Are there neuron mediated reactions faster than reflexes?

Are there neuron mediated reactions faster than reflexes?

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I'm interested in how fast the human body can respond to a stimulus. I know the fastest reflex, the blink reflex, operates around 100ms from stimulus to reaction. I also know that the blink reflex is known as the fastest reflex in the human body. My interest is in the fastest responses to stimuli I can find in the body.

Are there any faster responses to stimuli within the human body which use neurons but are not categorized as a reflex (due to some technicality), meaning they could be faster than the fastest reflex? To the best of my understanding a reflex is defined by the use of neurons to convey the information, I'm just wondering if there are any grey areas which don't qualify as a reflex but may be faster. I don't want to potentially write off an entire class of neurological behavior in my research simply because I stopped at the blink reflex.

A reflex as fast as the blink in a neural circuit:

I would consider suppression of outer hair cells in the cochlea to be a reflex; the faster component of this reflex is about the same as the blink reflex, around 100 ms. The hair cells themselves aren't considered neurons, but the pathway that suppresses their motility certainly is.

A much much faster non-neuronal "reflex":

That said, the outer hair cells themselves also dance along quite fast in response to sensory input, even faster than the typical hearing range for humans, faster than 20kHz! In some ways, this is a reflex because you are taking sensory (specifically, auditory) information and turning it into a motor response, but all the "action" is taking place within one cell, and it isn't a neuron.

A more classical reflex that is substantially faster than 100 ms

Reflexes in the periphery can be much faster than 100 ms. The myotatic reflex, or stretch reflex, can be as fast as 30 ms in the knee - this is the reflex that is tested when a physician smacks you on the knee with a hammer (used as a test of spinal and peripheral nerve function, not as a punishment). It's likely there are other stretch reflexes that are faster just because distances to the spinal cord are shorter, but these might be more difficult to test (in this paper they report latencies as fast as 20 ms).

Eyeblink reflexes can also be faster than 100 ms!

For example, see this paper: strong auditory stimuli evoked blinks within about 20ms!

tl;dr: I'd check your source that 100 ms is the fastest reflex! I stuck with mostly human examples here (some of the hair cell work is in other mammals), but you will find even faster reflexes if you look at smaller organisms, such as insects.

In a paper studying Rhesus macaques, Huterer and Cullen showed that latency of the vestibulo-ocular reflex (measured from head movement to eye muscle contraction) can be as little as 5 milliseconds1.


1: Huterer, M., & Cullen, K. E. (2002). Vestibuloocular reflex dynamics during high-frequency and high-acceleration rotations of the head on body in rhesus monkey. Journal of neurophysiology, 88(1), 13-28.

Are there neuron mediated reactions faster than reflexes? - Biology

Reflexes: Involuntary and rapid actions

Control: Your spinal cord usually controls your reflexes

Autonomic reflexes: Body functions such as digestion or blood pressure

Pulling your hand away from a hot object, blinking because it's very bright or kicking when someone taps the tendon below your kneecap - these are all innate reflex actions. They happen rapidly, you don't control them and the result is always the same.

Most reflexes don't have to travel up to your brain to be processed, which is why they take place so quickly. A reflex action often involves a very simple nervous pathway called a reflex arc.

A reflex arc starts off with receptors being excited. They then send signals along a sensory neuron to your spinal cord, where the signals are passed on to a motor neuron. As a result, one of your muscles or glands is stimulated.

The knee-jerk reflex involves a sudden kicking movement of your lower leg after the tendon just below your kneecap has been tapped. Doctors often trigger this reflex to test the function of your nervous system. If the reaction is exaggerated or absent, it may indicate a damage to the central nervous system.

Most reflexes go completely unnoticed because they don't involve a visible and sudden movement. Body functions such as digestion or blood pressure, for example, are all regulated by reflexes. These reflexes are known as autonomic reflexes.

Lab 12 Nervous Physiology Testing Reactions

1) Differentiate between a reflex and reaction
2) Explain the impact that anticipation and learning has on the rate of reactions
3) Compare the differences within and between individuals based on the patterning of external stimulus leading to the reaction response.

