Amygdala Flashcards
Name the six neuronal oscillations from lowest to highest frequency.
Delta.
Theta.
Alpha.
Mu.
Beta.
Gamma.
When are delta waves seen?
<4 Hz.
Deep sleep.
When are theta waves seen?
4-7 Hz.
Sleep and wakefulness.
When are alpha waves seen?
8-13 Hz.
Largest over occipital cortex during quiet wakeful states.
When are mu waves seen?
8-13 Hz.
Cortical specific, largest over motor and somatosensory cortices, similar to alpha waves.
When are beta waves seen?
15-30 Hz.
When are gamma waves seen?
30-90 Hz.
Attentiveness or highly active cortex, underpin attentional processes like working memory, intrinsically generated.
What are spindles?
8-14 Hz.
Seen during sleep.
What are ripples?
8-200 Hz.
Brief bursts of high neural activity.
Why does each postsynaptic potential increase in size throughout the period of stimulation?
AP causes Cav channels to open, leading to calcium influx and NT release.
When another AP arrives soon after the first, the second postsynaptic potential occurs at an elevated level of intracellular calcium since the calcium pump hasn’t returned to resting levels.
This triggers more NT release and hence a larger postsynaptic potential.
Describe the first stage of sleep.
Theta waves.
4-8 Hz.
Large amplitudes of 50-100 uV.
Describe the second stage of sleep.
Sleep spindles.
10-12 Hz.
Occur periodically in bursts that last for a few seconds.
Spontaneously occurring K complexes.
Sharp, high voltage, bi-phasic wave that lasts for more than 0.5 seconds.
Describe the third and fourth stages of sleep.
Delta waves.
0.5-4 Hz.
Describe REM sleep.
High frequency brain rhythms similar to those seen in the awake state (alpha, beta and gamma).
Body is immobilised except eyes and respiratory muscles.
Why is non-REM sleep sometimes referred to as slow-wave sleep?
Due to the large, slow, high amplitude theta and delta rhythms generated during this time.
Non-REM sleep involves increased activity of the parasympathetic ANS, which results in what?
Reduced muscle tension.
Reduced temperature and energy consumption.
Reduced heart rate, respiration and kidney function.
Minimal movement.
Increased digestive processes.
Why are K complexes thought to exist?
They are thought to be responses to internal or external stimuli, e.g. respiratory interruption or touch on the skin.
Where are K complexes mostly localised?
Frontal and superior frontal cortices.
REM sleep involves increased activity of the sympathetic ANS, which results in what?
Reduced core temperature.
Increased, irregular heart and breathing rates.
What are the suprachiasmatic nuclei (SCN)?
Bilateral structure found in the anterior hypothalamus. Regulates circadian rhythms in the body.
Name the three neuropeptides expressed by the SCN.
Vasoactive-intestinal peptide (VIP).
Gastrin-releasing peptide (GRP).
Arginine-vasopressin (AVP).
When is VIP expressed and what is its function?
Increases during dark period/night time.
Controls daily circadian rhythms and maintains internal synchronisation of the SCN.
When is GRP expressed?
Activated by direct light input.
Increases in the morning and peaks around midday.
What is the function of AVP?
Coordinates circadian feeding rhythms and thirst controlling neurons.
How does light reset the oscillations in the SCN?
Melanopsin-containing retinal ganglion cells project directly to the SCN via the retino-hypothalamic tract.
Describe the indirect pathway that the SCN projects circadian information down.
Projects down into the cord and back up into the pineal gland where melatonin is produced.
Name the five key NTs of the sleep-wake cycle.
Noradrenaline.
Serotonin.
Acetylcholine.
Hypocretin.
Histamine.
What is the function of melatonin?
It is released as the environment darkens. It promotes and maintains sleep.
Brain levels of nitric oxide are at their highest during wakefulness and rise rapidly as we become more sleep deprived. What is the result of this?
It triggers the release of adenosine.
What does the release of adenosine result in?
Inhibits the acetylcholine, noradrenaline and serotonin modulatory systems, causing the brain to fall into the slow-wave synchronous theta and delta activity of non-REM sleep.
What causes the synchronous activity during delta rhythms?
Neural interconnections within the thalamus, and between the thalamus and cortex.
How does the thalamus project to the cerebral cortex?
In a bi-directional thalamo-cortical network which modulates the flow of sensory and motor information to and from the cortex.
What neurons make up the bi-directional thalamo-cortical tract?
Excitatory relay neurons.
Inhibitory neurons.
GABAergic inhibitory reticular neurons.
Interneurons.
Which neurons generate sleep spindles and K complexes, and what do this represent?
GABAergic inhibitory reticular neurons.
Represents synchronised oscillatory electrical activity between these neurons and the thalamo-cortical relay neurons.
Where are GABAergic inhibitory reticular neurons located?
In a sheet-like nucleus that covers most of the rostral, lateral and ventral parts of the thalamus.
Adenosine levels decrease while we sleep, which results in what?
Increased activity in the acetylcholine, noradrenaline, serotonin and histamine systems.
Where is noradrenaline expressed from?
The locus coeruleus in the pons.
The locus coeruleus has one axon branch in where and the other in where?
Cerebral cortex and cerebellar cortex.
How does noradrenaline affect the neurons of the locus coeruleus?
Makes them more responsive to sensory stimuli and increases the brain’s responsiveness - an important feature as you wake up.
Where is serotonin expressed from?
Raphe nuclei.
When do raphe nuclei neurons fire most rapidly?
When you are awake and active.
What are the key components of the reticular activating system, and what is its purpose?
Locus coeruleus and raphe nuclei.
Arouse and awaken the forebrain.
Acetylcholine is expressed within the basal forebrain for what purpose?
To regulate general brain excitability during arousal and sleep-wake cycles.
Acetylcholine is expressed within the midbrain and pons for what purpose?
Projects to the thalamus to regulate the excitability of sensory relay nuclei.
Describe the cholinergic pathway and its function.
Sensory relay nuclei project up to the telencephalon to provide a cholinergic link between the brainstem and basal forebrain. This pathway is key to activation and wakefulness.
Which neurons express histamine?
Midbrain neurons.
Which neurons express hypocretin?
Neurons of the lateral hypothalamus.
What is the function of hypocretin?
Excite neurons of the cholinergic, noradrenergic, serotonergic, dopaminergic and histaminergic systems.
Inhibits REM sleep by promoting wakefulness and facilitating neurons that enhance motor behaviours.
Regulates neuroendocrine and autonomic systems.
Just before we wake, which hormones are released and why?
Glucocorticoids, e.g. cortisol.
To prepare the brain and body for physical and cognitive activity.
