20
(my comment reiterating the answer seemed useful, so I've reproduced it here)
There are "NMDA receptors" in our body. There is not NMDA naturally in our body*. "NMDA receptor" is just a name people gave to one of the receptors that normally binds glutamate. They could have called it something else, like the "slow glu receptor", or "Glutamate Receptor A", ...
13
Generally, cold suppresses sweetness. As an example, consider soft drinks that are usually served cold: they taste sweeter when warm (like you said with your examples of drinks).
Our taste receptors send a stronger signal to the brain when activated by warmer substances and so the perception of sweetness, in this case, is lessened when we consume cold food ...
10
Short answer
The mechanism of action of serotonin-specific reuptake inhibitors, a commonly-prescribed class of antidepressants, is a downregulation of 5HT1A receptors through negative feedback. This downregulation of receptors takes time.
Background
Serotonin-specific reuptake inhibitors (SSRIs) are a class of antidepressants commonly prescribed to treat ...
9
The enzyme responsible for the breakdown of acetylcholine (Ach), i.e., acetylcholinesterase, rapidly degrades, and inactivates Ach in the synaptic cleft after release. This process is particularly fast, as the synapse has to be cleared of neurotransmitter for a next action potential to occur (Čolović et al., 2013). So no, Ach does not leak away under ...
7
One of the many advantage of an all-or-none system is that resources can be conserved for timing events that require synchronized collaboration between many cells (like locomotion). Binary behavior may also partially be a side effect of speed and efficient long-distance information transfer (which is one of the great advantages of neurons as cells in the ...
7
Receptors
Any drug or compound with specific effects has a receptor. You can read about this general concept in Goodman and Gillman's The Pharmacological Basis of Therapeutics. Chapter 1 introduces the concept, chapters 3 and 5 expand further. As far as the history of this concept is concerned, receptors mediating the specificity of action was first clearly ...
6
There are an estimated 100 billion neurons within the human brain. In general a minor variation in the number of neurons should not effect individuals too much, however when there is a more significant loss, such as brain injury or in some forms of dementia cognitive abilities do decline. So in this sense yes the number of neurons does relate to intelligence....
6
Short answer
Widening of the action potential increases neurotransmitter release;
Generally, an action potential results in the release of about one vesicle of neurotranmitters;
An action potential does not have to lead to neurotransmitter release - the chance being anywhere between 9 - 100%, depending on the synapse under investigation.
Background
...
6
how is one type of neurotransmitter secreted rather than another
Most neurons release a single major neurotransmitter. JM97 commented a link about cells releasing more than one, but that is talking about "extra" neurotransmitters are short peptides, different from the major neurotransmitters like glutamate, GABA, acetylcholine, dopamine, norepinephrine, etc ...
6
First there was opium. Then the active components of opium (morphine etc.) were defined and called opiates. Then the receptors for opiates were discovered, along with their endogenous ligands (enkephalins etc.), and since those endogenous ligands were not derived from opium and indeed (being peptides) were not chemically related to opiates, a new term was ...
5
One thing I think you're missing: a perceptron model and a spiking model aren't mutually exclusive. In fact, in perceptrons, people usually use a sigmoid function. That's not a coincidence: it kind of simulates a spike. If you were to model an organism such as C. elegans, whose neurons aren't spiking (but use "graded action potentials"), you would use ...
5
Unlike a computer, the speed at which any brain can perform a computation is related to the number of synapses it goes through. This means fewer synapses in series correlate with decreased reaction time.
An example of fewer neurons correlating with a decrease in reaction time is exemplified in sensory neurons. All sensory nerve cell bodies are all located ...
5
I know of no correlation between number of neurons in cortex and intelligence. This question is fraught with controversy because there has been very little work on it but much speculation. Some have suggested that the connectivity between neurons is what is important rather than the number which is logically possible but remains to be supported by definitive ...
5
When discussing the control of gut motility there is more to mention than the use of serotonergics and opioids - a number of peptide and nonpeptide neurotransmitters are important. Somatostatin and nitric oxide are two examples which each happen be inhibitory of intestinal motor function, but by two completely different mechanisms. A bit of understanding in ...
5
Neurons encode the "largness" of the stimulus in firing frequency. Neurotransmitters are stored in vesicules near the end of the axon. It has been shown that neurotransmitter release follows Poisson-distribution and that usually a single "packet" (quantum) is released - this is known as quantal release. Although the actual number of molecules in a single ...
