20 votes
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Is NMDA produced in the body?

(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 ...
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13 votes
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Why do Hot/Cold drinks taste sweeter once returning to room temperature?

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 ...
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  • 2,573
10 votes

Why do antidepressants have a delayed onset of action?

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 ...
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9 votes
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Can acetylcholine leak away from the synapse and cause spasms?

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 ...
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7 votes
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Humans have Cannabinoid receptors. Does that mean we're meant to consume cannabis?

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 ...
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6 votes

Is there a correlation between total neurons and intelligence?

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 ...
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6 votes

Could an action potential produce few or more neurotransmitters based on the stimulus received?

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 ...
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6 votes
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If action potential is "all or nothing" then how are finely tuned signals sent from one neuron to another?

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 ...
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6 votes
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What is the definition of an opioid, beyond that it's something that stimulates opioid receptors?

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 (...
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5 votes

Could an action potential produce few or more neurotransmitters based on the stimulus received?

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-...
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  • 3,078
5 votes

What controls gut motility?

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 ...
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5 votes

Is there a correlation between total neurons and intelligence?

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 ...
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5 votes

Is there a correlation between total neurons and intelligence?

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 ...
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5 votes
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Why do classic psychedelics not cause withdrawal, despite high tolerance?

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 (...
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5 votes
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Is every neurotransmitter receptor an ion channel?

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 ...
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5 votes

Humans have Cannabinoid receptors. Does that mean we're meant to consume cannabis?

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 ...
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5 votes
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Where are neurotransmitters secreted?

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 ...
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4 votes

Hebbian theory "fire together" clarification

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 ...
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4 votes
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What are the physiological roles of Hydrogen sulfide?

$H_2S$ 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 $CO_2$ ...
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4 votes

Why has evolution made neurons use spiking?

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 ...
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4 votes
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What controls gut motility?

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 ...
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4 votes

Oscillatory electrical system using a chain of neurons

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 ...
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4 votes
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Why do SRIs help in serotonergic neurotransmission?

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 ...
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4 votes
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How do different sensory stimuli differ in nerve signal?

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 ...
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4 votes
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How does receptor downregulation/upregulation work?

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 ...
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4 votes

difference between neurotransmitters and hormones

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, ...
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4 votes
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Inhibitory effect of GABA through GABA(A) receptors

Great question! This apparent contradiction has puzzled many neuroscience students before you. Short Answer: This is often called "shunting inhibition," in particular when excitatory and inhibitory ...
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4 votes
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Is the ACh receptor more permeable to sodium ions?

Short answer No. There are differences in Na+ versus K+ permeability, but you have it backward: potassium is actually slightly more permeable; however, these differences are not the only factors ...
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4 votes

Are neurotransmitters part of the endocrine system?

Short answer Synaptic signaling can be seen as a type of paracrine signaling, and is hence not an example of an endocrine system. Background Khan Academy has a nice accessible overview on this ...
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