Reactions are an important to everyday activities. They are a reflexive behavior that we use to protect ourselves. Where we are able to use one of our senses to initiate a response to a stimulus, even without having to think about what that response will be. Because the time required for most of reactions and reflexes to occur are very short, less than one second, we use the typical measure of millisecond (msec) as opposed to using the whole second. As the numbers will always be thousandths of a whole second and whole numbers are much easier to deal with than decimals or fractions.

Figure 1. Pathway for a reaction response to a stimulus, note the interplay between cortical structures and the afferent and efferent pathways.

But what makes reactions different from reflexes? Reflexes are unconscious, involuntary and unintentional response to a stimulus on a receptor. While, a reaction is a deliberate conscious response to a specific stimulus that is voluntary and intentional. We can test our reflexes through use of a reflex hammer on specific tendons throughout the body. To perform this reflex test, the tester strikes the hammer on a specific spot within the tendon. The reflex response may be measured on a subjective grading scale to determine the tone of the muscle. We cannot learn how to control the response to test, the reflex just happens. This is different from the concept of reactions and testing of reactions.
While the reaction is a reflex, it is unlike the muscle tendon reflex as they are specific purposeful actions made in response to a specific stimulus. Since reactions being both cognitive and purposeful, we are able to learn how to react and thus anticipate the appropriate response. The ability to modify and modulate reactions occurs because reactions involve input from our primary motor cortex through a prolonged reflex loop. Where to speed up the response, the primary motor cortex can actually send opposing signals to the agonist and antagonist muscles of the desired movement and upon the initiation of the reaction will stop the opposing signals and allow for the coordinated actions within the reflex, see figure 1. The more often we utilize the reaction pathway, the more we can modify the speed of reaction to any given stimulus and in doing so can be seen to have &ldquofaster reactions&rdquo relative to a novice in the activity or to what we were able to react to prior to learning the appropriate response.
Reactions become very important to our successful performances in many activities we perform daily, whether it be playing a musical instrument, dancing, playing sports or doing athletic things, playing video games, or even just driving a car. The more often we are exposed to a situation reactions to that stimulus tend to occur more quickly than when first exposed to the situation. There are different activities that can improve our reaction skills, all of which depend on the signal used to initiate the reaction, including noises (like a starting gun at a race), objects flying at you (like catching a ball before you get hit by it), or falling to the floor (like catching the plate before it hits the floor and your mom or dad gets upset). Because of what they do to our physiology, stimulants that we consume can alter the speed that reactions form to a stimulus and will make a person appear to react much faster than if they were to react to the same stimulus when sober.
When testing reactions, we normally measure it through reaction time to respond to a stimulus through movement of limb (hand, finger, foot). It is important to remember that limb dominance and habitual utilization can influence the responses seen. As the more often we use a limb or pattern of motion, the more &ldquoingrained&rdquo the motion becomes while the less often we use the limb or pattern of motion the more likely we are to over-exaggerate the response, as we are not certain as to the pattern for response. The over-exaggeration can be seen with the person responding prior to the stimulus or generating too large of a response than what the habitually utilized the limb would produce. Additionally, the speed by which neurons function can slow and the reduction in the speed of neuron activity can slow our reactions. This reduction in conduction speed and longer reaction time can lead to the same over-exaggeration that is seen from the non-habitually used limb and with progressive aging can lead to overall slower movements for the person so that they can ensure their ability to react to a stimulus appropriately.
The purpose of the experiment here is to test reactions to visual signals where we will examine the differences that exist between dominant (habitually used) and non-dominant (not habitually used) hands. Further we will look at differences that may exist between genders (male or female), habitual use of playing video games, acute exposure to a stimulant, and age of the volunteer.

Part 1: Testing with the meter-stick
I. Choose slip of paper to indicate order of testing Anticipation or No Anticipation
II. Based on slip of paper indicate order that you will test reactions
Test #1:
Test #2:

Testing with no anticipation:

1. Determine who will be tested first.
2. Have the person being the test subject to sit on a chair and place the dominant arm on the table so that the hand is off the table, but the rest of the arm is on the table. Have them turn their hand so that the thumb is facing up (toward the ceiling) and the fingers are facing forward.

Positioning of the hand of the test subject.

3. Have the person acting as the tester, stand and face the person being tested with the meter-stick being held vertically, turn the meter-stick so that the numbers face the thumb side of the hand.

Positioning of the meter-stick for testing reaction time.

4. In that position, have the subject pinch their index finger and thumb together so that they are touching the meter-stick.
5. Have the person relax their pinch so that the meter-stick is free and being held by the tester in the air between the subject's thumb and index finger, but not touching either one of the fingers.
6. Align the zero mark of the meter-stick with the top of the subject&rsquos fingers. Ask the subject if they are ready. And tell them that once they see the meter-stick drop try to catch the meter-stick between their index finger and thumb.
7. Without warning, release the ruler and let it drop and have the subject catch it as quickly as possible as soon as they see it fall.

Process used for testing of reaction times by catching the falling meter-stick.

8. Record in centimeters the distance the ruler fell, by reading the distance at the top of the subject&rsquos finger in the correct results table.

Identification for where to read the mark for distance that meter-stick fell prior to being caught.

9. Repeat steps 6-9 for a total of 5 times. Following the fifth trial, switch partner roles.
10. Repeat steps 3-10 for the next partner and then for the other (non-dominant) arm of each partner.

Testing with anticipation: This time after asking them if they are ready, you will give them a countdown to the drop of the meter-stick.

11. Have the person being the test subject to sit on a chair and place the dominant arm on the table so that the hand is off the table, but the rest of the arm is on the table. Have them turn their hand so that the thumb is facing up (toward the ceiling) and the fingers are facing forward.
12. Have the person acting as the tester, stand and face the person being tested with the meter-stick being held vertically, turn the meter-stick so that the numbers face the thumb side of the hand.
13. In that position, have the subject pinch their index finger and thumb together so that they are touching the meter-stick.
14. Have the person relax their pinch so that the meter-stick is free and being held by the tester in the air between the subject's thumb and index finger, but not touching either one of the fingers.
15. Align the zero mark of the meter-stick with the top of the subject&rsquos fingers. Ask the subject if they are ready. And tell them that once they see the meter-stick drop try to catch the meter-stick between their index finger and thumb.
16. Countdown from 5 to 1, and on &ldquo1&rdquo release the ruler, let it drop and have the subject catch it as quickly as possible as soon as they see it fall.
17. Record in centimeters the distance the ruler fell, by reading the distance at the top of the subject&rsquos finger.
18. Repeat for a total of 5 times. Following the fifth trial, switch partner roles.
19. Repeat steps 14-18 for the next partner and then for the other (non-dominant) arm of each partner.

Table 1. Conversion of average time (msec) for reaction based on the distance that the meter-stick fell prior to be caught.

Superficial Reflexes

  1. Biceps and Brachioradialis C5/C6
  2. Triceps C7 (Note: Some references include C6 OR C8, however C7 is predominantly involved.)
  3. Patellar L2-L4
  4. Ankle S1

Superficial Reflexes

Corneal reflex (blink reflex)

  1. Involuntary blinking in response to corneal stimulation
  2. Afferent: nasociliary branch of ophthalmic branch (V1) of trigeminal nerve (5th nerve)
  3. Efferent: facial nerve (7th nerve)
  1. Contraction of superficial abdominal muscles when stroking abdomen lightly
  2. Significant if asymmetric–usually signifies a UMN lesion on the absent side.
  1. Contraction of cremaster muscle (that will pull up the scrotum/testis) after stroking the same side of superior/inner thigh
  2. Absent with:
  3. testicular torsion
  4. upper/lower motor neuron lesions
  5. L1/L2 spinal cord injury
  6. ilioinguinal nerve injury (during hernia repair)
  1. The plantar reflex can be:
  2. Normal (Toes down-going)
  3. Absent
  4. Abnormal or "Babinski Present"
  5. Note: It is incorrect to say ‘negative Babinski '

Visceral Reflexes

Anal reflex (anal wink)

  1. Reflexive contraction of the external anal sphincter upon stroking the skin around the anus (afferent: pudendal nerve efferent: S2-S4)

Bulbocavernosus reflex

  1. Anal sphincter contraction in response to squeezing the glans penis or tugging on an indwelling Foley catheter
  2. Reflex mediated by S2-4 and used in patients with spinal cord injury

DTR Scale

We are not big believers in grading reflexes (grading muscle power is much more useful). Nevertheless, if you need something beyond “absent,” “present,” “brisk,” or “hyperactive” then use below. If you have a hyperactive reflex don’t forget to look for clonus.

