homeostasis, circadian rhythms and sleep

Question 1

what is homeostasis?

Answer 1

the maintenance of equilibrium by active regulation of internal states eg cardiovascular function, body temperature, food and energy regulation and fluid emulation

Question 2

what do many homeostatic functions show?

Answer 2

• daily rhythms
  circadian rhythms (daily cycle)
  circannal rhythms (yearly cycle)

Question 3

what are circadian rhythms?

Answer 3

• a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours

Question 4

what is the suprachiasmatic nucleus (SCN)?

Answer 4

a bilateral structure located in the anterior part of the hypothalamus.
It is the central pacemaker of the circadian timing system and regulates most circadian rhythms in the body

Question 5

How does light info reach the SCN?

Answer 5

the retina carries photic information via the retinohypothalamic tract (RHT) to the SCN

Question 6

characteristics of sleep

Answer 6

• slow-wave sleep
  progression decrease in spinal reflexes and heart rate, synchronised cortical activity
• REM sleep
  absent spinal reflexes, rapid eye movements, increased body temp, dreams

Question 7

how is sleep an active process?

Answer 7

• EEG shown abundant neuronal activity in cortex during sleep; waves of activity, several different levels

Question 8

disorders of sleep

Answer 8

• insomnia
• hypersomnia (narcolepsy)
• sleep-wake schedule disturbance
• partial arousal
• anxiety/psychological disturbance/drugs

Question 9

pharmacological treatment of sleep disorders

Answer 9

• morphine, benzodiazepines, barbiturates DO NOT produce natural sleep patterns
• melatonin and tryptophan DO induce natural sleep patterns