The Subgenual Organ Complex in Stick Insects: Functional Morphology and Mechanical Coupling of a Complex Mechanosensory Organ

Leg chordotonal organs in insects show different adaptations to detect body movements, substrate vibrations, or airborne sound. In the proximal tibia of stick insects occur two chordotonal organs: the subgenual organ, a highly sensitive vibration receptor organ, and the distal organ, of which the function is yet unknown. The distal organ consists of a linear set of scolopidial sensilla extending in the tibia in distal direction toward the tarsus. Similar organs occur in the elaborate hearing organs in crickets and bushcrickets, where the auditory sensilla are closely associated with thin tympanal membranes and auditory trachea in the leg. Here, we document the position and attachment points for the distal organ in three species of stick insects without auditory adaptations (Ramulus artemis, Sipyloidea sipylus, and Carausius morosus). The distal organ is located in the dorsal hemolymph channel and attaches at the proximal end to the dorsal and posterior leg cuticle by tissue strands. The central part of the distal organ is placed closer to the dorsal cuticle and is suspended by fine tissue strands. The anterior part is clearly separated from the tracheae, while the distal part of the organ is placed over the anterior trachea. The distal organ is not connected to a tendon or muscle, which would indicate a proprioceptive function. The sensilla in the distal organ have dendrites oriented in distal direction in the leg. This morphology does not reveal obvious auditory adaptations as in tympanal organs, while the position in the hemolymph channel and the direction of dendrites indicate responses to forces in longitudinal direction of the leg, likely vibrational stimuli transmitted in the leg’s hemolymph. The evolutionary convergence of complex chordotonal organs with linear sensilla sets between tympanal hearing organs and atympanate organs in stick insects is emphasized by the different functional morphologies and sensory specializations.

Human first-order tactile neurons can resolve spatial details on the scale of single fingerprint ridges

Fast-adapting type 1 (FA-1) and slow-adapting type 1 (SA-1) first-order tactile neurons provide detailed spatiotemporal tactile information when we touch objects with fingertips. The distal axon of these neuron types branches in the skin and innervates many receptor organs associated with fingerprint ridges (Meissner corpuscles and Merkel cell neurite complexes, respectively), resulting in heterogeneous receptive fields that include many highly sensitive zones or ‘subfields’. Using raised dots that tangentially scanned a neuron’s receptive field, here we examined the spatial resolution capacity of FA-1 and SA-1 neurons afforded by their heterogeneous receptive fields and its constancy across scanning speed and direction. We report that the resolution of both neuron types on average corresponds to a spatial period of ∼0.4 mm and provide evidence that a subfield’s spatial selectivity arises because its associated receptor organ measures mechanical events limited to a single fingerprint ridge. Accordingly, the sensitivity topography of a neuron’s receptive fields is quite stable over repeated mappings and over scanning speeds representative of real-world hand use. The sensitivity topography is substantially conserved also for different scanning directions, but the subfields can be relatively displaced by direction-dependent shear deformations of the skin surface.Significance StatementThe branching of the distal axon of first-order tactile neurons with receptor-organs associated with fingerprint ridges (Meissner and Merkel end-organs) results in cutaneous receptive fields composed of several distinct subfields spread across multiple ridges. We show that the spatial selectivity of the subfields typically corresponds to the dimension of the ridges (∼0.4 mm) and that neurons’ subfield layout is well preserved across tangential movement speeds and directions representative of natural use of the fingertips. We submit that the receptor-organ underlying a subfield essentially measures mechanical events at an individual ridge. That neurons receive convergent input from multiple subfields does not preclude the possibility that spatial details can be resolved on the scale of single fingerprint ridges by a population code.

Symmetry breaking during morphogenesis of a mechanosensory organ

Actively regulated symmetry breaking, which is ubiquitous in biological cells, underlies phenomena such as directed cellular movement and morphological polarization. Here we investigate how an organ-level polarity pattern emerges through symmetry breaking at the cellular level during the formation of a mechanosensory organ. Combining theory, genetic perturbations, and in vivo imaging assisted by deep learning, we study the development and regeneration of the fluid-motion sensors in the zebrafish’s lateral line. We find that two interacting symmetry-breaking events — one mediated by biochemical signaling and the other by cellular mechanics — give rise to a novel form of collective cell migration, which produces a mirror-symmetric polarity pattern in the receptor organ.