2 Answers 2

This is going to take some serious ground-up modifications to terrestrial animal biology.

In order to have a reaction time fast enough to dodge a bullet, we're going to have to increase the conduction velocity of the nerves from some velocity measured in mere metres per second to something closer to lightspeed. Metal cored and sheathed nerves would fulfill this requirement. Then, we will have to replace the nerves slow diffusion-based signalling mechanism with something much faster. so instead of relying on chemical diffusion, we could have a mechanical connection between nerves. This could be a mechanism in the transmitting neuron which, on receiving an appropriate electrical signal, rotates a certain amount, and which is physically linked to a sodium gate that also relies upon rotation to be opened. Being mechanically connected means that the transmission speed would occur not at the speed of chemical diffusion, but at the speed of sound in the junction rod.

Having reduced the response time of the brain and nerves, the main limiting factor will be the muscles and body. Mammalian muscles are relatively slow. While there are some things that can be done to speed up muscle contraction speed and response time, the fact is that it is unlikely that muscles are going to be able to be made able to contract at a rate much greater than is currently the case. However there are alternatives.

The nature of muscles is that they must contract bit by bit, a few micrometers at a time, but on relaxing, they may be stretched by external forces much more rapidly. So, in order to maximise the velocity at which a limb can bend, we can increase the ratio of joint-to-muscle vs joint-to-load, so that less force is applied, but is applied more quickly. Additionally, in the directions most likely to be needed to dodge, we can replace the muscles entirely and replace it with a highly elastic muscle-ligament combination. In the event of a stressful situation in which it may be necessary to move quickly, the more powerful antagonist muscle would contract, along with the weaker agonist muscle, stretching the elastic ligament. Then, if it is necessary to dodge, the relevant antagonist muscles could be deactivated, resulting in the stored energy in the elastic ligament being applied to the joint much more rapidly than the muscles are capable by themselves. It would also be possible to have both a powerful antagonist muscle and a smaller muscle-elastic ligament combination in each direction of movement, so as to provide two 'gears' to each direction of movement, slow and powerful, and weak but fast.

To complete the perception-reaction loop, we need faster eyes. This is relatively easily achieved, as human eyes are by no means the fastest in the animal kingdom. Even with optical pigments in traditional retinal cells, by making the cells smaller, they could be made to react faster, but with a more radical redesign, it might be possible to substitute a more responsive photosensor more akin to an electro-optical camera sensor.

Finally, this bullet-dodging superman wouldn't likely look like a traditional superman, with bulging muscles and a Mr Universe physique. all that muscle has mass, and the lower the mass, the easier it is to move. Instead, expect a being with long, slender limbs and a slender body, rather more like a grey alien than a human.

However, despite appearing to be slender and fragile, this being would not only be able to dodge with superhuman speed, but could also be an incredibly dangerous martial artist. While its limbs might weigh half as much as an average human's, it would be able to achieve a limb speed perhaps ten times that of a human. Given the relationship between impact energy and mass and speed being E = 1/2MV^2, half the mass equates to half the energy, but ten times the speed equates to a hundred times the energy, for a total impact energy fifty times that of a human's. This slender, lanky, wimpy-looking being could literally demolish a human with a single blow.

Of course, this being's adaptations require that it be aware of the potential attack in order to dodge it. In the event of being threatened, it would crouch, and its muscles would tense up, holding its limbs half-flexed while it stretched its elastic ligaments. It could see a nearby assailant contract his trigger finger, or see the flash of a longer-ranged shot, and within milliseconds, it could deactivate its antagonist muscles, the elastic ligaments contracting to propel it out of the line of fire.

