Objectives
- Describe the neuronal and nonneuronal structures in the brain and their primary functions
- Describe the key features of electrical and chemical signalling in the nervous system and have some insight into the clinical relevance of this knowledge
- Give and account of how these basic features of neuronal function give rise to computing power of neural networks in the brain.
- Understand that higher brain functions arise from normal asynchronous activity in brain circuits and the sanfer of synchrony as expressed in epilepsy
Neuronal and Non-Neuronal structures
Neuronal structures
You have about 100 billion neurons. Big number but not that big compared to other things.
Each neuron has a cell body and dendrites which receive synapses and where local potentials meld and sometimes trigger APs. you need ligand gated ion channels for the initiation of an AP which is found on the dendrites and cell body. Then the axon hillock is where an local potentials sum to cross threshold and create an AP.
Non-Neuronal structures
Non neuronal structures includes the: ependyma and meninges, as well as gila
Glia
- Microglia These phagocytose dead tissue and debris (Basically macrophages)
- Astrocytes These make up 20-50% of brain volume and - regulate blood brain barrieri - contribute to structural integrity - regulate ECF K+ at nodes of ranvier - ensheathe synapses dendrites etc to metabolise adn release neurotransmitters - connect to one another to form a syncytium
- Oligodendrocytes myelinate CNS
A note on glia biology
glia are the source of many brain tumours and also a current field of research on how the syncytium functions and effects the brain.
Signalling in the brain
Terminology
Emergence
Emergence is the biological concept of a whole thing having functionality that is more then the sum of its parts. Just how a bicycle has the ability to glide along and be powered by your feet which is not a function that is evenly divisible to its parts and is only present as a whole and is not the sum of its parts, your conscious being is the emergent sum of the individual connections, thresholds and interaction of neurons and non-neuronal structures in the brain. These rigid structures complying to the basic laws of chemistry and physics have the emergent functionality of your conscious being and there are a few ways this is achieved.
It is hard to understand as a whole but using a small example of the interactions are neural networks, an early type of AI modeled after the human brain.
Some basic interactions are: