Term
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Definition
- Sensory receptors transduce different forms of energy in the “real world” into nerve impulses
Examples of transducers: microphone, speakers |
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Term
| What do CHEMORECEPTORS sense? |
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Definition
| Chemicals in the environment (taste, smell) or blood |
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Term
| What do THERMORECEPTORS sense? |
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Definition
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Term
| What do MECHANORECEPTORS sense? |
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Definition
Stimulated by mechanical deformation of the receptor (touch,hearing)
Examples: cutaneous touch and pressure |
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Term
| What do PHOTORECEPTORS sense? |
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Definition
Light
Examples: rods and cones in the retina of eye |
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Term
| What do NOCICEOTORS sense? |
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Definition
-Pain receptors that depolarize when tissues are damaged
~Stimuli can include heat, cold, pressure, or chemicals
~Glutamate and substance P are the main neurotransmitters
~Perception of pain can be enhanced by emotions and expectations
~Pain reduction depends on endogenous opioids
may be activated by chemicals released by damaged tissues, such as ATP |
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Term
| What do PROPRIOCEPTORS sense? |
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Definition
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Term
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Definition
Pain, cold, and heat receptors are naked dendrites
~Touch and pressure receptors have special structures around their dendrites. |
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Term
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Definition
| Sight, hearing, equilibrium, taste, and smell |
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Term
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Definition
Fast adapting
~responds very quickly but then reduces its firing rate
~first rapid then slows way down
~is NOT steady |
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Term
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Definition
Constant rate as long as stimulus is applied
~slow to change
~nice and steady |
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Term
| Law of Specific Nerve Energies |
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Definition
Information from a given nerve fiber can only be experienced as one stimulus type
~The sensation produced by the “adequate” or normal stimulus is the one the brain will perceive |
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Term
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Definition
| Stimuli produce depolarizations called generator potentials |
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Term
| Generator Potential: Tonic |
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Definition
In tonic receptors, the generator potential is proportional to the intensity of the stimulus
~Increased intensity results in increased frequency of action potential after threshold is reached |
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Term
| Generator Potential: Phasic |
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Definition
Pacinian corpuscles are phasic receptors, so if pressure is maintained, generator potential is diminished
~This is a function of the structure of the receptor |
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Term
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Definition
-There are many more receptors that respond to cold than to hot
~Located close to the epidermis
~Stimulated by cold and inhibited by warm
~Some cold receptors also respond to menthol |
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Term
| Myelinated Pain Receptors (Nociceptors) |
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Definition
| Sudden, sharp pain is transmitted |
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Term
| Unmyelinated Pain Receptors (Nociceptors) |
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Definition
| Dull, persistent pain is transmitted |
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Term
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Definition
The pain experienced by a hot stimulus is sensed by a special nociceptor called a capsaicin receptor
~Serves as an ion channel for sodium and calcium
~Also a receptor for the chemical found in chili peppers |
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Term
| Meissner Corpuscles (touch and pressure receptors) |
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Definition
Structure: Dendrites encapsulated in connective tissue
Sensation: Changes in texture; slow vibrations
Location: Upper dermis (papillary layer) |
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Term
| Pacinian Corpuscles (touch and pressure receptors) |
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Definition
Structure: Dendrites encapsulated by concentric lamellae of connective tissue structures
Sensation: Deep pressure; fast vibrations
Location: Deep in dermis |
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Term
| Ruffini Endings (touch and pressure receptors) |
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Definition
Structure: Enlarged dendritic endings with open, elongated capsules
Sensation: Sustained pressure
Location: Deep in dermis & hypodermis |
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Term
| Merkel’s discs (touch and pressure receptors) |
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Definition
Structure: Expanded dendritic endings
Sensation: Sustained touch and pressure
Location: Base of epidermis (stratum basale) |
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Term
| Somatesthetic: From pressure receptors and proprioceptors |
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Definition
-Carried by large myelinated fibers that ascend the dorsal columns of the spinal cord on the ipsilateral side
-Synapse in the medulla oblongata
-The second tier of neurons cross sides as they ascend the medial lemniscus to the thalamus, where they synapse.
-Third-order neurons go to the postcentral gyrus. |
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Term
| Somatesthetic: From heat, cold, and pain receptors |
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Definition
-Carried into spinal cord by thin myelinated and unmyelinated neurons
-Synapse within spinal cord onto second-order neuron.
