Special Senses

What are the visual pigments?

1.) Rhodopsin (is in rods) 2.) Photopsin (is in cones) (3) -each photopsin has a different opsin and each opsin has a different amino acid sequence allowing its retinal to absorb a different wavelength of light allowing us to see different colors.

So once taste has been sensed how does it get to the brain?

1.)Afferent fibers synapse with 2nd order in the solitary nucleus of the medulla. 2.)From there, second order synapses with 3rd order in the thalamus. 3.)From here the fibers project to the gustatory cortex and also to the hypothalamus and limbic system

What are the two cells associated with taste buds?

1.)Supporting or sustentacular cells 2.)Taste cells or gustatory cells.

Rods converge?

100 rods may converge onto each ganglion cell resulting in vision that is fuzzy and indistinct. The brain doesn't know which rod was activated. Rods do not provide sharp images or color vision. Colors disappear edges of objects appear fuzzy in low light.

What are some characteristics of the semicircular canals?

3 canals in different planes. Each canal is about 2/3 of a circle and has an enlarged swelling at one end called an ampulla which houses the crust ampullaris. This monitors rotational head movements aka dynamic equilibrium.

What makes up the vestibular apparatus?

3 semicircular ducts-receptors here monitor change in head rotation called "dynamic equilibrium" Vestibule-receptors here monitor head position with respect to gravity and linear acceleration called "static equilibrium" The vestibule has 2 chambers-the saccule and utricle

What is Meniere's Syndrome? What causes it?

A labyrinth disorder that affects all three parts of the internal ear. Repeated attacks of vertigo, nausea, and vomiting. Balance is so disturbed that standing erect is nearly impossible. Characterized as a howling tinnitus. The cause is unknown but it may result from excessive endolympth that distorts the membranous labyrinth. Causes the membrane to rupture allowing perilymph and endolymph to mix.

How does transmission of sound occur in the inner ear?

Airborne sound strikes the tympanic membrane and sets it vibrating, the motion is amplified and transferred to the oval window by the auditory ossicles (stapes) which sets the cochlear fluid in motion, since the fluid can't be compressed, the round window bulges laterally.

How does taste stimulate digestion?

An important role of taste is to trigger digestive reflexes and this occurs in the solitary nucleus via synapses with parasympathetic nuclei to increase secretion of saliva and gastric juice.

Why do animals choose certain foods in preference to others?

Animals choose certain foods in preference to others because of what the body needs. Salt depleted animals preferentially select salty foods. If there is a low blood sugar animals select sweet foods. If calcium is depleted select drinks with increased calcium chloride. This mechanism is probably located in CNS.

How are mild and severe cases of Meniere's disease treated?

Anti-motion drugs, low salt diet, diuretics to reduce endolymph volume. Severe cases may require draining excessive endolymph or removal of entire malfunctioning labyrinth usually deferred until hearing loss is complete.

How are macula receptors activated?

Any change in head position causes the heavy otolith membrane to slide bending hairs in one of the maculae. The mechanically gated channels open and allow cations to enter the hair cell which will depolarize the cell. Hair cells release NT continuously and movements of hairs just modifies the amount. Receptors in the maculae detect: 1.)Static equilibrium-or orientation of the head with respect to gravity. 2.)Linear acceleration and changes of head position.

What do rods do? What are some characteristics?

Are responsible for non-color vision under condition of low light are more numerous, far more sensitive to light than cones. They are bipolar neurons "dendritic" light sensitive part is cylindrical. Contains 700 membranous discs looks like a roll of coins, membranes of discs contain the visual pigment: Rhodopsin.

Describe the olfactory pathway!

Axons of olfactory sensory neurons form olfactory nerves synapse in olfactory bulbs (distal end of the tracts) with mitral cell. These are the 2nd order neurons whose axons form the olfactory tracts and travel to olfactory cortex.

Vestibular nuclei integrate information on?

Balance, vision, and body position and send commands to brain stem motor centers that control extrinsic eye muscles (III, IV, VI), reflexes of neck, limb and trunk muscles. This allows us to remain focused on visual field and quickly adjust body position.

Rods and cones synapse with?

Bipolar cells synapse with ganglion cells. Ganglion cells are in a single superficial layer closest to the vitreous body. Axons turn and leave the eye as the optic nerve. These are the only cells that conduct APs and carry visual message to the brain.

