A +P Exam 3 ( Special senses)

Special Senses

Receptors

Receptors located in the head only

General senses

Receptors

Widely distributes receptors throughout the body

Special Senses

Receptor structure

Distinct, specialized receptor cells, typically associates with bipolar neurons

General senses

Receptor structure

Mostly modifies nerve endings, either free or capsulates

Special senses

Stimulus energy

Detects light, sounds, acceleration, and chemical stimuli

General senses

Stimulus energy

Detects mechanical, thermal, chemical, and pain-related stimuli, vibration, and pressure.

Similarities of general and special senses

Detects stimuli from environment or inside the body

Preforms sensory transduction, converting a stimulus into an electrical signal

Allow the nervous system to process sensory information and produce perception

Ultimately communicate sensory information through action potential

Layers of the eyeball

Fibrous tunic

Outer later- Sclera and Cornea, made up of connective tissue

Sclera

Part of the Fibrous tunic, white, tough connect tissue that protect the eye and helps maintain its shape

Cornea

Part of the Fibrous tunic, the transparent front portion of the eye, contains three layers of tissue. The sodium pump takes water out of the eye, keeping it clear.

Helps transmit light into the eye

Layers of the eyeball

Vascular tunic

Middle layer, Choroid, ciliary body, Iris and pupil, contains melanocytes

Choroid

Part of Vascular layer, Blood-vessel-rich, brown membrane containing melanocytes. Helps prevent light from scattering inside the eye

Ciliary body

Part of the Vascular Tunic, Connects the choroid and involves in controlling the lens

Iris

Part of the Vascular Tunic, Color portion of eye, contain smooth muscle that controls the pupil size. Difference in melanin in stroma causes the color

Pupil

Part of the Vascular Tunic, Opening in the center of the iris that allows light to enter.

Sphincter pupillae

Iris smooth muscle, circular muscle that constricts (decreases pupil size, parasympathetic

Dilator pupillae

Iris smooth muscle, Muscles that dilate (decrease pupil size) symoathetic

Nervous tunic

Inner layer, Retina, Photoreceptors, bipolar cells, ganglion cells

Retina

Part of the Nervous tunic, contains the cells responsible for detecting light

Pigemented layer

Part of the retina, absorbs light, prevents scattering, and stores vitamin A

Neural layer

Part of the retina, contains photoreceptors, bipolar cells, ganglion cells

Photoreceptor cells

Rods

More sensitive to light, better for dim-light vision, lower visual acuity ( detail) - Rhdopsin

Photoceptor cells

Cons

Requires more light(less Sensity), better for bright-light vision, provide color vision, higher visual acuity (more detail) - Photopsin

Fovea

Retinal structure, Contains only cones and the sharpest detailed color vision

Optic Disc

Retinal structure, where the optic never leaves the eye, it has no photoreceptors, so its a blind spot

Internal structures of the eye

Lens

Made of proteins called crystallin’s, focuses light onto the retina

Internal structures of the eye

Aqueous humor

Water fluid, nourishes the cornea and lens, maintains eye pressure, continuously forms and drains, and removes waste products

Glaucoma

Disruption of aqueous humor drainage can cause…intraocular pressure increases, damaging blood vessels and optic nerve, leading to blindness

Internal structures of the eye

Vitreous humor

Jelly-like substance, transmits light. Supports the lens and retina, maintains eye shape, forms during embryonic development and lasts a lifetime

Accessory structures

Eyebrows and eyelids

helps keep sweat from running into the eye, protects the eye from foreign objects, and helps spread tears across the eye’s surface when blinking

Accessory structures

Tarsal glands

Sebaceous glands embedded in each eyelid secrete oil along the border of the lid, which helps keep lids from sticking together, “eye crusties”

Accessory structures

Conjunctiva

A thin, transparent mucous membrane cover the white portion of the eye ( sclera) and lines the inside of the eye. Provided lubrication and is very thin, allowing blood vessels underneath to be visible. The lining of the visible outer surface of the eye

Conjunctivitis

“Pink eye” Inflammation of conjunctivitis, caused by viruses, bacteria, or allergies

Accessory structures

Lacrimal apparatus

tear production, continually produces and drains tears.

Tears - Lacrimal apparatus

Water, Mucus, Antibodies (protect from pathogens), lysozyme (enzyme that destroys bacteria)

Protection,lubrication,cleansing,

Tears drain into…

nasal cavity through the lacrimal duct system, why your nose may run when you cry

Phototransduction

Converting light into graded receptor potential

Cataract

Clouding of the lens, causes a decease in vision, blurry vision, difficuly with night vision, faded color

Light travel

Ganglion cells→Bipolar cells→ Photoreceptors

Signal is proceed in photoreceptors

Lacrimal Caruncle

Produces “Eye Crusties”, Small fleshy bump in the medial corner of the eye, contains sebaceous and sweat glands.

Reflection

Visible light bounces off the surface and reaches our eyes

Refraction

Occurs when light hits the cornea and lens, bends when it passes through a different medium at an oblique angle

Myopia

Nearsightedness, visual image is focused in front of the retina. Distant objects appear blurry.

