BIO 232 wk 5

Lacrimal gland function

produce tears 

Nasolacrimal canal function

drain tears

Conjunctiva function and location

Conjunctiva — mucous membrane in inner eyelids

covers sclera anteriorly, protects and lubricates eye (not apart of the eye tunics) 

eyelashes function

Eyelashes — keep airborne debris away from eye 

eyelids function

Eyelids — protection from mechanical injury, keep eye moist 

eyebrow function

Eyebrow — defer fluids laterally from the eye 

3 tunics of the eye wall

1. fibrous

2. vascular

3. retina

2 parts of the fibrous tunica

1. cornea

2. sclera

function of cornea and sclera, what is unique about the cornea

1. Cornea - lets light enter eye, avascular  

2. Sclera - protects eye, anchors extrinsic eye muscles

3 components of the vascular tunica and their functions

1. Iris - colored part of eye with smooth muscles that control size of pupil

2. Ciliary body - smooth muscle that anchors the suspensory ligaments of the lens

3. Choroid - forms the posterior vascular tunica, blood supply

Where do all 3 eye tunics get their blood supply

from the choroid of the vascular tunica

What is the function of the pupil?

control the amount of light entering the eye

name the 2 muscles of the iris (2 names for each muscle) , their functions, innervations

1. Inner sphincter muscle/circular muscle — constricts pupil, parasympathetic control 

2. Outer dilator muscle/radial muscle — dilates pupil, sympathetic control

What are 2 layers of the retina

1. pigmented outer layer - nourishes the photoreceptors, absorbs light prevents it from scatter

2. neural inner layer with photorecptors, bipolar cells, ganglion cells, amacrine and horizontal cells

What is the optic disc

 Optic disc: site where optic nerve leaves the eye 

• lacks photoreceptors “blind spot” 

explain the macula lutea and the fovea centralis

 Macula lutea: oval region lateral to the optic disc containing a high concentration of cones 

• ganglion and bipolar cells and the retinal blood vessels are pushed aside for increased visual acuity, also creates the depression in the retina 

Fovea centralis: central depression in the macula lutea, contains only cones 

what is macular degeneration

Macular degeneration — may cause loss of vision in the center of the visual field causing blurriness 

what is retinal detachment

Retinal detachment — pigmented and neural layers separate and the vitreous humor flows between them —> permanent blindness (deprives photoreceptors of nutrients

• pattern of vascularization in retina makes it susceptible to retinal detachment

Where is vitreous humor located? What is its functions (3)

Vitreous humor in posterior segment —

1. transmits light,

2. supports posterior surface of lens,

3. contributes to intraoccular pressure 

The anterior segment of the eye can be subdivided into the ____ and ___. Name the contents in each.

2 chambers of the anterior segment

• Anterior chamber = cornea and iris 

• Posterior chamber = iris and lens 

Aqueous humor is in the ____ segment. It is produced by _____. Aqueous humor functions (3)

• Aqueous humor anterior segment — plasma-like fluid produced by ciliary capillaries 

• supports, nourishes, and removes wastes

Aqueous humor drain into the _____ which drains into the _____

canal of Schlemm —> sclera venous sinus 

Explain glaucoma

Glaucoma — caused by build up of aqueous humor from improper drainage = increase pressure within eye = can compress retina and optic nerve = damage optic nerve leading to blindness 

What separates the anterior and posterior segments of the eye?

crystalline lens

Along with the cornea the ___ is also avascular

crystalline lens

talk about the 2 types of cells making up the lens.

name their make up

name their location

1. lens epithelium - cuboidal cells on anterior aspect of the lens

2. lens fibers - contain crystallines (folded proteins) that form the body of the lens 

Discuss how aging makes the lens become more convex and less elastic

The cuboidal cells of the lens epithelium is constantly differentiating into new lens fibers causing the lens to continually grow throughout aging making it become less elastic and more convex. This impair the lens’ ability to precisely focus light

explain cataract

Cataract — clouding of lens = vision is like looking through frosted glass

What electromagnetic radiation? What is its span?

what can our eyes actually see

 Electromagnetic radiation — encompasses all energy waves from short gamma rays to long radio waves 

• our eye respond to a small portion of this spectrum called visible spectrum (400-700 nanometers) 

• Different cones in the retina respond to different wavelengths in the visible spectrum 

We see color because objects ___ some wavelengths and ____ others

white ___

black ____

• We see color because objects absorb some wavelengths and reflect others (grass reflects green light, white reflects all wavelengths of light, black absorbs all wavelengths of light) 

refraction

Refraction — when light passes from one transparent medium to another its speed changes and refracts/bends 

