Study Guide 8 notes - Neuromodulation and Circadian Rhythms Practice Flashcards

These flashcards cover neuromodulation systems, circadian rhythm mechanisms involving the SCN and ipRGCs, and the physiological architecture of sleep and melatonin regulation based on the lecture notes.

Diffuse modulatory systems

Systems of neuromodulators which act through volume transmission, typically characterized by projections originating from a small set of core neurons in specific nuclei.

Volume transmission

The mechanism through which diffuse modulatory systems act to release neuromodulators across large areas of the CNS.

Noradrenergic system

A major neuromodulatory system that utilizes norepinephrine to regulate attention, arousal, sleep-wake cycles, learning, memory, anxiety, pain, mood, and brain metabolism.

Serotonergic system

A major neuromodulatory system that utilizes serotonin; it is involved in sleep/wake cycles, stages of sleep, and control of mood and emotional behaviors.

Dopaminergic system

A major neuromodulatory system using dopamine that controls voluntary movements and serves as a reward system reinforcing adaptive behaviors.

Cholinergic system

A major neuromodulatory system using acetylcholine that is implicated in arousal, sleep-wake cycles, learning, and memory.

Suprachiasmatic nucleus (SCN)

The "master clock" located in the hypothalamus that regulates the rhythmic activity of all organ systems and controls circadian fluctuations.

Intrinsically photosensitive retinal ganglion cells (ipRGCs)

Light-responsive cells containing melanopsin that synapse with the SCN via the retinohypothalamic tract to entrain circadian rhythms.

Melanopsin

The photopigment through which intrinsically photosensitive retinal ganglion cells (ipRGCs) respond to light.

Retinohypothalamic tract (RHT)

The pathway through which light signals are transferred from the retina to the anterior hypothalamus and SCN.

Entrainment

The process of determining the SCN's phase based on light signals received via ipRGCs.

Molecular CLOCK and BMAL1

The molecular mechanisms regulated by ipRGCs that help govern circadian rhythms.

Block scheduling

A shift pattern (e.g., nights for a month, days for $2$ months) recommended to allow the SCN and bodily functions sufficient time to adjust to a new schedule.

Electroencephalography (EEG)

A method used to pick up electrical signals (EPSPs) caused by the activity of groups of neurons to characterize different patterns of sleep.

EEG signal generation

Mostly generated through calcium ion flow through cortical pyramidal neurons perpendicular to the surface, creating EPSPs.

Stage $1$ ($N1$)

A stage of non-REM sleep characterized by theta waves.

Stage $2$ ($N2$)

A stage of non-REM sleep characterized by sleep spindles and k complexes.

Stage $3$ ($N3$)

A stage of non-REM sleep characterized by delta waves.

REM ($R$) stage

A sleep stage characterized by fast random waves, where the proportion of this stage increases throughout the night.

Sleep cycle length

Typically about $90\,\text{minutes}$ in a healthy human, including all four stages ($N1$, $N2$, $N3$, and $R$).

Superior cervical ganglion (SCG)

A structure in the pathway between the SCN and the pineal gland involved in signaling the inhibition of melatonin.

Pineal gland

The brain structure where melatonin production is inhibited by light signals and promoted by the lack of light signals.

Melatonin feedback inhibition

A physiological mechanism where increased melatonin release decreases SCN activity.

Blue light

Visible light with the shortest wavelength and highest energy that mimics sunlight and activates ipRGCs to suppress melatonin.

Second-messenger pathways

The pathways through which diffuse modulatory systems change activity to modulate long-term or short-term excitability.

Source of projections

A common feature of neuromodulatory systems where each neuromodulator is localized in one or two specific nuclei.

Thermosensitive SCN neurons

Neurons likely existing in the SCN due to close interactions with temperature-sensitive neurons or involvement in body temperature control pathways.

Jet lag melatonin use

The exogenous use of melatonin to induce sleep by suppressing SCN activity during extreme shifts in light/dark exposure.

Melatonin production peak

The point during the circadian cycle occurring in the middle of the night when light signals are absent.

ipRGC light-response independence

The characteristic where ipRGC response to light is independent of the response of rods and cones.