Ch 15 pt 2) Special Senses Flashcards

1
Q

Functional Anatomy of Photoreceptors

A

Photoreceptors are modified nuerons with a cell body, synaptic terminal, and two segents

  • Outer Segment) Light Reciving Area
    • Has visual pigments (photopigments) which change chape as they absorb light
    • Inner Segment) Joins the Cell body
      • cilium) connects inner segment to outer segment
      • Outer Fiber) connects cell body to inner segemnt
      • Inner fiber) connects cell body to synaptic terminal of bipolar cells.
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2
Q

Comparing Rod and Cone vision

A
  • Rods) Very senative to Light
    • Only has a single pigment so vision is in grey tones only
    • Pathways of rods converge into one ganglion which causes fuzy, indisticnt images
      • as many as 100 rods can synapse with one ganglion cell
  • Cones) Require bright light to activate
    • Have three pigments (red, green, blue) which allows for colored sight
    • Detailed, high-resolution vision
      • cones synapse with fewer ganglion than rods
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3
Q

Color Blindess

A
  • Cones lack one or more cone pigments
    • Inhereted on X chromosome which makes it more common in males
  • Most common type is red-green whrere red or green cones are absent
    • red could appear green or vise versa.
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4
Q

How do photoreceptors translate incoming light into electrical signals

A
  • Retinal) Light absorbing molecule
    • combines with one of four protiens (opsin) to form visual pigments
    • Depending on type of oposin bound, the retinol will aborb diffrent wavlengths of light
  • Opsins (four types)
    • Rods) Rhodopsin
    • Cones) Red, green and blue oposin,
    • Cone wavlengths overlap allowing us to precieve color.
  • Retinal Isomers (Retinal is bent until it absorbs light)
    • Bent) 11-cis-retinal
    • Straight) All-trans-retinal
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5
Q

Phototransduction

A
  • Process by which pigment captures of photon energy is converted into a graded receptor potential
  • Capturing light
    • Job of Deep Purple pigment Rhodopsin
  • Three stepts of Rhodopsin formation and breakdown
    • Pigment Synthesis) Opsin and 11-cis retinal combine to form rhodopsin in the dark
    • Pigment Bleaching)When Rhodopsin absorbs light, 11-cis retinal strightens to All-Trans-retinal. retinal and opsin seperate
    • Pigment Regenration) All-trans Retinal is converted back to 11-cis. Rhodopsin is regenrated,
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6
Q

Light Transduction Reaction

A
  • When Light Changes Oposin’s shape
    • Light-Activated rhodopsin activated G-protien transudcin
    • Transducin Activates PDE, which breaks down cyclic
      GMP (cGMP)
  • In dark
    • cGMP holds cation channels of outer segment open: Na+ and Ca2+ enter and depolarize cell
  • In light
    • cGMP breaks down, channels close, cell hyperpolarizes;
    • Hyperpolarization is signal for vision!
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7
Q

Information Processing In the Retina

A
  • Information is recived by photoreceptors.
    • Photoreceptor cell will genereate a graded potentional
    • Not an AP
  • Light Hyperpolarizes photoreceptors which causes them to Stop releasing the inhibitor Glutamate to the Bipolar cells
    • Bipolar cells depolarize (no inhibitior) which releases nuertoransmiter to ganglion cell
    • Ganglion cells Generate and Transmit AP to optic nerve (II) to brain
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8
Q

Light Adaption

A
  • Moving from darkness to bright Light we see Glare
    • Both rods and cones are stimulated at the time
    • Pigments are broken down and Pupils constrict
  • Visual activity improves over 5-10 mins
    • Rods are turned off
    • Retinal Sensitivity Decreases
    • Cones and Nuerons rapidy adapt
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9
Q

Dark Adaptation

A
  • When moving from bright light to darkness we see blackeness
    • Cones do not funciton in low light
    • Bright light turns off Rod pigments and they need time to adjust
    • Pupils dilate
  • Rhodopsin will begin to accumilate so Rod sentivity increaes
    • takes 20-30 mins
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10
Q

Night Blindness

A
  • Nyctalopia (night blindess) is a condition where rod funtion is seriouly hampered.
    • Caused by vitiman A difiency
  • Retinitis Pigmentosa) disiese that destroys rods
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11
Q

Visual Pathways in the Brain

A
  • Axons of Retinal Ganlion cells form the Optic Nerve
    • Medial fibers of optic nerce cross over at Optic Chaisma
    • Continue as Optic Tracts
  • Each Optic Tract
    • Contains Fibers from both lateral (temporal) and medial (nasal) aspects of the oppisit eye
    • Each ceriries information from same half of visual field.
  • Fibers of Optic Tracts continue on to Thalamus
  • From the thalamus, thalamic nuerons project to the promary visual cortex in the occipital lobe
    • Perception of images occurs here
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12
Q

Depth Perception

A

Both eyes view images from slightly diffrent angles: visual cortex fuses images into a 3D image which leads to depth percetion

  • Loss/Destruction of one eye elimanates depth perception.
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13
Q

Visual Processing

A
  • Retinal Cells split into input chnnels that include info about
    • Color and brightess
    • Angle, Direction, and speed of movment (of edges)
    • Sudden chenges in brightness or color
  • Ganglions pass info to the thalamus to be processed for depth perception.
    • cone Imput is emphesized
  • Primary Visual Cortex)
    • Forms visual association areas
  • Infor is also passed to other lobes where objects are identified and position in space is deteremined.
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14
Q