The olfactory receptor is a ____________ sensory neuron?

Bipolar. Each olfactory cell has a single dendrite embedded in the epithelium that terminates in a knob from which olfactory cilia radiate and lie on nasal epithelium covered with mucus. The mucus is a solvent that dissolves odorants.

__________ taste is not elicited by a single class, mostly organic? What elicits this taste?

Bitter taste. Usually long-chain organic N compounds. Alkaloids (drugs, caffeine, nicotine, strychnine) Intense bitter taste usually causes food rejection and this protects us against deadly plant toxins who are alkaloids and have bitter taste.

Which taste cell have the lowest threshold?

Bitter!

How is bitter, sweet, and umami transduced?

Bitter, sweet, and umami use a second messenger system. The receptor is coupled to a common G protein and activation leads to release of Ca from intracellular stores. Ca opens cation channels from the inside which will depolarize the cell. The NT probably released is serotonin, ATP, Ach, glutamate, and NE

What is glaucoma?

Build up of aqueous humor which increased IOP. This will push lens against vitreous body which will in turn pushes the retina against the choroid. This will compress blood vessels that nourish the retina. Retinal cells die and damage is irreversible. It can be halted with drugs or surgery.

What are cataracts? Do they cause blindness?

Cataracts can cause blindness. Cataracts cause clouding of the lens and occurs as the lens thickens with age. They are results of: a complication of diabetes, a result of heavy smoking, and exposure to UV radiation. This causes vision to appear milky. Treatment is replacement of the lens with a plastic one.

The receptors for taste (gustation) and smell (olfaction) are what type of receptors? What do they respond to?

Chemoreceptors that respond to chemicals in AQUEOUS solution. The chemical cause EPSPs on receptors. They allow us to separate undesirable from pleasant food and elicit digestive, emotional, and behavioral responses.

In the dark, retinal has a bent shape called?

Cis-retinal. When it absorbs a photon of light it changes to a straight line forming the trans-retinal. This change, in turn causes opsin to change shape and assume its "activated" form.

What is one very specific aspect of cochlear fluid?

Cochlear fluid is very high in K, this is the only time that K enter cells.

What are the cones responsible for? What is the visual pigment?

Color vision, need bright light. Cones are also bipolar photoreceptor cells. The dendritic, light sensitive part of conical. Conical segment contains the disc with the visual pigment: photopsin. There are 3 separate variations of photopsin in cones with slightly different AA sequences in the opsin portion of the molecule. This allows cones to respond to 3 different colors: blue, green, red.

What are some characteristics of the crista ampullaris?

Composed of supporting cells and hair cells. The function of hairs same as maculae and cochlea, here the stereocilia are embedded in a cupula. Cupula is a gelatinous mass, lacks otoliths and doesn't respond to gravity. Dendrites of vestibular neurons encircle base of hair cells.

What is sensorineural deafness?

Damage to the neural structures typically results from loss of hair cells throughout life or can be destroyed by loud noises (tear off cilia) or degeneration of cochlear nerve, strokes, tumors.

How do taste cells adapt?

Different taste cells have different thresholds or intensity. BITTER have the lowest threshold. Also, taste cells adapt rapidly. It begins in 3-5 seconds and is complete within 1-5 minutes.

The special sensory receptors are?

Distinct receptor cells that are confined to the head and highly localized

What happens if the body continues to rotate at constant rate?

Endolymph comes to rest and moves at the same speed as the body and there is no more stimulation of the hair cells. When your blindfolded you can't tell your moving. When you stop spinning, the endolymph keeps moving and reverses hair bending, alters membrane voltage.

What are the 3 structures of the ear?

External ear-involved with hearing only Middle ear-involved with hearing only Inner ear-involved with hearing and equilibrium

T or F? The nasal cavity contains mechano, pain, and temp receptors?

False- The nasal cavity also contains pain and temp receptors that respond to irritants such as ammonia, chlorine, menthol. These signals are transmitted on CNV trigeminal.

T or F? The skeletal muscles attached to the auditory ossicles are voluntary controlled?

False. These skeletal muscles are involuntary. They contract to limit ossicle movement with loudness.

In the Organ of Corti what are hair cells?

Hair cells are the mechanoreceptors with stereocilia. Stereocilia don't move by themselves. Hair cells synapse with sensory neurons.

