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special senses
ch 15 special senses
67
Physiology
Undergraduate 1
10/15/2010

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Term
Where are the special senses of the body localized?
Definition
in the head(cephalic region)
Term
List the different special senses
Definition

1.taste

2.smell

3.vision

4.hearing

5.equilibrium

Term
What is the scientific term for taste?
Definition
gustation
Term
On what structure in the body are most of the taste structures located?
Definition
in papillae on the tongue
Term
List and describe the three types of papillae
Definition

1.fungiform papillae-most numerous type. Found mostly on the tongue, but also on other parts of the mouth. Contain taste buds

 

2.circumvallate papillae-large papillae and form a V shape on the posterior 2/3 portion of the tongue. Contain papillae

 

3.filiform-small papillae that project from the tonge to provide the surface of the tongue with friction. DO NOT contain papillae

Term
Which papillae actually contain taste cells?
Definition
fungiform and circumvallate
Term
List and describe the three types of cells that make up a taste bud. What is the function of each?
Definition

1.basal cells- these do mitosis and give rise to new supporting cells

 

2.supporting cells-provide physical support to the taste cells and can differentiate into new taste cells when the taste cells are dead or damaged

 

3.taste cells(gustatory cells)-contain taste receptors for tastants and when stimulated will activate neurons for taste

Term
Describe the receptor for taste
Definition
it is a protein that is embedded in the cell membrane of the gustatory cell and is sensitive to chemicals called tastants. The gustatory cell is an EPITHELIAL cell, not a neuron.
Term

What are the chemicals that the taste receptors bind called?

 

What molecule is required for this chemical to be able to bind to the receptor?

 

How does the mouth supply this molecule?

Definition

tastants

 

water

 

produces saliva, which is mostly water

Term
What is special about capsaicin?
Definition
it is a chemical in food that binds to pain receptors, therefore the person does not adapt to it. This gives a sensation of "taste" in "hot" foods
Term

Are the receptors for taste on a neuron? explain

 

What crainal nerve contains the axons that will carry the signals for taste?

 

Which lobe of the brain will interpret this information?

Definition

NO! the receptors are on gustatory cells,which are EPITHELIA cells. The binding of the tastant to the receptor causes an increase of calcium influx into the tastant cell. The Ca++ binds to synaptic vesicles that will dock with the membrane and release of neurotransmitter to a nerve ending at the bottom of the taste cell.

 

CN VII, IX, or X

 

Insula

Term
What mechanisms are thought to be used to generate action potentials for taste?
Definition

a. sweet,bitter,umami-G-protein pathways that lead to Ca++ influx

 

b.salty-Na+ ions open channels, causing positive influx that depolarizes the membrane and leads to Ca++ influx

 

c.sour-hydrogen ions cause ion channels to open and depolarize the membrane, leading to Ca++ influx

Term
List the four traditional tastes. What is the newly proposed taste called?
Definition
sweet(elicited by carbohydrates), salty(elicited by metallic ions), sour(elicited by hydrogen ions)and bitter. Umami(elicited by the amino acid glutamate)
Term
Which taste seems to be universal on the taste map? Explain why this might be
Definition
Bitter. If bitter substances, which are often due to spoiled food, pass over the back of the tongue it causes a gag reflex, thus the food is expelled by the body rather than swallowed and introduced into the digestive tract
Term
Give an example of how each taste might play a role in homeostasis
Definition

a.sweet-need for carbs as fuel to make ATP

 

b.salty-need for ions

 

c.sour-need for vitamin C

 

d.bitter-expel spoiled foods

 

e.umami-need for protein intake

Term
Describe adaptation of taste and taste association
Definition

a.adaptation is when there is a diminished sensitivity to the sensation over time. Partial adaptaion will occur in 3-5 secs and complete adaptation is achieved within a few mins.

 

b.taste association is when you refer to a taste and something the brain has stored before

Term
What tissue in the nose contains the receptors for smell? Where is this tissue located?
Definition

olfactiory epithelium

 

located on the superior nasal concha of the ethmoid bone

Term
List and describe the three types of cells involved in smell. What is their function? Explain how this set up is different from the setup and reception of taste stimulus
Definition

a.bipolar neurons-contain the receptors for odorants(chemical stimuli)

 

b.supporting cells-columnar EPITHELIA cells that physically support the bipolar neurons and can differentiate into bipolar neurons to replace dead or damaged ones

 

c.basal cells-epithelial cells that undergo mitosis to give rise to supporting cells

for smell, the receptors are on a neuron and for taste they are on an EPITHELIA cell that conveys the message to a neuron below it

Term
What is unique about the olfactory cells?
Definition
they are the only neurons in the body that are replaced(60 day turnover)
Term
What are the chemicals that bind to smell receptors called? What molecule is needed for these chemicals to bind to the receptor? How does the nose supply this molecule?
Definition

odorants

 

water

 

olfactory glands produce mucus and coat the olfactory epithelia with it

Term
What mechanism is thought to produce action potentials in the olfactory cells?
Definition
G-protein,second messenger pathway.(lec.ink)
Term

What is the pathway of neurons from the olfactory epithelium to the brain?

a. What types of cells do the bipolar neurons synapse with?

b.in what special structure does this synapse occur?

c.What is the synapse ratio?