Chemical Senes

A
  • Senses of Smell (olfaction) and taste (gustation)
  • Chemoreceptors) respond to chemicals in aqueous solutions
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15
Q

Sense of Smell

A
  • Olfactory Epithelium) Organ of Smell
    • located in roof of nasal cavity
    • Contains Olfactory Sensory Nuerons
  • Supporting Cells) Support olfactory receptor cells
  • Olfactory Stem Cells) Diffrentiate to replace sensory nuerons
    • replace every 30-60 days
  • Bundles of axons of olfacory receptor cells form olfacotry nerve (I)
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16
Q

Specificity of Olfacotry Receptors

A
  • Smells can contains hundreds of diffrent odorants
    • Humans have 350 diffrent oforant receptors
    • Each receptor can respond to one or more odorants
  • Pain and Temp receptors are also in the nasal cavity
  • In order to smell a substance
    • It must be in a gasseous state
    • be able to dissolve in epitheliam nuerons
  • Dissolves oderants bind to receptor proteins in olfactory nuerons which generates a AP
    • AP is conducted to the olfactory bulb
17
Q

Olfacotry Pathway

A
  • Olfacotry nerves synapse with mitral cells when entering the olfacotry bulb
    • Mitral cells are second-order nuerons.
    • Amplify, refine, and relay singals
  • Smell (mitral) impules travel on olfactory tracts to olfactory cortex in brain
  • Info is sent to the frontal lobe/ thalamus
    • smell is conscioulsy interreted and identified
  • Info is also sent to hypothalamus, amygdala, and other limbic regions
    • emotional repsonse is elicited
18
Q

Location and Structure of Taste Buds

A
  • Taste Buds) Sensory organs for taste
    • most of our 10,000 taste bude are located on the tounge papillae (peglike projections of tounge mucosa)
  • Types of Papillae
    • Fungiform) Tops of mushroom shaped structures house most taste buds; scattered across tounge
    • Foliate papillae: on side walls of tongue
    • Vallate papillae: largest taste buds with 8–12 forming “V” at back of tongue
    • Few on soft palate, cheeks, phaynx and epiglottis
  • Taste Bud consists of 50-100 epithelial cells of two types
    • Gustatory epithelial cells) taste receptor cells
    • Basal Epithelial Cells) stem cells that divide every 7-10 days
19
Q

Five Basic Taste Sensations

A
  • Sweet—sugars, saccharin, alcohol, some amino acids
  • Sour—taste is produced by acids (hydrogen ions in solution)
  • Salty—metal ions (inorganic salts); sodium chloride tastes saltiest
  • Bitter—alkaloids such as quinine and nicotine, caffeine, and nonalkaloids such as aspirin
  • Umami—amino acids glutamate and aspartate
    • example: like beef taste
  • Tastes likes/Dislikes have hometatic value
    • Indicates potentially harmful substance
20
Q

Physooligy of Taste

A
  • To be able to taste a chemical, it must
    • be dissolved in saliva
    • Diffuse into taste pore
    • Contact Gustatory cell hairs
  • Diffrent Gustatory cells have diffrent thresholds for activation
    • Bitter most sensitive
21
Q

Gustatory Pathway

A
  • Two main cranial Nerve Pairs carry taste impules from tounge to the brain
    • Facial (VII), Glosopharyngeal (IX) and Vagus (X)
  • Receptors →Afferent fibers via cranial nerves→Medulla oblongata→ 2nd neuron to → Thalamus→ 3rd neuron to→ Gustatory Cortex in Insula
  • Hypothalamus and Lymboc system are involved
    • allow us to appreciate taste
22
Q

Role of Taste

A
  • Triggering Reflexes of digestion
    • Increased saliva in mouth
    • Increased gastric juice in stomach
    • Protective reflexes (gagging, vomiting)
  • Taste is 80% smell
23
Q

External Ear

A
  • Auricle (pinna) External ear structure that funnels sound waves into auditory canal
    • Helix) Rim
    • Lobule) Earlobe
  • External Acoustic Meatus) Auditory canal
    • short curved tube lined hairs, sebacous glands, and ceruminous (earwax) glands
    • Transmits sound waves
  • Tympanic Membrane) Eardrum
    • Boundary between external and middle ear
    • Thin connective tissue membrane
    • vibrates in response to sound. Tranfers energy to bones of middle ear
24
Q

Middle Ear (Tympanic Cavity)

A

Small, Air-filled, mucosa-lined cavity in temporal bone

  • Flanked latterally by eardrum and medially by bony wall with oval and round windows
  • Epitympanic recess) roof of middle eat cavity
  • Mastoid Antrum) Canal for communication with mastoid air cells in mastoid process
  • Pharyngotympanic (auditory) tube
    • Connects middle ear to nasopharynx
    • Usually flattened, but can be opened by yawning or swallowing to equalize pressure in middle ear cavity
25
Q

Otitis Media

A
  • Middle ear infection commonly seen in children with sore throats
  • Acute infections form and causes eardrum to buldge and become inflamed
    • can be defeaning
26
Q

Ear Ossicles

A
  • Auditory Ossicles) three bones in tympanic cavity
    • Malleus) the hammer, secured to eardrum
    • Incus) the Anvil
    • Stapes) “stirrup”, base fits into oval window
  • Synovial joints allow maleus to articulates with incus which articulates with stapes
  • Suspened by ligaments; transmit vabration of eardrum to the oval window
  • Tendor tympani and stapedius
    • contract in response to loud sounds to protect ears.