Glossary

  • Central nervous system – a term for the brain and spinal cord, excluding the peripheral nerves
  • Chromosomes – are found in every cell in the body and contain the person’s unique DNA profile
  • Disturbed night-time sleep –  episodes of wakefulness during the night, accompanied by inappropriately high body temperature and increased heart rate
  • Dopamine – a neurotransmitter that is produced in several areas of the brain. Although very important in controlling movements, it may also be involved in the sleep-wake cycle
  • Epworth Sleepiness Scale – a self test that measures levels of excessive sleepiness. The test outlines everyday activites where the patient rates how easily they would fall asleep
  • Excessive sleepiness – a common symptom of narcolepsy where the patient experiences irresistible sleepiness at intervals throughout the day. It should be distinguished from lethargy or fatigue which may have different causes
  • Hypnagogic / hypnopompic hallucinations – vivid and often frightening, dream-like experiences which occur during the transition between sleep and wakefulness
  • Hypocretin (Orexin) – a neuropeptide that is released from cells within a structure known as the hypothalamus, located in the brain. It is thought to be involved in the regulation of the sleep-wake cycle
  • Hypothalamus – a small complex structure that is found deep in the brain and has a role in the control of many metabolic processes such as temperature regulation, hormone regulation, hunger and thirst. It is also crucial for controlling the sleep-wake cycle and damage to part of it may cause narcolepsy
  • Myotonic Dystrophy – a chronic, slowly progressive neuromuscular disease which runs in families and causes muscle wasting and stiffness as well as excessive sleepiness
  • Neuropeptide – a peptide or small protein that is used as a signal and released from cells within the brain
  • Neurotransmitter – a chemical that is used as a signal and is released from cells within the central nervous system
  • Non REM sleep or Non Rapid Eye Movement Sleep – there is usually little or no eye movement during this stage of sleep. Vivid dreaming is rare and the body’s muscles are not paralysed as in REM sleep
  • Noradrenaline – a neurotransmitter that is released in the brain the spinal cord and is synthesised from Dopamine. It is important in arousal processes and inhibits sleep, particularly dream or REM sleep
  • Orphan disease – a rare disease that affects less than 5 per 10,000 people within a community
  • Parkinson’s disease – a common neurodegenerative disease that primarily affects a person’s ability to control and initiate voluntary movements. Deficiency of the chemical dopamine in the brain causes many of the motor symptoms. Non-motor symptoms including sleep problems are also very common and often overlooked
  • REM Sleep or Rapid Eye Movement sleep – a normal stage of sleep characterised by rapid movements of the eyes and low muscle tone. REM sleep in adult humans typically occupies 20-25% of total sleep, about 90-120 minutes of a night's sleep. During a normal night of sleep, humans usually experience about 4 or 5 periods of REM sleep usually corresponding to vivid dream activity
  • Serotonin – a neurotransmitter that is found in cells in the brain and spinal cord and in some cells of the gut
  • Sleep-wake cycle – your body’s internal clock which tells your body to be awake during the day and asleep at night
  • SSRIs (Selective serotonin reuptake inhibitors or serotonin-specific reuptake inhibitor) – a class of anti depressants often used to treat cataplexy
  • Traumatic Brain Injury – significant traumatic injury to the brain can cause a variety of problems that can take a long time to recover. Sleep problems such as daytime sleepiness affect the large majority of subjects. Similar symptoms can also occur after damage due to other causes such as brain infections or strokes
  • Voluntary muscles – muscles that are under our conscious control and move "to command"