-Cross sides and ascend lateral spinothalamic tract
-Synapse on third-order neurons in thalamus and continue to the postcentral gyrus |
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Term
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Definition
The receptive field is the area of skin that, when stimulated, changes the firing rate of a neuron
-The size of a receptive field depends on the density of receptors in that region of skin.
-There are few receptors in the back and legs, so the receptive fields are large.
-There are many receptors in the fingertips, so the receptive fields are small.
-A small receptive field = greater tactile acuity. |
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Term
| Two-point Touch Threshold |
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Definition
| Receptive fields can be measured by seeing at what distance a person can perceive two separate points of touch |
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Term
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Definition
Receptors that are most strongly stimulated inhibit those around them
~This allows us to perceive well-defined sensations at a single location |
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Term
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Definition
| Detect chemical changes within the body |
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Term
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Definition
Include tase and smel
~Taste responds to chemicals dissolved in food and drink.
~Smell responds to chemical molecules in the air. |
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Term
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Definition
Receptors are called taste buds
- Cells release neurotransmitters onto sensory neurons, microvilli come into contact with chemicals and then each taste bud has taste cells sensitive to each category of tastes |
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Term
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Definition
1. Salty
2. Sour
3. Sweet
4. Umami
5. Bitter |
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Term
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Definition
Salty: Na+ enters taste cell and depolarizes it.
Sour: H+ enters cell and depolarizes it.
Sweet and umami: Sugar or glutamate binds to receptor and activates G-proteins/ 2nd messengers to close K+ channels.
Bitter: Quinine binds to receptor, activates G-protein/2nd messenger to release Ca2+ into the cell. |
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Term
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Definition
Receptors are located in the olfactory epithelium of the nasal cavity
- Bipolar neurons with ciliated dendrites projecting into the nasal cavity
- Proteins in the cilia bind to odors |
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Term
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Definition
- Provides a sense of equilibrium
- Located in the inner ear
- Consists of:
~ Otolith organs
o Utricle and saccule
~ Semicircular canal |
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Term
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Definition
- Consists of a bony labyrinth surrounding a membranous labyrinth
o Between the two is fluid called perilymph.
o Within the membranous labyrinth is fluid called endolymph.
o Endolymph has an unusually high K+ concentration. |
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Term
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Definition
- Provide information about linear acceleration:
o Utricle: horizontal
o Saccule: vertical
- Specialized epithelium called the macula houses hair cells.
o Stereo cilia are embedded in a gelatinous otolithic membrane. |
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Term
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Definition
| Modified epithelial cells with 20−50 hairlike extensions called stereocilia (not true cilia) and one kinocilium (true cilium) |
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Term
| How They Work: Sensory Hair Cells |
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Definition
o When stereocilia bend toward the kinocilium, K+ channels open, and K+ rushes into the cell.
o Cells release a neurotransmitter that depolarizes sensory dendrites in the vestibulocochlear nerve.
o Bending away from the kinocilium hyperpolarizes sensory dendrites.
o Code for detection of direction |
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Term
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Definition
o Project along three planes to detect rotation:
- Each canal contains a semicircular duct filled with endolymph.
-At the base of each duct is an enlarged area called the ampulla.
- Hair cells are embedded in the crista ampullaris, with stereocilia stuck into a gelatinous cupula |
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Term
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Definition
o The vestibulocochlear nerve synapses in the medulla.
o The medulla sends neurons to the oculomotor area of the brain stem to control eye movements and down the spinal cord to adjust body movements. |
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Term
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Definition
o When a person’s body is spinning, eye movements are toward the opposite direction of the spin to maintain a fixation point.
o When the body comes to a stop, the cupula is bent by fluid inertia and eye movements are still affected.
o The jerky eye movement produced is called nystagmus. |
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Term
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Definition
o Nystagmus can cause a loss of equilibrium called vertigo
- Can be accompanied by dizziness, pallor, sweating, nausea, and vomiting |
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Term
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Definition
o Characterized by:
- Frequency, measured in hertz (Hz). Higher frequencies have higher pitches.
o Human range is 20−20,000 Hz.
- Intensity or loudness, measured in decibels |
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Term
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Definition
| o Sound waves are funneled by the pinna (or auricle) into the external auditory meatus, which channels them to the tympanic membrane (eardrum) |
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Term
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Definition
o Cavity between the tympanic membrane and the cochlea
o Contains three bones called ossicles:
- Malleus incus stapes
- Vibrations are transmitted and amplified along the bones.
