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36: Sensory Systems - Biology

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36: Sensory Systems

36: Sensory Systems - Biology

Figure 1: This shark uses its senses of sight, vibration (lateral-line system), and smell to hunt, but it also relies on its ability to sense the electric fields of prey, a sense not present in most land animals. (credit: modification of work by Hermanus Backpackers Hostel, South Africa)

In more advanced animals, the senses are constantly at work, making the animal aware of stimuli—such as light, or sound, or the presence of a chemical substance in the external environment—and monitoring information about the organism’s internal environment. All bilaterally symmetric animals have a sensory system, and the development of any species’ sensory system has been driven by natural selection thus, sensory systems differ among species according to the demands of their environments. The shark, unlike most fish predators, is electrosensitive—that is, sensitive to electrical fields produced by other animals in its environment. While it is helpful to this underwater predator, electrosensitivity is a sense not found in most land animals.


36: Sensory Systems - Biology

Figure 1. This shark uses its senses of sight, vibration (lateral-line system), and smell to hunt, but it also relies on its ability to sense the electric fields of prey, a sense not present in most land animals. (credit: modification of work by Hermanus Backpackers Hostel, South Africa)

In more advanced animals, the senses are constantly at work, making the animal aware of stimuli—such as light, or sound, or the presence of a chemical substance in the external environment—and monitoring information about the organism’s internal environment. All bilaterally symmetric animals have a sensory system, and the development of any species’ sensory system has been driven by natural selection thus, sensory systems differ among species according to the demands of their environments. The shark, unlike most fish predators, is electrosensitive—that is, sensitive to electrical fields produced by other animals in its environment. While it is helpful to this underwater predator, electrosensitivity is a sense not found in most land animals.


Sensory Systems

Cellular Physiology ( http://www.driesen.com/sensory_systems.htm http://isc.temple.edu/neuroanatomy/lab/neuexam/sensory.htm )

As far back as ancient times, sensory systems were divided into five modalities: hearing, smell, taste, touch, and vision. Others have been recognized and fall within the somatovisceral category that previously included touch (mechanoreception) and, more recently, position and movement (proprioception), heat and cold (thermoreception), and pain (nociception) Gebhart (1995) . While sensation may be thought of as originating in the external world (exteroceptive), there are sensations that originate internally (interoceptive). This internal sensory information, which arises from the viscera, blood vessels, and muscles and is used to regulate body temperature, heart and respiratory rate , and blood pressure, may not be recognized at a conscious level.

Each sensory system begins with a receptor cell and its primary afferent neuron that makes specific connections with other nerve fibers. The groups of neuronal fibers, and the nuclei that relay this peripheral information into and throughout the central nervous system , define the sensory system. These neurons are essentially tuned to a specific sensory energy. It is this specificity that defines the sensation. For example, a peripheral sensory endorgan can be replaced with an artificial device such as a cochlear implant in a deaf patient. In this case, the implant electrically stimulates the peripheral ganglion cells that relay the electrical information to the central auditory system, producing the sensation of sound.

The initiation of a receptor response is dependent on an adequate stimulus, as defined by Sherrington Sherrington (1947) , in which a specific stimulus is needed to initiate a response in a specific sensory receptor. The process whereby a stimulus energy is converted into the electrochemical energy occurs at the level of the receptor cell and is known as transduction. This conversion process allows for the coding of the sensory stimulus by the nervous system . For example, in hearing (bending of stereocilia) and touch (deformation of Pacinian corpuscles), mechanical energy is converted into the flow of ions (electrochemical) through ion channels in the membrane that generate cell membrane potentials known as receptor potentials. The initiation of a response is dependent on four factors: modality, intensity, location, and timing. As indicated above, in relation to specificity, the type of stimulus energy (sound, light, etc.), and the specificity of the receptors needed to sense that energy defines the modality. The intensity of a perceived stimulus at the cellular level is reflected in how long and fast the neurons fire, and how many neurons are firing. Thus, timing plays a role in this process, because an increase in stimulus rate results in an increase in firing rate, while an increase in stimulus amplitude results in an increase in receptor potential. For some sensory systems there is a close relationship between the subjective measurement of intensity, as defined by perception, and the objective measurement, as defined by the neuronal response both types of responses are described by a power function, as proposed by Stevens Stevens (1957) . However, this response is not strictly linear. For example, measurement of basilar membrane displacement in the cochlea Rhode and Robles (1974) in response to sound, or the measurement of an FA receptor response to touch on the skin Vallbo and Johansson (1984) , shows a stimulus-response relationship that is nonlinear. Moreover, inherent in the response is the intensity threshold necessary to activate the receptor and, eventually, the sensation. For example, what is the lowest stimulus that an individual can perceive a specific sound? At the cellular level, the threshold is defined by the sensitivity of the receptor and the neuronal cells. Stimulation of the receptor cells occurs at a local level and is the result of a passive flow of current. Stimulation of the neurons is dependent on reaching the threshold necessary to generate an action potential in the many neurons that encode and relay a signal to and throughout the central nervous system. The generation of action potentials will generate a sensation depending on the strength of the stimulus.

