IB Biology: B3.3-Intercostal Muscles as Antagonistic Muscles

Front

What are intercostal muscles?

Back

Intercostal muscles are the paired muscle sheets found between the ribs, made up of the external and internal intercostal muscles.

Front

Where do intercostal muscles originate and insert?

Back

Intercostal muscles use the ribs as their origin and insertion points.

Front

How do the external and internal intercostal muscles lie in relation to each other?

Back

The external and internal intercostal muscles lie at angles opposite each other.

Front

What happens when the external intercostal muscles contract?

Back

Contraction of the external intercostal muscles pulls the ribs and the ribcage upwards and outwards, increasing the volume of the chest during breathing in.

Front

What happens when the internal intercostal muscles contract?

Back

Contraction of the internal intercostal muscles pulls the ribs and the ribcage downwards and inwards, decreasing the volume of the chest during breathing out.

Front

Why don't both intercostal muscles contract at the same time?

Back

Both muscles are antagonistic, so they do not contract at the same time. When the external intercostal muscles contract, the internal ones relax and vice versa.

Front

What is the role of titin fibres in intercostal muscle contraction?

Back

Contraction of the external intercostal muscles stretches the internal intercostal muscles and the titin fibres, creating potential energy for the next contraction.