5
Short answer
Withdrawal effects are generally associated with drugs that induce feelings of euphoria by stimulating the reward center of the brain, either directly (cocaine, morphine) or indirectly (alcohol, nicotine). The classic hallucinogens have little effect on the dopaminergic pathways and hence do not cause serious withdrawal effects as observed with ...
5
is every neurotransmitter receptor also an ion channel?
No.
There are two general types of receptors for neurotransmitters, ligand gated ion channels and receptors that activate second messenger systems, for example, G protein coupled receptors. They are sometimes referred to as ionotropic and metabotropic receptors. This figure from Principles of Neural ...
5
In addition to De Novo's excellent answer, I would like to add that sometimes, the fact that we have receptors for something is precisely a sign that we should not consume that thing.
When it comes to taste and smell in particular, many receptors are evolutionarily conserved precisely because their physiological role is to warn us of a danger. For example, ...
5
There are proteins (in truth, small peptides) released by neurons, but these are not the most typical or canonical type so I don't know where you got that information. Wikipedia has a list. Most are amino acids or derived from amino acids. They are transported into vesicles and then released when these vesicles fuse with the plasma membrane.
...
4
They are two different mechanisms.
Opium is arguably one of the oldest herbal medicines, being used as analgesic, sedative and antidiarrheal drug for thousands of years. These effects mirror the actions of the endogenous opioid system and are mediated by the principal μ-, κ- and δ-opioid receptors. In the gut, met-enkephalin, leu-enkephalin, β-endorphin ...
4
The use of spikes is a mixture of their computational advantages and the limitations of the biological substrate in which they are implemented:
They can travel long distances at high speeds because they can profit from the saltatory conduction which is much faster than diffusion and it can be maintained over long distances. A digital signal is less prone to ...
4
Dr. Helen Fisher's conclusions are plain bunkum. What does it even mean when she says associated with a particular neurotransmitter? The sheer work required to even get at this question is vast and difficult so it is unsurprising that she is venturing as much as a guess.There is scientific evidence to support different neurotransmitters systems can go awry ...
4
Strictly stated, Hebb's rule applies only to existing synapses, and not to the formation of new synapses. (This answer applies to biological neurons, not to ANNs).
Synapse formation is a topic of active research. During development (and in fact continuously even during adulthood), many synapses are created and destroyed. It is not unreasonable to suspect ...
4
$H_2S$ is the end product of sulfur related respirations (like sulfate respiration, sulfur respiration, etc...).
By aerob (oxygen) respiration the oxygen in $O_2$ has 0 oxidation number, by $CO_2$ the oxygen has -2 oxidation number, so it was reduced while the carbon was oxidized.
By the thiosulfate respiration of Salmonella enterica the following reaction ...
4
Short answer
A single pacemaker neuron can generate oscillatory behavior.
Background
Given our exchange in the comments, I will focus on single neurons with intrinsic oscillatory behavior. For example, thalamocortical relay neurons and inferior olive neurons have intrinsic oscillatory properties, mainly through the interaction of a hyperpolarization-...
4
Excellent question.
Different neurotransmitters operate at different temporal scales (and even the same transmitter can operate at different temporal scales). Examples of the fastest-acting neurotransmitters are glutamate, GABA, and acetylcholine (with the caveat that they can also act more slowly). These neurotransmitters (usually) open ion channels in the ...
4
I think the short answer to your question is that the contents of different types of sensory stimulation are communicated to different populations of cells in the brain (note this transmission is mostly glutamatergic, not cholinergic). From there, the remaining associations and experiences derive from connectivity with other networks of brain neurons that ...
4
Both internalization (sometimes with degradation) and changes in gene expression can occur; the circumstances leading to the down regulation determine which (or both). It isn't necessary for receptors to be bound to their ligand to be internalized, though, and it isn't the internalization of receptors that causes changes in gene expression (I suppose it is ...
4
At heart, the distinction between neurotransmitters and hormones is how they are transmitted - not necessarily a difference in the chemicals themselves.
Neurotransmitters are sent over synapses, between neurons. They may be small molecules (e.g. dopamine) or larger molecules such as proteins (e.g. substance P). Conversely, hormones are sent through the ...
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