Once a response is initiated, a change in stimulus is necessary to maintain a perceived sensation, as well as a receptor cell response. If a stimulus remains constant over time, the response of the receptor cell undergoes adaptation, resulting in a decrease in the receptor potential and, thus, a decrease in sensation. For example, there is evidence from the receptor cells (i.e., hair cells) of the auditory system that bending of the stereocilia (see record on Hearing ) results in the stretching of tip links or filaments that open the ion channels of transduction, resulting in receptor cell depolarization or excitation. Bending of the stereocilia with a constant force results in a decrease in tip link tension by a mechanical mechanism involving actin and myosin molecules Hudspeth and Gillespie (1994) . This interaction resets the tip link tension, causing a decrease that, in turn, resets the transduction channel to a resting state despite the bending of the stereocilia. The sensory cell, via the transduction channel, is now able to respond to any new change in stimulus. Adaptation can take place either slowly or rapidly, as demonstrated in touch receptors. Through the process of adaptation the receptors and neurons can encode and convey the ever-changing sensory environment to the brain.

A feature of sensory systems that contributes to their specificity is their spatial arrangement. This arrangement contributes to the localization of a stimulus and to the ability to discern the physical characteristics of that stimulus (e.g., size, shape, frequency, etc.). For example, touch receptors in the finger-tips and lips occur in clusters, offering a more stimulus sensitive arrangement than receptors in the back of the hand, which are less clustered and more randomly organized. Receptors for taste that are sensitive to salts, acids, bases, sugars, and proteins are arranged on different parts of the tongue, relaying this specific information to the central nervous system. The basilar membrane of the cochlea is tonotopically organized, responding in a low- to high-frequency arrangement along its length, from apex to base, respectively. This organization is the result of its physical characteristics, being thin and wide at the apex and thick and narrow at the base. Consequently, a low frequency tone of 20 Hz maximally stimulates the basilar membrane near the apical end, whereas a frequency of 20 kHz maximally stimulates the membrane at the basal end. In turn, the receptor cells that overlie these regions and transduce this mechanical energy into electrochemical energy are maximally stimulated as a result of this displacement. The spatial arrangement of receptor cells in their various sheets of epithelia defines the region whereby an adequate stimulus excites a particular receptor. For example, a touch receptor has a defined area, or receptive field, in the skin within which a stimulus excites the cell. In the cochlea, the basilar membrane and, thereby, the overlying receptor cell, are maximally stimulated or tuned to some specific frequency (best frequency) due to the tonotopic arrangement. The intensity threshold at the best frequency will be low for a receptor response. However, excitation still occurs at frequencies either above or below the best frequency, however, a greater stimulus energy (high threshold) is needed to activate the receptor (see Fig. 7 in Hearing ).

