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Behavioral Endocrinology > biological rhythms > Flashcards

biological rhythms Flashcards

1
Q

rhythm

A

any process that varies through time

-has a constant period

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2
Q

period

A

time interval

= length of time to complete one cycle

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3
Q

frequency

A

number of completed cycles per unit of time

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4
Q

cycle

A

repeating unit

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5
Q

phase

A

any point in a cycle

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6
Q

amplitude (strength/ intensity)

A

amount of change above or below the average value

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7
Q

exogenous

A

factors outside of the organism

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8
Q

endogenous

A

factors within the organism

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9
Q

circadian rhythm

A

period around 24 hours a day (ex: sleep wake cycle, body temperature)

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10
Q

ultradian rhythm

A

period less than 24 hours

ex: circatidal: 12.4 hours

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11
Q

infradian rhythms

A

period greater than 24 hours, less than 1 year

  • circanular: moon phases
  • ovulatory cycle
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12
Q

circannual rhythm

A

BR approximately 1 year

-ex: seasonal changes

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13
Q

Zeitberger

A

environmental time cue/temporal synchronizer

  • something in the environment the cues internal rhythm to synchronize with external cue
  • most primary zeitberger is light
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14
Q

free running

A

biological rhythms NOT synchronized by environmental cues

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15
Q

entrainment

A

synchronization of endogenous rhythms with periodic cue in the environment

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16
Q

reason for jet lag

A

MAJOR phase shift: quick adaptation of activity levels, but other rhythms/physiological rhythms/processes lead to a rapid phase shift

17
Q

biological blocks

A

internal timing mechanisms that are responsible for generating rhythms and allowing entrainment to take place

18
Q

arrhythmia

A

activity present but a lack of rhythm

-happens when SCN is lesioned

19
Q

restoration of SCN rhythm

A

SCN tissue transplants–> restoration in circadian functioning in SCN lesioned recipient so that the period of the recipient’s rhythm matches that of the donor, regardless of the original rhythm

20
Q

humoral output

A

diffusible signal responsible for LOCOMOTOR activity

  • SCN transplant studies in hamsters
  • SCN tissue transplanted into the brain of an arrhythmic, SCN lesioned hamster
  • restored circadian rhythms but NOT endocrine function
  • b/c no neural connectivity was re-established, hypothesized that rhythms in locomotor activity could be supported by diffusible SCN signal
  • transplants sealed in semipermeable membrane
21
Q

neural output

A

mediates ENDOCRINE function

22
Q

eye pathway

A

light–> ganglion layer and inner retina to rods and cone photo receptors–> R’s and C’s send info to ganglion cells–> intrinsically photosensitive retinal ganglion cells contain melanospin–> encodes and transmits light information into the SCN via the RHT

23
Q

SCN: central vs. peripheral oscillators

A

SCN acts a central oscillator and coordinates/acts as a master clock for the peripheral oscillators
-peripheral oscillators have different phase relationships and the SCN makes sure that these rhythms are properly synchronized

24
Q

Estrogens and scalloping

A

on day of estrus, F hamsters in chronic dark conditions have an earlier onset of running behavior= phase advanced (rising levels of estrogens–> earlier onset of behavior)

scalloping can be eliminated via ovariectomy

but E replacement to OVX free running F rats–> decreased period of locomotor activity onset, suggesting direct effect of E on clock

25
Q

Glucocorticoids CR

A

cortisol: highest in morning just when you wake (if nocturnal, highest post wake prior to activity onset)

corresponds with activity levels and locomotor activity

26
Q

gonadotropins

A

LH

  • patterns of LH release dependent on E feedback (+/-) and signals from SDN
  • LH surge is a product of estradiol signals from the ovaries AND a circadian signal from the SCN
  • SCN sends direct and indirect projections to GnRH system to appropriately time LH surge
27
Q

Swann and Turek: Splitting

A

constant light–> split in activity levels so that there are 2 distinct LH pulses

  • decreased period–> more LH pulses
  • SDN controls activity of hormones, and when activity splits, you get a double hormone pattern
28
Q

sex steroid hormones: estrogen and t CR

A

Estrogens: no CR
testosterone: CR of T in males that persists under constant conditions

29
Q

Melatonin CR

A

=darkness hormone

  • same pattern of release for diurnal and nocturnal animals: high at night, low in day
  • light-dark cycle, NOT tied to activity levels
  • secreted ONLY at night
  • duration of melatonin secretion reflects lengths of photoperiod= day length
30
Q

pathway of melatonin release

A

light–> melanospin expressing retinal ganglion cells–> RHT–> SCN–> PVN–> multi synaptic pathway–> pineal–>melatonin

enzymes that produce melatonin are inhibited when there is light

31
Q

type 1 seasonal breeder

A

driven by endogenous and exogenous signals
ex: reproduction in Syrian golden hamsters
(breed in spring/summer, respond favorably to light (day=long) so when days get short, use that cue to shut down reproduction (b/c you don’t breed in winter b/c baby will be born in unfavorable conditions)

32
Q

type 2 seasonal breeder

A

truly endogenous, driven by circannual clocks; without external cues, rhythm persists (ex: ground squirrel)

33
Q

type 1 seasonal breeder syrian golden hamster example steps

A
  1. decrease in mating behavior is happening in the fall to the point where they are at reproductive quiescence (complete cessation of reproductive activity)
  2. photo refractory: will not respond to short day length–> increase in reproductive behaviors, happens end of winter/early spring
  3. photorefractoriness STOPS after exposure to long days
  4. photosensitivity: must be exposed to long days in order to show response to short days of fall and winter
34
Q

SCN as a clock and calendar: melatonin example

A

clock: day vs. night pattern of melatonin
calendar: short day vs. long day pattern (seasonal)–> varies in duration

**SCN controls the rhythm of sexual activity and physiology b/c of DURATION of melatonin secretion determines the biological response

(gonads are smaller in the winter when melatonin duration is high, testes larger in summer when melatonin duration in low)

35
Q

variations in breeding practices among short and long day breeders: interpretation of melatonin signals and relation to fertility

A

melatonin signal encoded differently by short and long day breeders (short day= sheep, long=hamster)

long days: eye–> RHT–> SCN–> pineal–> decrease M duration–> sheep will be anovulatory, hamster will be fertile

short days: sheep will be ovulatory, hamster will be infertile

36
Q

hypothalamic interpretation of M will impact GnRH release, LH/FSH release, and release of ovarian/testicular hormones

A

if hypo interprets M as inhibitory
-lower GnRH–> lower FSH/LH–> lower sex hormones

if hypo interprets M as stimulatory
-higher GnRH–> higher FSH/LH–> higher sex hormones

short day breeder
-high duration of M–> enhance GnRH…

long day breeder
-low duration of M–> enhance GnRH…

37
Q

estradiol, melatonin, long day and short day breeders, reproductive transitions

A

melatonin is altering estradiol feedback on AVPV and ARC

  • seasonal reproductive transitions are a result of changes in ability of estradiol to inhibit GnRH
  • Sheep: long days
  • -estradiol–> inhibit GnRH–> decreased LH/FSH–> blocking ovulation (E has higher levels during long days)

Sheep during short days: estradiol concentrations go down, decreased negative feedback–> higher GnRH–> higher LH/FSH–> ovulation–> sex behavior

38
Q

seasonal changes in ARC kisspeptin cells and GNRH neurons

A
  • breeding season: increase in number of kiss1 cells in caudate
  • and increase in % of GnRH cells with kiss 1 input

Behavioral Endocrinology (12 decks)

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