How a Muscle Contracts

Name: How a Muscle Contracts
Author: StemPy Lab

How a signal from a nerve reaches a muscle fibre, why calcium ions switch the contraction on, and how the myosin heads pull the actin filaments in the cross-bridge cycle. Why the bands of the sarcomere change while the filaments keep their length, how a muscle tires, and how red and white fibres differ. It covers the unit of the Indian syllabus (NCERT, NEET) and the matching topic of A-Level, IB and AP.

3 lessons, about 1 h 20 min3 simulations10 problems3 practice questionsPython in every lesson

Created by StemPy Lab

Course outline (3 lessons)

Lesson 1about 25 min
The signal from the nerve to the muscle
A muscle contracts when the central nervous system sends a signal along a motor neuron. At the neuromuscular junction, the neurotransmitter acetylcholine makes an action potential in the sarcolemma. The action potential spreads through the fibre and releases calcium ions from the sarcoplasmic reticulum, and the calcium binds to troponin and uncovers the sites on the actin.
1 simulation1 practice question1 Python program3 problems
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Lesson 2about 30 min
The sliding filament theory and the cross-bridge cycle
In the sliding filament theory, the myosin heads bind to the actin, pull it toward the centre of the A band, let go and bind again, using the energy of ATP. The thin filaments slide over the thick ones, so the sarcomere gets shorter. The A band keeps its length, but the I band and the H zone shorten.
1 simulation1 practice question1 Python program4 problems1 Python lab
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Lesson 3about 25 min
Fatigue, red fibres and white fibres
Repeated contractions make lactic acid when the muscle breaks glycogen down without oxygen, and this causes fatigue. Red fibres hold much myoglobin and many mitochondria and work with oxygen. White fibres hold little myoglobin, depend on anaerobic breakdown and are tired sooner.
1 simulation1 practice question1 Python program3 problems1 Python lab1 question set1 note
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Muscle Contraction: Timed Test

20 questions · 15 min

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How a Muscle Contracts

Course outline (3 lessons)

The signal from the nerve to the muscle

The sliding filament theory and the cross-bridge cycle

Fatigue, red fibres and white fibres

Test Your Learning

Your teacher

Discussion (0)