Definition

The bipolar cells are filaments of CN I. They pass the info to mitral cells, whose axons form the olfactory TRACT in the CNS.

a.mitral cells(multipolar)

b.glomerulus located in the olfactory bulb of the brain

c.many bipolar receptor cells: one mitral cell

Term
List some olfactory disorders and briefly describe them
Definition

a.anosmias- loss of sense of smell

 

b.uncinate fits- interpretation of pleasant smells as unpleasant

Term

Describe olfactory adaptation.

Do nociceptors adapt? WHY or WHY NOT?

Definition

decreased sensitivity to stimulus over time. This can occur in smell by the release of GABA from inhibitory neurons or by downregulation

 

NO. The brain must always be aware of stimuli that is harmful to body tissue

Term
What is sight the neurological perception of?
Definition
light energy
Term

List and describe the 3 layers of the eye

Which of these layers contain the receptors for light?

What are the receptors called?

What 2 forms of receptors are they?

Definition

a.fibrous layer-includes the sclera,& the cornea(clear anterior portion that allows light to pass into the eye)

 

b.vascular layer-includes the choroid(pigmented layer that is vascular;absorbs excess light energy),iris(colored portion of the eye that controls the size of the pupil) & ciliary body(ciliary processes that make aqueous humor

 

c.neural layer-includes pigmented layer(different than the choroid)&retina(sensory part).

a.retina

b.photoreceptors

c.rods and cones

Term

Into what two chambers is the eye divided?

What fluids fill these chambers?

Definition

anterior and posterior segments

 

aqueous humor fills the anterior and vitreous humor fills the posterior

Term
What is glaucoma and how can it form?
Definition
a disorder where the scleral venous sinus gets blocked and the aqueous humor cannot drain from the anterior segment. This places pressure onto the lens, which in turn places pressure on the vitreous humor. This pressure can damage photoreceptors in the retina and cause loss of vison
Term
Describe the pupil
Definition
it is a round opening in the circular smooth muscle called the iris. The function of the pupil is to allow light to pass to the retina in the back of the eye
Term
What part of the eye controls the size of the pupil?
Definition
the iris. It is a smooth muscle that contracts to control the amount of light entering the eye
Term
Describe the lens and its function
Definition
The lens is a bioconvex solid structure that accommodates (focuses) light onto the retina
Term
What structure controls the shape of the lens?
Definition
the ciliary muscle and the zonule
Term

What is accommodation?

List the clinical terms for normal, nearsighted and farsighted vision.

Determine if the focus point is prior to or after the retina for nearsighted and farsighted.

Definition

the act of focusing light

emmetropic=normal,myopic=nearsighted, hyperopic=farsighted

 

nearsightedness-focus point is in front of the retina

farsightedness-focus point is behind the retina

Term

Explain the visible light spectrum.

Of what broader classification of radiant energy is the visible spectrum?

Definition

It is a range of light energy that can stimulate photoreceptors in the retina that is interpreted by the brain as images

 

the electromagnetic spectrum

Term
Describe a quanta/photon
Definition
a discrete packet of energy that travels in waves  through space
Term
How does light enery travel through space?
Definition
in a wave pattern. wavelength determines the amt of energy carried by the photon. The shorter the wavelength, the higher the energy
Term
What symbol is used to indicate a wave of light? What is the unit of measurement for a light wave?
Definition
greek symbol lambda( ). Unit is nm (      m).
Term
What color light has the most energy? The least?
Definition

violet

red

Term
List and describe the three types of neurons in the retina
Definition

photoreceptors-contain the receptors for light energy. Come in rods(dim light,grayscale) and cones(brightlight,color). These are bipolar classification nuerons.

