What 2 organisms are given as an example to show the range of species that have evolved timing systems important to behavior?

organisms from bacteria to humans

What is the term for the study of biological rhythms?

It studies timing of events both __ and ___ to an animal.

What is the term for the study of biological rhythms?

It studies timing of events both within and external to an animal.

- chronobiology

Organisms have developed timing systems to respond to what?

rapidly fluctuating environments

Daily cycle refers to fluctuations in day and night, including:  (3)

Yearly cycle refers to fluctuations in season, including: (2)

Daily cycle refers to fluctuations in day and night, including:  (3)

Yearly cycle refers to fluctuations in season, including: (2)

-temperature, humidity, light

- temperature, number of hours of light

Another term for daily rhythms is what?

circadian rhythms

When graphing a variable against time in order to observe a biological rhythm, the rhythm you observe depends on what 2 factors?

when and how often you measure

Diurnal vs. nocturnal animals differ dramatically with respect to rhythms in:  (4)

sleep/wake

wheel running

mating

hormone sensitivity

List a couple reasons why we should care about biological rhythms.

- public safety

- experimental controls

- educational policy

- shift-work

- air travel

Give an example of how circadian rhythms relate to public safety.

single vehicle accidents occur more than 4 times as often during the middle of the night (with approximate peak between 3-5 A.M.)

What medical intervention example was given regarding the importance of studying circadian rhythms?

Alzheimer's pateint with sleep consolidation problems had more normal sleep pattern after light therapy.

Compare the circadian rhythm of testosterone level in young men to old men.

old men had almost exact same pattern as young men, just downshifted (so always lower than young men)

On the graph from the slide about human alertness rhythms and educational policy, alertness rating closely followed the pattern of what other variable?

oral temperature

2 explanations for circadian rhythms are that they are a byproduct of a homeostatic mechanism or that they're caused by endogenous factors.  Explain each, then state the question that needs to be researched to determine which is correct.

1) ie, we become sleepy because we have been awake all day

2) biological clocks within organism, often interacting with or being entrained by exogenous factors

... Does the rhythm persist in the absence of environmental changes?

What is the name of the graph that has graphs of 24 hour blocks of activity stacked on top of each other to identify gradual shifts in cycles?

actogram

When alternating an experimental animal's circadian rhythms, what are 2 zeitgebers that can be used for entrainment?

- schedules rest/activity

- scheduled light/dark cycle

Match 'flying east' and 'flying west' to 'phase delay' and 'phase advance'.  Which takes fewer days for people to adjust their sleep-wake cycles to?

east = phase advance,  west = phase delay.

flying west is an easier adjustment for people.

How long was Kleitman & Richardson's 1938 cave stay?  What rhythm did they try to switch to? If it worked, what did they plan to conclude? What were the results?

32 days.  28-hour rhythm was the target.

Would conclude that the 24-hr cycle is just a reaction to the surrounding world.

Results mixed; body temp did have rhythm of 25 h.

In 1962 Michael Shiffre stayed in a deeper cave for 62 days.  Used phone to send body temp patterns to surface.  What were his results?

His sleep rhythm persisted w/ a free-running period of a little more than 24 h.

What are the 4 criteria for a circadian rhythm?

- persist in the absence of periodic influences (endogenous)

- but, drifts away from 24h period w/o synchronizers (free-running)

- entrain to rhythm of 24 hours in presence of cues

- change phase slowly after an abrupt change in the environment

Where is the clock mechanism for circadian rhythms?

the suprachiasmatic nucleus (the SCN)

Describe SCN activity in rats (nocturnal) as measured by glucose uptake.

stronger activity during light phase ("day"), when they rest, than dark phase/'night' when they are active

What are the fx of SCN lesion & 3 examples?

Fx of severing SCN connections to rest of brain?

Fx of SCN removal then transplantation?

What are the fx of SCN lesion & 3 examples?

Fx of severing SCN connections to rest of brain?

Fx of SCN removal then transplantation?

- all rhythms disrupted (eg cortisol secretion, drinking, activity)

- within-SCN rhythmic activity intact, not in disconnected structures (SCN can live in petri dish & still exhibit rhythms in neuron firing)

- SCN reinstates rhythmicity after implant/transplantation

What happens to the period of a given rhythm after an SCN transplant?

animal will have period of donor, not its original period

For SCN transplant study, what was the mutant hamster type called? How long was its free-running period?

tau-mutant hamsters / 18-hr free-running period

Woman w/ SCN lesion from surgery had erratic activity cycle.  How was this improved upon and what does it imply about zeitgebers?

- staff organized her days w/ scheduled bed-times, wake-times & meals

- Exogenous zeitgebers (in this case a social one) can play an important role if endogenous rhythms are knocked out.

2 endocrine rhythms and 1 behavioral rhythm regulated by the SCN:

melatonin secretion, ovarian cycle

Wheel-running activity

What secretes melatonin and what incoming pathway to it drives the process?  What happens to M secretion in total darkness?  How is pattern disrupted?

- pineal gland; incoming pathway from SCN

- persists as free-running rhythm

- SCN lesion

How do SCN connections regulate the ovarian cycle?

- SCN has connections to the GnRH cells in the hypothalamus.

- LH release patterns are in complete lock-step w/ activity rhythms

I don't need to say it but SCN lesion disrupts (duh)

What is unique about SCN regulation of wheel-running activity? What is one possible specific mechanism for this?

