1/19 Britton Special Senses I Flashcards by Aditi Iyer

Q

What are the five special senses?

A

taste
smell
vision
hearing
equilibrium

HVEST

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Q

Taste

Sensory receptor:
Sensory organ:

A

Taste receptor; Taste bud

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Q

Hearing

Sensory receptor:
Sensory organ:

A

Hair cell
cochlea

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Q

Vision

Sensory receptor:
Sensory organ:

A

rods and cones
retina

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Q

Equilibrium

Sensory receptor:
Sensory organ:

A

hair cell
vestibular aparatus

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Q

Smell

Sensory receptor:
Sensory organ:

A

olfactory cell
olfactory epithelium

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Q

Gustation

A

Action of tasting

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Q

How many taste buds does a typical adult have

A

3,000-10,000

Children have more taste buds than adults

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Q

Taste buds are found on 3 types of ______ distributed on the ______ surface of the tongue

A

Papillae; dorsal surface of the tongue

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Q

What taste buds are found on the anterior 2/3s of the tongue

A

Fungiform

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Q

Where do fungiform taste buds have the highest density

A

At the tip of the tongue

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Q

What taste buds are large papillae arranged in a chevron (V-line) at the rear of tongue

A

Circumvallate

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Q

What taste buds are present on the posterolateral surface of the tongue

A

Foliate

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Q

Additional taste buds are found on:

A

oral mucosa of the palate, pharynx, epiglottis

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Q

Components of taste bud

Each taste bud is composed of ______
50-100 ______
numerous _____ cells and support cells
all arranged around a ______ on the dorsal surface of the tongue

A

epithelial cells
taste cells - receptors
basal cells
central taste pore

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Q

Taste receptor is stimulated by:

A

Tastant

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Q

In taste buds, epithelial cells are all arranged around _____ on the _____ of the tongue

A

central taste pore; dorsal surface

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Q

Each taste bud is composed of:

A

Epithelial cells (taste cells/receptors, basal cells, support cells)

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Q

_______ in the taste receptors project into the taste pore
_______ provide the receptor surface for taste
are exposed to _______ dissolved in saliva

A

microvilli
microvilli
chemicals

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Q

How often are taste receptor cells replaced and by differentiation of what cells?

A

Every 10 days via differentiation of basal cells

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Q

A branching terminal network of ____ are interwoven around the taste receptor cells

A

Nerve fibers

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Q

Taste bud receptors are afferent or efferent?

A

Afferent sensory fibers

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Q

Taste receptors are modified ______ cells that respond to ______ stimuli

A

epithelial; chemical (tastants)

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Q

Taste receptors are _____ receptors

A

chemoreceptors

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Taste receptors are the site of:

Sensory transduction

Taste receptors are innervated by ____ sensory nerve fibers penetrating the ______

afferent; basal lamina

# Taste Bud Innervation 1. the nerve fibers branch extensively and receive synaptic input from the ______ receptors 2. each taste bud is innervated by how many sensory nerve fibers? 3. each nerve fiber receives Input from how many taste buds?

1) Taste receptors 2) 50 sensory nerve fibers 3) 5 taste buds

What are the 5 different taste modalities?

- sweet - salty - bitter - sour - umami

What is the common stimulus for sweet sensation?

Sucrose

What is the common stimulus for salty sensation?

NaCl

What is the common stimulus for sour sensation?

Acid

What is the common stimulus for bitter sensation?

Quinine

What is the common stimulus for umami sensation?

Monosodium glutamate (MSG)

What do salty and sour chemicals activate what channel?

Ligand gated channels

Salt is sensed by _____ ions sour taste is triggered by ______ mediated via _______

Na+ ions; protons (H+ ions); epithelial sodium channel (ENaC)

Sweet, Bitter, and Umami chemicals activate what channel?