 

bipolar cells- bipolar classification

 

ganglion cells-bipolar neurons that receive info form the bipolar cells and their axons carry info to the brain as CN II

Term
Describe/diagram the pathway of light through the eye and past the neurons in the retina
Definition
light will enter the anterior aspect of the eye, travel through the lens, into the posterior segment to the retina. In the retina, light will pass the ganglion cells, then the bipolar cells, then stimulate the photoreceptors
Term
Describe/diagram the path that graded and action potentials take from the neurons to the brain. Which of the neurons generate graded potentials and which generate action potentials?
Definition
light stimulates the photoreceptors and they generate a graded potential. The photoreceptors pass the info chemically  to the bipolar neurons, which also only generate a graded potential. The bipolar neurons pass the info chemically to the ganglion cells, which generate a true action potential
Term

What is the structure of the eye called where the axons carry action potential? Are there photoreceptors here?

a.What is this structure commonly referred to as?

b.What cranial nerve do these axons form when they leave the eye?

Definition

this area is the optic disc,allowing the axons from the ganglion cells to pass through the eye wall. NO photoreceptors

 

a.blindspot

b.CN II(optic nerve)

Term
Describe the density of rods and cones on the retina using the terms macula lutea and fovea centralis
Definition
the cones are dense in the center of the retina, called the macula lutea, and are the most dense in the direct dead center of the retina called the fovea centralis. Rods are most dense on the periphery of the retina
Term
What are the different situations in which rods and cones are used for vision
Definition
rods are for dim light(low energy) and for grayscale. Cones are for bright light(higher energy) and for color
Term

Describe/or draw and label the structure of a photoreceptor.

Which part of the photoreceptor contains the receptors for light?

Definition

the outer segment is the rod/cone shaped part and is modified dendritic ending. The outer segment is connected to the inner segment by the connecting stalk. The inner segment attaches to the soma(cell body),which gives rise to the axon.

 

out segment

Term

Define opsin, retinal, and rhodopsin. How are they related?

Where do opsin and retinal come from?

Definition

opsin is a visual protein

retinal is a vitamin A derivative

rhodopsin is opsin bound to retinal

 

In their bound(rhodopsin) form, they play a role in photoransduction that keeps rodsin their "on" position. When detached, the rods turn "off"

 

opsin is a pigment made by protein synthesis and retinal is made from vitamin A from the food we eat

Term
Describe bleaching of retinal. How is it returned from this condition?
Definition
bleaching is when light strikes 11-cis retinal and turns it into all-trans retinal. The all-trans retinal detaches from opsin and the opsin no longer gives off the purple light. The condition is returned when the lights are dim or off and an enzyme that uses ATP uses all-trans retinal and returns it to 11-cis retinal,which binds to opsin
Term
What is the pinna and what is it used for?
Definition
collection of sound waves and funneling them into the external auditory canal(meatus) This structure is also called the auricle
Term

What is the external auditory canal? What is its function?

 

What special glands are found in this canal? What product do they secrete? What is the function of this product?

Definition

The structure leading from the outer opening of the ear to the tympanic membrane. This canal leads sound waves to the tympanic membrane.

 

sebaceous and sudoriferous glands. They secrete oil and sweat,respectively. The modified sweat glands secrete cerumen(ear wax) to trap debris in the air entering the canal

Term
What is the name of the membrane at the end of the external auditory meatus? What is its function?
Definition
Tympanic membrane(tympanum). Vibrates when sound waves hit it and transmit the wave to the first ossicle, malleous.
Term

What are the names and order of the ossicles in the middle ear? What is their function?

 

 

Definition
malleous then incus then stapes. These bones transmit info from soundwaves as vibration across the air-filled tympanic cavity(middle ear)
Term
How are sound waves amplified in the middle ear?
Definition
the tympanic window is 20x larger than the oval window, so the soundwave info reaching it as bone vibrations gets amplified 20x
Term

Describe the characteristics of sound.

Explain frequency and amplitude and the units used to measure them.

Definition

sound is a disturbance in the air molecules that travels in waves through space.

 

frequency is the nember of waves/second of sound. The smaller the wave, the higher the frequency. Measured in hertz(Hz)

 

amplitude is the loudness of the soundwave and is indicated by the height of the wave(amplitude). The unit of measurement is in decibels(dB).

