What role do calcium ions play in contraction of the sarcomere? (4 marks)

  1. When an action potential arrives at the motor end plate it causes depolarisation to occur in the sarcolemma of the effector muscle cells.2) Depolarisation spreads via T-tubules to the sarcoplasmic reticulum leading to release of stored calcium via voltage gated calcium ion channels into the cytoplasm of the skeletal muscle cell (sarcoplasm).3) Cytosolic calcium ions can then bind to troponin inducing a conformational change that removes tropomyosin from the actin-myosin binding site of the actin filament. 4) The myosin head is then able to bind to the actin filament allowing the process of cross-bridge cycling to begin resulting in muscle contraction.Extra (beyond A level)- Calcium is pumped back into the sarcoplasmic reticulum via SERCA pumps in its membrane. As the calcium ion concentration in the cytosol returns to normal; relaxation of the muscle can occur.
BW
Answered by Ben W. Biology tutor

5948 Views

See similar Biology A Level tutors

Related Biology A Level answers

All answers ▸

Outline how the first neurone communicates with the second neurone at a synapse.


Discuss the endocrine and exocrine functions of the pancreas.


Explain two properties of water that are vital for aquatic life and explain how these arise


How does the structure of the grana optimise its function?


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