GPCR's

Sweet sensation activates _____

T1R family (GPCR)

Bitter activates ______ (GPCR)

T2R family

_____ is coupled to a Gs protein, called ______

T2R; gustducin

Umami activates _____ (GPCR)

Glutamate receptor (mGluR4)

When stimulated, each of the taste receptor ion channels/GPCRs generate a:

Receptor potential

______ of taste receptor contains various ion channels and GPCRs

Apical membrane

Sensory Transduction in Taste Receptors Explain the steps of sensory transduction

1. Stimulation by chemical tastants 2. Ion channel or GPCR signaling pathway generates receptor potential (depolarization) 3. Intracellular Ca2+ increases through opening of voltage gated Ca2+ channels or release from intracellular stores 4. Vesicles fuse to basolateral membrane for synaptic transmission (mediated by serotonin) 5. Serotonin binds to receptors on primary sensory neurons and AP is elicited

What do taste receptors synapse with? _____ from fungiform papillae _____ from posterior 1/3 of the tongue _____ from palate, pharynx, elsewhere

- primary afferent sensory neurons (1st order) from branches of 3 cranial nerves - CN 7 - CN 9 - CN 10

All primary sensory nerves for taste synapse with ____ order neurons in the ____ in the _______

2nd; nucleus of the tractus solitarius (NTS) in the medulla

NTS relays information to the ______

Thalamus (3rd order)

Thalamus projects to the ______ _______

Gustatory cortex

# Sensory Coding for Taste Taste is coded in the sum of ____ in each cranial nerve in response to a specific ______

neural activity; taste modality

Each taste has its own distinct _____

Nerve response patterns

The response of different ______ and the subsequent integrations of the ______ generated encode taste

taste receptors; AP's

Ageusia

Absence of taste

Hypogeusia

Diminished taste sensitivity

Dysgeusia

Unpleasant perception of taste (metallic, foul, rancid)

Abnormalities in taste detection can be caused by damage to what nerves?

CN 7 and 9 (due to neurological disorders such as Bell's palsy, multiple sclerosis, infections)

Abnormalities in taste detection can be caused by ______ deficiency

Vitamin B3, zinc

Problems in taste detection can be caused by ______ (4)

- poor oral hygiene - adverse side effect of drugs which cause xerostomia - aging - tobacco use

Olfactory epithelium is a specialized portion of:

Nasal mucosa

What are the 3 structures of the olfactory epithelium?

- olfactory sensory neurons - supporting columnar cells - basal stem cells

1. OSN's are the ____ receptors for olfactory ____ 2. Each OSN is a _ nerve cell 3. Each OSN projects a ________ which terminates in ____ into the mucus layer of the nasal cavity epithelium 4. What are present on the cilia? 5. OSN axons pass through the ____ to the ____

1. sensory, transduction 2. bipolar 3. dendrite, olfactory cilia 4. membrane odorant receptors (GPCR's) 5. cribriform plate, olfactory bulb

Supporting columnar cells secrete _____ that proves the appropriate environment for ____ detection

Mucus; odor

______ generate new olfactory sensory neurons as needed

Basal stem cells

Structure of the Olfactory Bulb 1. _____ are primary sensory afferents (1st order) 2. the _____ is the site where OSN synapse with dendrites of ____ 3. _____ cells are 2nd order sensory neurons whose axons enter the olfactory tract and (ascend/ descend) to the olfactory cortex

1. Olfactory sensory nerves 2. glomerulus, mitral cells 3. mitral cells-ascend (synapse with 3rd order to gustatory center in brain)

1. there are _______ human genes for olfactory receptors= 3% of the human genome 2. the olfactory system is an extremely discriminative and sensitive _______ system 3. # of distinct odors

1. 1000, olfactory 2. chemosensory system 3. > 1 million

All olfactory receptors are _____

G-Protein Coupled Receptors (GPCR's)

What is a smell?