Of course, if caught flat-footed, this being would not have the advantage of having energy stored in its elastic ligaments, and given the likely energy requirements associated with keeping the elastic ligaments stretched, it could not go about with them constantly pre-stretched. In such a case, it would be far more likely that it would be hit by an incoming bullet, though it may be able to achieve a less-serious hit.

Finally, this being, no matter how human it might look, would not be even remotely human. The differences between a human and this being are so great that even if human cells had been genetically engineered to create this being, it is so heavily modified that it would be unable to successfully reproduce with a human partner.

How Did The Jendrassik Maneuver Increased Reaction Time?

When observing our individual, we observed that that the Jendrassik maneuver increased reaction time. We believe this is so because it acts as a distraction due to the individual concentrating on the maneuver. This tells us that even though simple reflexes don’t directly involve the brain, the brain does still have influence on simple reflexes.

Reflexes can be an indication of nervous system health. When the reflexes are not acting properly or are absent, it can tell a physician if there may be a problem with the nervous system or in the region of nerves. Testing reflexes can tell a physician if something is wrong before the patient shows other noticeable signs of nervous system damage.

(120 x〖10〗^(-2) m)/0.154s - 0.002s = 7.79m/s.

Pupillary light reflex protects the internal parts of the eye that are can be damaged with intense light. Constricting allow less light to penetrate the eyes.

No, the mean reaction times varied between all of the conditions set. Our results showed distraction with the greatest mean reaction time and warning with the least reaction time.

Distractions, randomness, and sound increased reaction time. Giving a warning and regular visual cues decreased the reaction time.

Yes. The eye and the ears have different modes of transmission of information to the brain. The eyes uses photoreceptors (rod and cone cells) that are stimulated by image and light that has traveled into the eye. The photoreceptors synapse with ganglion cells that become the optic nerve. The optic nerve then sends the image information to the brain for processing. For the ear, the sound waves enter the auditory canal, the eardrum vibrates, the bones of the ear then amplify the vibrations, which then causes pressure waves that vibrate the basilar membrane. The basilar membrane then moves and small hairs bend which causes the stimulus for the hair cells to open ions channels that then result in the release of neurotransmitters, which stimulate afferent neurons. The brain then interprets the auditory signal. From our results we observed that auditory reaction time is greater than visual reaction time. We believe the transmission and processing from the brain may have an influence on this.

Author summary

Postmitotic neurons migrate from their site of origin to their final destination in the developing brain to form functional structures. These neurons typically follow defined routes through the tissue. Previous studies investigating progress along such route have identified neurotransmitters—chemicals that transmit the signals between neurons—as important regulators in neuronal migration using mostly rodent brain slice cultures and cultivated neurons. In this study, we use live zebrafish embryos to test the influence of neurotransmitters on migrating hindbrain neurons. First, we demonstrate that calcium transients can be measured in these neurons using genetically encoded reporters. Next, we use optogenetic channels to specifically de- or hyperpolarize the plasma membrane of the neurons to show that the polarization state is linked to migratory speed. Finally, we use a screening method to identify the neurotransmitter systems involved in migration progress control. We summarize these findings in a model that suggests that there are regions of influence for different neurotransmitters that act successively on the neurons to ensure their timely arrival at their destination.

Citation: Theisen U, Hennig C, Ring T, Schnabel R, Köster RW (2018) Neurotransmitter-mediated activity spatially controls neuronal migration in the zebrafish cerebellum. PLoS Biol 16(1): e2002226.

Academic Editor: Charles Stevens, The Salk Institute for Biological Studies, United States of America

Received: February 15, 2017 Accepted: November 22, 2017 Published: January 4, 2018

Copyright: © 2018 Theisen et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the paper and its Supporting Information files. Source code for “Phainothea” can be found on GitHub

