AP Ch. 16

in the dark

1. dark current (caused by entry of na+ and ca2+) causes photoreceptor cell to be depolarized at -40 mV. a graded potential (which is a local current or ions) is transmitted along the inside of cell. 2. voltage-gated ca2+ open, and neurotran. gutamate released from photoreceptor 3. binding of glutamate hyperpolarize bipolar cell, causing inhibition 4. there is no release of neurotran from bipolar cells 5. no nerve signal is generated from ganglion

Central Nervous System Pathways for Hearing

1. movement of basilar membrane produces nerve signals propagated along cochlear nerve to nucleus within medula oblangata 2. some secondary neurons relay nerve signals to corticulus of midbrain 2. secondary relay nerve signals to superior celivary nucleus within pons, then relayed to inferior colluculus of midbrain 3. nerve signals relayed from inferior colliculus to thalamus 4. nerve signals relayed from thalamus to primary auditory cortex of temporal for sound perception

in the light

1. stimulation by light causes photoreceptor to be hyperpolarized at -70mV because of decreased entry of na+ and ca2+ 2. voltage-gated ca2+ channels close and no glutamate is released 3. the bipolar is no longer inhibited and depolarizes 4. bipolar releases neurotrans 5. neurotrans binds to receptors in ganglion and nerve signal is initiated to brain

Visual Pathways

At the optic chiasm, some axons from the optic nerve decussate. The optic tract on each side then contains axons from both eyes. Visual stimuli information is processed by the thalamus and then interpreted by visual association areas within the occipital lobe of the cerebrum. Visual sensory input involved in reflexes is relayed to nuclei within the midbrain

Sound Wave Interpretation at the Basilar Membrane

High-frequency sounds (red arrow) generate pressure waves that cause the basilar membrane to displace close to the base of the cochlea. Medium-frequency sounds (green arrow) generate pressure waves that cause the basilar membrane to displace near the center of the cochlea. Low-frequency sounds (blue arrow) generate pressure waves that cause the basilar membrane to displace near the helicotrema.

Equilibrium Pathways.

Information from the vestibular complex is sent to multiple parts of the brain, so posture and body movement may be adjusted accordingly.

The photopigment in rods is called

Rhodopsin is involved in the transduction of dim light and is most sensitive to light at a 500-nm wavelength

Function of the Crista Ampullaris.

Rotation of the head causes endolymph within the semicircular duct to push against the cupula covering the hair cells, resulting in bending of their stereocilia and an alteration in the frequency of nerve signal propagation.

How We Hear.

Sound waves enter the external ear and then (a) are transmitted to the middle ear. (b) Sound is amplified within the middle ear and transmitted to the inner ear, where (c) sound energy is transduced to nerve signals that (d) are transmitted along the auditory pathway to the brain.

fibrous tunic, or external tunic.

The external layer of the eye wall. It is composed of the posterior sclera and the anterior cornea.

retina also is known as the internal tunic or neural tunic

The internal layer of the eye wall. an outer pigmented layer and an inner neural layer

vascular tunic

The middle layer of the eye wall, also called the uvea. the choroid, the ciliary body, and the iris.

photoreceptors

The outer segments of both rods and cones consist of stacks of discs embedded in the pigmented layer. (b) Membranes of the discs contain photopigments. Each photopigment is composed of an opsin and a retinal.

accomodation

The process of making the lens more spherical to view close-up objects

The dendritic ending of each gustatory cell is formed by a slender gustatory microvillus, sometimes called a taste hair. Many gustatory microvilli extend through an opening in the taste bud, called the taste pore, to the surface of the tongue.

This is the receptive portion of the cell.

Bleaching Reaction and Regeneration of Rhodopsin.

When light waves reach the rod, cis-retinal is transformed to trans-retinal, which then disassociates from opsin in a process called the bleaching reaction. Rhodopsin is re-formed when trans-retinal is converted back to cis-retinal, which then reunites with opsin.

The semicircular ducts are responsible for detecting ____ acceleration

angular (shake head no)

Sensory receptors

are components of the nervous system that provide us with information about both our external and internal environment.

