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The sensory nervous system is a part of the
nervous system In biology, the classical doctrine of the nervous system determines that it is a Complex system, highly complex part of an animal that coordinates its Behavior, actions and Sense, sensory information by transmitting action potential, signals ...

nervous system
responsible for processing
sensory
sensory
information. A sensory system consists of
sensory neuron Sensory neurons, also known as afferent neurons, are neuron A neuron or nerve cell is an membrane potential#Cell excitability, electrically excitable cell (biology), cell that communicates with other cells via specialized connections called sy ...
s (including the sensory receptor cells),
neural pathway A neural pathway is the connection formed by axon An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences Despite the various English dialects Dialect The term dialect (from Lat ...
s, and parts of the
brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tiss ...

brain
involved in sensory
perception Perception (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the powe ...

perception
. Commonly recognized sensory systems are those for
vision Vision or The Vision may refer to: Perception Optical perception * Visual perception Visual perception is the ability to interpret the surrounding environment (biophysical), environment through photopic vision (daytime vision), color visio ...
,
hearing Schematic diagram of the human ear Hearing, or auditory perception, is the ability to perceive Sound, sounds through an organ, such as an ear, by detecting Vibration, vibrations as periodic changes in the pressure of a surrounding medium. Th ...
,
touch The somatosensory system is a part of the sensory nervous system The sensory nervous system is a part of the nervous system responsible for processing sense, sensory information. A sensory system consists of sensory neurons (including the sen ...
,
taste The gustatory system or sense of taste is the sensory system The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons (including the sensory re ...

taste
, smell, and
balance Balance may refer to: Common meanings * Balance (ability) in biomechanics * Balance (accounting) * Balance or weighing scale Arts and entertainment Film * Balance (1983 film), ''Balance'' (1983 film), a Bulgarian film * Balance (1989 film), ''Bal ...
. In short, senses are
transducers A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another. Transducers are often employed at the boundaries of automation Automation describ ...
from the physical world to the realm of the mind where we interpret the information, creating our
perception Perception (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the powe ...

perception
of the world around us. :Organisms need information to solve at least three kinds of problems: (a) to maintain an appropriate environment, i.e.,
homeostasis In , homeostasis is the state of steady internal, , and conditions maintained by . This is the condition of optimal functioning for the organism and includes many variables, such as and , being kept within certain pre-set limits (homeostatic r ...
; (b) to time activities (e.g., seasonal changes in behavior) or synchronize activities with those of
conspecifics Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species In biology, a species is the basic unit of biological classification, classification and a taxonomic ran ...
; and (c) to locate and respond to resources or threats (e.g., by moving towards resources or evading or attacking threats). Organisms also need to transmit information in order to influence another's behavior: to identify themselves, warn conspecifics of danger, coordinate activities, or deceive. The
receptive field The receptive field, or sensory space, is a delimited medium where some physiological stimuli can evoke a sensory neuronal response in specific organism In biology, an organism () is any organic, life, living system that functions as a ...

receptive field
is the area of the body or environment to which a receptor organ and receptor cells respond. For instance, the part of the world an eye can see, is its receptive field; the light that each rod or
cone A cone is a three-dimensional Three-dimensional space (also: 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called parameter A parameter (from the Ancient Greek language, Ancient Greek wikt:πα ...

cone
can see, is its receptive field.
Receptive field The receptive field, or sensory space, is a delimited medium where some physiological stimuli can evoke a sensory neuronal response in specific organism In biology, an organism () is any organic, life, living system that functions as a ...

Receptive field
s have been identified for the
visual system The visual system comprises the sensory organ A sense is a biological system A biological system is a complex network which connects several biologically relevant entities. Biological organization spans several scales and are determined b ...
,
auditory system The auditory system is the sensory system The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons (including the sensory receptor cells), neur ...
and
somatosensory system The somatosensory system is a part of the sensory nervous system The sensory nervous system is a part of the nervous system responsible for processing sense, sensory information. A sensory system consists of sensory neurons (including the sen ...
.