The Effect of CO2, Intracellular pH and Extracellular pH on Mechanosensory Proprioceptor Responses in Crayfish and Crab

Proprioceptive neurons monitor the movements of limbs and joints to transduce the movements into electrical signals. These neurons function similarly in species from arthropods to humans. These neurons can be compromised in disease states and in adverse environmental conditions such as with changes in external and internal pH. We used two model preparations (the crayfish muscle receptor organ and a chordotonal organ in the limb of a crab) to characterize the responses of these proprioceptors to external and internal pH changes as well as raised CO2. The results demonstrate the proprioceptive organs are not highly sensitive to changes in extracellular pH, when reduced to 5.0 from 7.4. However, if intracellular pH is decreased by exposure to propionic acid or saline containing CO2, there is a rapid decrease in firing rate in response to joint movements. The responses recover quickly upon reintroduction of normal pH (7.4) or saline not tainted with CO2. These basic understandings may help to address the mechanistic properties of mechanosensitive receptors in other organisms, such as muscle spindles in skeletal muscles of mammals and tactile as well as pressure (i.e., blood pressure) sensory receptors. KEYWORDS: Proprioception; Sensory; Invertebrate; Carbon Dioxide; Protons; Mechanosensory; Intracellular pH; Extracellular pH

Peningkatan Kecerdasan Anak Melalui Pemberian ASI dalam al-Qur’an

<p>Todays health researchs prove that the breast milk contains a lot of content that is not found in milk formula, especially immunologic substances. Breast milk contains anti-infective agents that are clean and free of contamination. Immune substances that exist in immunoglobulins, secretory, and lactoferrin as well as the presence of factors that can stimulate Lactobacillus bifidus to protect baby’s digestive tract. Lately also known that breast milk can increase children’s intelligence. It could be due to nutritional milk, methods, or durations of breastfeeding. Research shows that a Taurine, Decosahexanoic acid (DHA) and Arachidonic acid (AA) exist in breast milk is very useful in the formation of the baby’s brain cells and accelerate the stimulus from the receptor organ to the brain, so that the response can be given in a fast time. Yet long before the WHO, researchers and human rights activists has been intensifying exclusive breastfeeding, the Koran was first called to breastfeed <em>h</em><em>}</em><em>awlayn kâmilayn</em> two full years. The Relevances between the activity of breastfeeding for two full years and the brain development of baby will be discussed in this paper.<strong></strong></p>

Human Body Scents: Do they Influence our Behavior?

Pheromonal communication in the animal world has been of great research interest for a long time. While extraordinary discoveries in this field have been made, the importance of the human sense of smell was of far lower interest. Humans are seen as poor smellers and therefore research about human olfaction remains quite sparse compared with other animals. Nevertheless amazing achievements have been made during the past 15 years. This is a collection of available data on this topic and a controversial discussion on the role of putative human pheromones in our modern way of living. While the focus was definitely put on behavioral changes evoked by putative human pheromones this article also includes other important aspects such as the possible existence of a human vomeronasal organ. If pheromones do have an influence on human behavior there has to be a receptor organ. How are human body scents secreted and turned into odorous substances? And how can con-specifics detect those very odors and transmit them to the brain? Apart from that the most likely candidates for human pheromones are taken on account and their impact on human behavior is shown in various detail.

Mechanisms of Sound Localization in Mammals

The ability to determine the location of a sound source is fundamental to hearing. However, auditory space is not represented in any systematic manner on the basilar membrane of the cochlea, the sensory surface of the receptor organ for hearing. Understanding the means by which sensitivity to spatial cues is computed in central neurons can therefore contribute to our understanding of the basic nature of complex neural representations. We review recent evidence concerning the nature of the neural representation of auditory space in the mammalian brain and elaborate on recent advances in the understanding of mammalian subcortical processing of auditory spatial cues that challenge the “textbook” version of sound localization, in particular brain mechanisms contributing to binaural hearing.

SA-I Mechanoreceptor Position in Fingertip Skin May Impact Sensitivity to Edge Stimuli

Background:The skin plays a role in conditioning mechanical indentation into distributions of stress/strain that mechanoreceptors convert into neural signals. Solid mechanics methods have modelled the skin to predict the in vivo neural response from mechanoreceptors. Despite their promise, current models cannot explain the role that anatomical positioning and receptor organ morphology play in producing differences in neural response. This work hypothesises that the skin's intermediate ridges may help explain, in part, the sensitivity of slowly adapting type I (SA-I) mechanoreceptors to edge stimuli.Method:Two finite-element models of the fingertip were built, validated and used to analyse the functionality of the intermediate ridges. One of the two-dimensional, cross-sectional models included intermediate ridges, while the other did not. The analysis sought to determine if intermediate ridges (1) increase the magnitude of strain energy density (SED) near the SA-I location and (2) help differentiate one 2.0-mm indenter from two 0.5-mm wide indenters with a 1.0-mm gap.Results:Higher concentrations of SED were found near the tips of the intermediate ridges, the anatomical location that coincides with the SA-I receptors. This first result suggested that the location of the SA-Is in the stiffer epidermal tissue helps magnify their response to edge stimuli. The second result was that both models were equally capable of predicting the spatial structure within the in vivo neural responses, and therefore the addition of intermediate ridges did not help in differentiating the indenters.Conclusion:The finding, a 15%–35% increase in response when the sampling point lies within the stiffer tissue at the same depth, seeks to inform the positioning of force sensors in robotic skin substrates.