The spatial arrangement at the sensory periphery is maintained by neurons as they relay information to the cerebral cortex. For example, in the auditory system, the first order neurons or ganglion cells innervate a specific receptor cell that overlies a specifically tuned region of the basilar membrane. As the auditory neuron leaves the cochlea, each one lies adjacent to nerves innervating neighboring regions, one with a higher and the other with a lower frequency specificity. Thus, each fiber relays information from a specific frequency region. This specificity can be seen in electrical recordings from individual neuronal fibers, which show that each one is tuned, or is most sensitive to, a specific or best frequency. As the relay neurons ascend through the system centrally, they maintain the tonotopic information. Electrical recordings from the different nuclei of the brain stem, midbrain, and cortex show regions with distinct frequency selectivities. Thus, the frequency map at the periphery is maintained centrally. Similar to the auditory system, each sensory system maintains a topographic map, whereby the strictly ordered relationship with neighboring neurons at the periphery is maintained throughout the system centrally. However, the information that is relayed to and integrated in the various sensory nuclei becomes more complex. Sensory signals are contrasted and refined through the divergence of fibers to multiple regions of a nucleus or through the convergence of multiple synapses on a single cell. Included in this process are inhibitory neurons that contribute to functions such as localizing a low-frequency stimulus in hearing or regulating selective attention in vision. In addition, fibers within a particular sensory pathway decussate so that information is shared with both sides of the brain. This sharing of signals can be a part of the integration process, as in sound localization, in which excitation is maintained on one side of the brain stem, while inhibition is activated on the other side. Also, the crossing over of fibers can provide redundancy in some systems so that damage in a part of the pathway may have less severe effects overall. Finally, the brain itself can contribute in the regulation and integration of sensory stimuli by sending signals back out to the periphery. Eye movements are regulated in response to different stimuli and in response to different sounds, using various muscles. At the cellular level, studies of the inner ear show that efferent projections, originating in the brain stem and synapsing on receptor cells of the cochlea, regulate and contribute to the dynamics of auditory signal processing. Thus, organisms are not passive receptors of sensation, but active interlopers in the processing of sensory information as perceptions and ideas on the basis of the external environment.

Table 1 . Sensory Systems, Modalities, and Cell Types.

Sensory SystemsModalityStimulusReceptor TypesReceptor Cell-Types
VisualVisionLightPhotoreceptorsRods, Cones
AuditoryHearingSoundMechanoreceptorHair Cells
VestibularBalanceGravityMechanoreceptorHair Cells
SomatosensorySomatic Senses Dorsal Root Ganglion Neurons
TouchPressureMechanoreceptorCutaneous Mechanoreceptor
ProprioceptionDisplacementMechanoreceptorMuscle and Joint Receptors
Temperature SenseThermalThermoreceptorCold and Warm Receptors
PainChemical, Thermal, MechanicalChemoreceptor, Thermoreceptor, MechanoreceptorPolymodal, thermal, and mechanical nociceptors
ItchChemicalChemoreceptorChemical Nociceptor
GustatoryTasteChemicalChemoreceptorTaste Buds
OlfactorySmellChemicalChemoreceptorOlfactory Sensory Neurons

Adapted from Kandel et al. (2000) Principles of Neural Science, McGraw-Hill, New York, N Y. p. 414.


Biology of Sensory Systems, 2nd Edition

Biology of Sensory Systems has thus been completely revised and takes a molecular, evolutionary and comparative approach, providing an overview of sensory systems in vertebrates, invertebrates and prokaryotes, with a strong focus on human senses.

Written by a renowned author with extensive teaching experience, the book covers, in six parts, the general features of sensory systems, the mechanosenses, the chemosenses, the senses which detect electromagnetic radiation, other sensory systems including pain, thermosensitivity and some of the minority senses and, finally, provides an outline and discussion of philosophical implications.

  • Greater emphasis on molecular biology and intracellular mechanisms
  • New chapter on genomics and sensory systems
  • Sections on TRP channels, synaptic transmission, evolution of nervous systems, arachnid mechanosensitive sensilla and photoreceptors, electroreception in the Monotremata, language and the FOXP2 gene, mirror neurons and the molecular biology of pain

Updated passages on human olfaction and gustation. 

Over four hundred illustrations, boxes containing supplementary material and self-assessment questions and a full bibliography at the end of each part make Biology of Sensory Systems essential reading for undergraduate students of biology, zoology, animal physiology, neuroscience, anatomy and physiological psychology. The book is also suitable for postgraduate students in more specialised courses such as vision sciences, optometry, neurophysiology, neuropathology, developmental biology.