- effects of SCN not depend on synaptic transmission!  Depend on a humoral factor instead.

- possibly secretion of a calcium-binding protein

What information is obtained from the duration of nightly melatonin secretion?

- daylength

Explain how pinealectomy as well as replacement of melatonin after PXY implicate melatonin as being crucial for seasonal behavior?

- PXY eliminates seasonal behav. change (eg breeding) & physiology (eg weight reduction, winter fur growth) when switched from long to short days

- replacement = reinstatement of seasonal responses (depending on duration of daily melatonin admin.)

Explain the experiment showing dependence of seasonality on melatonin duration.

- 4 hr M admin. = summer behav.; 12 hr admin. = winter behav regardless of time of day

- only duration matters NOT dose: increase in dose 100-fold didn't change results

- 3 hr break in M admin. = summer behav.; 1 hr break = winter behav.

What can melatonin do for circadian rhythms?

Who can this fact help medically & how?

What is another helpful (but controversial) use?

What is a use of it unrelated to circadian rhythms?

What can melatonin do for circadian rhythms?

Who can this fact help medically & how?

What is another helpful (but controversial) use?

What is a use of it unrelated to circadian rhythms?

- entrain them

- retinally blind ppl if they receive M at same time every day (bcz they are otherwise free-running)

- recovery from jet lag

- sleep inducing effect (but this depends on dose)

ask dmitri about slide 36. tau? prc?

I get the main idea but what's tau & PRC?

prc = phase response curve.

What are the 3 main ways Gonadal Steroids affect Circadian systems? (examples where possible)

1) the fundamental properties of the circadian system

2) amplitude and timing of specific measured rhythm endpoints (peak activity, CBT min/max, sleep onset, etc.)

3) Estrous effects on rhythmic expression of activity, temperature, sleep and cognitive function

Hamster sexual dimorphism for waking phase activity pattern & relation to gonadal steroids?

- free-running males have 2 bouts of activity; females have more stable & coherent pattern

- OVX makes female more male-like

- castration has little effect on male activity pattern

Sexual dimorphism for temperature rhythms in humans & rats (w/ relation to gonadal steroids / hormones) ?

temp. rhythms affected by P and E in females;

male temp. rhythms insensitive to hormonal fluctuations

Effect of female rep. cycle on circ. rhythms in 3 species:

1) humans - ovulation induces decrease in activity & subsequent temp. increase

2) degus - estrus = increase in activity & body temp.

3) hamsters - estrus assoc. w/ body temp. & activity increase AND an earlier activity onset

What is the possible site of action for gonadal steroids in affecting circadian rhythms? (is from slide on fx of female rep. cycle on rhythms but it doesn't explicitly say that this is only for that specific situation...)

ER-beta receptors in SCN

On actogram of estrus-related activity in degus, which accompanying actogram clearly shows change on/after day of estrus?

Temperature

Are sex differences in adults that are caused by gonadal hormones due to activational or organizational effects?  Give example w/ hamsters.

- many of them are activational although there are some that are organizational.

- hamsters:  OVX female similar activity pattern to male but castrated male does not decrease incidence of splitting of the 2 activity bouts.

What range of temperatures & hours of sun per day are observed in Fairbanks Alaska?

What do animals have to do to survive this?

What range of temperatures & hours of sun per day are observed in Fairbanks Alaska?

What do animals have to do to survive this?

-40 to +75 degrees

3 hours (winter) to 21 hours (summer)

- have to transform themselves from one season to another

What example graph was given that shows people change with the seasons too? Briefly describe the trend.

Seasonal weight gain:  starts rising after August with peak in December, drops dramatically in January (which is counterintuitive... winter's not over...)

Describe the seasonal changes in hamster reproductive status, including specific timeframe.

What changes occur in the hamster at beginning and end of timeframe?

Describe the seasonal changes in hamster reproductive status, including specific timeframe.

What changes occur in the hamster at beginning and end of timeframe?

- Large increase in rep. status starting Vernal equinox (in March), ending Autumnal equinox (September)... plateaued throughout (not hill shape).

- 'spontaneous' testicular regeneration followed by pineal-induced testicular degeneration at end of plateau.

In reproductive regression, which two factors are correlated?  What's the difference between summer vs. winter?

- decreased testis size = decreased steriod production

- T level in summer::winter is ~ 4::0

A news article in the powerpoint suggested which method for resetting teens' messed up sleep cycles (and what do they call the syndrome when they are messed up) ??

- avoiding blue light for the 1st two waking hours then getting a good dose of it.

- 'delayed sleep phase syndrome'

What did the CNN.com article say was the impact of starting high school later on...

total sleep time?  teenage car accidents?

How many hours of sleep did it say teens need?

What did the CNN.com article say was the impact of starting high school later on...

total sleep time?  teenage car accidents?

How many hours of sleep did it say teens need?

- extra hour of sleep

- fewer car accidents

- 8 to 10 hours

(Acc. to journal article:) What is different about adolescents and young adults sleep?  When is delay greatest and what does the delay cause?

- they phase-delay their sleep (aka go to bed later & wake up later) [but the waking up later part gets cut short bcz of school --> chronic sleep deprivation]

*delay is greatest on weekends and holidays