Stimulus

Sensory systems code for four aspects of a
stimulus A stimulus is something that causes a physiological response. It may refer to: *Stimulation Stimulation is the encouragement of development or the cause of activity generally. For example, "The press provides stimulation of political discourse." ...
; type (
modality Modality may refer to: Humanities * Modality (theology), the organization and structure of the church, as distinct from sodality or parachurch organizations * Modality (music), in music, the subject concerning certain diatonic scales * Modalities ...
), intensity, location, and duration. Arrival
time Time is the continued sequence of existence and event (philosophy), events that occurs in an apparently irreversible process, irreversible succession from the past, through the present, into the future. It is a component quantity of various me ...

time
of a sound
pulse In medicine Medicine is the science Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity, awareness, or understanding of someone or something, such as facts ( descriptive knowledge) ...

pulse
and
phase Phase or phases may refer to: Science * State of matter, or phase, one of the distinct forms in which matter can exist *Phase (matter) In the physical sciences, a phase is a region of space (a thermodynamic system A thermodynamic system is a ...
differences of continuous sound are used for
sound localization Sound localization is a listener's ability to identify the location or origin of a detected sound In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'natur ...
. Certain receptors are sensitive to certain types of stimuli (for example, different
mechanoreceptor A mechanoreceptor, also called mechanoceptor, is a sensory receptor Sensory neurons, also known as afferent neurons, are neurons in the nervous system In Biology, biology, the nervous system is a Complex system, highly complex part of an ...
s respond best to different kinds of touch stimuli, like sharp or blunt objects). Receptors
send impulses
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 Sensory neurons, also known as afferent neurons, are neuron A neuron or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapse SyNAPSE is a DARPA program that aims to ...
.


Senses and receptors

While debate exists among neurologists as to the specific number of senses due to differing definitions of what constitutes a
sense A sense is a biological system used by an organism for sensation, the process of gathering information about the world and responding to Stimulus (physiology), stimuli. (For example, in the human body, the brain receives signals from the senses ...

sense
,
Gautama Buddha Gautama Buddha, popularly known as the Buddha (also known as Siddhattha Gotama or Siddhārtha Gautama or Buddha Shakyamuni), was an , a religious leader and teacher who lived in (c. 6th to 5th century BCE or c. 5th to 4th century BCE). He ...

Gautama Buddha
and
Aristotle Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher A philosopher is someone who practices philosophy Philosophy (from , ) is the study of general and fundamental quest ...

Aristotle
classified five ‘traditional’ human senses which have become universally accepted:
touch The somatosensory system is a part of the sensory nervous system The sensory nervous system is a part of the nervous system responsible for processing sense, sensory information. A sensory system consists of sensory neurons (including the sen ...

touch
,
taste The gustatory system or sense of taste is the sensory system The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons (including the sensory re ...

taste
, smell,
sight Visual perception is the ability to interpret the surrounding environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biolo ...
, and
hearing Schematic diagram of the human ear Hearing, or auditory perception, is the ability to perceive Sound, sounds through an organ, such as an ear, by detecting Vibration, vibrations as periodic changes in the pressure of a surrounding medium. Th ...
. Other senses that have been well-accepted in most mammals, including humans, include
nociception Nociception (also nocioception, from Latin ''nocere'' 'to harm or hurt') is the Somatosensory system, sensory nervous system's process of encoding noxious stimuli. It deals with a series of events and processes required for an organism to receive a ...
,
equilibrioception The sense of balance or equilibrioception is the perception Perception (from the Latin ''perceptio'', meaning gathering or receiving) is the organization, identification, and interpretation of Sense, sensory information in order to repr ...
, kinaesthesia, and
thermoceptionThermoception or thermoreception is the sensation and perception Perception (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally ...
. Furthermore, some nonhuman animals have been shown to possess alternate senses, including
magnetoception Magnetoreception (also magnetoception) is a sense Sense relates to any of the systems and corresponding organs involved in sensation, i.e. the physical process of responding to Stimulus (physiology), stimuli and providing data for perception. Dur ...
and
electroreception Electroreception or electroception is the biological ability to perceive natural electrical Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a ...
.