- The stapes is attached to the oval window, which transfers the vibrations into the inner ear. |
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Term
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Definition
o The cochlea is the hearing part of the inner ear.
o Three chambers:
- The upper chamber is a portion of the bony labyrinth called the scala vestibuli.
- There is also a lower bony chamber called the scala tympani.
- Both chambers are filled with perilymph. |
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Term
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Definition
o The cochlea also contains a portion of the membranous labyrinth called the scala media, or cochlear duct, filled with endolymph.
- Middle chamber |
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Term
| Sound Transmission: Oval Window |
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Definition
o Vibrations from the oval window of the middle ear displace perilymph in the scala vestibuli.
o Vibrations pass into the cochlear duct through the endolymph.
o Next, vibrations pass into the perilymph of the scala tympani.
o Vibrations leave the inner ear via the round window. |
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Term
| Sound Transmission: Cochlear Duct |
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Definition
o Where along the cochlear duct sound waves are transmitted depends on the frequency of the sound.
- Low-frequency sounds travel further down the spiral of the cochlea. |
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Term
| Spiral Organ (Organ of Corte) |
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Definition
o Sensory hair cells are located on the basilar membrane of the scala media.
- Inner hair cells: form one row that runs the length of the basilar membrane. Each is innervated by 10−20 sensory neurons.
- Outer hair cells: arranged in rows. They are innervated by motor neurons that make them shorten when depolarized and elongate when hyper polarized |
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Term
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Definition
o Stereocilia are embedded in a gelatinous tectorial membrane.
o When sound waves enter the scala media, the tectorial membrane vibrates, bending stereocilia.
- Opens K+ channels
- K+ rushes in, depolarizing the cell
- Releases glutamate onto sensory neurons |
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Term
| Detecting Sound Frequency |
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Definition
- Hair cells located closest to where the vibrations are displaced into the scala media are stimulated more often.
- Outer hair cells magnify this effect, which allows us to differentiate between very similar pitches. |
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Term
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Definition
Vestibulocochlear nerve
Medulla oblongata
Inferior colliculus of midbrain
Thalamus
Auditory cortex of temporal lobe; said to be tonotopic = areas represent different sound frequencies. |
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Term
| Hearing Impairment: Conduction Deafness |
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Definition
o Conduction deafness: Sound waves are not conducted from the outer to the inner ear.
- May be due to a buildup of earwax, too much fluid in the middle ear, damage to the eardrum, or overgrowth of bone in the middle ear
- Impairs hearing of all sound frequencies
- Can be helped by hearing aids |
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Term
| Hearing Impairment: Sensorineural/perceptive deafness |
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Definition
o Sensorineural/perceptive deafness: Nerve impulses are not conducted from the cochlea to the auditory cortex.
- May be due to damaged hair cells (from loud noises)
- May only impair hearing of particular sound frequencies and not others
- May be helped by cochlear implants |
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Term
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Definition
Transduce light energy into nerve impulses
- Only a limited part of the electromagnetic spectrum can excite photoreceptors. |
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Term
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Definition
- Light passes through the cornea and into the anterior chamber of the eye.
- Next, it passes through the pupil, which can change shape to allow more or less light in.
- Then it passes through the lens, which can change shape to focus the image.
- Finally, it hits the retina, where photoreceptors are found. |
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Term
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Definition
The iris can increase or decrease the diameter of the pupil.
- Constriction: contraction of circular muscles via parasympathetic stimulation
- Dilation: contraction of radial muscles via sympathetic stimulation |
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Term
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Definition
When light passes from one medium to another, it bends.
- Curvature at the point of refraction can also bend light.
- Changing the curvature of the lens allows fine control of focus.
- The image is flipped upside down in this process |
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Term
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Definition
Visual fields are the part of the external world projected onto the retina.
- The right side is projected onto the left side of the retina.
- The left side is projected onto the right side of the retina. |
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Term
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Definition
- Suspended from suspensory ligaments
o Attached to muscles called ciliary bodies |
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Term
| Lens Accommodation: close vision |
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Definition
Accommodation is the ability of the lens to keep an object focused on the retina as the distance between the eye and the object moves.
