Noradrenaline, locus coeruleus, wakefulness and mood
The locus coeruleus, a small group of neurones in the brainstem, makes most of the brain's noradrenaline, which promotes wakefulness (alertness) and lifts mood.
Remember
The locus coeruleus makes the noradrenaline that promotes wakefulness and lifts mood, so amphetamines (stimulant drugs) and some antidepressants (medicines for depression), by raising it, increase alertness and improve mood.
Noradrenaline (also called norepinephrine) is a neurotransmitter used in both the central and the autonomic nervous system. In the brain, most of it is made by a small group of neurones called the locus coeruleus. This group is a nucleus (a cluster of neurones) in the dorsal pons, a part of the brainstem, and its axons spread widely through the brain.
Noradrenaline from the locus coeruleus promotes wakefulness (alertness) and lifts mood.
The medicines show this. Amphetamines (stimulant drugs) increase noradrenaline, and so they increase wakefulness and mood. In depression a drowsy, low-mood state can occur, and some antidepressants (medicines for depression) raise noradrenaline to combat it.
Other functions belong to other systems. At the neuromuscular junction (where a motor nerve meets a muscle fibre), the transmitter is acetylcholine. Dopamine from the substantia nigra (which contains dopamine neurones) serves movement. In the brain, serotonin is made by the raphe nuclei, cell groups in the brainstem.
Key facts
- Where it is made
- most noradrenaline in the brain is made by the locus coeruleus, which lies in the pons of the brainstem.
- Roles in the brain
- noradrenaline promotes wakefulness and lifts mood.
- Amphetamines
- they increase noradrenaline, and so increase wakefulness and mood.
- Some antidepressants
- they raise noradrenaline, which combats the drowsy, low-mood state that can occur in depression.
- Acetylcholine
- it is released by motor neurones at the neuromuscular junction, so it, not noradrenaline, starts voluntary muscle contraction.
- Dopamine from the substantia nigra
- it mainly serves movement.
- Serotonin
- in the brain, it is made by the raphe nuclei in the brainstem.
Exam traps
- Noradrenaline does not start voluntary muscle contraction, because motor neurones release acetylcholine at the neuromuscular junction.
- The substantia nigra contains dopamine neurones and serves movement, so it is not the main source of the brain's noradrenaline, which is the locus coeruleus.
- The raphe nuclei make serotonin rather than noradrenaline, even though serotonin also contributes to mood and to sleep and wakefulness.
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