biological rhythms and sleep Flashcards
What are circadian rhythms
- not exactly 24hrs its a free running (no alarm clock e.g) rhythm
- waking/sleeping, body temp etc
What are endogenous circadian rhythms
daily rhythms such as sleep
What is a zeitgeber
trains/resets the biological clock (SUNLIGHT IS IMPORTANT)
What regulates the circadian rhythm
suprachiasmatic nucleus (SCN)
Describe the SCN
- above the optic chiasm, part of the hypothalamus
STUDY: Ralph and Menaker - switched the SCN of 20hr cycle hamsters with 24hr cycle hamsters, endogenous rhythms switched - SCN IMPORTANT
How does the SCN recieve input
from the retinal ganglian cells in the eyes VIA the retinohypothalamic pathway
How does the SCN alter circadian rhythms
- production of proteins = PER and TIM proteins (these promote sleep and inactivity)
- controlling activity levels in other brain areas = regulates the pineal gland (secreates melatonin) which increases sleepiness
What occurs in sleep
- decrease in brain activity
- decreased response to stimuli
What occurs in brain death
no brain activity
What occurs in a coma
extended period of unconsciousness, low steady brain activity
What occurs in a vegetative state
no awareness of surrounding
What occurs in a minimally conscious state
limited speech comprehension
What do big waves and small waves mean
BIG WAVES - synchornisation (deep sleep)
SMALL WAVES - desynchronisation (excited) irregular waves with low amplitude
What are the 4 distinct stages + REM sleep
- RELAXATION (alpha waves)
- STAGE 1 (mostly alpha waves and beta waves)
- STAGE 2 (sleep spindles and K-complexes (transition from awake to asleep))
- STAGE 3 & 4 (slow wave sleep)
- REM sleep (EEG resembles stage 1, postural muscles are paralysed)
What part of the midbrain is responsible for arousal, and damage leads to decreased arousal and can lead to coma
RETICULAR FORMATION
