Lec 27 Flashcards
Circadian Rhythm: Core Temperature & Alertness
raise while awake and lower while sleeping
Circadian Rhythm: GH & Cortisol
Highest during sleep, but do raise randomly while awake
Circadian Rhythm: Potassium
excretion of K+ by kidneys is the highest during the day
Circadian Rhythm: Mimosa leaf movements
facilitate harvesting light (leaves extend during the day)
Circadian Rhythm: arthropod Drosphila activity
internal clock to be more active during the day and synchronized with light. <24 hour clock
Luciferase expression
Unicell devision, Arthopod Drosophila activity, Mouse core body temperature
Circadian Rhythm: regulation
regulated by an internal clock;
Circadian Rhythm: that depend on sleep
GH, Prolactin
Zeitgebers
“time givers” Environmental ques entrain our biological rhythms to the earth’s 24 hour cycle .
Zeitgebers: Environmental Ques
*** LIGHT, temp, sound, humidity, social interactions, availability of food.
free-run
absence of environmental ques allows our inherent rhythms or our biological clocks to run free. Shifts right gradually (later in the day)
Circadian Rhythm: Humans natural rhythm interval
24.5 - 25.5 hours
sleep-wake cycles
remain stable with the removal of environmental ques but lengthen to 25 hours. (free running)
Low point of body temperature shifts from the endo of the sleep period to the beginning however it shifts back when entrained again.
Suprachiasmatic nucleus (SCN)
in hypothalamus ; its our internal clock; near optic chiasm
SCN: lesions
circadian rhythms are abolished even with environmental ques present. (high frequency rhythms)
SWS1 SWS2
two levels or non-REM sleep
isolated SCN cells
still generate a rhythm. They dont need other cells
Clock genes
produce proteins that inhibit further transcription.
2 families: Period (per1-3) & Cryptochrome(Cry1-2)
Day = high levels of mRNA and low protein
Night = high nuclear protein levels , attenuated gene expression. Synced by light exposure
GFP
used to show the gene expression rhythm through the day
ganglion cells
Entrainment of the SCN to light; uses photopigment melanopsin. sends signal to SCN via retinohypothalamic tract
melanopsin
photopigment within ganglion cells used to detect light
retinohypothalamic tract
Passage between ganglion cells to the SCN to sense light
Proof Ganglion cells detect light (2)
- mice without rods or cones can still sense light (by patch clamp)
- Melanopsin found in ganglion cells (probably can sense light this way)
GABA
primary synchronizing signal (expressed in SCN neurons)
AVP or VIP
expressed in SCN neurons (along with GABA)
VPAC2
receptor for VIP (Vasoactive intestinal peptide) ; when disrupted , it disrupts circadian rhythms by reducing amplitudes and coherence.
Blocking V1a & V1b
reduce jet lag
Time to return to former rhythm
8 days
SCN controls endocrine and metabolic rhythm (2 ways)
- connections to brain involving sleep an wakefulness & release of sleep dependent hormones (PRL and GH)
- Through specific connections to neuroendocrine systems (adrenocorticotropic axis) and the autonomic nervous system, the SCN can drive rhythms independently of sleep. (release of melatonin by the pineal gland and cortisol by adrenal gland)
GH secretion during sleep
highly episodic and occurs primarily during the first few hours of sleep
Circadian rhythm
ACTH and cortisol excretion occurs during the day with the circadian rhythm
