Sleep

Question 1

Define Sleep

Answer 1

• State of partial unconsciousness from which a person can be aroused by stimulation
• With the onset of sleep, the RAS nuclei cease activity; cells in the thalamus and cortex become hyperpolarized and insensitive to synaptic input; consciousness is lost
• Cortical activity is depressed (except during REM sleep) but brain stem activity continues

Question 2

What are the two major types of sleep?

Answer 2

Non-rapid eye movement (NREM)

&

Rapid eye movement (REM)

Always four stages of NREM sleep, followed by REM sleep; repeated in sequence

Question 3

What are the stages of NREM (NonRapid Eye Movement) sleep?

Answer 3

Stage 1

Stage 2

Stage 3

Stage 4

Question 4

Describe Stage 1 NREM sleep

Answer 4

Stage 1 - eyels are closed and relaxation begins; the EEG shows alpha waves; one can be easily aroused (will often not realize that one has been asleep)

Question 5

Describe Stage 2 NREM sleep

Answer 5

Stage 2 - EEG pattern is irregular with sleep spindles (high-voltage wave bursts);

arousal is more difficult

Question 6

Describe Stage 3 NREM sleep

Answer 6

Stage 3 - sleep deepens; theta & delta waves appear; vital signs decline; some dreaming is common

Question 7

Describe Stage 4 NREM sleep

Answer 7

Stage 4 - EEG pattern is dominated by delta waves; skeletal muscles are relaxed; arousal is difficult

Question 8

Which stages of sleep are considered to be most restorative and deep?

Answer 8

• Stages 3 & 4
  
  • • they allow hormone output required for cellular repair & immune system function
• Sleep-walking, bed-wetting, and night-terrors occur during these stages
  
  • – typically ends by puberty; adult sleep-walking often associated with drug / alcohol misuse or degenerative disorder
• Sense of muscles “jerking” occurs during Stage 4

Question 9

What are the stages of REM (Rapid Eye Movement) sleep?

Answer 9

Brain stem nuclei become active again, causing depolarization of cortical neurons

EEG pattern reverts to the stage 1 pattern (alpha waves resembles the awake but relaxed brain)

Vital signs increase and greatest brain oxygen usage occurs

Skeletal muscles (except ocular muscles) are inhibited (RAS dampened)

Most dreaming takes place

Question 10

What happens to the skeletal muscles during REM sleep?

Answer 10

• The cortex can process information and vivid dreams occur, but there is no motor output or sensory input
• Exception: front eye field not affected (thus rapid eye movements)
• Most dreaming takes place
• Awakened during REM sleep, temorary paralysis

Question 11

What is the importance of REM sleep?

Answer 11

REM sleep may be a reverse learning process where superfluous info is purged from the brain

sorting out of emotional components and conflicts

Those deprieved of REM sleep may become moody and depressed.

Question 12

Describe sleep patterns

Answer 12

Alternating cycles of sleep and wakefulness reflect a natural circadian rhythm

Approximately 90 minutes in length

KEY: sleep 1.5, 3, 4.5, 6, or 7.5 hours for best initial wakefulness

Although RAS activity declines in sleep, sleep is more than turning off RAS

Brain is actively guided into sleep my nuclei of the hypothalamusTwo nuclei (suprachiasmatic and preoptic) contain many melatonin receptors

Question 13

Where is Melatonin secreted?

Answer 13

Melatonin is secreted by pineal gland once blue wavelengths of light stop stimulating the retina.

Question 14

What are common sleep disorders?