• from less dense to more dense medium — light bends toward perpendicular  

Thicker lens means light bends ____ and the focal distance is ____

• Thicker lens = light bends more = shorter focal distance 

Real image

• light passing through the lens bends and forms a real image that is upside down and reversed right to left 

Pathway of light entering the eye (7)

Pathway of light entering the eye 

1. Cornea 

2. Aqueous humor 

3. Pupil 

4. Iris

5. Lens 

6. Vitreous humor 

7. Neural layer of retina with photoreceptors (inner layer of retina) 

Pathway of light refraction in the eye (3)

Pathway of refraction in the eye 

1. Cornea ** most refractory power, but constant 

2. Entering the lens 

3. Leaving the lens 

what is the function of the lens?

to change its curvature to change how light is bent to allow focusing of images

The human eye is best for ____ vision. Because _____

Eyes are best for distance vision! Requires minimal adjustments of the lens for proper focusing 

far point of vision 

• far point of vision — the maximum distance from the eye at which an object can be seen clearly when the eye's ciliary muscle is completely relaxed (lens does not need to change shape) = 20 ft 

During distance vision the

• ciliary muscle is ___

• suspensory ligaments are ____

• the lens is _____

• lens is at its _____ refractory power

• _______ focal point distance

• under _____ nervous system activation

• Ciliary muscles are relaxed 

• Suspensory ligaments are taught = lens is flat/thin = lens at lowest refractory power 

• Shorter focal point distance 

• Under sympathetic activation 

What are the 3 steps of close vision

Accommodation — changing sense shape via ciliary muscles to increase refractory power 

• Ciliary muscles contract 

• Tension release in suspensory ligaments = lens is thick

• Under parasympathetic control 

Constriction (of pupil) — pupillary reflex constricts the pupils to prevent divergent light rays from entering the eye 

Convergence — medial rotation of the eyeballs toward the object being view 

During close vision

• ciliary muscle is ___

• suspensory ligaments are ____

• the lens is _____

• lens is at its _____ refractory power

• _________ focal point distance

• under _____ nervous system activation

• Ciliary muscles contract 

• Tension release in suspensory ligaments = lens is thick = higher refractory power

• shorter focal point distance

• Under parasympathetic control 

Emmetropic vs Myopic vs Hyperopic (how can they be corrected)

Problems of refraction 

Emmetropic eye — normal eye with light focused properly on retina 

Myopic eye (nearsighted) — focal point is in front of retina (eyeball too long) 

• Corrected with concave lens 

• Lasik procedure - flatten cornea to change refractory power

Hyperopic eye (farsighted) — focal point is behind retina (eyeball too short) 

• Corrected with convex lens 

rods vs cones on

• color vision

• sensitivity to light (what light does it function in)

• acuity

• how many are there relatively

• location in the retina

What gives cones their high acuity? How does it differ from rods?

Each cone synapses with a single bipolar and ganglion cell (straight line to higher visual centers) detailed and high resolution) 

Visual input from many rods feed into a single ganglion cell = fuzzy indistinct images 

Photo-transduction

Photo-transduction - light energy converted into graded receptor potential 

____ and _____ combine to form visual pigments. Explain how this is done.

• Retinal and opsins combine to form visual pigments 

Depending on the type of opsin to which retinal is bound, retinal absorbs different wavelengths of the visible spectrum.

Where is retinal made from? Name 2 isomers of retinal and their function

2 isomers of retinal: 

• 11-cis retinal — binds to opsin

• All-trans retinal — isomer caused by light hitting it changing its shape. Isomerization of retinal initiates electrical impulses in the optic nerve 

visual pigment in rods is ______ (_____+____)

Rhodopsin = visual deep purple pigment in rods (opsin + 11-cis retinal) 

visual pigments in cones are called ________ (____+_____). Name the 3 visual pigments in cones.

Photopsins = refers to all 3 visual pigments in cones (opsin + 11-cis retinal) ***each type of cone has a different opsin

1. Blue photopsin 

2. Green photopsin

3. Red photopsin 

How are we able to see different colors?

how do we yellow, orange, white?

We can see different colors by activation of more than one type of cone 

• yellow light stimulates both red and green cone receptors, 

• but if the red cones are stimulated more than the green cones, we see orange instead of yellow. 