Taste buds

are cylindrical sensory organs containing taste receptors and have the appearance of an onion

Rods

are longer and narrower than cones. Each eye contains more than 100 million rods, and they are primarily located in the peripheral retina. Rods are activated by dim (low-intensity) light such as when you are in an unlit room at night, and provide no color recognition.

Amacrine cells

are positioned between the bipolar and ganglion cells and help process and integrate visual information as it passes between bipolar and ganglion cells.

Horizontal cells

are sandwiched between the photoreceptor and bipolar cells in a thin web. These horizontal cells regulate and integrate the stimuli sent from the photoreceptor cells to the other cell layers.

Cataracts

are small opacities within the lens that, over time, may coalesce to completely obscure the lens.

Tactile receptors

are the most numerous type of sensory receptor. They are mechanoreceptors located in the skin and mucous membranes. unencapsulated or encapsulated

olfactory glomeruli

balls in olfactory bulbs (detect faint odors)

MODALITY OF STIMULUS (STIMULATING AGENT)

chemoreceptors- chemicals dissolved in fluid (taste, H+) thermore.- temp. (skin and hypothalamus) photore.- light, color, movement (eye) mechanore.- deformation from touch, pressure, vibration, stretch (tactile in skin) nociceptors- pain (pain in organs)

The junction of the ocular conjunctiva and palpebral conjunctiva is called the ____ _____. (This junction is what prevents a contact lens from moving behind the eye.)

conjunctival fornix (contains goblet to lub and moisten eye, blood vessels to supply, and nerve endings for foreign objects)

adaptation

decrease in sensitivity to a continuous stimulus

Tonic receptors

demonstrate limited adaptation. In response to a constant stimulus, tonic receptors continuously generate nerve signals and only slowly decrease the number relayed to the CNS. (head position)

Maculae

detect both the orientation of the head when the body is stationary and linear acceleration of the head. (a) The maculae are located within the walls of the saccule and utricle. (b) An enlarged view of a macula shows the apical surface of the hair cells covered by a gelatinous layer overlaid with otoliths, called the otolithic membrane. (c) An individual hair cell has numerous microvilli called stereocilia and a single, long kinocilium.

transducer

device or organ designed to convert energy from one form to another (always electrical)

STIMULUS ORIGIN (LOCATION OF STIMULUS)

extroreceptors- external (skin, smell, taste, etc) intero.-within body (walls of viscera and blood vessels) proprio.-joints, skeletal muscle, tendon (muscle spindles)

four types of papillae of the tongue

filiform- short, spiked, anterior 2/3 of tongue. no taste buds but help manipulate and detect texture fungiform- blocklike, tip and side. only few buds vallate- least numerous but largest. v shape on posterior dorsal foliate- ridges on posterior lateral side. house few during childhood

Vitreous humor

fills the posterior cavity, helps to maintain eye shape and support the retina to keep it flush against the back of the eye

SENSORY RECEPTOR DISTRIBUTION (LOCATION OF RECEPTOR)

general- throughout body somatic-skin, joints, muscles, tendons (touch) visceral- walls of viscera and blood vessels (stretch stomach) special- only in head (smell, taste, vision, hearing, equil.)

hyperopia

have trouble seeing close-up objects, and so are called farsighted. The cause of hyperopia is a short eyeball; parallel light rays from objects close to the eye focus posterior to the retina

Conductive deafness

involves any interference with the transmission of sound waves from the pinna, through the external acoustic meatus, tympanic membrane, and ossicles. Examples of conductive deafness would include rupture of the tympanic membrane, fusion of the ossicles, or middle ear inflammation (otitis media).

Sensorineural deafness

involves malformation or damage to either the structures of the inner ear or the cochlear nerve. Examples would include damage to cilia of the inner ear from loud sounds (e.g., rock concerts or firing a weapon) or trauma to the cochlear nerve from a blow to the head.

accommodation

involves stimulation of the ciliary muscles by the parasympathetic division of the ANS when viewing objects closer than 20 feet. In response, the ciliary muscles contract to reduce tension in the suspensory ligaments, so the lens becomes more spherical or curved.

Otitis media

is an infection of the middle ear.

