Chapter 6C

Question 1

biological rhythms

Answer 1

A biological rhythm is a repeated biological process that is regulated by internal mechanism aka our
biological clock.

Question 2

biological rhythms related to sleep

Answer 2

• circadian rhythms (sleep-wake cycle)
• ultradian rhythms (sleep cycles made up of REM and NREM sleep

Question 3

Sleep and
Circadian
Rhythms

Answer 3

• a nights sleep follows predictable stages and a specific sequence of events
• our sleep wake cycle is an example of a circadian rhythm and is controlled by our internal body clock, the suprachiasmatic nucleus

Question 4

what features follow a circadian cycle

Answer 4

• our levels of arousal
• hormone secretions
• metabolism
• heart rate and temperature
  these all follow a circadian cycle

Question 5

sleep and ultradian rhythms

Answer 5

• within a night sleep, we shift between non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep.
• a sleep cycle is an example of an ultradian rhythm
• one cycle of NREM and REM sleep lasts for about 90 minutes and adults get between 4-6 cycles per night
• time in REM sleep increases and NREM decreases as the nigh progresses
• less than 24 hours

Question 6

ultradian rhythms example

Answer 6

• sleep stages
• blood circulation
• pulse
• heart rate
• thermoregulation
• blinking
• appetite
• arousal

Question 7

suprachiasmatic nucleus (SCN)

Answer 7

• suprachiasmatic nucleus is known as a biological clock
• the SCN receives information about the amount of incoming light from the eyes and adjusts our sleep wake cycle accordingly
• does this by sending neuronal messages to the nearby pineal gland to secrete more or less of the hormone melatonin into the blood.

Question 8

what does melatonin do

Answer 8

melatonin makes us sleepy, it does not make us sleep, just calmer and more relaxed

Question 9

triggering our biological rhythms

Answer 9

• there are environmental cues that regulate our circadian rhythms. the main influence is light (natural and artificial)
• also triggering biological rhythms are internal cues
  hormone levels fall into this category

Question 10

The SCN-pineal gland pathway

Answer 10

light-induced activation of SCN prevents the production of melatonin by pineal gland

Low levels of light
trigger the pineal
gland to produce
melatonin → causing
sleepiness

Question 11

The role of cortisol

Answer 11

• Cortisol makes us feel more alert and is released from
  the adrenal glands early in the day to wake us up

Question 12

how does light increase and decrease drowsiness

Answer 12

When light is detected (by the retina), the suprachiasmatic nucleus (SCN)
sends inhibitory messages to the pineal gland, whereas when no light is
detected, the SCN sends excitatory neural messages to the pineal gland.
 When the pineal gland receives excitatory neural messages from the SCN,
it produces and releases melatonin which induces/increases drowsiness.
 Conversely, when the pineal gland receives inhibitory neural messages
from the SCN, it reduces the production and release of melatonin which
reduces drowsiness (and increases alertness).