How is the nerve supply of the inner ear?

Hair cells of sacculi, ureiculi, cristae ampullaris synapse at their base with sensory fibers of the vestibular nerve and joins the cochlear nerve to form CN VIII or the vestibulocochlear nerve

How does hearing occur?

Hearing is a response to vibrating air molecules that enter the external acoustic meatus and cause the tympanic membrane to vibrate. The stapes rests on the oval window which is the beginning of the inner ear that is a fluid filled chamber. The sense organ of hearing is in the cochlea which is the Organ of Corti.

What are horizontal cells? Amacrine cells?

Horizontal cells connect laterally between rods and cones and bipolar cells. Possibly inhibit bipolars? Amacrine cells are not well understood.

How is sour taste transduced?

Hydrogen Ion opens cation channels which cause direct depolarization.

How is the auditory pathway to the brain?

Impulse conducted along afferent fibers of cochlear nerve enter the brain at the pontomedullary junction and synapse in the cochlear nuclei of the medulla. Most decussate, some do not. Most project to the superior olivary nucleus, some to the inferior colliculus and then on to the thalamus then to the primary auditory cortex.

What is the receptor involved with hearing and balance?

In both senses fluid moves to stimulate mechanoreceptors. These receptors are in the inner ear.

Special sensory receptors are housed?

In either complex sense organs (eye, ear) or distinct epithelial structures (taste, smell)

Where does conversion of light energy into AP's occur?

In the retina. The retina is the layer of nervous tissue lining the back of the eye. It consists of 3 layers posterior to anterior. Photoreceptors, bipolar cells, ganglion cells.

What is the macula sacculi?

Lies vertically on the wall, hairs protrude horizontally responds best to vertical movements (elevator). Hair cells synapse with fibers of vestibular nerve.

So where do the mitral cell axons do when they get to the brain?

Mitral cell axons pass through the hypothalamus, amygdala and limbic system where emotional responses to odors are elicited. Some smells are associated with danger (smoke, skunk) which can stimulate the fight or flight. Appetizing odors can stimulate salivation, gastric activity. Unpleasant odors can trigger sneezing and choking.

Widely distributed general receptors are mostly?

Modified dendrites of sensory neurons.

How does motion sickness happen?

Motion sickness is probably due to sensory input "mismatches". Visual inputs tell the brain one thing and the vestibular inputs another. There is brain confusion which stimulates the emetic center. OTC anti-motion drugs depress vestibular inputs.

How does excitation of hair cells occur?

Movement of the cochlear fluid ultimately moves stereocilia which opens mechanically gated ion channels. Cations enter (K, Ca). K and Ca entry causes depolarization of hair cells which causes a graded potential, hair cells release glutamate which will excite afferent cochlear fibers.

T or F? Cones converge?

No they do not converge. Each cone has its own ganglion cell. This permits detailed high visual acuity.

What are the primary taste sensations?

Normal taste sensations are complicated mixtures but when tested with pure chemical compounds taste sensations can be grouped into 1 of 5 basic modalities. The primary taste sensations are: SWEET, SOUR, SALTY, BITTER, and UMAMI. We perceive hundreds of different tastes; these are combinations of stimulation of the 5.

How is smell transduced?

Odorants bind to integral protein receptors linked to a G protein. A subunit of G protein breaks away activating an adjacent membrane protein ADENYLATE CYCLASE that converts ATP to cAMP. cAMP is the second messenger, it opens Na channels from inside. Na depolarizes the cell leading to AP conduction.

What are some characteristics of olfactory epithelium?

Olfactory epithelium contains millions of receptor cells which are olfactory neurons. These neurons are bipolar neurons surrounded by columnar supporting cells. At the base of epithelial cells lie olfactory stem cells.

What is otitis media?

Otitis media is a middle ear infection and a common result of a sore throat.

Where does the inner ear begin?

Oval window.

How does adaptation of olfactory receptors occur?

Receptors adapt, 50% in the first second, the slowly. So smell adaptation appears to come from the CNS.

Smell receptors detect _____________ in solution? Where are smell receptors found?

Receptors detect odorants in solution. Receptors are found in olfactory epithelium which is a patch of PCCE in the roof of nasal cavity. Laterally it covers the superior nasal concha.

What are some characteristics of equilibrium and head orientation?

