Diffuse Modulatory Systems Flashcards
What are the midbrain nuclei involved in the dopaminergic diffuse modulatory system?
The substantia nigra and ventral tegumental area (VTA).
What are the four central dopaminergic pathways?
The nigrostriatal system, the mesolimbic pathway, the mesocortical pathway, and the tuberoinfundibular pathway.
What is the nigrostriatal system?
Dopaminergic projections from the substantia nigra to the striatum (basal ganglia circuits). Accounts for 80% of the brain’s dopamine.
What is the mesolimbic pathway?
Dopaminergic projections from the ventral tegumentum area (VTA) to the nucleus accumbens (ventral striatum). The nucleus accumbens is activated to inhibit the ventral pallidum (like the globus pallidus).
What is the mesolimbic pathway associated with?
Feelings of reward and desire.
What is the mesocortical pathway?
Dopaminergic projections from the VTA to the frontal cortex and surrounding structures. Affects mood via higher pathways.
What is the tuberoinfundibular pathway?
Dopaminergic projections from the arcuate nucleus (hypothalamus) to the anterior pituitary (inhibition of prolactin release).
What dopaminergic nucleus projects to the dorsal striatum?
The substantia nigra pars compacta.
What are the axonal specializations that allow for extrasynaptic release of neurotransmitter?
Varicosities.
What part of the neuron contains dopamine re-uptake in extrasynaptic and classical synaptic neurotransmitter communication?
The part that released the neurotransmitter/dopamine. This would be the varicosities for extra-synaptic release and the synaptic bulb for classical synaptic release.
What is the purpose of having extra-synaptic neurotransmitter release?
To have neuromodulatory actions (as opposed to selectively activating select neurons as with classical synaptic release).
What is the hypothalamic nucleus involved in the histamine diffuse modulatory system?
The tuberomammillary nucleus.
What is the effect of activating H1 receptors in regards to the sleep/awake cycle?
H1 activation promotes wakefulness and attention (why antihistamines cause drowsiness).
What type of GPCR are H1 receptors?
Gq (increased intracellular Ca2+ and PLC, ect).
Where are H1 receptors usually found in the CNS?
They are post-synaptic receptors.
Where are H3 receptors usually found in the CNS?
They are pre-synaptic receptors and serve to prevent excessive histamine release.
What type of GPCR are H3 receptors?
Gi (decreased cAMP).
What are the nuclei that make up the acetylcholinergic diffuse modulatory system?
The basal nucleus of Maynert, the medial septal nuclei, and the pontomesencephalo-tegmental complex.
What is the basal nucleus of Maynert involved in?
It is involved in memory (decreased in Alzheimer’s).
What are the medial septal nuclei involved in?
The reward pathway (addiction, ect).
What nuclei make up the pontomesencephalo-tegmental complex?
The lateraldorsal tegmental nucleus and pedunculopontine nucleus
Where is the pontomesencephalo-tegmental complex located?
In the midbrain.
What acetylcholinergic complex projects axons to the reticular formation to cause muscle atonia during REM sleep?
The pontomesencephalo-tegmental complex (pedunculopontine nucleus).
What structures make up the epithalamus?
The habenula, the habenular commissure, and the pineal gland.
What is the habenula involved with?
Regulating the diffuse modulatory systems.
What fiber bundle conveys acetylcholinergic axons from the medial septal nuclei to the habenular nuclei?
The stria medullaris (remember, the septal nuclei are involved in feelings of reward, and so sends axons to the habenular nuclei which are involved in punishment)
What does the stria medullaris mediate?
The medial septal nuclei are involved in feelings of reward, and so sends axons to the habenular nuclei which are involved in punishment.
What nuclei makes up the serotoninergic diffuse modulatory system?
The raphe nuclei (located mid-line around the pontine-medullary junction).
What effect of serotonin do enkephalinergic interneurons mediate in the dorsal horn of the spinal cord?
Serotonin promotes enkephalinergic interneurons to inhibit pain signals in the dorsal horn (serotonin is involved in pain modulation).
What is the role of the medial habenular nucleus?
It is one of the main regulators of the descending serotonin pathways from the raphe nuclei that modulate pain.
What midbrain nucleus acts as an intermediate center for projections from the medial habenular nucleus to the raphe nuclei?
The interpenduncular nucleus.
What fiber bundle conveys habenular axons to the interpenduncular nucleus?
The fasciculus retroflexus.
What is the principle catecholaminergic nucleus involved in the noradrenergic diffuse modulatory system?
The locus coeruleus.
What receptor is activated on dorsal horn neurons via descending fibers from the locus coeruleus that results in pain inhibition?
Alpha-2 receptors (Gi).