• When all cones are stimulated equally, we see white

Adaptation to bright light (from dark to bright) 

Adaptation to bright light (from dark to bright) 

1. Dramatic decrease in retinal sensitivity - rod function is lost

2. Switching from rod to cone system - visual acuity gained 

Adaptation to dark 

Adaptation to dark 

1. Cones stop functioning - visual acuity lost 

2. Rhodopsin accumulates in the dark and retinal sensitivity is restored 

Pathway from rods and cones to the visual cortex (6)

Pathway to the visual cortex 

1. rods and cones —> bipolar cell —> ganglion cells

2. Ganglion cell axons joint to from optic nerve

3. Optic nerve travels through optic canals

4. Medial fibers of optic nerves decussates at optic chiasma 

5. Optic nerve synapses in thalamus (lateral geniculate body) 

6. Optic radiation fibers the relay to visual cortex in occipital lobe 

Other optic tract fibers end in the (2)

Other optic tract fibers end in the 

1. Superior colliculi (corpora quadrigemina) for visual reflexes 

2. Pretectal nuclei (anterior to superior colliculi) for pupillary reflexes 

A small subset of visual fibers contain ___ (circadian pigment). 2 functions of it are _____ and ______.

A small subset of visual fibers contain melaopsin (circadian pigment) which (1) mediated pupillary light reflexes, (2) sets daily biorhythms 

Depth perception

Depth perception — achieved by 2 eyes viewing same image from slightly different angles 

• 3D vision results from cortical fusion of slight different images 

• Presbyopia

• loss of lens elasticity with age 

• Anisocoria

• difference in pupil size 

The cells involved in olfaction are located in the _________. located _______.

 Olfactory epithelium (pseudostratisfied epithelium) - located on the roof of the nasal cavity covering the superior nasal concha

Discuss the anatomy the cells involved in olfaction

Olfactory sensory neurons are bipolar and embedded within the olfactory epithelium. Bodies are within the olfactory epithelium  

• Olfactory cilia radiate out from the dendrites of olfactory sensory neurons into the mucous and increase the receptive surface area 

• Superiorly the unmyelinated axons of the  olfactory sensory neurons and join together to form  the olfactory nerve.  

• CNI passes through the cribriform plate of the ethmoid bone and synapse with mitral cells in the olfactory bulb. 

• Mitral cell axons join to become the olfactory tract   

Name 2 other types of cells in the olfactory epithelium and their functions

Olfactory cells are supported and protected by supporting cells that make up the majority of the olfactory epithelium 

Olfactory stem cells differentiated to replace olfactory sensory neurons. This is because olfactory sensory neurons have a lifespan oof 30-60 days and they can be destroyed by blowing your nose. 

• located at the base of the olfactory epithelium 

Physiology of smell (how are odor chemicals detected) 4 steps talk about what channels open

1. Odors are in gaseous state go be detected and then are dissolved in mucous of the factory epithelium.

2. Dissolved odorant binds to receptor protein on olfactory sensory neuron 

3. G-protein-coupled mechanism where a chain of enzymes are activated ending in the synthesizing of cAMP 

4. cAMP opens Na+ Ca2+ channels

1. Na+ influx causes depolarization triggering an action potential 

2. Ca2+ influx causes adaptation of signal transduction to decrease the response to a prolonged stimulus 

• Olfactory receptors (proteins) respond to many different odor causing chemicals 

Role of mitral cells and their path

Mitral cells = second order olfactory sensory neurons that become the olfactory tract 

Olfactory tract relays information to the olfactory cortex

1. Information is sent to area just above the orbit for smells to be identified 

2. Information is also sent to the hypothalamus, amygdala and limbic system for emotional responses to odors. 

1. Dangerous odors stimulate the ______________

2. Appetizing odors stimulate the _______________

3. Unpleasant odors tigger _______________

1. Dangerous odors stimulate the sympathetic nervous system. 

2. Appetizing odors stimulate the parasympathetic nervous system, salivation, and the digestive tract. 

3. Unpleasant odors tigger sneezing and choking (protective reflex) 

Name the 4 papillae (which does not contain taste buds)

Papillae — projections of the tongue mucosa 

1. Filiform (does not contain taste buds) 

2. Fungiform — 1-5 taste buds per papillae 

3. Foliate — back lateral side of the tongue 

4. Circumvallate — back of tongue many taste buds 

Each taste bud is composed of ______-______, ____ cells

Each taste bud is composed of 50-100 epithelial cells

discuss the anatomy of the 2 types of epithelial cells in taste buds

Gustatory epithelial cells - taste receptors cells 

1. Long microvilli called gustatory hairs project from the tips of all gustatory epithelial cells and extend through a taste pore to the surface of the epithelium, where they are bathed by saliva

Basal epithelial cells - dynamic stem cells that differentiate into gustatory epithelial cells every 7-10 days. This is because taste buds are subject to friction and burning. 