Praise from the reviews of the first edition:

"An excellent advanced undergraduate/postgraduate textbook." ASLIB BOOK GUIDE

"The emphasis on comparative biology and evolution is one of the distinguishing features of this self-contained book. . this is an informative and thought-provoking text. " TIMES HIGHER EDUCATIONAL SUPPLEMENT


Chapter 17. Sensory Systems

Figure 17.1. This shark uses its senses of sight, vibration (lateral-line system), and smell to hunt, but it also relies on its ability to sense the electric fields of prey, a sense not present in most land animals. (credit: modification of work by Hermanus Backpackers Hostel, South Africa)

Introduction

In more advanced animals, the senses are constantly at work, making the animal aware of stimuli—such as light, or sound, or the presence of a chemical substance in the external environment—and monitoring information about the organism’s internal environment. All bilaterally symmetric animals have a sensory system, and the development of any species’ sensory system has been driven by natural selection thus, sensory systems differ among species according to the demands of their environments. The shark, unlike most fish predators, is electrosensitive—that is, sensitive to electrical fields produced by other animals in its environment. While it is helpful to this underwater predator, electrosensitivity is a sense not found in most land animals.


Contents

Sensory systems code for four aspects of a stimulus type (modality), intensity, location, and duration. Arrival time of a sound pulse and phase differences of continuous sound are used for sound localization. Certain receptors are sensitive to certain types of stimuli (for example, different mechanoreceptors respond best to different kinds of touch stimuli, like sharp or blunt objects). Receptors send impulses in certain patterns to send information about the intensity of a stimulus (for example, how loud a sound is). The location of the receptor that is stimulated gives the brain information about the location of the stimulus (for example, stimulating a mechanoreceptor in a finger will send information to the brain about that finger). The duration of the stimulus (how long it lasts) is conveyed by firing patterns of receptors. These impulses are transmitted to the brain through afferent neurons.

While debate exists among neurologists as to the specific number of senses due to differing definitions of what constitutes a sense, Gautama Buddha and Aristotle classified five ‘traditional’ human senses which have become universally accepted: touch, taste, smell, sight, and hearing. Other senses that have been well-accepted in most mammals, including humans, include nociception, equilibrioception, kinaesthesia, and thermoception. Furthermore, some nonhuman animals have been shown to possess alternate senses, including magnetoception and electroreception. [4]

Receptors Edit

The initialization of sensation stems from the response of a specific receptor to a physical stimulus. The receptors which react to the stimulus and initiate the process of sensation are commonly characterized in four distinct categories: chemoreceptors, photoreceptors, mechanoreceptors, and thermoreceptors. All receptors receive distinct physical stimuli and transduce the signal into an electrical action potential. This action potential then travels along afferent neurons to specific brain regions where it is processed and interpreted. [5]

Chemoreceptors Edit

Chemoreceptors, or chemosensors, detect certain chemical stimuli and transduce that signal into an electrical action potential. The two primary types of chemoreceptors are:

  • Distance chemoreceptors are integral to receiving stimuli in gases in the olfactory system through both olfactory receptor neurons and neurons in the vomeronasal organ.
  • Direct chemoreceptors that detect stimuli in liquids include the taste buds in the gustatory system as well as receptors in the aortic bodies which detect changes in oxygen concentration. [6]

Photoreceptors Edit

Photoreceptors are capable of phototransduction, a process which converts light (electromagnetic radiation) into, among other types of energy, a membrane potential. The three primary types of photoreceptors are: Cones are photoreceptors which respond significantly to color. In humans the three different types of cones correspond with a primary response to short wavelength (blue), medium wavelength (green), and long wavelength (yellow/red). [7] Rods are photoreceptors which are very sensitive to the intensity of light, allowing for vision in dim lighting. The concentrations and ratio of rods to cones is strongly correlated with whether an animal is diurnal or nocturnal. In humans rods outnumber cones by approximately 20:1, while in nocturnal animals, such as the tawny owl, the ratio is closer to 1000:1. [7] Ganglion Cells reside in the adrenal medulla and retina where they are involved in the sympathetic response. Of the

