Biopsychology Of Morivation And Internal Regualtion Flashcards
Rhictor 1922
Hypothesised that animals have an internal mechanism that spontaneously generates this rhythm
Describe a Endogenous Circadian rhythm.
An internal cycle, last about a day.
Stay up all night- get more and more tired-perk up as day breaks
Animals in 24hr darkness still have a 24hr cycle (DeCoursey 1960)
Humans always skip back into a 24hr cycle
Blind and deaf individuals also keep a Normal circadian cycle
Richter 1967
Theorised that we all have a biological clock-a mechanism in our brain that generates this cycle.
Rhythms are maintained even with brain damage (anaesthesia)
It is in the suprachiasmatic nucleus (SCN) hypothalamus. Damage to this disrupts the circadian cycle.
How does the biological clock work?
SCN controls the pineal gland (an endocrine gland posterior to the thalamus)
This releases melatonin (a hormone that makes us feel sleepy)
What is zeitgeber?
The clock is internal, but still responds to the environment. A feedback system allows us to adapt to change. The rhythms can exist without light but will periodically reset. The zeitgeber is the stimulus that changes the clock. This useful for changing seasons, light is the main one, others include exercise, noise, Temp, tides.
(Purple in Scandinavian countries are insomniac during the winter) p
Describe Jet Lag
Disrupts rhythms by crossing time zones. Sleeping at the wrong times can. Cause depression, lack of concentration as it is a mismatch between biological clock and external stimuli. Raises cortisol levels.
Describe the role of light on a circadian cycle
Branch of the optic nerve goes straight from retina to SCN- input from this pathway come directly from a specialised retinal ganglion cell.
Special photo pigment-melanopsin-not like rods or cones; respond directly to light, no need for rod or cone input.
SCN gets a general gauge of light intensity and time of day.
Different stages of sleep can be detected by EEG. What are the stages of sleep?
The 4 stages of sleep have different brain activity to relaxed wakefulness.
Stage 1&2: irregular, high but declining, bursts of activity
Stage 3&4: slow waves sleep. Neuronal activity high, synchronised REM (paradoxical sleep) muscles relaxed but lots of activity
What happens during REM?
We see PGO waves (pons-geniculate-occipital)
If animals are deprived of sleep, these waves pop up during wakefulness (during hallucinations)
What happens if we lesion the pons? (In cats)
Animal still has REM sleep and dreams but muscles are not relaxed. They act out the dream.
Name 4 sleep disorders
Insomnia: stress, shifting circadian rhythm
Sleep apnea: inability to breath-old age, obesity
Narcolepsy: Attacks of sleep during the day.
Periodic limb movement disorder: involuntary movement of limbs
Describe sleep as a means of conserving energy
A form of hibernation. Amount of sleep needed varies across species depending on;
1) safety from predators
2) how much time they need to find food
3) whether they need to surface for air (Dolphins sleep on one side of their Brian at a time)
What happens when you are deprived of sleep?
Dizziness, hallucinations, and eventually the immune system fails. Sleep enhances memory and consolidates it.
Is there a biological function of REM sleep?
Only mammals and birds have REM.
1) it strengthens memory
2) filters pointless connections
3) moisturises the eyeballs
Freud thought dreams were unconscious wishes. What are 2 other theories?
1) activation-synthesis hypothesis
Effort to make sense of distorted info
PGO waves from pons activates part of the cortex which synthesises a story- not always in REM
2) the clinco-anatomical hypothesis
Dreaming is thinking
Senses suppressed so mind is working by itself
Motor cortex suppressed so no action
Pre-frontal cortex suppressed so no working memory to link a believable story together