Funding: European Commission Marie Curie Actions FP7 (grant number 623612 -Cdh2_neuromigration). UT was funded under the fellowship regime. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Abbreviations: ACh, acetylcholine AchE, acetylcholinesterase AcheH, Ache GPI-anchored isoform H AMPA, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor atoh1a, atonal 1a ChR2, channelrhodopsin CMV, cytomegalovirus CNQX, 6-cyano-7-nitroquinoxaline-2,3-dione DMSO, dimethyl sulfoxide F, fluorescence intensity F/F0, fluorescence over background F0, background intensity value FFT, fast Fourier transform GCaMP6, circular permutated green florescent protein-Calmodulin-M13 peptide 6 GFP, green fluorescent protein GlyRa1, glycine receptor alpha1 subunit GPI, glycosylphosphatidylinositol H2B, Histone 2B hpf, hours post fertilization KCC2, solute carrier family 12 (potassium/chloride transporter), member 5b MHB, midbrain-hindbrain boundary MK801, dizocilpine NMDA, N-methyl-D-aspartate PM, plasma membrane ric3b, RIC3 acetylcholine receptor chaperone b ROI, region of interest SwiChR, mutated channelrhodopsin THN, tegmental hindbrain nuclei neuron UAS, upstream activating sequence URL, upper rhombic lip WISH, whole mount in situ hybridization wt, wild-type Y226F, glycine receptor alpha1 subunit Y226 mutated to F

Neurologic Examination of the Term and Preterm Infant

Deep Tendon Reflex Assessment

Deep tendon reflexes vary with maturity ( Kuban et al., 1986 ). In a study of preterm infants of more than 27 weeks' postconceptional age, the pectoralis major reflex was elicited in all, and by 33 weeks' gestation, essentially all demonstrated the Achilles, patellar, biceps, thigh adductor, and brachioradialis reflexes. Infants of less than 33 weeks' gestation had decreased elicitation rates for patellar and biceps reflexes and had overall decreases in reflex intensity compared with their older counterparts. Contrary to conventional wisdom, head position had no effect on the reflexes.

Neurons, especially outside your brain, are pretty slow, as this video beautifully demonstrates. The speed of transmission depends on the quality of the cabling. For fast long distance communication with distant parts of the body the Nervous system has its axonic cabling covered with a myelin sheath, which speeds up nerve impulses by a factor of 10, via saltatory conduction. Within the computational centers in the brain where the neuron-body to neuron-body distances are much shorter, myelinization is less of an issue, and more lossy communication can occur.

It is tempting to think that after 400 million years of multicellular evolution, neurons are about as fast as they can get. That's actually not the case. Evolution optimized for the best combination of speed and low energy consumption it could, and if you look at the actual process, it seems a bit of a kludge.

It's not inconceivable that if we were to redesign a human body under our no-energy-constraints current situation, we could get significantly faster conduction, bounded upward by the electromagnetic propagation speed of $c$ . Significant upgrades could be achieved at the neurotransmitter bottleneck, for instance. Of course, we don't need a million-fold speed increase to have merely faster reaction times, so relatively minor tweaks could work. Some of them could even evolve biologically as we move away from the food-being-an-issue as a species, but genetic engineering is a faster way to get there.

Breathe, Walk and Chew: The Neural Challenge: Part I

Dimitri Ryczko , . Jean-Marie Cabelguen , in Progress in Brain Research , 2010

Commissural interneurons (cINs)

The cINs are glycinergic and send ascending and descending branches on the contralateral side ( Dale, 1985 Soffe et al., 1984 ). They elicit a strychnine-sensitive inhibition of contralateral rhythmically active MNs and premotor interneurons. Some cINs also have an additional ipsilateral axonal branch, which may be responsible for recurrent on-cycle inhibition of other cINs, dINs, and MNs ( Roberts et al., 1997 ). This inhibition from cINs to dINs is crucial to allow the latter cells to fire on rebound and therefore to drive swimming ( Li et al., 2007 Roberts et al., 2008 ). However, this rebound cannot be the only mechanism contributing to rhythm generation, because the surgically isolated hemicord can still generate a rhythm. Moreover, blocking glycinergic inhibition in the hemicord does not abolish rhythmic activity ( Soffe, 1989 ).

Watch the video: Οι Επιστήμονες το απέδειξαν - το σημείο του Σταυρού έχει υπερφυσική δύναμη! Πολύ Ενδιαφέρον! (February 2023).