- Contraction of the ciliary muscle allows the suspensory ligaments to relax and the lens to thicken.
o This is good for close vision. |
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Term
| Lens Accommodation: distant vision |
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Definition
Relaxation of the ciliary muscle pulls on the suspensory ligaments, causing the lens to thin.
- This is good for distant vision |
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Term
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Definition
Nearsightedness
Distant images are brought to a point of focus in front of the retina.
- Often due to an elongated eyeball
- Corrected by concave lenses in eyeglasses |
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Term
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Definition
Farsightedness
Distant images are brought to a point of focus behind the retina.
- Often due to a short eyeball
- Corrected by lenses that are convex |
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Term
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Definition
Asymmetry between the cornea and lens
- Corrected by cylindrical lenses |
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Term
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Definition
Neuron axons in the retina are gathered at a point called the optic disc (blind spot).
- Blood vessels also enter here. |
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Term
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Definition
Photoreceptors (rods and cones) are in the inner layer.
- These synapse on a middle layer of bipolar cells, which synapse on the outer layer of ganglion cells. |
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Term
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Definition
Consist of:
- Outer segment; full of flattened discs with photopigment molecules
- Inner segment |
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Term
| Retinal Pigment Epithelium |
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Definition
- Located under the rods and cones
- Help vision by:
o Phagocytizing shed outer discs
o Absorbing scattered light
o Delivering nutrients to rods and cones
o Suppressing immune attack in retina
o Participating in visual cycle of retina
o Stabilizing ionic concentrations in area |
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Term
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Definition
o Allow black-and-white vision in low light
o Contain the pigment rhodopsin, which absorbs green light best
- Absorption causes rhodopsin to dissociate into retinaldehyde and opsin.
o Retinaldehyde (also called retinal) is derived from vitamin A.
- Called the bleaching reaction |
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Term
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Definition
- When a person enters a dark room after being in the light, there are fewer photopigments in the rods and cones.
- After about 20 minutes, more visual pigments are produced, and the person’s eyes adapt to the dark. |
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Term
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Definition
In the dark, photoreceptors inhibit (hyperpolarize) bipolar cells.
o Na+ channels in rods and cones are always open, depolarizing the photoreceptor.
o This allows the photoreceptor to release inhibiting neurotransmitter in the dark. |
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Term
| When Light Hits Photoreceptors |
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Definition
| Photoreceptors are hyperpolarized, and inhibition on bipolar cells is lifted |
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Term
| Effects of Light on Retinal Cells |
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Definition
| Bipolar cells can now stimulate ganglion cells |
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Term
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Definition
Cones are less sensitive to light, but allow color vision and greater visual acuity.
- Trichromatic vision involves three types of cones.
S: short wavelengths, blue
M: medium wavelengths, green
L: long wavelengths, red |
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Term
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Definition
- Instead of opsin, photopigments have photopsins
o Photopsins vary in each type of cone |
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Term
| Visual Acuity and Sensitivity |
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Definition
Vision is best at one point in the retina, called the fovea centralis.
- Here, other layers of the retina are pushed aside, so light falls directly on a group of cones.
- Each cone has a 1:1 relationship with a ganglion cell (usually it is 105:1), which allows great visual acuity.
- Only works in good light.
o Convergence of lots of rods onto a single ganglion cell increases light sensitivity. |
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Term
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Definition
o Produced by contraction of extrinsic eye muscles
o Three types of movement
1. Saccadic eye movement: high-velocity movements that keep the image focused on the fovea centralis (good when reading)
2. Smooth pursuit movements: match the speed of a moving object
3. Vergence movements: allow both eyes to converge so image is at the fovea of both eyes |
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Term
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Definition
Have a photopigment of their own called melanopsin:
- Sends information about illumination (brightness of light)
- Helps control pupillary reflex (constriction in bright light)
- Sets circadian rhythms in suprachiasmatic nucleus of hypothalamus |
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Term
| Ganglion Cell Receptive Fields: on center fields |
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Definition
o Area of the retina with photoreceptors that send input to that ganglion cell
o Some ganglion cells have on-center fields:
- A light in the center of the receptive field stimulates the ganglion cell strongly.
- A light toward the edge of the receptive field inhibits the ganglion cell. |
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Term
| Ganglion Cell Receptive Fields: off center fields |
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Definition
Some ganglion cells have off-center fields:
- A light in the center of the receptive field inhibits the ganglion cell.
- A light toward the edge of the receptive field stimulates the ganglion cell. |
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