lecture 22: sleep Flashcards
biorhythm
inherent timing mechanism that controls or initiates various biological processes
ex. eating
- linked to cycle of days and seasons produced by the earths rotation around the sun
- dominated by circadian rhythm of daylight activity
biological clocks
behavior is not only driven by external cues from the environment
endogenous rhythm: control comes from within
how is biological clock controlled
neural system that times behavior by synchronizing it to temporal passage of real day
animals can anticipate events before they happen (migration)
regulates feeding times, sleeping times, metabolic activity, gene expression
mearuing biological rhythms
each days activity is plotted under the preceding days activity in a column, a pattern of activity emerges over time
period: time required to complete a cycle of activity
different types of rhythms
circannual - yearly
infradian - less than a year
circadian - daily
ultradian - less than a day
free running rhythms
rhythm of bodys own devising in the abscence of all external cues
- body has own rhythms with period of 25-27 hours
sleep wake cycle shifts an hour or so every day
examples of free running rhythms
hamsters: nocturnal
in constant darkness, free running period shorter than 24 hours
in constant light, free running periods longer than 24 hours
sparrows: diurnal
in constant darnkess, free running periods longer than 24 hrs
in constant light, free running periods shorter than 24 hours
zeitgebers
environmental event that entrains biological rhythms, a time setter
- an entrained biological clock allows an animal to synchronize its daily activity across seasonal changes
examples of zeitgebers
light pollution: exposure to artifical lighting disrupts circadian rhythms, can impact rate of accidents, fatigue, emoitonal states, obesity, diabetes
jet lag: fatigue and disorientation resulting from rapid travel through time zones and exposure to changed light-dark cycle
associated with altered sleep rhythms, fatigue, stress
suprachiasmatic rhythms
suprachiasmatic nucleus (SCN) - main pacemaker of circadian rhythm; located just above optic chiasm
evidence for SCN role
- damage to SCN affects daily activities
- SCN cells increase metabolic activity during light period
- cells are more electrically active in light period
- SCN neurons maintain rhythmic activity in abscence of input and output
- cells in dish retain periodic rhythm
other clocks in the body
intergeniculate leaflet (thalamus)
pineal gland (releases melatonin)
nearly every cell in the body has its own clock
0 animals can still display rhythmic behaivor without an SCN
rhythmicity in SCN cells
if SCN neurons are isolated, each remains rhythmic but rhythmicity of some cells is different from that of other cells
- cellular rhythm must be synchronized to eachother via GABA synapses and to zietgebers
retinohypothalamic pathway
neural route from subset of cone receptors in retina to SCN
- allows light to entrain rhythmic activity of SCN
- begins with specialized retinal ganglion cells containing melanopsin
- can be activated by rods/cones or directly by light
subdivisions of SCN
core: ventral, non rhythmic
shell: dorsal, rhythmic
- axons cross bilaterally
- synapse in core and then entrain the shell
