25
votes
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Is C. elegans always observed with precisely 302 neurons? Are there ever individual viable exceptions?
According to the highly respected WORMATLAS: A Database of Behavioral and Structural Anatomy of Caenorhabditis elegans, the number is invariable in this animal, one of the most studied in the world.
...
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12
votes
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The human brain in numbers I: neurons
First of all, let me clear out that these numbers are calculated, not observed (obviously, nobody has counted the number of neurons in any part of brain). So, take these with a grain of salt.
I was ...
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12
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Do self-exciting neurons exist?
Short Answer
Yes, autapses exist, though the role of excitatory autapses in particular is unclear.
Long Answer
A lot of your assumptions are wrong for biological neurons (I'm suspecting you have a ...
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10
votes
Is C. elegans always observed with precisely 302 neurons? Are there ever individual viable exceptions?
Many Nematodes do not use traditional hox genes instead the have a strange set up which controls cell placement directly. This means individual adults of many nematode species have the exact same ...
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9
votes
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Why can't our eyes smoothly transition from side to side without focusing on a moving object?
Short answer
Smooth pursuit is driven by retinal slip, which is determined by external input registered peripherally in the retina.
Background
The smooth pursuit system is a system designed to ...
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8
votes
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Would the human body react faster to touch or sight
A "touch" or "haptic" sensation will be much faster due to several reasons:
Haptic feedback can be processed without the presence of any higher-order cognitive processing, therefore meaning that the ...
- 2,603
8
votes
Can turkeys run around when their head is cut off like chickens do?
The brain does not control all bodily movements. Some movements are to a great extent controlled by neural networks in the spinal cord. The spine contains a network which is pre-programmed to control ...
- 52.3k
7
votes
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Are there nerves in the umbilical cord?
Short answer
There are no functional nociceptors present in the umbilical cord.
Background
Having had the opportunity to cut the umbilical cord of one of my kids, I can anecdotally confirm neither ...
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7
votes
What is synaptic bias?
Often artificial neurons are created with conventions that zero is "rest" and 1 is "threshold". The unit starts at 0, and when it reaches 1 it will send an input to all of its targets and be reset ...
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7
votes
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Are there any known rules that neurons always follow while transmitting/receiving signals?
Short Answer:
"Always" is always a dangerous term in biology.
Longer Answer:
What does a neuron do if it does not get stimulated/receives no signal for a long time. Will it die ... or try to find ...
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7
votes
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Functional unit
In biology, functional unit of a system refers to the smallest structural element that is capable of performing the tasks typical for that system (MP Hlastala, Physiology of Respiration).
In the ...
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7
votes
Is there a quantitative report for cortical homunculus?
I think you'd appreciate reading an 80-year update (Catani, 2017)) of the original paper (Penfield & Boldrey, 1937).
Four things come to mind (with commentary from Catani 2017 sprinkled throughout:...
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6
votes
Can the dendrites of sensory neurons be a meter long?
Short answer
Axons can be over a meter long, but dendrites are never that long. Distance in the body is covered by axons. The dendritic part of skin receptors is generally considered to be the ...
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6
votes
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Cortical projections from layers 2/3 back to 4?
Excitatory neurons in layer 4 are not all stellate in all cortical areas, for example see Smith and Populin, 2001 who show clearly that in auditory cortex most excitatory cells in layer 4 are ...
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6
votes
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What is this structure in human brain?
Short answer
Based on shape and approximate position, I think it is the corpus callosum.
Background
I think it is the corpus callosum (Fig. 1). The corpus callosum is approximately 10 cm in length ...
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6
votes
Neuron connectivity- how are they connected physically
Neurons are suspended, as you say, in an extracellular matrix. Brain tissues are a little bit more specific. Here I quote a few summaries from literature to answer and give your a perspective on your ...
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5
votes
Accepted
Is there a map of the individual motor axons in the limbs?
No it is not possible to map axons at that fine of a scale between individuals.
You mention a possible use for controlling bionic arms. There are a bunch of problems with that approach.
Like @kmm ...
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5
votes
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Why ambidextrous persons are so rare?
While not specifically answering why ambidextrous persons are rare, one potential explanation is that mixed-handedness and/or ambidexterity seems to be related to adverse effects. For instance, some ...
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5
votes
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Why are the posterior and anterior inferior temporal cortex called area TEO and area TE respectively?
These are very old names for primate cortical areas, originally from the anatomist Constantin von Economo and also used by von Bonin and Bailey (1947) (where the TEO region name seems to originate).
...
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5
votes
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What makes synapses stay "fixed"?
Synapses are held together by adhesion molecules, like cadherins and neuroligins/neurexins, so they aren't just loose adjacent membrane, they are securely anchored in place.
The adhesion molecules ...
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5
votes
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Why is gyrification advantageous?
Short answer
The structural anatomy of the cerebral cortex is closely related to its functionality. The cortex is a thin sheet of only a few cell layers deep. Expansion of processing power requires ...
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5
votes
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Why is the chordate nerve cord described as hollow when it appears to be solid?
Your book is talking about an embryonic structure, the neural tube. This structure forms from an invagination of the neural plate, a collection of cells on the dorsal surface of the early embryo. The ...
- 44.1k
5
votes
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Why does Sanjay Gupta's brain look so unusual? (brain model shown on CNN) The subdivisions don't look like the lobes I learned in school
I don't know exactly what brain model he has, but if you search for "brain model" you'll find lots that have the precentral gyrus and postcentral gyrus colored separately from the frontal ...
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5
votes
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Does communication with new parts of body requires internal changes in brain?
I think you'd benefit from reading about the concept of "critical periods" - basically, at different times during development, the brain is learning specific tasks, associating sensory ...
- 44.1k
4
votes
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What is the specific role of the cerebellum when it comes to 'coordinating movement'?
The principal function of the cerebellum, which was detected years ago, is to calibrate detailed movements rather than initiating movements or deciding which movements to execute (Ghez et al, 1985). ...
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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 ...
- 44.1k
4
votes
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Why is the thalamic reticular nucleus called a nucleus?
The thalamic reticular nucleus (TRN) is a thin layer of GABAergic cells adjacent to the thalamus (Fig. 1). Because of its strategic location between the thalamus and cortex, the TRN is often ...
- 52.3k
4
votes
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Where does the initial action potential come from?
The very first evoked spike is most likely triggered by spontaneous activity, as even neurons with no synaptic connections are able to fire action potentials (Luhmann et al. 2016). Later in life ...
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4
votes
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What parts of the visual system could be responsible for a fixed, monocular scotoma?
Yes. You're right.
A scotoma only affecting one eye (i.e., one that is not perceived when one eye is closed) is diagnostic of a lesion upstream from the optic chiasm.
See Brust's Practice of Neural ...
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