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*No corresponding eponymous name.
Mechanoreceptors of Somatosensation
Name Historical (eponymous) name Location(s) Stimuli
Free nerve endings * Dermis, cornea, tongue, joint capsules, visceral organs Pain, temperature, mechanical deformation
Mechanoreceptors Merkel’s discs Epidermal–dermal junction, mucosal membranes Low frequency vibration (5–15 Hz)
Bulbous corpuscle Ruffini’s corpuscle Dermis, joint capsules Stretch
Tactile corpuscle Meissner’s corpuscle Papillary dermis, especially in the fingertips and lips Light touch, vibrations below 50 Hz
Lamellated corpuscle Pacinian corpuscle Deep dermis, subcutaneous tissue Deep pressure, high-frequency vibration (around 250 Hz)
Hair follicle plexus * Wrapped around hair follicles in the dermis Movement of hair
Muscle spindle * In line with skeletal muscle fibers Muscle contraction and stretch
Tendon stretch organ Golgi tendon organ In line with tendons Stretch of tendons

Vision

Vision is the special sense of sight that is based on the transduction of light stimuli received through the eyes. The eyes are located within either orbit in the skull. The bony orbits surround the eyeballs, protecting them and anchoring the soft tissues of the eye ( [link] ). The eyelids, with lashes at their leading edges, help to protect the eye from abrasions by blocking particles that may land on the surface of the eye. The inner surface of each lid is a thin membrane known as the palpebral conjunctiva    . The conjunctiva extends over the white areas of the eye (the sclera), connecting the eyelids to the eyeball. Tears are produced by the lacrimal gland    , located beneath the lateral edges of the nose. Tears produced by this gland flow through the lacrimal duct    to the medial corner of the eye, where the tears flow over the conjunctiva, washing away foreign particles.

The eye in the orbit

This diagram shows the lateral view of the eye. The major parts are labeled.
The eye is located within the orbit and surrounded by soft tissues that protect and support its function. The orbit is surrounded by cranial bones of the skull.

Movement of the eye within the orbit is accomplished by the contraction of six extraocular muscles    that originate from the bones of the orbit and insert into the surface of the eyeball ( [link] ). Four of the muscles are arranged at the cardinal points around the eye and are named for those locations. They are the superior rectus    , medial rectus    , inferior rectus    , and lateral rectus    . When each of these muscles contract, the eye to moves toward the contracting muscle. For example, when the superior rectus contracts, the eye rotates to look up. The superior oblique    originates at the posterior orbit, near the origin of the four rectus muscles. However, the tendon of the oblique muscles threads through a pulley-like piece of cartilage known as the trochlea    . The tendon inserts obliquely into the superior surface of the eye. The angle of the tendon through the trochlea means that contraction of the superior oblique rotates the eye medially. The inferior oblique    muscle originates from the floor of the orbit and inserts into the inferolateral surface of the eye. When it contracts, it laterally rotates the eye, in opposition to the superior oblique. Rotation of the eye by the two oblique muscles is necessary because the eye is not perfectly aligned on the sagittal plane. When the eye looks up or down, the eye must also rotate slightly to compensate for the superior rectus pulling at approximately a 20-degree angle, rather than straight up. The same is true for the inferior rectus, which is compensated by contraction of the inferior oblique. A seventh muscle in the orbit is the levator palpebrae superioris    , which is responsible for elevating and retracting the upper eyelid, a movement that usually occurs in concert with elevation of the eye by the superior rectus (see [link] ).

Questions & Answers

explain respiratory centers
Tharshana Reply
which enzyme help in excretion of bile
Sakshi Reply
how conversion of Beta-carotiene into vitamin-A takes place
Sakshi
best reference books for anatomy pls suggest that
Sakshi
what is gross anatomy
Saroj Reply
The study of large structure of the body
Mablean
what is scrotum
Dakshit Reply
a bag of skin near the penis which contains the testicles
Mablean
hi
Sardar
its me Sardar from kpk pakistan
Sardar
Why are you on my digits
Mablean
hi
Kryme
how does it work?
Uriah Reply
I want to know the fertilization process in human
Nana Reply
Which plane divides the body into right and left parts
Kaeze
sagittal plane
Irvin
Thank you
Kaeze
Homestatic regulations usually involves a (n) _ that detects a particular stimulus, and a(n) _that respond to the stimulus by communicating with a (n) _whose activity has an effect on the same stimulus.
Kaeze
A cell is producing proteins to be transported out of that cell. They will be processed on ribosomes that are
Kaeze
what are diseases in the bood
Azoyenime Reply
Haemophilia
Aliyu
right hypochondriac rision how meain word
Ganesh Reply
Diabetes insipidus or diabetes mellitus would most likely be indicated by ________.
Ganesh
oral cavity how miean
Ganesh Reply
oral cavity how mean what
Suresh
seems to me every one is here a doctor and worse part is that even they donot know what to ask.
Muhammad
they know what to ask the problem is how to ask it.too much broken english.
George
dear George ongeche I think if they ask these kind questions and telling themselves as HCPs or medical student's .these are the basic ones go ask something more interesting .
Muhammad
what is blood red
Ahmad Reply
what is human anatomy?
Arpita Reply
tell me what is human anatomy?
Arpita
what is Openstax?
Arpita
arpita jana I think it's not the forum to ask such basic question...
Muhammad
study of structure of an object in this case human body.
Suresh
what are deferent between trasemicacid and vitamin k
Ubah Reply
This medication is used to treat heavy bleeding during your menstrual period. Tranexamic acid works by slowing the breakdown of blood clots, which helps to prevent prolonged bleeding. It belongs to a class of drugs known as antifibrinolytics
Muhammad
jj
John
In the body, vitamin K plays a major role in blood clotting. So it is used to reverse the effects of “blood thinning” medications when too much is given; to prevent clotting problems in newborns who don’t have enough vitamin K; and to treat bleeding caused by medications including salicylates, sulfo
Muhammad
Vitamin K plays a key role in helping the blood clot, preventing excessive bleeding. Unlike many other vitamins, vitamin K is not typically used as a dietary supplement. Vitamin K is actually a group of compounds. The most important of these compounds appears to be vitamin K1 and vitamin K2. Vitami
Muhammad
how much tha total vertebrea bone
Muhammad
26 vertebrea bone
Bhumi
wathe is blood function
dhena Reply
Blood, fluid that transports oxygen and nutrients to the cells and carries away carbon dioxide and other waste products. ... It is a tissue because it is a collection of similar specialized cells that serve particular functions. These cells are suspended in a liquid matrix (plasma), which makes the 
Ashiish
how tissue carries waste matrial
Nadeem
how many bone in human body?
Islam Reply
what is endocrin? plese help many people.
Islam
206
Nadeem
heart layers
Suresh
endoceime is the inner layer of heart
pandit
What is buffer?
Peer Reply
a buffer is a solution that resists a chemical change.
George
Yup it also balances the solutions
Peer

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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