Receptors

The initialization of sensation stems from the response of a specific receptor to a physical
stimulus A stimulus is something that causes a physiological response. It may refer to: *Stimulation Stimulation is the encouragement of development or the cause of activity generally. For example, "The press provides stimulation of political discourse." ...
. The receptors which react to the stimulus and initiate the process of sensation are commonly characterized in four distinct categories:
chemoreceptors A chemoreceptor, also known as chemosensor, is a specialized sensory receptor Sensory neurons, also known as afferent neurons, are neurons in the nervous system In Biology, biology, the nervous system is a Complex system, highly complex ...
,
photoreceptors
photoreceptors
,
mechanoreceptors A mechanoreceptor, also called mechanoceptor, is a sensory receptor Sensory neurons, also known as afferent neurons, are neuron A neuron or nerve cell is an electrically excitable cell Cell most often refers to: * Cell (biology), the fu ...
, and
thermoreceptorsA thermoreceptor is a non-specialised sense Sense relates to any of the systems and corresponding organs involved in sensation, i.e. the physical process of responding to Stimulus (physiology), stimuli and providing data for perception. During sensa ...
. All receptors receive distinct physical stimuli and transduce the signal into an electrical
action potential In physiology Physiology (; ) is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence ...

action potential
. This action potential then travels along
afferent neurons Sensory neurons, also known as afferent neurons, are neuron A neuron or nerve cell is an electrically excitable cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * ...
to specific brain regions where it is processed and interpreted.


Chemoreceptors

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 Gas is one of the four fundamental states of matter (the others being solid Solid is one of the four fundamental states of matter (the others being liquid A liquid is a nearly incompressible fluid In physics, a fluid is a su ...
in the
olfactory system The olfactory system, or sense of smell, is the sensory nervous system, sensory system used for smelling (olfaction). Olfaction is one of the special senses, that have directly associated specific organs. Most mammals and reptiles have a main ol ...

olfactory system
through both olfactory receptor neurons and neurons in the
vomeronasal organ The vomeronasal organ (VNO), or Jacobson's organ, is the paired auxiliary olfactory Olfaction, or the sense of smell, is the special sense through which smells (or odors) are perceived. It occurs when an odor binds to a olfactory receptor, re ...

vomeronasal organ
. * Direct chemoreceptors that detect stimuli in
liquids A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric process, isochoric flow) refers to a fluid flow, flow in which the material density is constant within a fluid par ...
include the
taste buds Taste buds contain the taste receptor cells, which are also known as gustatory cells. The taste receptors are located around the small structures known as lingual papillae, papillae found on the upper surface of the tongue, soft palate, upper e ...

taste buds
in the
gustatory system The gustatory system or sense of taste is the sensory system The sensory nervous system is a part of the nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, ph ...
as well as receptors in the
aortic bodies The aortic bodies are one of several small clusters of peripheral chemoreceptors located along the aorta, aortic arch. They are important in measuring Partial pressure, partial pressures of oxygen and carbon dioxide in the blood, and Acid–base hom ...
which detect changes in
oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

oxygen
concentration.


Photoreceptors

Photoreceptors are capable of
phototransduction Visual phototransduction is the sensory transduction of the visual system The visual system comprises the sensory organ A sense is a biological system A biological system is a complex network which connects several biologically releva ...

phototransduction
, a process which converts light (
electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. ...

electromagnetic radiation
) into, among other types of
energy In physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regula ...

energy
, a
membrane potential Membrane potential (also transmembrane potential or membrane voltage) is the difference in electric potential The electric potential (also called the ''electric field potential'', potential drop, the electrostatic potential) is defined as the ...

membrane potential
. The three primary types of photoreceptors are:
Cones A cone is a three-dimensional space, three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the Apex (geometry), apex or vertex (geometry), vertex. A cone is fo ...

Cones
are photoreceptors which respond significantly to
color Color (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American Engli ...

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)."eye, human." Encyclopædia Britannica. Encyclopædia Britannica Ultimate Reference Suite. Chicago: Encyclopædia Britannica, 2010. 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 Diurnal ("daily Daily or The Daily may refer to: Journalism * Daily newspaper A newspaper is a Periodical literature, periodical publication containing written News, information about current events and is often typed in black ink with a ...
or
nocturnal Nocturnality is an animal behavior Ethology is the scientific Science (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was original ...
. In humans rods outnumber cones by approximately 20:1, while in nocturnal animals, such as the
tawny owl The tawny owl (also called the brown owl) (''Strix aluco'') is commonly found in woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the ''plurale tantum'' woo ...

tawny owl
, the ratio is closer to 1000:1. Ganglion Cells reside in the
adrenal medulla The adrenal medulla ( la, medulla glandulae suprarenalis) is part of the adrenal gland The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldostero ...
and
retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well ...

