Chapter 28 - Sleep and Wakefulness

Question 1

Sleep requirements. What does the book say about: adults, infants, teenagers.

Answer 1

Adults: 7-8 hours
Infants: 17 hours
Teenagers: 9 hours

Question 2

What are the evolutionary disadvantages to sleeping?

Answer 2

Animals are vulnerable to predators when sleeping.

Question 3

Mention a couple of hypotheses for why we sleep.

Answer 3

1. The brain needs downtime to replenish brain glycogen levels.
2. Energy conservation due to cold nights.
3. Sleep is necessary for memory.

Question 4

What are the results from experiments where people are placed in environments without time cues for 5- to 8- days?

Answer 4

People generally wake up later each day. The leading hypothesis is not that the natural circadian rythm is 26 hours anymore. It seems to be closer to 24, which makes most sense.

Question 5

What is an important sensory system that influences circadian rythm?

Answer 5

Photosensitive retinal ganglion cells that contain melanopsin.

Question 6

What happens to mice that are genetically modified so that the gene for melanopsin is knocked out?

Answer 6

Their circadian rythms are impacted, but not entirely - indicating other systems still at work.

Question 7

Light information from the retinal ganglion cells that contain melanopsin travel along the what and end up where?

Answer 7

They travel along the retinohypothalamic tract and end up in the suprachiasmatic nucleus of the anterior hypothalamus.

Question 8

Activation of the suprachiasmatic nucleus by the retinal ganglion cells evokes responses in another part of the hypothalamus. Which?

Answer 8

Activation of the suprachiasmatic nucleus by the retinal ganglion cells evokes responses in the paraventricular nucleus of the hypothalamus.

Question 9

Activation of the suprachiasmatic nucleus by the retinal ganglion cells evokes responses in the paraventricular nucleus of the hypothalamus. From there the signal does a fun little loop. Where?

Answer 9

Neurons synapsing in the paraventricular nucleus travel along the spinal cord, descending toward the cervical ganglia (the sympathetic chain). These ganglia project to the pineal gland.

Question 10

Retinal ganglion cells - > suprachiasmatic nucleus - > paraventricular nucleus of the thalamus - > superior cervical ganglion - > pineal gland. What do we think this does to the pineal gland?

Answer 10

It influences the secretion of melatonin, a sleep-promoting neurohormone.

Question 11

Besides the neural network, what is a likely link between melatonin secretion by the pineal gland, and photoreceptors in the retina?

Answer 11

We see that melatonin synthesis increases as light fromt he environment decreases.

Question 12

What happens to experimental animals when you’ve removed their suprachiasmatic nucleus?

Answer 12

Their circadian sleep-wake cycle is abolished.

Question 13

What are the different sleep stages?

Answer 13

Awake
Stage I
Stage II
Stage III
Stage IV
REM

Question 14

How long does it typically take for someone to go from stage I to stage IV?

Answer 14

About an hour.

Question 15

During a typical night, how long do the periods of REM sleep last?

Answer 15

The first one lasts about 10 minutes, and the following last increasingly longer.

Question 16

How many REM periods do we typically have during a night’s sleep?

Answer 16

About 5.

Question 17

Sleep and erectile dysfunction. What’s the connection here?

Answer 17

Spontaneous penile erection occurs during REM sleep, a fact that is clinically important in determining whether a complaint of impotense has a physiological or psychological basis.

Question 18

How can we argue that sleepwalking is not someone acting out their dreams?

Answer 18

The body is paralyzed during REM sleep, and sleepwalking and sleeptalking actually happens during non-REM sleep and are not usually accompanied or motivated by dreams.

Question 19

What is the cause of the relative paralysis during REM sleep?

Answer 19

The relative physical paralysis during REM sleep arises from increased activity in GABAergic neurons in the pontine reticular formation that project to inhibitory neurons that synapse in turn with lower motor neurons int he spinal cord.

Question 20

How do we determine which sleep stages feature dreams?

Answer 20

Researchers have awakened people up during different stages and asked them.

Question 21

Which sleep stages features dreams?

Answer 21

Subjects awakened from REM sleep usually recall elaborate, vivid, and often emotional dreams; subjects awakened during non-REM sleep report fewer dreams, and when dreams do occur, they are more conceptual, less vivid, and tend to be less emotion-laden.

Question 22

Do we need REM sleep?

Answer 22

Probably, but people survive without and with lesser amounts. Humans have less REM sleep as they grow older (OMG! Non-REM sleep causes aging!!)

Question 23

Do we need non-REM sleep?

Answer 23

Absolutely! We don’t function without.