Through what function does input become output in a neuron?

Question

I've never taken any biology courses, so this is kind of a shot in the dark.

Obviously there are more than one, but do we know Any biological, neurological processes that can be put in terms of a mathematical function? I know that there are different types of systems in the nervous system... i'm just wondering what determines the output given the input, in other words what happens to the action potential as it travels through an individual neuron. Perhaps they've measured such in individual giant squid neurons?

With over 100 billion neurons, i can't imagine the process needs to be too significant in order to achieve emergence, yet i really have no idea what types of processes can turn raw data into sensation, perception, and awareness...

Thanks!

Very helpful, but I'm more looking for How the input signal is modified to become a different output signal in an instance where the signal is being modified instead of just passed along. Maybe i'm missing something? Further, I was hoping to get some kind of mathematical function, for instance in neuron z, the input electrical signal is modified by the function f(z)=rx^2/logA ... Maybe we don't know such a thing yet?

Answer 1

As sami said we have neurotransmitters- chemical substances stored in small packets at the terminals of the nerve. As the action potential moves along the axon, there occurs influx of sodium ions , reaches the terminal where along with sodium channels, calcium channels are also opened because they are voltage gated. These calcium channels cause the small packets to adhere to the nerve membrane. Then through exocytosis the transmitter is released into the space. It reaches the next neuron , opens the gates , influx of sodium ions and so on till it reaches the somatosensory cortex. Here, sensation from the particular receptor ie the specialised nerve ending from which the action potential arose is perceived and iterpreted. Labeled line principle states that a receptor is unique for a single modality.

Answer 2

Neurotransmitters are chemicals activated by changes in ACTION POTENTIALS
Substances that act as neurotransmitters can be roughly categorized into three major groups: (1) amino acids (primarily glutamic acid, GABA, aspartic acid & glycine), (2) peptides (vasopressin, somatostatin, neurotensin, etc.) and (3) monoamines (norepinephrine NA, dopamine DA & serotonin 5-HT) plus acetylcholine (ACh). The major "workhorse" neurotransmitters of the brain are glutamic acid (=glutamate) and GABA. Neurotransmitters can be broadly classified into small-molecule transmitters and neuroactive peptides. Around 10 small-molecule neurotransmitters are known: acetylcholine, 5 amines, and 3 or 4 amino acids are neurotransmitters. .

It is important to appreciate that it is the receptor that dictates the neurotransmitter's effect.

Some examples of neurotransmitter action:

Acetylcholine - voluntary movement of the muscles
Norepinephrine - wakefulness or arousal
Dopamine - voluntary movement and emotional arousal
Serotonin - memory, emotions, wakefulness, sleep and temperature regulation
GABA (gamma aminobutyric acid) - motor behaviour
Glycine - spinal reflexes and motor behaviour
Neuromodulators - sensory transmission-especially pain
Mechanism of action
Within the cells, small-molecule neurotransmitter molecules are usually packaged in vesicles. When an action potential travels to the synapse, the rapid depolarization causes calcium ion channels to open. Calcium then stimulates the transport of vesicles to the synaptic membrane; the vesicle and cell membrane fuse, leading to the release of the packaged neurotransmitter, a mechanism called exocytosis.

The neurotransmitters then diffuse across the synaptic cleft to bind to receptors. The receptors are broadly classified into ionotropic and metabotropic receptors. Ionotropic receptors are ligand-gated ion channels that open or close through neurotransmitter binding. Metabotropic receptors, which can have a diverse range of effects on a cell, transduct the signal by secondary messenger systems, or G-proteins.

Neuroactive peptides are made in the neuron's soma and are transported through the axon to the synapse. They are usually packaged into dense-core vesicles and are released through a similar, but metabolically distinct, form of exocytosis used for small-molecule synaptic vesicles.

Post-synaptic effect
A neurotransmitter's effect is determined by its receptor. For example, GABA can act on both rapid or slow inhibitory receptors (the GABA-A and GABA-B receptor respectively). Many other neurotransmitters, however, may have excitatory or inhibitory actions depending on which receptor they bind to.

Neurotransmitters may cause either excitatory or inhibitory post-synaptic potentials. That is, they may help the initiation of a nerve impulse in the receiving neuron, or they may discourage such an impulse by modifying the local membrane voltage potential. In the central nervous system, combined input from several synapses is usually required to trigger an action potential. Glutamate is the most prominent of excitatory transmitters; GABA and glycine are well-known inhibitory neurotransmitters.

Many neurotransmitters are removed from the synaptic cleft by neurotransmitter transporters in a process called reuptake (or often simply 'uptake'). Without reuptake, the molecules might continue to stimulate or inhibit the firing of the postsynaptic neuron. Another mechanism for removal of a neurotransmitter is digestion by an enzyme. For example, at cholinergic synapses (where acetylcholine is the neurotransmitter), the enzyme acetylcholinesterase breaks down the acetylcholine. Neuroactive peptides are often removed from the cleft by diffusion, and eventually broken down by proteases.



While some neurotransmitters (glutamate, GABA, glycine) are used very generally throughout the central nervous system, others can have more specific effects, such as on the Autonomic nervous system, by both pathways in the sympathetic nervous system and the parasympathetic nervous system, and the action of others are regulated by distinct classes of nerve clusters which can be arranged in lamilar pathways around the brain. For example, Serotonin is released specifically by cells in the brainstem, in an area called the raphe nuclei, but travels around the brain along the medial forebrain bundle activating the cortex, hippocampus, thalamus, hypothalamus and cerebellum. Also, it is released in the Caudal serotonin nuclei, so as to have effect on the spinal cord. In the peripherial nervous