The Fundamentals of Neurons and Neurotransmitters

‭Lecture 02 - Fundamentals of Neurons & Neurotransmitters‬

‭🧠‬‭The nervous systems consists primarily of two classes of cells‬
‭○‬ ‭neurons‬
‭○‬ ‭glial cells‬
‭Glial Cells‬
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‭ ‬‭considered the‬‭glue‬‭of the nervous system‬
‭○‬ ‭binds the brain together to facilitate neural functioning and assist neurons in doing their jobs‬
‭🧠‬‭consist of various kinds‬
‭○‬ ‭astrocyte cells‬
‭○‬ ‭oligodendrocyte cells‬
‭■‬ ‭schwann cells‬
‭○‬ ‭microglial cells‬

‭Astrocytes‬
‭🧠‬‭found in the‬‭central nervous system‬
‭🧠‬‭helps create/compose the‬‭Blood Brain Barrier‬
‭○‬ ‭keeps toxins out of the nervous system‬‭(preventing‬‭any hindrance to the brain function)‬
‭🧠‬‭plays crucial role in neural development‬
‭○‬ ‭creates scaffolding in the brain‬
‭🧠‬‭plays a role in responding to injury‬
‭○‬ ‭releases a chemical response to hinder the injury‬

‭Oligodendrocyte‬
‭🧠‬‭found in the‬‭central nervous system‬
‭🧠‬‭insulates the axons of neurons (the info highway)‬
‭○‬ ‭insulates through‬‭myelination‬
‭■‬ ‭wrapping‬‭myelin sheaths‬‭on the axons‬
‭○‬ ‭this ensures the signal reaches the end of axon‬

‭Schwann Cells‬
‭🧠‬‭exact same‬‭functions as‬‭oligodendrocyte cells‬‭, but‬‭are found in neurons outside of the central nervous system‬
‭○‬ ‭found in the peripheral nervous system‬‭(basically‬‭everything except the brain and spine)‬

‭Microglial Cells‬
‭🧠‬‭found in the‬‭central nervous system‬
‭🧠‬‭“scavenger neurons”‬
‭○‬ ‭their function is to eat/dispose of dead or dying neurons‬
‭Neurons‬
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‭ ‬‭the communicative unit of the nervous system‬
‭○‬ ‭transmit signals from one part of the nervous system to another‬
‭🧠‬‭diff kinds‬
‭○‬ ‭motor neurons‬‭- carry motor info‬‭(i.e. how each part‬‭of the body should move)‬

, ‭○‬ ‭sensory neurons‬‭- carry exclusive sensory info)‬
‭■‬ ‭certain ones carry‬‭only‬‭visual info, certain ones‬‭carry‬‭only‬‭auditory info, etc.‬
‭○‬ ‭interneurons‬‭- the powerhouse of the brain, as it‬‭helps compute info to guide behaviour‬
‭■‬ ‭the classification of most neurons (90%)‬
‭■‬ ‭process a wide variety of info‬
‭●‬ ‭memory‬
‭●‬ ‭language‬
‭●‬ ‭attention‬
‭●‬ ‭etc‬
‭Action Potential‬
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‭ ‬‭action potential‬‭= trigger for a signal to be sent‬‭through a neuron‬
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‭ ‬‭the signal is triggered by get excited by surrounding neurons‬
‭○‬ ‭the action potential is triggered when a certain positivity threshold is met‬
‭🧠‬‭the number of signals sent by neurons mean a stimuli is more‬
‭○‬ ‭i.e. louder, brighter, more painful, etc..‬
‭🧠‬‭resting potential = -70‬
‭🧠‬‭action potentials = spikes in positivity‬
‭Propagation of the Signal Down the Axon‬
🧠
‭ ‬‭the signal starts of in the‬‭axon hillock‬‭(‭l‬ ike the‬‭head of the neuron‬‭)‬
🧠
‭ ‬‭travels through the axon‬
‭○‬ ‭passes through the myelin sheaths and‬‭nodes of ranvier‬
‭■‬ ‭gaps between the sheaths that regenerate action potential as the signal weakens as it travels‬
‭down the axon‬
‭Myelin Degradation -‬‭Multiple Sclerosis (MS)‬
🧠
‭ ‬‭progressive myelin degradation, presumably due to an autoimmune disorder‬
🧠
‭ ‬‭caused by the myelin being attacked by the immune system (i.e. autoimmune disorders)‬
‭○‬ ‭damage to myelin could cause damage to the axon‬
‭🧠‬‭it’s neurodegenerative (occurs over time)‬
‭🧠‬‭without myelin signals can’t transfer within the neuron‬
‭🧠‬‭symptoms‬
‭○‬ ‭impact to memory -‬‭forgetfulness‬
‭○‬ ‭impacts the senses‬
‭○‬ ‭impacts motor pathways and hinders capabilities of moving (i.e. walking becomes impaired)‬
‭🧠‬‭the symptoms are heterogenous‬
‭○‬ ‭differ across individuals depending on where the MS starts degradation of the myelin‬
‭🧠‬‭highest rates of MS in the world are in Canada‬
‭○‬ ‭this is due to the Northern geography and exposure to sunlight and temperatures‬
‭Motor Neuron Disease -‬‭Amyotrophic Lateral Sclerosis‬‭(ALS)‬
🧠
‭ ‬‭a rapidly progressing upper and lower motor disease‬
‭○‬ ‭results in death‬
‭🧠‬‭motor neurons get attacked‬