AB Lecture 9: sleep and biological rhythms

animals have a sense of

time

example of animals having a sense of time

• dog waits for their owner to come home

• pigs know if they’ve been in crates for longer or shorter periods of time

• chimps and their ability to exhibit delayed gratification

biological rhythm defintion

a cyclic change in behavior or internal physiological process that occurs at a regular rate in an organism

types of biological rhythms - 2

• exogenous

• endogenous

exogenous biological rhythm defintion

rhythms that depend on external stimuli in order to persist regularly

endogenous biological rhythm defintion

rhythms that are independent of external stimuli and rely on internal clock mechanisms

internal clock mechanism defintion

self-regulating, self-sustaining neural signals that occur at regular intervals

what are the different rhythm frequencies - 6

• high frequency

• ultradian

• circadian

• diurnal

• infradian

• annual

high frequency rhythm defintion and timing

rhythms that occur in short periods

• 30 minutes or less

example of a high frequency rhythm

heart rate

heart rate is what within species and age groups

conservative - similar

• younger and smaller animals tend to have a higher heart rate

ultradian rhythm definition

rhythms with a period between 30 minutes - 24 hours

examples of ultradian rhythms

• growth hormone production from the pituitary gland in cattle

  • every 3.5 hours

• natural feeding behavior

  • every 2-3 hours

  • dogs, cats, sheep, horses, pigs, cattle

circadian / diurnal rhythms defintion

rhythms that repeat approximately every 24 hours

• very common to see behaviors and hormones expressed in a 24-hour cycle

infradian rhythm defintion

longer than 24hr

infradian rhythm examples

reproductive cycles of polyestrous animals

• cows and sows

• mares

• ewes

annual rhythm defintion

repeats annually

example of an annual rhythm

seasonal breeders

• horses: long day breeders

• sheep/goats: short day breeders

what is the goal of seasonal breeders

spring births for a high probability of offspring survival

zugunruge definition

the anxious behavior that migratory animals exhibit when they are unable to migrate

• ex: when in captivity

what does zugunruge behavior look like - 2

• increased activity around/after dusk (wing-flapping, restlessness)

• change in sleep pattern (diurnal to nocturnal)

what is seen in some non-migratory animals

zugunruge

circadian rhythms require what to get started but doesnt need it to continue

requires stimulus

a circadian rhythm is influenced by a

zeitgeber

a zeitgeber is known as

entrainment

zeitgeber defintion

any external or environmental cue that sets, or resets, or synchronizes an organisms internal biological clock and a 24-hour circadian rhythms

example of circadian rhythms - 3

• sleep/wake cycle

• hormone secretion in most mammals

• body temperature

hormone secretion in most mammals cycle

• peak cortisol early in the day

• various zeitgebers - depends on hormone

  • food, light, activity, other hormones, etc.

circadian rhythm

body temperature rhythm

circadian rhythm

• peak in the afternoon, lowest in the early morning

• common across many species

circadian rhythm properties - 4

• must be ~24 hour period

• must be an endogenous rhythm (internal factor driven)

• must persist in constant conditions

  • free running rhythm

• must be able to reset or “entrain” to an environmental factor

the internal clokc mechanism is what part of the body

suprachiasmatic nucleus (SCN)

what is the SCN made up of

paired nuclei (cluster of cells) that regulates circadian rhythms

where is the SCN located

just above the optic chiasm

how do the cells work in the SCN

each cell is its own clock, with its own electrical signals

the cells in the nuclei work together to create a 24 hr rhythm

what is a diurnal rhythm

a 24 hr rhythm that relies entirely on external cues in order to persist

examples of diurnal rhythms when it comes to food

foraging and hunting

• foragers will alter their behavior depending on the temperature to conserve energy

• hunters will alter their behavior based on their prey

examples of diurnal rhythms - 2

• stereotypes (abnormal behaviors) in many species

  • bar biting in pigs peak 2 hours after feeding - only fed 1x a day

• poultry perching behavior

  • depends on amount of light (photoperiod) and timing of darkness

what two rhythms are hard to differentiate between

circadian and diurnal rhythms

• requires careful experimentation

reasons for sleeping - 4

• replenish neurotransmitters

• conserve energy

• consolidate memory

• fill time

what are the 4 behavioral indicators of alertness and sleep

• alert wakefulness

• drowsiness

• quiet sleep

• active sleep

properties of alert wakefulness behavior - 2

• eyes fully open

• EEG: low voltage, fast activity output

properties of drowsiness behavior - 3

• relaxed upper eyelids

• high arousal threshold / reduced alertness

• EEG: combination low voltage / high activity and high voltage / slow activity

properties of quiet sleep behavior - 2

• eyes closed or nearly closed, even more required to arouse

• EEG: all high voltage / slow activity

properties of active sleep (REM sleep) - 2

• eyes fully closed

• EEG: low voltage / fast activity (like wakefulness)

  • paradoxical sleep

relative sleep behavior of dogs

• 50% of time spent sleeping (20% of that in REM)

  • dependent on housing and schedule

relative sleep behavior of cats

• 45-65% of time sleeping (20% of that in REM)

relative sleep behavior and position of cattle

• 25% of time sleeping (20% of that in REM)

  • sleep lying down, but rarely in lateral

relative sleep behavior and positions of horses

• 20% of time sleeping

• sleep standing up the majority of the time, but must be in recumbency for REM sleep - usually only ~5 mins at a time

relative sleep behavior of pigs

• 30% of time sleeping

  • have many bouts of REM sleep, if in a stress-free environment

relative sleep behavior and positions of poultry

• very dependent on the light cycle

• definite difference in resting vs sleeping posture (head neutral vs head tucked)