Chemical in the air dissolved in the mucus

Perceiving an odor begins with the _______ and transport of ______ to the olfactory mucosa

Inhalation, aromas

Odorants bind to ______ on the _____ and initiate the sensory transduction cascade, leading to generation of ______ in the sensory ______ nerve

GPCR's, cilia, APs in the sensory olfactory nerve

Sensory Transduction in Olfactory Receptors 1) odorants bind to diverse ______ which are coupled to Gs proteins called _____ 2) ______ dissociate 3) Alpha subunit activates: 4) _____ acts as a second messenger to open ____ channels 5) Inward diffusion of Na+ produces a depolarization, which is a ____

1) GPCR's; Golf 2) alpha, beta, and gamma subunits 3) Adenylyl cyclase to catalyze cAMP production 4) cAMP; Na+ ion channels 5) action potential

In sensory transduction in olfactory receptors, ____ are specific to different types of odors

G proteins (of GPCRs)

Sensory Transduction in Olfactory Receptors 1. Action potentials are ______ ______ depending on the concentration of ______ 2. Action potentials can be ______ to produce specific patterns of activity for each stimulating odorant 3. contributes to _____ ____ of odors 4. Action potentials in the ____ are generated and propagated to synapses in the _____ within the ______

1) graded responses, odorants 2) summated 3) neural coding 4) olfactory nerve (CN I); glomeruli; olfactory bulb

Sensory Transduction in Olfactory Receptors AP frequency is proportional to: AP can be ______ by rapidly adapting receptors

1) concentration of odorants 2) attenuated -receptors have adaptation; stimulated and sustained smells will 'switch off' after a long exposure

Sensory Transduction in Olfactory Receptors 1) the ______ is the site where axons of olfactory nerves synapse with numerous dendrites from ______ cells and ______ cells 2) the mechanism of _______ of olfactory neurons with mitral cells generate ______ APs 3) this complex pattern of neuronal integration _______ the various odorant molecules 4) the axons of ______ cells (2nd order neurons) enter the olfactory tract and (ascend/descend) to the olfactory cortex

1) glomeruli; mitral cells; tufted cells 2) convergence/divergence, subsequent 3) discriminates 4) mitral cells; ascend

Sensory coding for smells created from activation of:

Multiple receptors and neurons

Anosmia

Inability to smell

Hyposmia

Diminished olfactory sensitivity

Hyperosmia

Enhanced olfactory sensitivity (common in pregnancy)

Dysosmia

Distorted sense of smell

Causes of Abnormalities in Odor Detection can be caused by:

1) damage to olfactory nerves (head trauma, tumors) 2) sinus infections 3) nasal congestion 4) nasal polyps 5) poor dental hygiene

Basic Mechanism of Vision The eyes convert _____ energy into AP's in the _____ nerve that are conducted to the _______ cortex, where they produce the sensation of vision

photon; optic; cerebral

2 components of vision

Optical and neuronal

Visual image is focused on _______ on the retina

Photoreceptors

the visual component is transduced by the _______ into a pattern of ______

Photoreceptors; graded receptor potentials

What are the layers of tissue present in the eye?

Outer layer; middle layer; inner layer

What is the outer layer of the eye made up of

Sclera and cornea

Protective white layer of the eyeball, no light can pass

Sclera

Transparent anterior portion through which light rays enter the eye

Cornea

What is the fluid part of the eye made up of

Aqueous humor and vitreous humor

What is the middle layer of the eye made up of?

Iris, ciliary body, choroid

Colored portion of the eye, in front of the lens

Iris

Adjusts the refractive power of the lens

Ciliary body

Nourishing vascular layer of the eye

Choroid

What is the inner layer of the eye made up of

Retina

Neural tissue containing photoreceptor cells, lines the posterior 2/3rds of the choroid

Retina

Formation of Images on the Retina 1) light rays ______ in all directions from their source 2) light rays that reach the _____ must be focused to a point on the _____ for optimal vision

1. diverge 2. pupil, retina

During refraction, light waves ____ as they pass through transparent materials of different densities

Bend

What is the mechanism that allows the formation of focused images on the retina?