1.3 million ganglion cells present in the retina, 1-2% are believed to be photosensitive ganglia. [8] These photosensitive ganglia play a role in conscious vision for some animals, [9] and are believed to do the same in humans. [10]

Mechanoreceptors Edit

Mechanoreceptors are sensory receptors which respond to mechanical forces, such as pressure or distortion. [11] While mechanoreceptors are present in hair cells and play an integral role in the vestibular and auditory systems, the majority of mechanoreceptors are cutaneous and are grouped into four categories:

  • Slowly adapting type 1 receptors have small receptive fields and respond to static stimulation. These receptors are primarily used in the sensations of form and roughness.
  • Slowly adapting type 2 receptors have large receptive fields and respond to stretch. Similarly to type 1, they produce sustained responses to a continued stimuli.
  • Rapidly adapting receptors have small receptive fields and underlie the perception of slip.
  • Pacinian receptors have large receptive fields and are the predominant receptors for high-frequency vibration.

Thermoreceptors Edit

Thermoreceptors are sensory receptors which respond to varying temperatures. While the mechanisms through which these receptors operate is unclear, recent discoveries have shown that mammals have at least two distinct types of thermoreceptors: [12] [ permanent dead link ] [ failed verification ]

  • The end-bulb of Krause, or bulboid corpuscle, detects temperatures above body temperature. detects temperatures below body temperature.

TRPV1 is a heat-activated channel that acts as a small heat detecting thermometer in the membrane which begins the polarization of the neural fiber when exposed to changes in temperature. Ultimately, this allows us to detect ambient temperature in the warm/hot range. Similarly, the molecular cousin to TRPV1, TRPM8, is a cold-activated ion channel that responds to cold. Both cold and hot receptors are segregated by distinct subpopulations of sensory nerve fibers, which shows us that the information coming into the spinal cord is originally separate. Each sensory receptor has its own “labeled line” to convey a simple sensation experienced by the recipient. Ultimately, TRP channels act as thermosensors, channels that help us to detect changes in ambient temperatures. [13]

Nociceptors Edit

Nociceptors respond to potentially damaging stimuli by sending signals to the spinal cord and brain. This process, called nociception, usually causes the perception of pain. [14] They are found in internal organs, as well as on the surface of the body. Nociceptors detect different kinds of damaging stimuli or actual damage. Those that only respond when tissues are damaged are known as "sleeping" or "silent" nociceptors.

  • Thermal nociceptors are activated by noxious heat or cold at various temperatures.
  • Mechanical nociceptors respond to excess pressure or mechanical deformation.
  • Chemical nociceptors respond to a wide variety of chemicals, some of which are signs of tissue damage. They are involved in the detection of some spices in food.

All stimuli received by the receptors listed above are transduced to an action potential, which is carried along one or more afferent neurons towards a specific area of the brain. While the term sensory cortex is often used informally to refer to the somatosensory cortex, the term more accurately refers to the multiple areas of the brain at which senses are received to be processed. For the five traditional senses in humans, this includes the primary and secondary cortices of the different senses: the somatosensory cortex, the visual cortex, the auditory cortex, the primary olfactory cortex, and the gustatory cortex. [15] Other modalities have corresponding sensory cortex areas as well, including the vestibular cortex for the sense of balance. [16]

Somatosensory cortex Edit

Located in the parietal lobe, the primary somatosensory cortex is the primary receptive area for the sense of touch and proprioception in the somatosensory system. This cortex is further divided into Brodmann areas 1, 2, and 3. Brodmann area 3 is considered the primary processing center of the somatosensory cortex as it receives significantly more input from the thalamus, has neurons highly responsive to somatosensory stimuli, and can evoke somatic sensations through electrical stimulation. Areas 1 and 2 receive most of their input from area 3. There are also pathways for proprioception (via the cerebellum), and motor control (via Brodmann area 4). See also: S2 Secondary somatosensory cortex.