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. These photosensitive ganglia play a role in conscious vision for some animals, and are believed to do the same in humans.


Mechanoreceptors

Mechanoreceptors are sensory receptors which respond to mechanical forces, such as
pressure Pressure (symbol: ''p'' or ''P'') is the force In physics, a force is an influence that can change the motion (physics), motion of an Physical object, object. A force can cause an object with mass to change its velocity (e.g. moving fr ...

pressure
or
distortion Distortion is the alteration of the original shape (or other characteristic) of something. In communications Communication (from Latin ''communicare'', meaning "to share" or "to be in relation with") is "an apparent answer to the painful di ...

distortion
. While mechanoreceptors are present in
hair cells Hair cells are the sensory receptor Sensory neurons, also known as afferent neurons, are neurons in the nervous system In Biology, biology, the nervous system is a Complex system, highly complex part of an animal that coordinates its Be ...
and play an integral role in the
vestibular The Vestibular (from pt, vestíbulo, "entrance hall") is a competitive examination and is the primary and widespread entrance system used by Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the ...
and
auditory system The auditory system is the sensory system The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons (including the sensory receptor cells), neur ...
s, the majority of mechanoreceptors are
cutaneous Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism ...
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 Form is the shape A shape or figure is the form of an object or its external boundary, outline, or external Surface (mathematics), surface, as opposed to other properties such as color, Surface texture, texture, or material type. A plane shap ...

form
and . * ''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

Thermoreceptors are sensory receptors which respond to varying
temperature Temperature ( ) is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy Thermal radiation in visible light can be seen on this hot metalwork. Thermal energy refers to several distinct physical concept ...

temperature
s. While the mechanisms through which these receptors operate is unclear, recent discoveries have shown that
mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be i ...
s have at least two distinct types of thermoreceptors:Krantz, John.
Experiencing Sensation and Perception
'. Pearson Education, Limited, 2009. p. 12.3
* The end-bulb of Krause, or bulboid corpuscle, detects temperatures above body temperature. * Ruffini's end organ 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.


Nociceptors

Nociceptors respond to potentially damaging stimuli by sending signals to the spinal cord and brain. This process, called
nociception Nociception (also nocioception, from Latin ''nocere'' 'to harm or hurt') is the Somatosensory system, sensory nervous system's process of encoding noxious stimuli. It deals with a series of events and processes required for an organism to receive a ...
, usually causes the perception of
pain Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain The International Association for the Study of Pain (IASP) is an international learned society A learned societ ...
. 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.


Sensory cortex

All
stimuli A stimulus is something that causes a physiological response. It may refer to: *Stimulation Stimulation is the encouragement of development or the cause of activity generally. For example, "The press provides stimulation of political discourse." ...
received by the
receptors Receptor may refer to: *Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a ne ...

receptors
listed above are transduced to an
action potential In physiology Physiology (; ) is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence ...

action potential
, which is carried along one or more
afferent neurons Sensory neurons, also known as afferent neurons, are neuron A neuron or nerve cell is an electrically excitable cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * ...
towards a specific area of the brain. While the term
sensory cortexThe sensory cortex can refer informally to the primary somatosensory cortex The primary somatosensory cortex is located in the postcentral gyrus, and is part of the somatosensory system The somatosensory system is a part of the sensory nervous s ...
is often used informally to refer to the
somatosensory cortex The somatosensory system is a part of the sensory nervous system that is associated with the sense of touch, but includes parallel receptors and nerve pathways for the sensations of temperature, body position and movement, and pain. This complex s ...
, the term more accurately refers to the multiple areas of the brain at which
sense A sense is a biological system used by an organism for sensation, the process of gathering information about the world and responding to Stimulus (physiology), stimuli. (For example, in the human body, the brain receives signals from the senses ...