Refraction

What structures in the eye allow refraction to occur?

cornea and lens

Properties of Light 1) on a concave surface: light waves striking the surface ______ 2) on a convex surface: light waves striking the surface ______ at a single point called the ______ ______

1) diverge 2) converge, focal point

Formation of Images on the Retina 1) the cornea and lens both have ______ surfaces and help to focus light rays on the retina 2) the _______ is responsible for most of the refraction 3) however, the curvature of the _____ can be adjusted for near and far vision-termed _______

1) convex 2) cornea 3) lens; accomodation

________ is the process by which the curvature of the lens is adjusted

accommodation (focusing)

The lens is suspended by ______ _____ extending from _______ that control tension on the lens

Zonular fibers; ciliary muscles

Ciliary muscle is _____ muscle and is controlled almost entirely by _____

Smooth; parasympathetic nerves

When focusing distant objects, tension on the lens is ______. The lens ______ and has (more/less curvature)

increased; flattens; less curvature

when focusing near objects, tension on the lens is ______. The lens rounds up and curvature (increases/decreases)

Released; curvature increases

The refractive power of the lens is greatest when:

Curvature is the greatest

Emmetropia

Correct focus

Myopia

Nearsightedness

Hyperopia

Farsightedness

Myopia: 1) Where do light rays focus? 2) Are far or near objects blurry? 3) How is this corrected?

1) in front of the retina 2) far/distant objects are blurry 3) with biconcave lens- cause light rays to diverge so rays are brought to focus on the retina

Hyperopia 1) Where do light rays focus? 2) near or far objects are blurry? 3) corrected with what type of lens?

1) beyond the retina 2) near objects are blurry 3) biconvex lens-add to the refractive power of the lens

What regulates the amount of light entering the eye

Pupil

Pupil size is controlled by the _____

Iris

What are the 2 muscles of the iris

- circular muscle layer - radial muscle layer

What muscle layer of the iris is controlled by parasympathetic neurons of the ANS

Circular muscle layer

The _____ of the iris constricts the pupil in bright light, termed ____

Circular muscle layer; miosis

What muscle layer of the iris is controlled by sympathetic neurons of the ANS

Radial muscle layer

The _____ of the iris dilates the pupil in dim light, termed ____

Radial muscle layer; mydriasis

The _____ is the neural portion of the eye

Retina

What are the 5 types of neurons in the retina?

- photoreceptors (rods and cones) - bipolar cells - ganglion cells - horizontal cells - amacrine cells

What are the 3 distinct layers of the retina and what is present in each layer?

- outer: contains rods and cones - middle: contains bipolar, horizontal, and amacrine cells - inner: contains ganglion cells

Rods are the receptors for _____ Cones are the receptors for _____

Night vision; color vision

Photoreceptors: Rods and Cones Outer Segment 1) composed of ______ ______ shaped in either regular stacks of discs (?) or flattened sacs(?) 2) contain the _______ _____ that react to light to initiate receptor potentials

1) membranous disks-(rods) and (cones) 2) photosensitive pigment

# Photoreceptors: Rods and Cones Inner Segment contains cell nucleus that synthesizes:

photosensitive compounds

Photoreceptors: Rods and Cones Synaptic Terminal region of synaptic contact with _____ or ______ cells

bipolar or horizontal cells

Each photosensitive compound is a compound molecule that contains:

- light absorbing retinal - opsin protein

What are the 2 configurations retinal exists in?

In the dark; 11-cis retinal In the light; 11-trans retinal

What determines which wavelengths of light are optimally absorbed by the photoreceptor

The type of opsin present

______ is needed for the synthesis of retinal

Vitamin A (deficiency leads to visual abnormalities)

Rods contain a single photopigment called:

Rhodopsin

How many pigments do cones contain?

3 (blue, green, red)

Cones differ in the _____ they contain

Types of photopigments (opsins)

1) Each opsin type has a sensitivity to light of ______ wavelengths 2) referred to as what color cones? 3) what are the wavelengths of the cones, respectively?

1. different 2. blue, green, red cones 3. short, medium, long

Color vision is:

Trichromatic

What is color sensation determined by?

