There are two motor neurons in an autonomic motor pathway. The first neuron is called a preganglionic neuron and its cell body is located in the brain or spinal chord. Its axon (very long) leaves the CNS and extends (as part of a spinal or cranial nerve) to an autonomic ganglion. The second neuron is called the post ganglionic neuron and its axon is short. The preganglionic neurons pass along nerve impulses from the CNS to the autonomic ganglia and the postganglionic neurons relay the impulse from the autonomic ganglia to the terminal target, which could be smooth muscle, cardiac muscle or a gland. The neurotransmitter that is released is always excitatory and is always Ach. The #2 neuron always produces an action potential. Wether the terminal target becomes excited depends on its receptors. They are usually cholinergeric and thus are either Nicotinic (excitatory) or muscarinic (inhibitory).
After browsing the internet, I learned that a malfunction in the autonimic system is called autonomic failure and is a result of the imbalance between the sympathetic and parasympathetic divisions of the autonomic nervous system. Signs that there is an imbalance include orthostatic hypotension and postprandial hypotension. These can cause dizzyness or lightheadedness. Elderly people are most likely to suffer from this condition and the drop in blood pressure is usually a result of the onset of a disease (diabetes, stroke) and the medications that are used to treat them. There is no cure for autonomic disorders, however there are medications that can treat the low blood pressure and the uncomfortableness that accompanies the episodes.
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Ericka,
ReplyDeleteYou are doing such an amazing job with your blogs...I have just finished reading all four of your postings and they are exactly what I had hoped for!You are summarizing the key points from each lecture and relating or researching related lecture topics of interest to your understanding of the material. Excellent! There are a few minor inaccuracies in this blog based (no doubt) on the fact that I haven't covered all of the material on the ANS, yet...hopefully this will all become clearer after our lecture next week!
Dana
PS The reference to layers in the brain (layers II and III) refer to the actual number of layers of cells in the cerebral cortex (which total VI layers). Each of these layers are stacked on top of one another in distinct columns like stacks of pennies. This level of organization allows for more efficient neural "communication" by establishing "near neighbors" that must communicate on a regular basis...very cool!