Term
List and briefly explain the components of the inner ear
Definition

a. vestibule-egg shaped,fluid filled cavity that contains the receptors for static equilibrium and leads to the semicircular canals and the cochlea

 

b. semicircular canals-three 2/3 circular, fluid filled canals that contain the receptors for dynamic equilibrium

 

c. cochlea- snail shaped fluid filled canal that contains the receptors for hearing

Term
Describe/diagram the parts of the cochlea
Definition
the cochlea  is a spiraled, three chambered,fluid filled canal. The superior chamber is the scala vestibule(begins at the oval window) and the bottom is the scala tympani(ends at the round window). These chambers are perilymph-filled. The middle chamber is the scala media(cochlear duct), formed by the floor of the scala vestibule(vestibular membrane) and the roof of the scala tympani(basilar membrane. This chamber is endolymph-filled. The organ of corti is found on the basilar membrane in the scala media and is covered by the tectorial membrane
Term
Describe the parts of the Organ of Corti? What are the functions of the special cells found there?
Definition
the organ of corti contains receptor cells(epithelia cells with receptors for sound), supporting cells and basal cells(same functions as in the taste buds). The epithelia cells' receptors are mechanorecpetors that are activated by the waves formed in the tectorial membrane and release NT to the nerve fibers below them.
Term
How is the set up and types of cells int he organ of corti similar to those of the taste bud?
Definition
exactly the same, only the receptor cells of the ned respond to chemicals callsed tastants and receptor cells in the organ of corti respond to mechanical waves
Term
Describe the mechanism of hearing starting from the external auditory meatus
Definition
the sound waves travel down the external auditory meatus and cause vibrations in the tympanic membrane, which then causes vibrations in malleous,then incus,then stapes. Stapes causes the oval window to vibrate, which causes waves to form in the perilymph of the scala vestibule. These waves cause waves in the vestibular membrane, which cause waves in the endolymph of the scala media. Those waves cause waves in the tectorial membrane, and are in the same frequency as the original sound wave. The tectorial membrane bends the hairs of the receptor cells in the organ of Corti and cause a release of NT to the cochlear nerve fibers below(help form CN VIII).
Term
List and describe some hearing disorders
Definition

a.deafness-can be sensorineoural,which inhibits transmission of sound from the CN to temporal lobe,or conduction, which inhibits transmission from the external auditory canal to the the organ of Corti.

 

b.tinnitus-characterized by a ringing or clicking sound. Thought to be caused by CN VIII degeneration,inflammation or as a side effect of some medication

 

c.meniere's syndrome-believed to be a disorder of the labyrinth(semicircular canals,vestibule). Characterized by a howling tinnitus and causes vertigo,nausea and vomiting. May be caused by mixing of lymph fluids or by and accumulation of endolymph

Term
What structures of the ear are responsible for equilibrium?
Definition
semicircular canals and vestibule
Term

Describe the difference between dynamic and static equilibrium.

 

What structures of the inner ear is responsible for these forms of equilibrium?

Definition
static equilibrium is balance in one plane of space. The vestibule is responsible for this. Dynamic is rotational equilibrium(all 3 planes of space at once). The semicircular canals are responsible for this.
Term
Describe the saccule and the utricle
Definition
membranous sacs within the vestibule for static equilibrium. Filled with endolymph and each contains a macula
Term

Describe the structure of the macula inside the saccule and utricle

 

list the 3 types of cells in the macula

 

describe otoliths and the otolithic membrane and their functions

Definition

a pad of cells within the utricle or saccule that contain receptors for static equilibrium

 

macula contain hair cells(receptor cellsfor static equilibrium). The receptors are mechanoreceptors

 

supporting cells and basal cells

 

The macula is covered in a jelly like membrane called the otolithic membrane. The membrane contains otolith crystals(Ca++ corbonate) that give the membrane mass.  This membrane moves with the movements of the head and are the mechanical stimulus for the receptors on the hair cells in the macula.

Term
Describe the mechanism for static equilibrium in the saccule and utricle
Definition
As the head moves in vertical or horizontal planes, the otolithic membrane bends the receptors(hairs) on the hair cells in the macula. This opens up ion gated channels and ions enter the cell,depolarizing it. This leads to release of NT to th nerve endings of the vestibular nerve (CN VIII) below the receptor cells and info goes to the brain as an action potential.
Term
Describe the structure of the semicircular canals
Definition
There is a semicircular canal in each plane of space. The canal is filled with perilymph and a membrane sac inside that is endolymph filled. The end of each tube widens as it meets the vestibule and this part is called the ampulla,which contains the crista ampullaris.
Term

Describe the crista ampularis.

Describe the three types of cells found in the crista ampularis and their functions.

Definition

It is a pad of epithila cells covered in a jelly-like mass called the cupula.

types include hair cells,supporting cells and basal cells,like in the macula. The receptors on the hair cells are mechanoreceptors. As the head moves in 3 dimensions of space,the capula moves and acts as the mechanical stimulus for the receptors.  This opens up ion gated channels and ions enter the cell, depolarizing it. This leads to release of NT to the nerve endings of the vestibular nerve(CN VIII) below the receptor cells and info goes to the brain as an action potential.

Term
What is vestibular nystagmus?
Definition
it is rapid flickering of the eyes back and forth in an attempt of the eyes to find a focus point
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