Major neurochemical pathways Flashcards
1
Q
Dopaminergic pathways
A
- 3 types
1. long paths: nigrostriatal, mesocortical and mesolimbic
2. short paths: tuberoinfundibular and incertohypothalamic pathway
3. ultrashort paths: found in amacrine cells in the retina and in the olfactory system
2
Q
Nigrostriatal pathway
A
- extrapyramidal pathway that is crucial for motor control
- most of the brain’s dopamine
- originates in the substantia nigra and travels to the amygdala and striatum via the medial forebrain bundle
- dopamine deficiency in Parkinsons disease or dopamine blockade due to antipsychotics can cause extrapyramidal side effects
3
Q
Mesolimbic pathway
A
- originates from ventral tegmental area and goes to the nucleus accumbens and hippocampus via medial forebrain bundle
- blockade of dopamine produces desirable antipsychotic effect by controlling positive psychotic symptoms
4
Q
Mesocortical pathway
A
- Originates in the Ventral Tegmental area and travels to the cingulate cortex and prefrontal regions via medial forebrain bundle
- low levels of dopamine or dopamine blockade in this tract is associated with negative symptoms (alogia, anhedonia, amotivation and apathy)
5
Q
Tuberoinfundibular pathway
A
- originates in hypothalamus and travels to the pituitary via the portal vessels
- dopamine acts as prolactin inhibitory hormone
- dopamine blockade serves to increase prolactin level
6
Q
Incertohypothalamic pathway
A
- internal connections within hypothalamus
- dopamine blockade causes disturbed thermoregulation and possible weight gain
7
Q
Cholinergic pathways
A
2 major cholinergic pathways
- brainstem pathway
- basal forebrain pathway
8
Q
Brainstem pathway
A
- cholinergic pathway
- forms part of the ARAS -ascending reticular activating system
- important for maintaining wakefulness and REM sleep state
- originates from pedunculopontine and laterodorsal tegmental nuclei and innervates thalamic relay neurons and reticular nuclei
9
Q
Basal forebrain pathway
A
- cholinergic pathway
- originates at the nucleus basalis of meynert in the basal forebrain and projects to the hippocampus, frontal cortex and amygdala
- degeneration of this pathway is implicated in Alzheimers
10
Q
Serotonergic pathways
A
- originate in the midbrain dorsal and medial raphe nuclei
- ascend to innervate the entire cortex, basal ganglia, thalamus and also descend to the spinal cord
11
Q
Noradrenergic pathways
A
-originates at the locus coeruleus (pons) and ascends to most of the cortex via the medial forebrain bundle
12
Q
Glutamatergic system
A
- glutamate is the most common excitatory neurotransmitter in the brain
- as a result almost all cortical descending tracts (from pyramidal cells) rely on glutamate for neurotransmission
- this large output of corticofugal fibres makes up most of the corona radiata
- all association and commisural fibres also use glutamatergic transmission
- many thalamic neurons are glutamatergic
- thalamocortical projections are also glutamatergic
- cerebellar output from deep nuclei, subthalamic nuclei to globus pallidus projections and braintem to spinal cord projections are also predominantly glutamatergic
13
Q
GABAergic system
A
- primary inhibitory neurotransmitter in the brain
- no specific pathway
- GABA is the major transmitter for cerebral interneurons throughout the cortex
14
Q
Interneurons
A
- usually short neurons
- connect two other neurons
- dont carry motor or sensory information but serve to modulate local neural circuitry
- 2 subtypes: parvalbumin-expressing interneurons and somatostatin expressing interneurons
15
Q
Parvalbumin (PV)-expressing interneurons
A
- 40% of interneurons
- reduction of these is seen in the frontal cortex in schizophrenia
- 2 subtypes: Basket cells and chandelier cells
