IB Biology: B3.3-Motor Units

Front

What are skeletal muscles?

Back

Skeletal muscles are neurogenic, meaning they only contract when they receive impulses from the central nervous system (brain) through motor neurons which terminate at synapses at neuromuscular junctions.

Front

What determines the intensity of muscle contraction?

Back

The intensity of muscle contraction depends on the number of total muscle fibres within the muscles that receive impulses from the CNS. If fewer muscle fibres receive impulses, the contraction is low; if more muscle fibres are stimulated, the contraction is more intense.

Front

What is a motor unit?

Back

A motor unit consists of one motor neuron together with hundreds of muscle fibres it stimulates via neuromuscular junctions.

Front

How do muscle fibres contract in a motor unit?

Back

When a nerve impulse passes along a motor neuron to the muscle fibres, all the muscles contract at the same time.