w4) neurobio of c.rhythms Flashcards
if removed tissue –> rhythms go away/also removed…?
What is the clock mechanism itself vs ticking hands of the clock?
think: is the clock showing time or the hands of the clock showing?
clock itself - drives the rhythm (even if tissue is removed)
ticking hands (allowing underlying rhythms to express EVEN WITHOUT ticking hands showing)- think of clock without hands but time still ticking without you being able to see time
pacemaker cells are also known as ? cells
- what role?
clock cells
keeps time
3 examples of non mammalian clocks
What are 3 animals/non-mammal clock examples?
silk moths
cockroach
sparrows
What determines where the “clock cells” or pacemaker are located in?
the organism - silk moths, cockroach, sparrow
silk moth example #1
What experiment was used to test the pacemaker making rhythms of silk moths?
hint: pupa closes –> emerges to adult
eclosion = pupa closes emerges to adult
DD = dark cycle, don’t need dark-light cycle, INTERNAL pacemaker
silk moth example #1
If silk moths and cockroaches have a DD cycle = what does it mean? what is not needed? is the pacemaker INTERNAL OR EXTERNAL?
DARK persisting cycle
no need dark light cycle
INTERNAL pacemaker
silk moth example #1
Was the donor tissue expressing time or the moth host?
donor tissue (brain) expressing time = shows BRAIN INTERNAL pacemaker cells not hands of clock
cockroaches example #2
What experiment was used to test the pacemaker making rhythms of cockroaches?
2 things tested/removed and showed no rhythms were?
whyat showed rhythm?
hint: just 1 ___ of cockroach
removing eyes/2 optic lobes showing no rhythmic,
answer = rhythm is in brain’s 1 OPTIC LOBE
S + C
what is the silk moth and cockroach experiments aim?
hint: both are smart (brain),
clock localization
S + C
clock localization was conducted in silk moths and cockroaches. What do both results show about the clock or hands of clock? aka WHAT is the pacemaker cells?
clock = INTERNAL = in the BRAIN
drives the rhythm (not transplanting the hands)
example #3 sparrows
What 2 parts of the brain is used in sparrows to become described as “distributed system” ?
hint: expressing OVER circadian rhythms
SCN
pineal gland
what is entrainment?
synchronzing to light dark cycles
example #3 sparrows
what are the 4 steps of blind sparrow experiment?
hint = 1) where 2) run… 3) remove feathers, 4) inject ink
1) using brain (SCN and pineal gland) to entrain/sync
2) free run
3) remove feathers entrain again
4) inject ink = block entrain
example #3 sparrows
What is a key finding of blind sparrows getting signal from light to entrain/sync to the clock?
uses BRAIN internal pacemaker cells not eyes (like mammals human)
What are 3 mammal clock examples?
humans
rodents
monkeys
mammal circadian clock
Where is the master circadian clock of humans located?
SCN
surpriachiasmatic nucleus
surpra (above) optic (cross x shape)
T?F
SCN functions are homologous but diff NT contribute diff to each mammal.
true
What does circadian systems ensure?
RHYTHMS =
behaivor and physio
What does circadian system coordinate with?
environment
what is 5 evidence that SCN is clock controlling the DONOR tissue (aka host recieving donor’s SCN is controlled by tissue)?
hint: TAIL-E
1) transplantation
2) ablation
3) isolation
4) location
5) explanation
TAIL-E
explain T-transplantation evidence for SCN as clock in mammals
transplant mutant animal’s SCN into arrhythmic animal (host)–> bring back MUTANT (DONOR) rhythms
TAIL-E
explain A-ablation evidence for SCN as clock in mammals
hint: ablate = lesions
lesions show activity rhythms ALL THE TIME
rhythm LOST = clock is SCN
TAIL_E
explain I-isolation evidence for SCN as clock in mammals
transplantation, ablation
isolate SCN and inputs –> rhythms STILL PERSISTS
TAIL_E
explain L-location evidence for SCN as clock in mammals
note: transplanation, ablation, isolation,
ideal spot to get direct info (light) IS FROM THE EYE
optic chiasm (SCN)