sense
s 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 visual cortex of the brain is the area of the cerebral cortex that processes visual perception, visual information. It is located in the occipital lobe. Sensory input originating from the Eye, eyes travels through the lateral geniculate nucleu ...

visual cortex
, the
auditory cortex The auditory cortex is the part of the temporal lobe The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals co ...

auditory cortex
, the
primary olfactory cortexThe primary olfactory cortex is a portion of the cerebral cortex involved in olfaction Olfaction, or the sense of smell, is the special sense through which smells (or odors) are perceived. It occurs when an odor binds to a olfactory receptor, re ...
, and the
gustatory cortex The primary gustatory cortex is a brain structure responsible for the perception of taste The gustatory system or sense of taste is the sensory system The sensory nervous system is a part of the nervous system responsible for processing sens ...
.Brynie, F.H. (2009). Brain Sense: The Science of the Senses and How We Process the World Around Us. American Management Association. Other modalities have corresponding sensory cortex areas as well, including the for the sense of balance.


Somatosensory cortex

Located in the
parietal lobe The parietal lobe is one of the four Lobes of the brain, major lobes of the cerebral cortex in the brain of mammals. The parietal lobe is positioned above the temporal lobe and behind the frontal lobe and central sulcus. The parietal lobe integrat ...

parietal lobe
, the
primary somatosensory cortex The primary somatosensory cortex is located in the postcentral gyrus The postcentral gyrus is a prominent gyrus In neuroanatomy, a gyrus (pl. ''gyri'') is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci (de ...
is the primary receptive area for the sense of
touch The somatosensory system is a part of the sensory nervous system The sensory nervous system is a part of the nervous system responsible for processing sense, sensory information. A sensory system consists of sensory neurons (including the sen ...

touch
and
proprioception Proprioception ( ), also referred to as kinaesthesia (or kinesthesia), is the sense A sense is a biological system used by an organism for sensation, the process of gathering information about the world and responding to Stimulus (physiology ...
in the
somatosensory system The somatosensory system is a part of the sensory nervous system The sensory nervous system is a part of the nervous system responsible for processing sense, sensory information. A sensory system consists of sensory neurons (including the sen ...
. This cortex is further divided into
Brodmann areas A Brodmann area is a region of the cerebral cortex, in the human brain, human or other primate brain, defined by its cytoarchitecture, or histological structure and organization of Cell (biology), cells. History Brodmann areas were originally d ...

Brodmann areas
1, 2, and 3.
Brodmann area 3 The postcentral gyrus is a prominent gyrus In neuroanatomy, a gyrus (pl. ''gyri'') is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci (depressions or furrows; sg. ''sulcus''). Gyri and sulci create the folded ...
is considered the primary processing center of the somatosensory cortex as it receives significantly more input from the
thalamus The thalamus (from Greek language, Greek Wikt:θάλαμος, θάλαμος, "chamber") is a large mass of gray matter located in the wikt:dorsal, dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the tha ...

thalamus
, has neurons highly responsive to somatosensory stimuli, and can evoke somatic sensations through electrical
stimulation Stimulation is the encouragement of development or the cause of activity generally. For example, "The press provides stimulation of political discourse." An interesting or fun activity can be described as "stimulating", regardless of its physica ...
. Areas 1 and 2 receive most of their input from area 3. There are also pathways for
proprioception Proprioception ( ), also referred to as kinaesthesia (or kinesthesia), is the sense A sense is a biological system used by an organism for sensation, the process of gathering information about the world and responding to Stimulus (physiology ...
(via the
cerebellum The cerebellum (Latin for "little brain") is a major feature of the hindbrain The hindbrain or rhombencephalon is a developmental Development of the human body is the process of growth to maturity. The process begins with fertilization ...

cerebellum
), and
motor An engine or motor is a machine A machine is a man-made device that uses power to apply forces and control movement to perform an action. Machines can be driven by animals and people A people is a plurality of person A person ( ...
control (via
Brodmann area 4 Brodmann area 4 refers to the primary motor cortex Primary or primaries may refer to: Arts, entertainment, and media Music Groups and labels * Primary (band), from Australia * Primary (musician), hip hop musician and record producer from South ...
). See also: S2
Secondary somatosensory cortex The human secondary somatosensory cortex (S2, SII) is a region of cortex Cortex or cortical may refer to: Science Anatomy * Cortex (anatomy), the outermost or superficial layer of an organ * Cortex (hair), the middle layer of a strand of hair * A ...
.


