This week the topic of last week was continued: Neurotransmitter systems.
I found good that the lecture was started with a revision of what had been done in the previous lecture. We then started with acethylcolinergic pathways as one of the diffuse brain systems. This pathway is thought to be linked to Alzheimer’s disease as the death of ACh cells was found together with early signs of the disease. Alzheimer’s disease is therefore characterized as a neurodegenerative disease and also as a form of dementia because it is linked to memory loss and cognitive impairment. To decelerate the progress of the disease the patients can take drugs which inhibit acethylcholinesterase to raise the acethylcholin levels in the brain. However, these drugs can neither cure the disease nor stop the progress completely.
ACh in the nucleus basalis of Meynert is also believed to play a role in learning progress by interpreting sensory stimuli.
Another diffuse brain system are the norepinephrine pathways. These pathways that ascend from the Locus Coeruleus widely innervate the brain as there are around twelve thousand neurons in the LC, each with around 250 thousand synapses. Each neuron can innervate both cortex and cerebellum. The NE pathways were found to react to salient environmental stimuli, leading to increased alertness, the enhancement of formation and retrieval of memory, and more focused attention, but they are also connected to mood, particularly to clinical depression, as norepineohrine increases restlessness and anxiety.
We went on to the dopamine pathways of the brain, the nigrostriatal pathway and the mesocortical and -limbic pathways. The dopamine pathways might be connected to Parkinson’s disease, as patients suffering from this disease were found to have low levels of dopamine in their basal ganglia. These low levels are a result of the death of dopamine neurons in the substantia nigra. There is no cure for the disease yet, but it is possible to improve movement related problems by giving the patients the drug L-Dopa which increases the dopamine levels in the basal ganglia.
The third diffuse brain system is the serotonin system. These pathways ascending from the Raphe nuclei in the brainstem innervate almost the whole brain. The serotonin system regulates wakefulness and arousal but was also found to play a role in mood. Together with the norepinephrine pathways it forms the reticular activation system of the brain.
After that we discussed the roles of hypothalamus and pituitary in controlling hormones and talked about the autonomic nervous system. The lecture was ended with an overall principle of neurotransmitter system functions, including that “everything influences everything” and that the change in the activity of one neurotransmitter system, for example through drugs, can widely influence other neurotransmitter systems, often in unpredictable ways, followed by a summary of what had been done in this lecture.
I really liked the references to current research status in some diseases and hope that the next weeks will include that as well and feature summaries of what has been done so far too.