Emmetropia

is the condition of normal vision, in which parallel rays of light are focused exactly on the retina

light adaptation

is the process by which your eyes adjust from low light to bright light conditions, such as when you wake up at night and turn on the bright light in the bathroom.

Olfaction

is the sense of smell, whereby volatile molecules (called odorants) must be dissolved in the mucus in our nasal cavity to be detected by chemoreceptors.

Internal to the olfactory epithelium is an areolar connective tissue layer called the _____ ______

lamina propria (have olfactory glands in the fibers)

Cones

occur at a density of less than 10 million per eye and are concentrated in the fovea centralis (the place of our most acute vision). Cones are activated by high-intensity light and provide color recognition and precise visual sharpness. Thus, when you notice the fine details in a colorful picture, the cones of your retina are responsible.

Phototransduction 1

occurs as light enters the eye and is transduced to an electrical signal by photoreceptor cells.

Referred pain

occurs when sensory nerve signals from certain viscera are perceived as originating not from the organ, but from somatic sensory receptors within the skin and skeletal muscle

The sensory receptor organ for smell is the ____ ____

olfactory epithelium (composed of Olfactory receptor cells (also called olfactory neurons), which detect odors, Supporting cells (also called sustentacular cells) that sustain the olfactory receptor cells, and Basal cells, which function as neural stem cells to continually replace olfactory receptor cells)

dark adaptation

outside on a sunny day into a darkened movie theater

phantom pain

pain from a limb that isn't there

The photopigment in cones is called

photopsin- Blue cones best detect wavelengths of light at about 420 nanometers (nm); green cones maximally absorb light at 531 nm; and red cones best detect light at 558 nm.

Cells of the Neural Layer

photoreceptor cells (rods-dim, cones-high light and color), bipolar cells , and ganglion cells.

Macular degeneration

physical deterioration of the macula lutea, is the leading cause of blindness

The area that the terminal endings of a single sensory neuron is distributed is called its ___ ____.

receptive field

equilibrium

refers to our awareness and monitoring of head position. Sensory receptors in the utricle, saccule, and semicircular ducts collectively called the vestibular apparatus, help monitor and adjust our equilibrium.

gustation

sense of taste, occurs when we come in contact with the molecules or ions of what we eat and drink. chemoreceptors located within taste buds on the tongue and soft palate. The tongue and soft palate also house mechano-receptors and thermoreceptors to provide us with information about the texture and temperature of our food, respectively.

The utricle and saccule detect head position during _____ equilibrium and linear acceleration (looking down)

static

The general function of all sensory receptors is to respond to a _____ and initiate sensory input to the central nervous system (CNS).

stimulus

sensation

stimulus that we are consciously aware of

Components of the Retina

the optic disc (no photoreceptors, blind spot), macula lutea (rounded, yellow, fovea centralis-a lot of cones, precise vision), and peripheral retina (rods, low light)

A detached retina occurs when

the outer pigmented and inner neural layers of the retina separate. Detachment may result from head trauma (soccer players and high divers are especially susceptible), or it may have no overt cause.

constriction of the pupil

the sphincter pupillae muscle to contract to decrease the light rays passing through the edges of the lens. This is required when looking at objects closer than 20 feet because the lens must become more curved, but the edges of the lens are unable to curve to the extent that occurs at the center of the lens.

Aqueous humor

transparent, watery fluid that circulates within the anterior cavity, provides nutrients and oxygen to both the avascular cornea (specifically, its inner epithelium) and lens.

presbyopia

vision gets worse with age

myringotomy

whereby a ventilation tube is inserted into the tympanic membrane. This procedure allows the infection to heal and the pus and mucus to drain from the middle ear into the external acoustic meatus

astigmatism

which causes unequal focusing and blurred images due to unequal curvatures in one or more of the refractive surfaces

2 features that allow sensory receptors to function as transducers

(1) Sensory receptors, like neurons and muscle cells, establish and maintain a resting membrane potential (RMP) (2) Sensory receptors contain modality gated channels within their plasma membranes.

cochlear implant

(1) an external microphone to detect sound (typically worn behind one ear), (2) a speech processor to arrange the sounds from the microphone, and (3) a transmitter connected to a receiver/stimulator (placed within the cochlea) to convert the processed sound into electrical impulses.