6 primary taste sensations 

1. Sweet - sugars, saccharin, alcohol, some amino acids 

2. Sour - hydrogen ions (acids) 

3. Salty - metal ions (inorganic salts) 

4. Bitter - alkaloids such as quinine and nicotine, and non-alkaloid such as aspirin 

5. Umami - amino acids glutamate and aspartate (beef, cheese, MSG) 

6. Fatty 

Pathway of taste (7)

1. Chemical dissolved in saliva 

2. Diffuse into taste pore 

3. Bind to receptors on gustatory hairs 

4. Depolarization of taste cell membrane causes neurotransmitter to be release 

5. Initiates graded potential that elicits an action potential in the afferent nerve 

6. Facial n (VII) and Glossopharyngeal n (IX) carry impulses from the anterior 2/3 of tongue and posterior 1/3 of tongue respectively. Vagus n. (X) carry impulses from taste buds in the epiglottis and lower pharynx (only in infants). All these afferent fiber synapse in the solitary nucleus of the medulla —> thalamus —> 

   
   

   1. Gustatory Cortex 

   2. Hypothalamus and limbic (appreciation of taste)

name the channel it opens

1. Salty -

2. Sour -

3. Salty -

4. Bitter, Sweet, Umami -

1. Salty - Na+ influx = depolarization 

2. Sour - H+ interacts with potassium channels 

3. Salty - metal ions (inorganic salts) 

4. Bitter, Sweet, Umami - G-protein-coupled receptor 

3 other receptors that influence taste

• Thermoreceptors, mechanoreceptors, and nociceptors also influence taste via, temperature, texture, spice 

2 parts of the inner labyrinth. Describe the anatomy and their contents

Bony labyrinth — channels worming through the temporal bone (vestibule, cochlear, semicircular canals) 

1. Perilymph 

Membranous labyrinth (runs within bony labyrinth) — series of membranous sacs 

1. Endolymph (potassium rich) 

Anatomy of the vestibule

Vestibule — egg shaped cavity of bony labyrinth 

• 2 sacs suspended in perilymph: contain maculae (equilibrium receptors that response to gravity and changes in head position) 

1. Saccule — extends into cochlea 

2. Utricle — extends into semicircular canals 

Cochlea is divided into 3 chambers

1.   Scala vestibui — perilymph 

2. Cochlear duct (scala media) — endolymph (potassium rich)

   
   

   1. Basilar membrane - support organ of corti/spiral organ (innervated by cochlear branch  

      
      

      1. Moving hair cells = hearing sensory receptors 

3. Scala tympani — perilymph 

4. Helicotrema — where the Scala vestibule and Scala tympani are continuous with one another 

Name their functions and their receptor regions

1. semicircular canals

2. vestibule

3. cochlear

pathway of sound reception (9)

1. Sound waves beat against tympanic membrane (tympanic membrane is the boundary b/w the external and middle ear ) 

2. Tympanic membrane pushes against ossicles —> vibrate the stapes 

3. Oval window moves

4. Vibration of perilymph in the Scala vestibuli —> Scala tympani 

5. Build vibrations are absorbed by round window (where the Scala tympani terminates) 

6. Vibration of perilymph in scala tympani also cause endolymph to vibrate in the cochlear duct 

7. Vibration of endolymph in the cochlear duct causes movement of the moving hair cells (hearing sensory receptors) of the organ of corti/spiral organ 

8. Stimulation of the moving hair cells opens mechanical gate ion channels = graded potential and release of neurotransmitters by hair cells 

9. Neurotransmitter causes cochlear nerve to transmit to the brain where sound is perceived

boundary b.w middle and inner ear

(oval and round windows are the boundary b/w the middle and inner ear) 

Pathway of sound reception to the brain (6)

1. Cochlear nerve passes through spiral ganglion

2. synapse in the cochlear nuclei in the medulla 

3. Nerves travel and synapse in the superior olivary nucleus in the medulla 

4. Nerves travel and synapse in the inferior colliculus (corpora quadrigemina) of the midbrain —> auditory reflex center

5. Nerves synapse once more in the medial geniculate body of the thalamus 

6. Impulses are sent to the auditory cortex in the temporal lobe

Discuss the sine wave and frequency and amplitude.

