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Lecture 8

Lecture notes for second half of lecture 8

Cell and Systems Biology
Course Code
Richard Stephenson

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One of the approcahes is the move towards studying
simpler animals. It's based on assumption, simple
animals evolved sleep for same reasons as complex
animals. Sometimes its useful to take an approach
that takes a global stance and try and come up wi
th answers. Instead of taking specific hypothese,
use drosophila, apply random approach to mutating
them (sleep mutating) that might lead to chacs tha
t might lead to fucntions of sleep. Droso have sle
ep like behaviour. Genome sequced long time back s
o easier to manipulate. Study them on mass. Apply
mutagenic subs, generate random mutations, study s
leep beheaviour, look for unusual behaviour like (
qty of sleep etc), go ahead and study those, apply
those to mammilian systems. And ultimately to dtr
mine genetic mechs applicabale to human conditions
. Can use droso in large numbers.
labs studied droso using infrared systems measurin
g their sleep. one of the goals is to produce dros
o that doesnt sleep. they failed to do so. the lin
es rep a certain amt of droso that get a certain a
mt of sleep. males more lazy, sleep more. there ar
e some mutants that sleep all the time, some dont
sleep much at all by comparison. the starred one h
as minisleep, problem with ion channel but they're
still getting like 5 hours of sleep. altho they d
ont sleep much, sleep quite a bit. its possible th
at they did produce mutations that had no sleep bu
t the mutations died before they could be measured.
Sleep is adaptative, takes time. the minimum amt o
f sleep might be linked to basic physiologic funct
ions. core sleep vs optional sleep. the actual tim
es and qts may not be directly linked though. opti
onal sleep reqd for non-physiologic functions ex a
nimal living in env where mvt is hazardous. study
of sleep patters is study of sleep regulation, mig
ht not tell about sleep functions.
Immoblization may max eff for restoration of thing
s, fat stores etc. It might be protective, might a

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nticipate over activity. May conserve energy under
conditions where activity might not be best optio
n. if the temp falls too low, waterfoal would stop
eating, become anorexic because energy consumed i
n diving is similar to acquire food. so they just
sit on watre surface keeping eye on predator. Anot
her issue, is assumed sleep risky. This increases
risk of predation. Most predation occurs in awake
animals rather than sleep. Data inconclusive. Slee
p is the safest time of day coz they sleep in safe
places. some dont though, how do they deal with t
his? Animals sleep on tree for ex.? How do they de
al with that? They could fall! Unihemispheric slee
p maybe. sleeping in groups ensuring some remain v
igilant and raise alarm. lions and hyenas prey on
zebra. zebra has evolved not to sleep, maybe they
have unihemispheric sleep. its been known that u c
an tether a horse standing up and they dont suffer
sleep loss. it seems likely horses switch to unih
emispheric sleep when rem sleep not viable.
A group of chipmunks kept in natural environment a
nd allowed to go about their normal patterns over
long periods. Two groups animals captured from thi
s environment. One had SCN (circa rhtyms gone) les
ioned. It doesnt affect the amount of sleep but af
fects when they get it. another group was sham ope
rated; instead of going and killing off scn via su
rgery, just did some other non surgical way to ens
ure it wasnt surgery that causes affects. The diff
erence in the 2 groups were their activity pattern
s. The data indicate the effects this had on survi
val. Over the short time, very few of these animal
s died. Over the long term, the introduction of we
asel, the long term survival of the group that had
the scn lesioned was compromised and the research
ers concluded that the problem was that these diur
nal animals, became active in night in burrows ins
tead of sleeping at night and the weasel could det
ect and catch them. Suggests that sleep is subserv
ing an important behv func by immobilisng them and
making them more difficult to find thus eco facto
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