sleep

Question 1

.Describe properties of biological rhythms

Answer 1

Zeitbgeber: cur that an organism uses to synchronize with its environment
Entrainment: process of shifting rhythms
Period: time between two similar points of successive cycles
Phase shift: shift in periodic activity due to a synchronizing stimulus
Free running: organism maintaining its own cycle without external cues

Question 2

Describe function of the suprachiasmatic nucleus (SCN

Answer 2

In mammals the circadian rhythm is maintained by the SCN
Located in the hypothalamus
SCN neurons can maintain electrical activity synchronized to previous light cycle

Question 3

Describe the methods, results, and implications of:
basic rodent circadian rhythm
SCN lesions
SCN transplants

Answer 3

1.Basic rodent circadian rhythm experiment
Compare activity in 24 hour periods from activity on a wheel. Manipulate the presence of light
They begin their activity just before it gets dark. If change when it gets dark they adapt
Without light at all they run on a 25 hour time (internal circadian rhythm)
2.SCN lesion studies
SCN lesions disrupt the circadian rhythm
If keep the zeitgeber then can still keep ok rhythm
Get rid of zeitgeber (no light at all) and it is apparent they have no rhythm
3.SCN transplant studies
Rhythm begins normally
After the lesion activity is more disorganized
Transplant with SCN of rodent with shorter circadian period
After a dealy the rhythm is expressed in free run and proves that SCN is the endogenous
driver of scicadian rhythm

Question 4

Describe molecular clock of SCN

Answer 4

SCN cells produce 2 unique proteins, clock and cycle
Clock and cycle bind to form a dimer
The dimer promotes transcription of period (per) and cryptochrome (cry)
Per and cry then dimerize
per/cry protein enters nucleus and inhibits transcription of more per/cry (neg feedback)
No new per/cry until the per/cry that is blocking degrades (about 24 hours in humans)
Light induced ipGRC activation releases glutamate onto SCN, glutamate promotes increased
Transcription of per, this shifts the phase of molec clock

Question 5

Describe basics of electroencephalography measurement

Answer 5

Measures neuronal electrical fields (EPSP and IPSP) NOT action potentials (theyre too short and
Go in too many directions
More specific, measures synchronized electrical ields of neural populations
Shows as oscillations or brain waves

Question 6

Describe features of the different sleep stages

Answer 6

NREM: non rem, 3 stages characterized by eye movements
REM: characterized by small amp, fast EEG waves, no postural tension, rapid eye movements
NREM1: transition out of wakefulness, heart rate slows, muscle tension decreases, eyes roll.
Diminish control over thought processes, decreasing alpha power, theta riples, vertex spikes,
Incomplete spindles
NREM2: diminished probability of dreaming, theta wave dominant, complete spindles, k complex
NREM 3-4: lowest prob of dreaming or other cog activity, most difficult to wake from, large-amp
Slow waves (delta), hippocampal sharp wave ripples, spindles cont
REM: muscles are relaxed, active EG with small amp, high freq waves (like awake),
Highest prob of dreaming

Question 7

Describe how sleep changes over the course of a night in terms of stages

Answer 7

Tends to go awake 1, 2, 3, 2, REM, 2, 3, 2, REM, 2, 3, 2, REM etc
May have small wakings after REM
REM episodes get longer
Cycles are 90-110 mins

Question 8

Describe basic across species similarities and differences with sleep

Answer 8

Differences: fish have ‘sleep like’ state, in dolphins and birds only one hemisphere enters SWS
At a time while the other remains awake
Similarities: nearly all mammals display NREM and REM

Question 9

.Describe possible functions of sleep
basic mechanisms of glyphatic syst
experimental test of sleep and mem consolidation

Answer 9

1.Describe basic mechanisms of glymphatic system
Fluid transport system that accesses all regions of the brain
Clears waste from the metabolically active brain
Occurs in extracellular and perivascular spaces
Happens through cerebrospinal fluid and interstitial fluid
Most active in sleep
‘Flushing’ the brain of waste filled interstitial fluid
2.Describe experimental test of sleep and memory consolidation
Hippocampal indexing theory: sleep facilitates reactivation of cortical hippocampal neural
Ensembles
NREM slow wave sleep appears more important than REM for memory consolidation
Sleep esp REM promotes neurocog development bc REM provides unique stimulation