Exam 4 Flashcards
cycles occur everywhere
- rhythms
- eating and drinking
- light (color is based on frequency and brightness is based on amplitude)
- neuroendocrine feedback
- sleeping
how does our body know when to sleep and when to be awake?
- light from sun entrains our sleep wake cycle
- day and night cycle occurs over 24 hours
- thus, our sleep wake cycle is set to 24 hours
- specific parts of the brain are activated by light and produce proteins during the day but not at night
- the neuroendocrine system is also important as it releases melatonin from the pineal gland
- melatonin is high at night but low during the day
pineal gland
releases melatonin into blood stream
melatonin induces sleep…
by receiving information from the suprachiasmatic nucleus (SCN) of the hypothalamus
SCN receiving light information
- information from the retina is sent via the optic tract to the thalamus (what nucleus)
- optic tract sends a small set of axons that synapse to the SCN
- information sent by these ganglion axons do not rely on photoreceptors
- ganglion cells of the retina contain a receptor called melanopsin, which is activated by blue light
- information is sent to the SCN by glutamate release from ganglion axon terminals
- release of glutamate activates SCN neurons and results in production of new proteins
retinal ganglion cells…
contain melanopsin and project light information to SCN
melanopsin
most sensitive to blue light
behavioral changes in animals
caused by light
specific genes and proteins are made in SCN
caused by light
specific genes in SCN are activated
caused by light
light activates specific genes in the SCN
- SCN cells in mammals make the proteins clock and cycle
- clock and cycle proteins bind together to form a dimer
- the clock/cycle dimer promotes transcription of 2 genes: period (per) and crypochrome (cry)
- proteins arising from per and cry bind to each other and to a third one, tau
- the per/cry/tau protein complex enters the nucleus and inhibits the transcription of per and cry
- no new proteins are made until the first set degrades and the cycle begins again approximately every 24 hours
molecular/genetic events of cyclic activity regulating sleep
- proteins clock and cycle binds together, forming dimer
- clock/cycle dimer binds to DNA, enhancing transcription of genes for per and cry
- per and cry bind together as complex that inhibits activity of clock/cycle dimer, slowing transcription of per and cry genes, and therefore slowing production of per and cry proteins
- per/cry proteins eventually break down or are modified so they no longer inhibit clock/cycle, allowing the process to start again; this cycle of gene transcription, protein interactions, and inhibition of gene expression takes about 24 hours to complete
- retinal ganglion cells detect light with melanopsin, and their axons in the retinohypothalamic tract release glutamate onto neurons in the SCN; the glutamate stimulation leads to increased transcription of the per gene, synchronizing/entraining the molecular clock to the day-night cycle
EEG measures cyclic brain activity
- EEG measures change in membrane potential (mV) over time (mSec)
- EEG measures thousands of neurons and their activity
- this activity is the avg of EPSPs, IPSPs, and action potentials
- the result comes in the form of brain waves called the “field potential”
- field potentials are cyclic (fluctuate up and down)
- cycle can be fast or slow, high or low (amplitude and frequency)
2 classes of sleep
slow-wave sleep (SWS):
- divided into 4 stages and is characterized by slow-wave EEG activity
rapid-eye-movement sleep (REM):
- characterized by small amplitude, fast-EEG waves, no postural tension, and rapid eye movements
dreaming
- occurs during SWS and REM
- during SWS events you experience during the day are replayed (replay is equal to how fast they occur in life)
- during REM replay also occurs, but replay is 10x faster than the experience
- dreaming induces memory consolidation and problem solving
stage 1 sleep
- shows waves of irregular frequency and smaller amplitude called sharp waves
- heart rate slows, muscle tension reduces, eyes move about
- lasts several minutes
stage 2 sleep
- defined by waves of 12 to 14 Hz that occur in bursts, called sleep spindles
- K-complexes appear (sharp negative EEG potentials)
stage 3 sleep
- continued sleep spindles
- defined by the appearance of large-amplitude, very slow waves called delta waves
- delta waves occur about once per second
stage 4 sleep
- delta waves are present about half the time
REM sleep
- active EEG with small-amplitude, high-frequency waves, like an awake person
- muscles are relaxed (called paradoxical sleep)
human sleep patterns change with age
- amount of REM sleep severely declines after one is no longer an infant
- amount of non-REM sleep also decreases with age
several regions regulate sleep/its different parts
- lesion experiments showed that diff sleep systems originate in diff parts of the brain
- lesions between the medulla and spinal cord showed signs of sleep and wakefulness, providing evidence that the change of sleep to wake is in the brain
brain is responsible for sleep wake cycle
transection of lower brainstem produces an isolated brain, which exhibits signs of alternating between wakefulness, SWS, and REM sleep, showing that systems controlling sleep are found in the brain
SWS is produced by forebrain
transection of brainstem at midbrain produces an isolated forebrain, which exhibits signs of constant SWS, showing that a forebrain system promotes SWS and that brainstem promote wakefulness and REM sleep
pons
induces REM
SCN
initiates beginning of sleep through light
forebrain
produces SWS
universal facial expression of emotion
anger sadness happiness fear disgust surprise contempt embarrassment
universal facial emotions
- there is cross-cultural similarity in expression
- the extent of cultural influence in under debate
adrenal glands
corticosteroids and norepinephrine and epinephrine are stress hormones
HPA axis (draw)
–
how does the emotional and physiological tie into the brain?
- the neuroendocrine axes
- areas within brain that produce neurotransmitters known to increase or decrease on physiological/emotional state (example: dopamine is released from VTA when reward is encountered)
brain self stimulation of reward center
- rats have an electrode placed into the midbrain
- these electrodes target medial forebrain bundle (large bundle of axons)
- these axons stem from the VTA and the substantia nigra, the primary regions of the brain that produces the neurotransmitter dopamine