The relative AP frequencies generated from each of the 3 colored cones (red, green, and blue)

Any spectral color can be produced by:

Mixing various proportions of these colors | blue, green, red

The photosensitive pigment of rods is

Rhodopsin

1) Rhodopsin is coupled with a G protein called ______ 2) when the G protein is stimulated, what subunits dissociate? 3) G-alpha activates ______, which catalyzes cyclic GMP degradation

1. transducin 2. alpha, beta, gamma 3. phosphodiesterase adenylyl cyclase

1) light stimulation of _____ in the rods leads to a structural change in ____ _____ and a conformational change in ______ 2) activation of the Gs-protein ______, in turn activates phosphodiesterase (PDE) 3) PDE hydrolyzes _____, reducing its concentration and leading to the closure of ______ _____ ____ channels in the membrane 4) produces a _______ receptor potential

1) rhodopsin, 11-retinal (cis-to trans-); opsin 2) transducin 3) cGMP, cGMP-gated Na+ channels 4) hyperpolarizing

What channels are present in the outer segment membrane of both rod and cone photoreceptors?

Cyclic GMP-gated ion channels

What is responsible for the light induced changes in electrical activity of photoreceptors?

Cyclic GMP gated ion channels

1) leads to a _____ in cGMP levels 2) closing of the ____ permeable channels 3) photoreceptor produces a _____ receptor potential

1. decrease 2. Na+ 3. hyperpolarizing

In the Dark 1) cGMP levels are _____ 2) cGMP binds to and opens _____ permeable channels 3) ____ enter 4) _______ receptor potential is generated in photoreceptor cells

1) high 2) Na+ 3) Na+ (or other cations) 4) depolarization

Explain the steps of response of photoreceptor to light

1) light is absorbed by photopigment 2) Retinal and Opsin dissociate 3) Transducin is activated 4) Phosphodiesterase is activated 5) cGMP levels in cytosol decrease 6) Na+ channels close 7) With less sodium entering the cell, the cell hyperpolarizes 8) Ca2+ channels close 9) Transmitter release is decreased 10) Graded potential in bipolar cell gets smaller

Explain the steps of the state of photoreceptor in the dark

1) cGMP levels are high 2) sodium channels are open 3) Sodium enters the cell, causing a depolarization that spreads from the outer segment to the terminal 4) Ca2+ open in response to depolarization 5) Calcium enters the cell, triggering exocytosis of transmitter 6) Transmitter causes graded potentials in bipolar cell

Vision 1) _____ ______ formed by the axons of ganglion cells of the retina 2) CN ____ exits each eye and combines in front of the brainstem to form the _____ ______

1) Optic Nerve (CN II) 2) CN II, optic chiasm

What does light from the left visual field strike?

the nasal retina of the left eye and the temporal retina of the right eye

The ganglion axons from the left eye retina _____ to the right brain at the optic chiasm while ganglion axons from the right eye retina stay on?

decussate; ganglion axons from the right eye stay on the same side

2 _____ ____ emerge from the optic chiasma to the associated lateral geniculate nucleus (LGN) of the ______

Optic tracts; thalamus

Where does the neural pathway terminate

Primary visual cortex

Anatomic Distribution of Rods and Cones ___ density throughout the retina, with a sharp peak in the ______

Low; fovea

Fovea

Small depression within the retina where visual acuity is the greatest

Anatomic Distribution of Rods and Cones Rods _____ density throughout the retina but absent in the _____ ____ _____ is the region on the retina where the optic nerve leaves the eye. There are no photoreceptors in this area so does not respond to light, forming a ______

High; fovea; optic disk; blind spot

Visual acuity

- Degree to which details of objects are perceived - defined as the shortest distance by which 2 lines can be separated and still be perceived as 2 lines

Visual acuity is often determined by using _____ viewed from a distance of 20 ft

Snellen Letter Charts

What is a disease in which there is gradual deterioration of visual acuity

Age-related macular degeneration

What causes color blindness genetically

Inherited abnormality inherited as recessive and X-linked 8% males, 0.4% females

What is the most common color blindess

Red/green color blindness

Transient blue-green color weakness occurs as a side effect in individuals taking ___

Viagra for the treatment of ED because the drugs inhibit retinal phosphodiesterase

What charts are used to test for color blindess

Isihara Charts