Visual cortex Edit

The visual cortex refers to the primary visual cortex, labeled V1 or Brodmann area 17, as well as the extrastriate visual cortical areas V2-V5. [17] Located in the occipital lobe, V1 acts as the primary relay station for visual input, transmitting information to two primary pathways labeled the dorsal and ventral streams. The dorsal stream includes areas V2 and V5, and is used in interpreting visual ‘where’ and ‘how.’ The ventral stream includes areas V2 and V4, and is used in interpreting ‘what.’ [18] Increases in Task-negative activity are observed in the ventral attention network, after abrupt changes in sensory stimuli, [19] at the onset and offset of task blocks, [20] and at the end of a completed trial. [21] [ relevant? ]

Auditory cortex Edit

Located in the temporal lobe, the auditory cortex is the primary receptive area for sound information. The auditory cortex is composed of Brodmann areas 41 and 42, also known as the anterior transverse temporal area 41 and the posterior transverse temporal area 42, respectively. Both areas act similarly and are integral in receiving and processing the signals transmitted from auditory receptors.

Primary olfactory cortex Edit

Located in the temporal lobe, the primary olfactory cortex is the primary receptive area for olfaction, or smell. Unique to the olfactory and gustatory systems, at least in mammals, is the implementation of both peripheral and central mechanisms of action. [ clarification needed ] The peripheral mechanisms involve olfactory receptor neurons which transduce a chemical signal along the olfactory nerve, which terminates in the olfactory bulb. The chemoreceptors in the receptor neurons that start the signal cascade are G protein-coupled receptors. The central mechanisms include the convergence of olfactory nerve axons into glomeruli in the olfactory bulb, where the signal is then transmitted to the anterior olfactory nucleus, the piriform cortex, the medial amygdala, and the entorhinal cortex, all of which make up the primary olfactory cortex.

In contrast to vision and hearing, the olfactory bulbs are not cross-hemispheric the right bulb connects to the right hemisphere and the left bulb connects to the left hemisphere.

Gustatory cortex Edit

The gustatory cortex is the primary receptive area for taste. The word taste is used in a technical sense to refer specifically to sensations coming from taste buds on the tongue. The five qualities of taste detected by the tongue include sourness, bitterness, sweetness, saltiness, and the protein taste quality, called umami. In contrast, the term flavor refers to the experience generated through integration of taste with smell and tactile information. The gustatory cortex consists of two primary structures: the anterior insula, located on the insular lobe, and the frontal operculum, located on the frontal lobe. Similarly to the olfactory cortex, the gustatory pathway operates through both peripheral and central mechanisms. [ clarification needed ] Peripheral taste receptors, located on the tongue, soft palate, pharynx, and esophagus, transmit the received signal to primary sensory axons, where the signal is projected to the nucleus of the solitary tract in the medulla, or the gustatory nucleus of the solitary tract complex. The signal is then transmitted to the thalamus, which in turn projects the signal to several regions of the neocortex, including the gustatory cortex. [22]

The neural processing of taste is affected at nearly every stage of processing by concurrent somatosensory information from the tongue, that is, mouthfeel. Scent, in contrast, is not combined with taste to create flavor until higher cortical processing regions, such as the insula and orbitofrontal cortex. [23]


COMMUNICATION I NERVOUS AND SENSORY SYSTEMS

The nervous system is a rapid communication system that interacts continuously with the endocrine system to control coordination of body functions. In the vertebrates it plays three basic roles: (i) it acquaints the organism with its external environment, and stimulates the organism to orient itself favorably to that environment (ii) it participates in regulation of the internal environment, and (iii) it serves as storage for information These functions are accomplished by the nerves, spinal cord, and brain in association with receptors (sense organs) and effectors (muscles and glands). The basic unit of nervous integration in all animals is the neuron, a highly specialized cell designed to conduct self-propagating impulses, called action potentials, to other cells. Action potentials are transmitted from one neuron to another across synpses which may be either electrical or chemical. The thin gap between neurons at chemical synapses is bridged by a chemical neuro-transmitter molecule, which is released from the synaptic knob, and can be either stimulatory or inhibitory.

