along in a rowing action. Another ATP molecule provides the energy to break down the cross bridge and the myosin head attaches to a different actin binding site further along the actin filament. Many cross bridges form and break very rapidly, pulling actin along. This shortens the sarcomere, which causes the muscle cells to contract.

MS
Answered by Maria S. Biology tutor

2668 Views

See similar Biology A Level tutors

Related Biology A Level answers

All answers ▸

Give two ways in which the structure of starch and cellulose are similar and different to one another.


What are the two main secondary structures of proteins?


Explain the differences between aerobic and anerobic respiration in terms of the roles of co-enzymes


What are three adaptations in a leaf for photosynthesis?


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2025 by IXL Learning