ch14 - circadian rhythms and sleep

circadian

biological/metabolic patterns in humans

2 main biological rhythms

ultradian and infradian rhythms

ultradian + example

happens multiples IN one day. ex: rest/activity cycle

infradian + example

cycles longer than a day. ex: menstrual cycle

other potential bio rhythm

endogenous circannual rhythms

endogenous circannual rhythm + example

annual cycle. ex: bird migratory patterns, hibernation

all animals/life have..

endogenous circadian rhythms

endogenous circadian rhythms regulate:

• eating

• drinking

• body temp

• hormones

• pee

• drug sensitivity

endogenous circadian rhythms can be ____ but NOT _____ by light and dark cycles, since they’re independent.

influenced/ changed

example of end. circadian being independent:

plant leaf still goes ⬆ for one half of the day and ⬇ for the other: maintains pattern even without L/D cues

purpose of circadian rhythm (3)

1. body’s internal 24 hour clock

2. optimizes energy use

3. keeps internal workings

free-running rhythm

rhythm with NO stimulus (not connected to outside world)

phase shift

change in stimulus (environment) = changes in activity (ex: time zones)

zeitgeber

“time giver”: external signals (light, food, meals) that set/reset internal bio ⏰

if external cues are removed, the rhythm will become…

free-running. body adjusts

Suprachiasmatic Nucleus (SCN)

part of hypothalamus that controls circadian rhythms

location of SCN 📍

dorsal to optic chains

damage to SFN leads to

inconsistent rhythms; de synchronization to L/B. still work, but activity pattern is ERRATIC

SCN info flow about body temp/hormones

SCN → hypothalamic nuclei → (ind.) pineal gland

if SCN lesion rats are placed in constant darkness (no L/D), activity pattern becomes ____ _____.

completely random

SCN lesions will damage

the endogenous rhythm

SCN is activated

by light

how does the SCN lock onto externals like L/D cycle?

mammals: retinal ganglion cell that conveys info to SCN

invertebrates: photoreceptors outside eye (pineal gland)

resetting SCN happens with the small branch of optic nerve called

retinohypothalamic tract! (retina→ SCN)

retinohypothalamic has a photopigment called ___, meaning they don’t need rods or cones.

melanopsin

how do cells in SCN know how to maintain circadian rhythm?

let’s find out👀

steps for circadian cell regulation (5):

1. combine to dimer

2. transport into nucleus

3. bind to DNA, transcribe per + cry genes

4. burn into proteins, form a dimer

5. either return to nucleus to inhibit transcription or break down

6. glutamate stimulates period + cryptochrome genes

tap to reveal steps of circadian regulation diagram!

your body’s preference for sleep/wake times may differ from other depending on (2):

• alleles for genes in SCN

• change with age

pineal gland is an ____ gland controlled by the ___.

endocrine/ SCN

pineal gland secretes ____.

melatonin😴

jet lag

disruption of rhythms due to time zones

jet lag is characterized by

sleepiness during day, awakeness during night

travelling WEST ___ our rhythms, while traveling EAST ____ them.

delays/ advances

jet lag remedies

none that were scientifically proven