The simplest organization of neurons into a system is the nerve net of Cnidarians, basically a plexus of nerve cells that, with additions, is the basis of nervous systems of several invertebrate phyla. With the appearance of ganglia (nerve centers) in bilateral flatworms, nervous system is differentiated into central and peripheral divisions. In vertebrates, the central nervous system consists of a brain and spinal cord. Fishes and amphibians have a three-part linear brain, whereas in mammals, the cerebral cortex has become a vastly enlarged multicomponent structure that has assumed the most important integrative activities of the nervous system. It completely overshadows the ancient brain, which is consigned to the role of relay center and to serving numerous unconscious but nonetheless vital functions such as breathing, blood pressure, and heart rate.

In human the left cerebral hemisphere is usually specialized for language and mathematical skills while the right hemisphere is specialized for visual, spatial, and musical skills.

The peripheral nervous system connects the central nervous system to receptors and effector organs. It is divided broadly into an afferent system, which conducts sensory signals to the central nervous system, and an efferent system, which conveys motor impulses to effector organs. This efferent system is subdivided into the somatic nervous system, which innervates skeletal muscles, and the autonomic nervous system, which innervates smooth and cardiac muscle and glands. The autonomic nervous system is subdivided into anatomically distinct sympathetic and parasympathetic systems, each of which sends fibers to most body organs. Generally the sympathetic system governs excitatory activities and the parasympathetic system governs maintenance and restoration of body resources.

Sensory organs are receptors designed especially to respond to internal or environmental change. The most primitive and ubiquitous sense is chemoreception. Chemoreceptors may be contact receptors, such as the vertebrate sense of taste, or distance receptors such as smell, which detects airborne molecules. In both cases, a specific chemical interacts with a particular receptor and results in impulses that are transmitted to, and interpreted by the brain. In spite of the similarity between these two senses, the sense of smell is far more sensitive and complex.

Receptors for touch, pain, equilibrium, and hearing are all mechanical force receptors. Touch and pain receptors are characteristically simple structures, but hearing and equilibrium are highly specialized senses based on special hair cells that respond to mechanical deformation. Sound waves received by the ear are mechanically amplified and transmitted to the inner ear where different areas of cochlea respond to different sound frequencies. Equilibrium receptors, also located in the inner ear, consist of two saclike static balance organs and three semicircular canals that detect rotational acceleration.

Vision receptors (photoreceptors) are associated with special pigment molecules that photochemically decompose in the presence of light and, in doing so, trigger nerve impulses in optic fibers. The advanced compound eye of arthropods is especially well suited to detecting motion in the visual field. Vertebrates have a camera eye with focusing optics. The photoreceptor cells of the retina are of two kinds: rods, designed for high sensitivity with dim light, and cones, designed for color vision in daylight. Cones predominate in the fovea centralis of human eyes, the area of keenest vision. Rods are more abundant in peripheral areas of the retina.


Sensory systems - Biology bibliographies - in Harvard style

Your Bibliography: Butler, J. and Maruska, K., 2016. Mechanosensory signaling as a potential mode of communication during social interactions in fishes. Journal of Experimental Biology, 219(18), pp.2781-2789.

Engelmann, J., Hanke, W., Mogdans, J. and Bleckmann, H.

Hydrodynamic stimuli and the fish lateral line

2000 - Nature

In-text: (Engelmann, Hanke, Mogdans and Bleckmann, 2000)

Your Bibliography: Engelmann, J., Hanke, W., Mogdans, J. and Bleckmann, H., 2000. Hydrodynamic stimuli and the fish lateral line. Nature, 408(6808), pp.51-52.

Hanke, W., Wieskotten, S., Marshall, C. and Dehnhardt, G.

Hydrodynamic perception in true seals (Phocidae) and eared seals (Otariidae)

2012 - Journal of Comparative Physiology A

In-text: (Hanke, Wieskotten, Marshall and Dehnhardt, 2012)

Your Bibliography: Hanke, W., Wieskotten, S., Marshall, C. and Dehnhardt, G., 2012. Hydrodynamic perception in true seals (Phocidae) and eared seals (Otariidae). Journal of Comparative Physiology A, 199(6), pp.421-440.

Kremers, D., Célérier, A., Schaal, B., Campagna, S., Trabalon, M., Böye, M., Hausberger, M. and Lemasson, A.

