Chapter 15: Special Senses

General senses

Senses found throughout the body; somatic and visceral

Somatic senses

Tactile, thermal pain, proprioception

Visceral senses

Detexts internal organ conditions (ex: internal pain)

Special senses

Senses founds in specialized organs and have something to do with our smell, taste, vision, balance, and hearing

Nociceptors

Receptors that respond to potentially damaging stimuli that result in pain like searing heat, excessive pressure, and inflammatory chemicals; found all over your body

Photoreceptors

Receptors that respond to light (ex: rods and cones); found in the retina of your eye

Chemoreceptors

Receptors that respond to chemicals in a soulition like molecules smelled/tasted, or changes in your blood (ex: tastebuds); found on your tongue and nasal cavity

Thermoreceptors

Receptors that respond to temperature changes

Cold receptors

Thermoreceptors that sense from 10^oC-40^oC, or 50^oF-105^oF; located in the epidermis

Warm receptors

Thermoreceptors that sense from 32^oC-48^oC, or 90^oF-118^oF; located in the dermis

Mechanoreceptors

Receptors that respond to mechanical force such as touch, pressure (including BP), vibration, and stretch

Tactile receptors

Receptors that respond to light pressure; found in the dermal papillae of hairless skin (especially the nipples, fingertips, soles of feet, and eyelids)

Baroreceptors

Receptors that activate when arterial blood pressure rises; found in the carotid sinuses, aortic arch, and in the walls of nearly every large artery of the neck and thorax

Proprioceptors

Receptors that respond to internal stimuli and advises the brain of our body movement by monitering how much the organs containing these receptors are stretched; found in skeletal muscles, tendons, joints, ligaments, and in the connective tissue coverings of bone and muscle

Meissner’s corpuscle

Detects light pressure, discriminative touch, and vibration of low frequency; located in the dermis

Pacinian corpuscle

Detects deep pressure, stretch, and vibration of high frequency; located in the dermis and hypodermis

Tactile discs

Detects light pressure; located on the basal layer of the epidermis

Ruffini corpuscles

Detects deep pressure and stretch; located deep in the dermis, hypodermis, and joint capsules

Free nerve ending

Detects changes in temperature, chemicals, pressure, and pain; locatedin most body tissues , especially connective tissue (ligaments, tendons, dermis, joint capsules), and epithelia

Root hair plexus

Detects movement of hair; located around the hair follicle in the dermis

Muscle spindle

Detects muscle stretch and length; located on skeletal muscles, particularly in the extremeties

Golgi tendon organ

Detects tendon tension and force of muscle contraction; located in the juunctions between muscles and tendons

Medulla oblongata

Detects changes in the CSF’s pH to regulate breathing rate; located in the brainstem

Hypothalamic chemoreceptors

Detects internal chemical changes and helps regular thirst, temperature, and endocrine functions

Aortic body

Detects blood O2, CO2, and pH levels; located along the aortic arch

Carotid body

Detects blood O2, CO2, and pH levels; located at the bifurcation of the carotid arteries

Fibrous layer

The outermost coat of the eyb=ebal composed of dense avascular connective tissue; has 2 different regions

Sclera

The white, tendon-like region of the eye; protects and shapes the eyeball, and also provides a sturdy anchoring site for the extrinsic eye muscles

Cornea

The transparent region that bulges anteriorly from its junction with the sclera; forms a window that lets light enter the eye

Vascular layer

The middle coat of the eyeball; has 3 regions

Iris

The colored part of the eye; acts as a reflexively activated diaphragm to vary pupil size

Choroid

The blood-vessel rich, dark brown membrane of the eye; nourishes alleye layers, helps absorb light, and contains a posterior opening where the optic nerve leaves the eye

Ciliary body

The thickened ring of tissue that encircles the lens; has 3 parts

Ciliary muscle

Makes up most of the ciliary body; consists of interlacing smooth muscle bundles that control the lens shape

Ciliary process

The posterior surface of the ciliary body; secretes the fluid that fills the cavity of the anterior part of the eyeball

Ciliary zonule (suspensory ligament)

Halo of fine fibers circling around the lens; helps hold it in its upright position

Retina

The innermost, delicate layer of the eyeball; contains millions of photoreceptors that convert light to energy, other neurons involved in processing responses to light, and glia

Pigmented layer of the retina

The single-cell-thick lining of the retina; absorbs light and prevents it from scattering into the eye, participates in photoreceptor renewal, and stores vitamin A

Neural layer of the retina

The transparent layer of the retina composed of photoreceptors, bipolar cells, and ganglion cells

Lens

The transparent, flexible structure enclosed in a capsule posterior to the iris; changes shape to precisely focus light on the retina

Pupil

The round central opening of the eye; allows for light to enter

Ora serrata

The junction where the retina extends anteriorly to the posterior margin of the ciliary body

Bipolar cell

A cell/neuron found in the neural layer of the retina; transmits visual info from photorecptors to the ganglionic cells

Ganglionic cell

A cell/neuron found in the neural layer of the retina;

Anterior margin

the anterior portion/edge of the retina; filled with aqueous humor

Anterior chamber

The space between the cornea and the iris

Posterior chamber

The space between the iris and the lens

Aqueous humor

The clear fluid similar in composition to blood plasma; helps support the eyeball internally by maintaining a constant intraocular pressure of about 16 mmHg supplies nutrients & oxygen, and carries away metabolic waste

Posterior margin

The posterior portion/edge of the retina; filled with vitreous humor

Vitreous humor

The clear gel in the posterior margin that binds tremendous amounts ofwater; transmits light, supports the posterior surface of the lens, and contributes to intraocular pressure

Rods

The dim-light and peripheral vision receptors; numerous, light-sensitive, and does not provide sharp images or color vision

Cones

The bright light vision receptors; provides high resolution color vision

Macula lutea

The oval region lateral to the blind spot of each eye; allows light to pass almost directly; 

Fovea centralis

The pit in the center of the macula lutea; area of sharpest central vision

External eye muscles

Lateral, medial, superior, and inferior rectus

Superior & inferior oblique

Conjuctiva

The transparent mucous membrane that lines the eyelids and folds back over the anterior surface of the eyeball

Lacrimal apparatus

Consists of the lacrimal gland and the ducts that drain lacrimal secretions into the nasal cavities

Refraction

The bending of light rays to focus them on the retina and create an imafge

Accomodation

The changing of lens shape to focus for near (or far) vision;

flat lens = far vision

round lens = close vision

Constriction

The narrowing of the pupil to control the amount of light entering the eye

Convergence

Binocular vision

What happens after light hits the photoreceptors in the retina?

It causes the pigment called retinal to change shape, activating the photopigment which ultimately triggers phototransduction (light → electrical signal)

List the four steps of formation of image on Retina in order

1. refraction

2. accomodation

3. constriction

4. convergence of eyeballs

What is labeled “A”?

Ciliary body

What is labeled “B”?

Ciliary muscle

What is labeled “C”?

Ciliary process

What is labeled “D”?

Anterior cavity

What is labeled “E”?

Cornea

What is labeled “F”?

Pupil

What is labeled “G”?

Iris

What is labeled “H”?

Lens

What is labeled “I”?

Conjuctiva

What is labeled “J”?

Retina

What is labeled “K”?

Choroid

What is labeled “L”?

Sclera

What is labeled “M”?

Fovea centralis