• Sine wave = illustration of sound wave where crest = high pressure, trough = low pressure 

• Sound is describe by frequency and amplitude (intensity of sound in dB) 

  • 
    

  • Loudness — subjective interpretation of sound intensity 

    • 
      

    • High amplitude = louder sound 

  • Pitch — perception of different frequencies

    • 
      

    • High frequency = higher pitch 

what frequencies can we hear

• Pitch — perception of different frequencies (we hear from 20-20,000 Hz) 

Inaudible sounds

Inaudible sounds do not excite hear cells in spiral organ 

high pitch vs low pitch sounds stimulate hair cells on the ____ and ____ of the basilar membrane

• High frequency sounds — stimulate hair cells by base of basilar membrane 

• Low frequency/pitch sounds — stimulate hair cells by the tip of the basilar membrane 

__________ cover hair cells superiorly

tectorial membrane cover hair cells 

Loudness is perceived by ________ causing increased ____ in action potentials

Loudness is perceived by greater displacement of hair cells, causing release of more neurotransmitter = increased frequency in action potentials 

• Loud sound move hair cells more, because the vibrations within the scala have greater amplitude. 

Sounds localization is perceived by the

superior olivary nuclei in the medulla 

2 types of deafness

Deafness 

1. Condition deafness — conduction build vibration in the inner ear is impaired 

   1. 
      

   1. Impacted earwax blocking external auditory meatus, perforated eardrum, osteosclerosis of ossicles, middle ear inflammation —> more common

2. Sensorineural deafness — damage to neural structures (cochlear hair cells —> auditory cortical cells) 

tinnitus

Tinnitus — ringing or clicking sound in the ears in the absence of auditory stimuli 

• symptom of cochlear nerve degeneration, symptom of inflammation of the middle/inner ear, side effect of some medications (aspirin) 

Meniere’s syndrome

Meniere’s syndrome — labyrinth disorder affecting the cochlea and semicircular canals —> vertigo, nausea, vomiting 

2 types of receptors in the vestibular apparatus

Vestibular apparatus = equilibrium receptors in the semicircular canals and vestibule 

1. 
   

1. Vestibular receptors monitor static equilibrium (linear acceleration and position of the head) 

2. Semicircular canal receptors monitor dynamic equilibrium (head rotation) 

Vestibular receptors are in the ____ which have 2 locations the ___ and ___. They both respond to _____ equilibrium

Maculae (utricle and saccule) sensory receptors for static equilibrium 

Urticular hairs respond to

Saccular hairs respond to

Urticular hairs respond to horizontal head movement (side to side, tilting) 

Saccular hairs respond to vertical movement (up and down like in an elevator) 

direction of hair cell bending causes depolarization vs hyperpolatization, how does that in turn relate to the rate of action potentials

Hair bent toward kinocilium 

• 
  

• Depolarization 

• Increase action potentials in vestibular nerve 

Hair bent away from kinocilium 

• Hyperpolarization 

• Decreased frequency of action potentials in vestibular nerve 

discuss how the otoliths and otolith membrane move during horizontal acceleration/deceleration and during head tilting.

During acceleration and deceleration inertia will cause the otoliths to move in the opposite direction. For example: when a car suddenly stop the otoliths in the utricle will side forward due to inertia. Or when an elevator starts moving upwards the otoliths in the saccule will slide downwards. 

During head tilting gravity is at play. So when the head tilts downward the otoliths of the utricle slide down. And when the head tilts backward the otoliths of the utricle slide backward. 

****If I were jolted to the right the otoliths in both ears would move to the left because of inertia, but the otoliths in the left ear are moving laterally and the otoliths in the right ear are moving medially 

discuss how the otoliths and otolith membrane move during vertical acceleration/deceleration

During upward acceleration the otoliths of the saccula will slide down (opposite due to inertia)

during vertical dropping the otoliths of the saccula slide up

Where are rotational movements sensed?

rista ampullaris = receptor of velocity changes in rotational head movements (dynamic equilibrium) 

Discuss how rotation is sensed. Name the gel-like mass covering the hair cells in the crisa ampullaris

When spinning the cupula moves in the opposite direction of the spinning due to inertia. If the spinning continues the cupula will return to its resting position. When the spinning stops the cupula will move in the direction of the spin due to inertia. 

While the cupula will lag in the opposite direction of the spin. In the one ear the hair cells will move toward the kinocilium while in the other ear the hair cells will move away from the kinocilum.