Receptors respond often without our being aware to head movements and head position. This sense also depends on inputs from vision and stretch receptors in muscles and tendons. The receptors cells are hair cells (modified epithelial cells) mechanoreceptors with stereocilia.

Responses to equilibrium signals are purely ____________?

Reflexive. Usually unaware of vestibular activity until impaired.

What is the equilibrium pathway to the brain?

Responses to body imbalance must be fast and reflexive so info from equilibrium receptors goes directly to reflex centers in brain stem rather than cortex. REMEMBER: vestibular apparatus detects movement and orientation of the head only CNS balance centers must also receive input about position of the rest of the body. Impulses from vestibular sensory neurons travel to 1 of 2 places.

This is a vitamin A derivative?

Retinal.

What is rhodopsin?

Rhodopsin is a globular membrane protein consisting of a protein portion (opsin) a nonprotein portion (retinal). All rods contain the same rhodopsin and are only able to perceive gray.

What is tinnitus? What is the mechanism?

Ringing or clicking in ears. This is usually a symptom of something else. Possibly cochlear nerve degeneration or inflammation of middle or inner ears or side effect of drugs (aspirin?) The MOA may be similar to phantom limb pain. Destruction of neurons in the auditory pathway and subsequent ingrowth of nearby neurons whose signals are interpreted as noise.

The vestibule has 2 chambers called the?

Saccule and utricle. Each chamber has a patch of epithelial hair cells called the macula. The macula hair cells have stereocilia that project into a gel-like mass.

___________ taste is elicited by ionized salts, mainly Na?

Salty taste

How is salty taste transduced?

Salty taste is caused by sodium influx through Na channels which cause direct depolarization.

So upon exposure to light?

So on exposure to light, retinal changes shape from cis to trans (activated)

___________ taste is produced by acids, specifically H ions?

Sour taste

What is space sickness?

Space sickness is caused by zero gravity which causes unfamiliar sensory input, too little input?

How are olfactory receptors activated?

Studies show at least 100 primary sensations of smell. Maybe even 1000 different odor receptors. Dissolved odorants bind to receptors in olfactory cilia membranes. Receptors are linked to a G protein which ultimately opens cation channels and generates a receptor potential. If threshold is reached an AP is conducted to the bulb.

_____________ taste is elicited by many organic substances, including: sugars, saccharin, alcohols, some amino acids, lead salts?

Sweet taste

What are some characteristics of taste buds?

Taste is a function of taste buds. There are 3K-10K, and they are mostly on the tongue. There are also some on the palate, tonsils, epiglottis, and proximal esophagus. Each bud consists of 50 epithelial cells of two types.

How is the taste pathway carried?

Taste is carried on 3 CN pairs. 1.)Facial Nerve-Chorda Tympani. This nerve transmits taste from anterior 2/3 of tongue. 2.)Glosso pharyngeal nerve-serves posterior third and pharynx. 3.)Vagus nerve-a few taste buds in epiglottis, lower pharynx

What does the Organ of Corti do?

The Organ of Corti converts vibrations in to APs. It is a patch of epithelium composed of hair cells and supporting cells

How is the taste cell activated?

The application of a tasting induces a graded depolarization potential in the taste cell called a receptor potential that causes the gustatory cell to release NT which binds to the associated sensory dendrites and triggers "generator" (local) potentials that elicit APs.

The middle ear is spanned by 3 tiny bones what are they?

The auditory ossicles: malleus, incus, stapes They are attached to walls by tiny skeletal muscles. They contact to limit ossicle movement with loud noises.

Where is the second place impulses from vestibular sensory neurons go?

The cerebellum also integrates inputs from the eyes and somatic receptors and coordinates skeletal muscle activity to maintain head position, posture, balance.

What are some characteristics of the cochlea?

The cochlea houses the Organ of Corti. This is the receptor for sound.

What are some characteristics of the inner ear?

The inner ear is a fluid filled chamber deep in the temporal bone. It houses receptors for balance and hearing.

How do photoreceptors translate light into APs?

The key is a light absorbing molecule called retinal that combine with proteins called opsins to form the 4 types of visual pigments (rhodopsin and 3 different photopsin) depending on the AA sequence of opsin retinal absorbs different wavelengths of visible light.

So in summary equilibrium receptors?