Visual cortex

The visual cortex refers to the primary visual cortex, labeled V1 or
Brodmann area 17 The visual cortex of the brain A brain is an organ (anatomy), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such a ...
, as well as the extrastriate visual cortical areas V2-V5. Located in the
occipital lobe The occipital lobe is one of the four major lobes of the cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex m ...

occipital lobe
, V1 acts as the primary relay station for visual input, transmitting information to two primary pathways labeled the
dorsal Dorsal (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Repu ...
and
ventral stream The two-streams hypothesis is a model of the neural processing of vision Vision or The Vision may refer to: Perception Optical perception * Visual perception Visual perception is the ability to interpret the surrounding environment using l ...
s. 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.’ Increases in Task-negative activity are observed in the ventral attention network, after abrupt changes in sensory stimuli, at the onset and offset of task blocks, and at the end of a completed trial.


Auditory cortex

Located in the
temporal lobe The temporal lobe is one of the four major lobes of the cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex m ...

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 hair cell, auditory receptors.


Primary olfactory cortex

Located in the temporal lobe, the
primary olfactory cortexThe primary olfactory cortex is a portion of the cerebral cortex involved in olfaction Olfaction, or the sense of smell, is the special sense through which smells (or odors) are perceived. It occurs when an odor binds to a olfactory receptor, re ...
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 nervous system, peripheral and central nervous system, central mechanisms of action. The peripheral mechanisms involve olfactory receptor neurons which signal transduction, transduce a chemical signal along the olfactory nerve, which terminates in the olfactory bulb. The
chemoreceptors A chemoreceptor, also known as chemosensor, is a specialized sensory receptor Sensory neurons, also known as afferent neurons, are neurons in the nervous system In Biology, biology, the nervous system is a Complex system, highly complex ...
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 glomerulus, 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

The
gustatory cortex The primary gustatory cortex is a brain structure responsible for the perception of taste The gustatory system or sense of taste is the sensory system The sensory nervous system is a part of the nervous system responsible for processing sens ...
is the primary receptive area for
taste The gustatory system or sense of taste is the sensory system The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons (including the sensory re ...

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 insular cortex, anterior insula, located on the insular cortex, insular lobe, and the frontal operculum (brain), operculum, located on the frontal lobe. Similarly to the olfactory cortex, the gustatory pathway operates through both peripheral and central mechanisms. 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 oblongata, medulla, or the gustatory nucleus of the solitary tract complex. The signal is then transmitted to the
thalamus The thalamus (from Greek language, Greek Wikt:θάλαμος, θάλαμος, "chamber") is a large mass of gray matter located in the wikt:dorsal, dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the tha ...

thalamus
, which in turn projects the signal to several regions of the neocortex, including the gustatory cortex. 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.


Human sensory system

The human sensory system consists of the following subsystems: *Visual system *Auditory system *Somatosensory system consists of the receptors, transmitters (pathways) leading to S1, and S1 that experiences the sensations labelled as tactition, touch,
pressure Pressure (symbol: ''p'' or ''P'') is the force In physics, a force is an influence that can change the motion (physics), motion of an Physical object, object. A force can cause an object with mass to change its velocity (e.g. moving fr ...

pressure
, temperature, vibration, temperature (warm or cold),
pain Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain The International Association for the Study of Pain (IASP) is an international learned society A learned societ ...
(including itch and tickle), and the sensations of muscle movement and joint position including Human position, posture, Human musculoskeletal system, movement, and facial expression (collectively also called proprioception) *Gustatory system *Olfactory system *Vestibular system *Interoception, Interoceptive system


Diseases

* Amblyopia * Anacusis * Color blindness * Deafness


See also

* Multisensory integration * Neural adaptation * Neural coding * Sensor * Sensory augmentation * Sensory neuroscience * Sensory systems in fish


References


External links

{{DEFAULTSORT:Sensory System Nervous system Sensory systems Sensory organs