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nervous system
central nervous system and peripheral nervous system
PNS
sends information to the CNS from the outside world, and transmits messages from the CNS to muscles and glands in the body
somatic nervous system
transmits information from receptor cells in the sense organs to the CNS
- also receives information from the CNS that directs muscles to act
autonomic nervous system
transmits information to and from internal body organs
sympathetic and parasympathetic
fight or flight
endocrine and autonomic nervous system
stressor is perceived
hypothalamus in brain activates pituitary gland and triggers activity in sympathetic branch of ANS
changes from parasympathetic to sympathetic
adrenaline is released from adrenal medulla into blood stream
increase heart rate, breathing rate
dilates pupils
inhibits digestion, saliva production
contracts rectum
once threat has passed back to parasympathetic nervous system
suprachiasmatic nucleus
nerve cells located in hypothalamus
one of the primary endogenous pacemakers
influential in maintaining circadian rhythms - sleep/wake cycle
just above optic chiasm
information about light directly from this
animal sytdies and SCN
DeCoursey et al
30 chipmunks - destroyed SCN
returned to natural habitat and observed for 80 days
significant proportion of them killed by predators
pineal glands and melatonin
SCN - passes info on day length and light that it receives to the pineal gland
night - pineal gland increases production of melatonin
limitation - beyond the master clock
SCN research may obscure other body blocks
numerous circadian rhythms in many organs
peripheral oscillators - lungs, pancreas and skin
influence by SCN and also act independently
Damiola et al - changing feeding patterns in mice could alter the circadian rhythms of cells in lover by up to 12 hours, whilst leaving rhythm of SCN unaffected
other complex influences on biological cycles
limitation - interactionist system
cannot be studied in isolation
total isolation studies are rare - in everyday life, pacemakers and zeitgebers interact, and it may make little sense to separate the two for the purpose of research
more researchers attempt to isolate the influence of internal pacemakers, the lower the validity of the research
ethics
studies justified because there are very similar mechanisms at work across species
existence of an SCN and pineal gland in the brain of animals means that generalisations can be made to human brain - mammalian brain has similar structures
ethics however
animals in DeCoursey et al - exposed to risk when returned to their habitat and most died