Light rays are refracted when

(1) they pass between two media of different densities, and (2) these media meet at a curved surface.

How We See.

(a) Light is refracted and then focused on the retina. (b) Light rays are transduced to nerve signals, and (c) these nerve signals are transmitted to the brain.

types of taste buds

-Gustatory cells (also called gustatory receptors), which detect tastants (taste-producing molecules and ions) in our food(7-9 days) -Supporting cells that sustain the gustatory cells -Basal cells, which function as neural stem cells to continually replace the relatively short-lived gustatory cells

when viewing objects at a distance greater than 20 feet away

-The eyes are facing forward and are not converging. -The ciliary muscles are relaxed and the lens is flatter so the light is refracted to a lesser extent (i.e., there is no accommodation). -The pupil is relatively dilated to allow a greater amount of light into the eye

Glaucoma

is a disease that exists in three forms, all characterized by increased intraocular pressure: primary angle-closure glaucoma, open-angle glaucoma, and congenital or juvenile glaucoma.

Motion sickness

is a sense of nausea, mild disorientation, and dizziness that some of us have felt while flying in an airplane or riding in an automobile. It develops when a person is subjected to acceleration and directional changes, but there is limited or discrepant visual contact with the outside horizon

Pneumatic retinopexy

is a treatment for upper retinal detachment. The physician inserts a needle into the anesthetized eye and injects a gas bubble into the vitreous humor. The gas bubble rises and pushes the neural layer back into its normal position.

Color blindness

is an X-linked recessive condition and occurs when an individual has an absence or deficit in one type of cone cell.

otoscope

is an instrument used to examine the tympanic membrane, which normally appears white and pearly, but in cases of severe otitis media is red (due to inflammation and sometimes bleeding) and may even bulge due to fluid pressure in the middle ear.

A lacrimal apparatus

is associated with each eye; it produces, collects, and drains lacrimal fluid

Phototransduction

is converting (or transducing) light energy into an electrical signal.

Loudness

is dependent upon the amount of back and forth motion of the vibrating object that establishes the degree of compression of the molecules (or the amplitude of the sound waves). Soft sounds cause relatively small movements of the basilar membrane in a relatively smaller area of the spiral organ

facial nerve (CN VII),

which innervates taste buds from the anterior two-thirds of the tongue

glossopharyngeal nerve (CN IX),

which innervates taste buds from the posterior one-third of the tongue

focusing of light

convergence of the eyes, accommodation of the lens, and constriction of the pupil.

encapsulated

end bulb, lamellated corpuscle, bulbous corpuscle, tactile corpuscle

phasic receptors

exhibit rapid adaptation to a constant stimulus. Phasic receptors generate nerve signals only in response to a new (or changing) stimulus and quickly decrease the number of nerve signals relayed to the CNS. (wearing glasses)

unencapsulated tactile

free nerve ending, root hair plexus, tactile disc

Angular acceleration

is detected by the sensory receptors housed within the semicircular ducts of the semicircular canals. (ampulla)

conjunctivitis

pink eye

Inner Hair Cells.

(a) The inner hair cells contain ion channels at their tips. (b) The ion channel is attached to its taller neighboring inner hair cell by a tip link protein. (c) Open ion channels allow K+ to move into the inner hair cell.

Photopigments

are the specific molecules that absorb light and that are embedded within the plasma membrane of the outer segment of both rods and cones. composed of opsin-protein and retinal-light absorbing vitamin A

Convergence of the eyes

is the voluntary contraction of the extrinsic eye muscles to move the eyes medially.

5 taste sensations

-Sweet tastes- organic compounds such as sugar or other molecules (e.g., artificial sweeteners). Salt tastes are produced by metal ions, such as sodium (Na+) and potassium (K+). Sour tastes are associated with acids in the ingested material, such as hydrogen ions (H+) in vinegar. Bitter tastes are produced primarily by alkaloids such as quinine, unsweetened chocolate, nicotine, and caffeine. Umami stimuli: Umami (u′ma-mē) is a Japanese word meaning "delicious flavor." It is a taste related to amino acids, such as glutamate and aspartate, to produce a meaty flavor.