The key point of equilibrium receptors: Bony labyrinth moves with body while fluids (gels) within the labyrinth move at different rates depending on the forces acting on them (gravity, acceleration, etc.). The fluids (gels) bend stereocilia on hair cells, stimulating them.

What is the macula utriculi?

The macula utriculi lies horizontally on the floor hairs are vertical when head is upright and responds best to accerleration in horizontal plan and tilting head to the side.

What are some characteristics of the middle ear?

The middle ear is an air filled chamber in the petrous temporal bone thats flanked laterally by the tympanic membrane. The medial wall has two openings: -Superior=Oval window -Inferior=Round window The anterior wall abuts the internal carotid and has opening of Eustachian tube (opens to the nasopharynx). The ear drum vibrates freely only if pressures are equal.

What receptors does the mouth contain?

The mouth contains chemoreceptors, thermoreceptors, mechanoreceptors, and nociceptors.

These are calcium carbonate protein granules that add density and inertia to the membrane?

The otolith membrane weighted with otoliths which are calcium carbonate protein granules that add density and inertia to the membrane.

What is vision?

The perception of objects in the environment by means of the light they emit. Our dominant sense houses 70% of the body's receptors. Half of the cortex used in processing it. Light causes a photochemical reaction. A change in chemical structure caused by light energy.

What is the MOA of basic taste sensation?

The precise chemicals are unknown although probable chemical receptors respond to: Na, K, Cl, adenosine, sweet, bitter, glutamate, H ions

Where is the primary auditory cortex?

The primary auditory cortex is on the superior temporal lobe. Also, because some information crosses, each auditory cortex receives impulses from both ears. Many collaterals pass through the RAS which activates the entire CNS in response to loud sounds.

T or F? The texture and temperature of food cannot enhance or detract from their taste?

The texture and temperature of food can enhance or detract from their taste.

What are some causes of blindness?

The two most common causes of blindness are: 1.) Cataracts 2.) Glaucoma

What are some characteristics of the olfactory cell axons?

The unmyelinated axons bundle and penetrate the cribriform plate forming the olfactory nerve. The axons synapse in olfactory bulbs. ** These are the only neurons exposed to the environment. They only live for 30-60 days and are replaced by basal (stem) cells.

What are the two divisions of the inner ear?

The vestibular apparatus The cochlea

What are some characteristics of the vestibular apparatus?

The vestibular apparatus includes the semicircular canals and the vestibule which houses receptors for head position.

Where is the first place impulses from vestibular sensory neurons go?

The vestibular nuclei in the brain stem. It is the main integrative center for balance. It also receives inputs from the visual and somatic receptors.

What do photoreceptor cells do?

They absorb light, initiate visual signals. The rods and cones are modified bipolar neurons. The outer segment is the receptive region and contains visual pigments. Visual pigments are molecule that change shape as they absorb light.

What are some characteristics of the taste cell?

They have a harsh life, only live 7-10 days. They are replaced by mitosis of surrounding epithelial (basal) cells. The apical tips have long microvilli: taste (gustatory) hairs extend through the taste pore to the surface of the epithelium where they are bathed in saliva. Hairs contain the receptor. Taste cells synapse with sensory dendrites at their base.

How are the crista ampullaris receptors activated?

They respond to rotational movements of the head because of inertia; fluid in the semicircular duct, briefly moves in the direction opposite of body rotation and deforms the cupula. The hairs bend in one direction, they depolarize generating more impulses bending cilia in opposite directions hyper polarizes hair cells and they generate fewer impulses.

What is trans-retinal?

Trans-retinal activates intracellular NZ that ultimately changes the membrane permeability of rods and cones. Rods and cones then stimulate the bipolar cells, causing them to depolarize and release NTs. Bipolars in turn, stimulate ganglion cells to fire APs sending signals to visual areas of the brain.

T or F? Chemicals in spicy foods stimulate nociceptors?

True.

T or F? Taste depends on smell?

True. Taste depends on smell, they work together.

________ taste is characterized as "delicious", meat and cheese and is caused maybe by glutamate and aspartate?

Umami taste

What are the special senses?

Vision, taste, smell, hearing, equilibrium

What is conduction deafness?

When something hampers sound conduction to inner ear like cerumen impaction or ruptured eardrum, otitis media or otosclerosis (auditory ossicle fusion or when bone growth fuses stapes to oval window)