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)
TAIL-E
explain E-explanation evidence for SCN as clock in mammals
transplantation, ablation, isolation, location
remove SCN tissue
RHYTHMS PERSIST
SCN terms
which part of hyothalamus is SCN relative to?
anterior hypothalamus
lateral to ventricle 3
SCN terms
What type of feedback is SCN clock generated by?
molecular feedback
SCN terms
the “core” of SCN is which part (plane) of the SCN?
which 2 neuronal projections?
hint: core of ventrolateral (ladder) has VIP and RHT
ventrolateral
* VIP (vasoactive intestinal polypeptides)
* RHT projections (retino hypothalamic tract)- retinal inputs
SCN terms
the “shell” of SCN is which part (plane) of the SCN?
which 2 main neuron?
hint: p___ the shell, gastrin
dorsalmedial
* AVP (arginine vasopressin)
* * GRP (gastrin releasing peptiudes)
SCN terms
Which NT is located in both SCN core (ventrolateral) and shell (dorsomedial)?
GABA (inhibitory)
SCN inputs
Name 3 main inputs to SCN
retina (RHT) - light, sight
IGL - arousal, day length
MRN- activity, exercise
SCN inputs
retina, IGL, MRN are inputs of SCN core or shell?
core - ventrolateral
SCN inputs
SCN shell inputs include which 2 regions?
hypothamalamus
limbic system
SCN input #1 - retina
How does light inputs in retina relate to SCN? what purpose does it have?
RESET extrinsic time cues (light)
ENTRAIN/sync to day liength
SCN input #1 - retina
retina contains what types of cells and what types of photopigment?
RGC - retinal ganglion cells
Opn4 (melanospin)
SCN input #1 - retina
What is melanospin Opn4 photopigment most sensitive to? why?
less sensitive to?
least sensitive to?
BLUE light- short wavelength 450
less - green
least- red
SCN input #1 - retina
What is melanospin Onp4 photopigment 2 roles?
photoreceptors - rods, cones
phase shifting (delay, advance) control
SCN input #1 - retina
What NT is released? excitatory/inhibitory?
Glu - Glutamate
excitatory
SCN input #1 - retina
Wha track does OpN4 (melanospin) use to project to the mammilian clock (SCN)?
RHT = retino hypothalamic tract
SCN input #2) - IGL
What 2 roles doe IGL (intergeniculate leaflet in thalamus) play in SCN?
think IGL lesions = slow entrainment, block length of circadian, cannot reset
hint: diff to retina (visual info only)
- circadian rhythm regulation (entrain, reset, length)
- TRANSMITS photic/non-photic info
SCN input #2 IGL
Is IGL REQUIRED to entrain cycles in animals?
no, in animals - modulatory role
SCN input #2 IGL
What 2 NT does IGL have to input to SCN?
GABA - inhibit
NPY - phase shift - advance
SCN input #3) MRN
What role does MRN (midbrain raphe nucleus) and Dorsal RN?
Which NT released?
mandatory or modulatory?
modulatory role for photic/non-photic inputs- NOT required for entrainment
entrainment, rhythms
serotonin (exc)
What type of effects will appear if MRN has lesions?
phase advance
lengthen actiivty
dec amplitude and precise of rhythms
SCN ouptuts
Are SCN outputs neuronal or non-neuronal?
Both!!! many outputs =
SCN ouptuts
What SCN core outputs is given?
hint: one sided, core is self sustaining
SCN core ouputs to SCN SHELL (but shell does not feedback to core!)
SCN ouputs
What neropeptides and NT does SCN shell outputs?
circadian - GABA, glu, VIP, AVP, PK
most outputs of SCN - SPZ
sub-para-ventricular zone is where most ouputs of SCN is. what 3 roles does it play?
which more in lateral SPZ?
which more in medial SPZ?
core body temp (lateral)
locomotor activity (medial)
slee wake rhythms (medial)
second most outputs of SCN - DMH
doso medial hypothalamic nucleus is the second most SCN outputs projected to. What 2 similar roles to SPZ does it play? what does it NOT play?
plays - locomotor actiivty, sleep wake rhythm (medial)
not invovled in - core body temp, melatonin
DMH ouput of SCN
What hormone is released and expressed from DMH?
cortisol - more when waking, promote readiness for env, stress
hormones
What hormone is released form the pineal gland? present in diurnal or nocturnal animals?
melatonin - promote sleep, hhighest midnight, present in BOTH animal types