Sensory Perception in Cetaceans: Part I—Current Knowledge about Dolphin Senses As a Representative Species

2016 - Frontiers in Ecology and Evolution

In-text: (Kremers et al., 2016)

Your Bibliography: Kremers, D., Célérier, A., Schaal, B., Campagna, S., Trabalon, M., Böye, M., Hausberger, M. and Lemasson, A., 2016. Sensory Perception in Cetaceans: Part I—Current Knowledge about Dolphin Senses As a Representative Species. Frontiers in Ecology and Evolution, 4.

Levenson, D. and Dizon, A.

Genetic evidence for the ancestral loss of short-wavelength-sensitive cone pigments in mysticete and odontocete cetaceans

2003 - Proceedings of the Royal Society of London. Series B: Biological Sciences

In-text: (Levenson and Dizon, 2003)

Your Bibliography: Levenson, D. and Dizon, A., 2003. Genetic evidence for the ancestral loss of short-wavelength-sensitive cone pigments in mysticete and odontocete cetaceans. Proceedings of the Royal Society of London. Series B: Biological Sciences, 270(1516), pp.673-679.

Lundmark, C.

Fish Vision

2010 - BioScience

In-text: (Lundmark, 2010)

Your Bibliography: Lundmark, C., 2010. Fish Vision. BioScience, 60(1), pp.88-88.

Mogdans, J.

Sensory ecology of the fish lateral‐line system: Morphological and physiological adaptations for the perception of hydrodynamic stimuli

2019 - Journal of Fish Biology

In-text: (Mogdans, 2019)

Your Bibliography: Mogdans, J., 2019. Sensory ecology of the fish lateral‐line system: Morphological and physiological adaptations for the perception of hydrodynamic stimuli. Journal of Fish Biology,.

NEWMAN, L. A. and ROBINSON, P. R.

Cone visual pigments of aquatic mammals

2005 - Visual Neuroscience

In-text: (NEWMAN and ROBINSON, 2005)

Your Bibliography: NEWMAN, L. and ROBINSON, P., 2005. Cone visual pigments of aquatic mammals. Visual Neuroscience, 22(6), pp.873-879.

Peichl, L., Behrmann, G. and Kröger, R. H. H.

For whales and seals the ocean is not blue: a visual pigment loss in marine mammals*

2001 - European Journal of Neuroscience

In-text: (Peichl, Behrmann and Kröger, 2001)

Your Bibliography: Peichl, L., Behrmann, G. and Kröger, R., 2001. For whales and seals the ocean is not blue: a visual pigment loss in marine mammals*. European Journal of Neuroscience, 13(8), pp.1520-1528.

Yokoyama, S. and Yokoyama, R.

ADAPTIVE EVOLUTION OF PHOTORECEPTORS AND VISUAL PIGMENTS IN VERTEBRATES

1996 - Annual Review of Ecology and Systematics

In-text: (Yokoyama and Yokoyama, 1996)

Your Bibliography: Yokoyama, S. and Yokoyama, R., 1996. ADAPTIVE EVOLUTION OF PHOTORECEPTORS AND VISUAL PIGMENTS IN VERTEBRATES. Annual Review of Ecology and Systematics, 27(1), pp.543-567.


36: Sensory Systems - Biology

The Sensory Biology Unit is focused on understanding the fundamental processes underlying the sensory innervation with particular focus on pain-related sensory neurons. The research is based on the knowledge that sensory systems use similar biological processes for signaling, adaptation and modulation, and for protection from injury. Important current projects include the understanding of migraine pain and its associated sensory disturbances. Furthermore, we apply molecules from the sensory system enhance ischemic protection in the eye and heart.

The current lab has several methods availbale that is used to study sensory biology these include:

  1. Cellular/molecular methods: western blot, immunohistochemistry, PCR, fluorescent microscopy.
  2. Ex vivo methods: myograph of rodent/human arteries and organ culture.
  3. In vivo methods: ERG OCT Fundus PV-loop, myocardial infarction, intravitreal microscopy and inflammatory model of migraine.

The Sensory Biology Unit a subdivision under the Department of Clinical Experimental Research (lead by Prof. Lars Edvinsson).at Rigshospitalet Glostrup


Watch the video: MN4 36 4 36 Visceral Motor System VMS FuncAv20635441,P36 (May 2022).