28a - Sleep Physiology & Disorders

Question 1

How do circadian rhythms influence sleep?

Answer 1

ambient light impinges on retinol ganglia cells that contain melanopsin. Retinol cells are inhibited by light and stimulated by darkness and sends AP to Suprachiasmic nucleus that then activates paraventricular nucleus (sympathetic) activates intermedialateral gray zone that modulate superior cervical ganglion. These activate pineal gland to synthesize and release melatonin. Melatonin stimulates drowsiness in brainstem neurons.

Question 2

What are the different stages of sleep?

Answer 2

Awake - alpha+beta
stage 1 - lightest sleep, theta
stage 2 - sleep spindles, K complexes, Theta
stage 3 - delta
stage 4 - deepest, delta (low freq, high V)
stage 5=REM - similar to awake (fast freq, low V), theta+beta

full cycle is 90 min.

Question 3

What are the physiological effects of sleep?

Answer 3

NREM - few eye movments, decreased HR, BP, RR, temp, fewer dreams, sleep walking. All maxed out at stage 4. PPT and LDT inactivated

REM - rapid eyes, muscle paralysis, HR, BP, RR, temp near awake levels, vivid and emotional dreams. Amygdala, parahippo, anterior cingulate, pedunculopontine and lateral dorsal tegmental areas active.
Frontal cortex and posterior cingulate inactive.

Question 4

What is the cellular and molecular physiology of sleep?

Answer 4

locus cerulius provides noradrenergic input, dopaminergic cortical input, medial and lateral raphe nuclei serotonergic circuits are all active during wakefullness.

Histamine from tuberomamillary nucleus is high during wakefullness and decreases during NREM and REM. antihistamines make you sleepy.

Question 5

How do you diagnose narcolepsy?

Answer 5

clinical presentation or low CSF hypocretin levels.
loss of hypocretin/orexin from posterior lateral hypothalamus.
genetic HLA gene DQ1.

Question 6

What are treatments for narcolepsy

Answer 6

methylphenidate and modafinil for daytime sleepiness

TCAs and SSRIs for cataplexy (instant drop into sleeping)

Question 7

How do you diagnose sleep apnea

Answer 7

apneic periods lasting longer than 10 seconds causing oxyhemoglobin desaturation of more than 4%.
more common in men and fatties.

Question 8

What are treatments of sleep apnea?

Answer 8

CPAP, lose weight

Question 9

How do you diagnose insomnia?

Answer 9

difficulty falling or remaining asleep. transient affects 50% of adults throughout their life.
chronic > 6 weeks affect 25% of adults.

Question 10

How do you diagnose REM sleep behavior disorder?

Answer 10

loss of atonia during REM sleep causing acting out.

Can be caused by EtOH withdrawals, TCA and SSRI use.

Question 11

How do you treat REM sleep behavior disorder?

Answer 11

clonazepam

Question 12

What parts of the brain are inactivated during REM?

Answer 12

frontal cortex and posterior cingulate cortex

Question 13

What parts of the brain are activated during REM?

Answer 13

PPT and LDT (awake zones) as well as amygdala, parahippocampal gyrus, anterior cingulate cortex

Question 14

What is main activator of sleep?

Answer 14

VLPO

Question 15

What are somnogens?

Answer 15

sleep chemicals
adenosine - declines in sleep
IL1b and TNF promote sleep
melatonin, made in darkness

Question 16

What is action of locus cerulius and when is it active/inactive?

Answer 16

provides noradrenergic input.
active during wakefullness.
Silent during REM and NREM.

Question 17

What is source of histominergic input for sleep/wakefullness?

Answer 17

tuberomamillary nucleus

Question 18

What is source of orexin?

Answer 18

lateral hypothalamic nucleus

Question 19

What does orexin do?

Answer 19

excitatory stimulus to forebrain and brainstem nuclei to facilitate wakefullness.
absent in 90% of narcoleptics

Question 20

What is the VLPO and what does it do?

Answer 20

ventrolateral preoptic nucleus. GABAergic and galanin neurons which inhibit arousal nuclei. Causes NREM sleep. Main sleep initiator

Question 21

What does multiple sleep latency test measure?

Answer 21

time required to fall asleep. People with sleep problems fall asleep faster in middle of day.

Question 22

What is epworth sleepiness scale?

Answer 22

self-report tendency to fall asleep

Question 23

When do you get morning wood?

Answer 23

REM sleep