Usually because of the shape of the eye

Hyperopia

Farsightedness, Visual image is focused behind the retina. Close objects are harder to see clearly .

Usually because of the shape of the eye

Sequence of phototransduction 1+2

• Light enters the eye and reaches the photoreceptors

• Light causes a change in the visual pigment rhodopsin in rods)

Sequence of phototransduction 3+4

• The pigment contains retinal and opsin, Retinal changes from cis- retinal to trans-retinal

• This activates a G-protein called transduin

Sequence of phototransduction 5+6+7

• This decreases Na+ Permeability in the photoreceptors out segment

• Less Na+ enters the cell, causing the photoreceptors to hyperpolarize

• The photoreceptor release less neurotransmitters

Light causes…

Hyperpolarization of photoreceptors

Depolarization of Bipolar cells

More action potential for Ganglion cells

Dark current events

• Na+ enters the outer segment

• This keeps the photoreceptor relatively depolarized ( -40mV)

• Photoreceptors continuously release neurotransmitters

Photoreceptors produce,,

Graded potentials

Bipolar cells produce…

Graded potential

Ganglion cells produce…

Action potential

Axons of the ganglion cells form the…

Optic nerve, that carries information toward the brain

Colorblindness

Result of a missing visual pigment, cones contain different opsins that respond to different wavelengths. When these are affected, we cannot detect wavelength normally, affecting color perception

Optic nerve damage

Causes damage to the affect eye, leading to blindness

Optic Chiasm damage

Losee of lateral ( peripheral) vision in both eyes

Chambers of the eye

Anterior chamber

Between the cornea and iris, contains aqueous humor

Chambers of the eye

Posterior chamber

Between the iris and lens, contains aqueous humor

Chambers of the eye

Vitreous chamber

Between the lens, in the front of the retina, contains vitreous humor

Aqueous humor forms and drains

Forms from blood through filtration near ciliary body, enters posterior chamber, then flows through pupil into anterior chamber, then is drained and reabsorbed back into the blood.

Structures of the lens

Biconvex, curves outward on both sides, made of crystallin’s that form a transparent layer, its elastic allowing it to change shape and adjust to focus. Grows througout life, less elastic and denser

Lens focuses on light

Light is refracted, or bent, when passing through cornea and lens. Cornea does most of refracting, but the lenses fine-tunes the focus so light land on the retina, mainly the fovea.

When looking at distant objects the lens will…

Flatten because it needs to bend light less

When looking at nearby objects the lens will…

Becomes rounder( Bulges) because it needs to bend light more, causes more eye strain, eyes have to make several adjustments.

When ciliary muscles contract the lens..

Becomes rounds/bulges, occurs when looking at nearby objects

When ciliary muscle relax the lens…

Becomes flatter, occurs when looking at distant objects

Lens accommodation

Process of changing the shape of the lens to focus light on the retina when looking at objects at different distance.

Nearby objects causes..

Ciliary muscles contract, lens round, eye converge ( move towards the middle), pupils constrict ( gets smaller)

Far objects causes…

Ciliary muscles relax, lens flatten, eyes straighten, pupils dilate

Astigmatism

Caused by unequal creatures of the cornea or lens, creates multiple focal points, resulting in blurry vision

LASIK

Surgical procedure that can correct myopia, hyperopia, and astigmatism. Improve visual acuity and provide a permanent alternative to corrective lenses

Light travels through the eye in this order…

Cornea→ Pupil→ lens → Vitreous humor→ Retina

Transduction- Retina signaling pathway, conversion if light into an electrical signal

Photoreceptors → Bipolar cells → Ganglion cells → optic nerve → brain

Dark causes…

Depolarization of photoreceptors

Hyperpolarization of Bipolar cells

less action potential for ganglion cells

Vision- Light adaptation

Rods system turns off- rods transducin move into inner segment, reducing sensitivity and increase visual acuity

Cones system rapidly adapts ( 5-10 mins)

Vision- Dark Adaption

Cones system turns off, Rhodopsin accumulates, transducin returns, takes longer (20-30 mins). Gained sensitive, reduce visual acuity

Vitamin A( carrots) is essential for

Normal rod function and dark adaption. Helps produce retinal , with combines with opsin to form rhodopsin in rods. Rhodopsin allows rods to detect light, especially in dim conditions

Lateral vision field is sent to the…portion of the eye

Medical Portion

Medical vision field is sent to the…portion of the eye

Lateral portion of the eyeball

Medial fibers once they have the lateral vision field, do what..

Cross, go to the opposite side of the brain from where they were taken in

Lateral Fibers once they have the medial vision field, so what…

Don’t cross, stay on same side of the brain as they were taken by the eye

Damages to the optic chiasm…

(Bitemporal Hemianopia) Affect only the lateral view of both eyes

Cut of entire optic nerve

Blindness in entire eye

Cut entire left optic tract

Loss of R vision in both eyes

Pupillary light reflex

Autonomic reflex( motor) that causes your pupil to constrict when light enters your eye, regulating how much light enters the eye

Direct response

Pupillary reflex- The pupil in the eye receiving light constricts

Consensual response

Pupillary reflex- The eye in the opposite eye also constricts