This question is about neuromuscular coordination and motor control.
Voluntary movements are initiated in the cerebrum, but their execution must be carefully integrated.
State the region of the brain that is primarily responsible for coordinating posture, balance, and the fine-tuning of voluntary motor movements.
Muscle contraction is controlled by motor units. A motor unit consists of a single motor neurone and all the muscle fibres it stimulates.
The table below displays typical data for motor units in two different muscles of the body:
| Muscle | Average number of muscle fibres per motor neurone | Primary function |
|---|---|---|
| Extraocular muscle (moves the eyeball) | 555 | Extremely precise, microscopic adjustments |
| Gastrocnemius (calf muscle) | 200020002000 | Large, powerful movements used in walking and jumping |
Explain how the central nervous system can vary the strength of a contraction in a muscle such as the gastrocnemius.
With reference to the data in the table, explain why the recruitment of motor units in the extraocular muscle allows for much finer control over movement than in the gastrocnemius.
39 exam-style questions on OCR GCSE Biology 3.1 Coordination and control – the nervous system, covering 3.1.1 Structure of the nervous system, 3.1.2 Coordinated response, 3.1.3 The reflex arc, 3.1.4 Structure of the eye, 3.1.5 Defects of the eye, 3.1.6 Structure and function of the brain, 3.1.7 Difficulties of investigating brain function, and 3.1.8 Limitations in treating nervous system damage. Each one has a worked solution and a mark scheme showing where the marks go.