SENSORY SYSTEM Flashcards
(142 cards)
1
Q
Sensation
A
Activation of sensory receptor cells at level of stimulus
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Perception
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Ability to see, hear or become aware of senses; dependant on sensation but not all sensations are perceived
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Receptors
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Cells or structures that detect sensations
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Transmembrane protein receptors
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Activated by ligand chemicals that usually open ion channels
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Transmembrane proteins
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Sensitive to mechanical or thermal changes and increase ion flow across membrane
6
Q
3 receptor structures:
A
- Free ending of dendrites
- Encapsulated ending
- Specialized receptor cell
7
Q
Free ending of dendrites
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Embedded in tissue and receives a sensation (pain and temperature receptors)
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Q
Encapsulated ending
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Encapsulated in connective tissue that enhance sensitivity (pressure and touch receptors)
9
Q
Specialized receptor cell
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Has structural components to interpret a specific type of stimulus (light receptors)
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Exteroreceptors
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Receptors located near a stimulus in the environment (somatosensory receptors located in skin)
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Interoreceptors
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Receptors that interpret stimuli from internal organs and tissues (eg. receptors that sense blood pressure in aorta)
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Proprioreceptors
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Receptors located near a moving part of the body interpreting positions of tissues as they move (eg. receptors in muscles)
13
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Ways that receptors can transduce stimuli into changes in membrane potential (3)
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- Some stimuli are ions and macromolecules affecting transmembrane proteins as they diffuse across membrane
- Some stimuli are physical variations in the environment affecting receptor cell membrane potentials
- Some stimuli are composed of electromagnetic radiation from visible light
14
Q
Chemoreceptors
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Receptors that detect chemical stimuli that arise from external environment (taste, smell, pain, solute concentration)
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Mechanoreceptors
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Interpret physical stimuli (pressure, vibration, sound, body position)
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Thermoreceptors
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Specialized class of mechanoreceptors that are sensitive to temperature changes
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Photoreceptors
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Detect light
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General sense
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Sensation of touch, pain, balance, and sensations from internal organs that are felt throughout the body
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Special sense
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Sense that has a specific organ devoted to it (eye, inner ear, tongue, nose)
20
Q
5 major submodalities of sensory:
A
- Chemical senses are taste and smell
- Touch is a general sense and includes chemical sensation of pain
- Pressure, vibration, muscle stretching and movement of hair sensed by mechanoreceptors
- Hearing and balance use mechanoreceptors
- Vision uses photoreceptors
21
Q
Free nerve endings stimuli
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Pain, temperature, mechanical deformation
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Mechanoreceptors stimuli
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Low frequency vibration (5-15 Hz)
23
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Bulbous corpuscle stimuli
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Stretch
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Tactile corpuscle stimuli
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Light touch, vibrations below 50 Hz
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Lamellated corpuscle stimuli
Pacinian corpuscle
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Hair follicle plexus stimuli
Movement of hair
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Muscle spindle stimuli
Muscle contraction and stretch
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Tendon stretch organ stimuli
Stretch of tendons
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Gustation
Special sense associated with tongue. Surface of tongue lined by stratified squamous epithelium
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Papillae
Raised bumps on tongue that contain structures for gustatory transduction. Contains taste buds that have gustatory receptor cells sensitive to chemicals within food
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What are gustatory receptor cells activated by
Taste molecules through the release of NT to dendrites of sensory neurons (facial, glossopharyngeal, vague nerves)
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Pre-8os taste (gustation)
Sweet, salty, sour, bitter
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8os taste (gustation)
Very savory
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Facial nerves
Connects to the anterior 1/3 of tongue
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Glossopharyngeal nerve
Connects to posterior 2/3 of the tongue and pharynx
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Vagus nerve
Connects with taste buds in extreme posterior of tongue and pharynx
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Pathway of gustation (2):
- Sensory neurons carry information to medulla (reflexes contribute to digestion by increasing secretion of saliva and gastric juices) then thalamus
- Neurons project to the cerebrum where taste is perceived
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Limbic system and hypothalamus function regarding gustation
Involved in emotional responses elicited by food
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Where are olfactory receptor neurons located
In small region of the walls of superior nasal cavity; olfactory epithelium - and contains bipolar sensory neurons
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Olfactory receptor neuron structure
Each neuron has dendrites that extend from apical surface of epithelium into mucus lining the cavity
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Pathway olfactory receptor neuron (3):
- Molecules are inhaled and pass over the olfactory epithelial region and dissolve into mucus
- Molecules bind to proteins that help transport them to olfactory dendrites
- Odorant-protein complex binds to a receptor protein within cell membrane of olfactory neuron dendrite and produce action potential
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Olfactory sensory neuron structure
Axons extends through opening in skull and into brain. Group of axon called olfactory tract connect to olfactory bulb on ventral surface of frontal lobe
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Pathway of olfactory sensory neuron
Olfactory tract connect to olfactory bulb and some travel to temporal lobe of cerebral cortex
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How can smell be a potent trigger of memories and emotion
Some axons of olfactory sensory neuron project to limbic system and hypothalamus where smell becomes associated with long-term memory and responses
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Audition
Transmission of sound waves into neural signal
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External ear
Collects and focuses sound waves
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Middle ear
Amplifies and transmits sound waves from outer ear to inner ear
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Inner ear
Transduces sound waves into neuronal signal
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External ear components (3)
- Auricle
- Auditory canal
- Tympanic membrane
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Auricle
Large, fleshy structure on each lateral aspect of the head functioning in directing sounds towards auditory canal which enters skull
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Tympanic membrane
Eardrum at the end of the canal and vibrates when struck by sound waves
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What part of the ear is responsible for directing sound waves towards inner ear
Outer and middle ear
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Conductive deafness
Interference with directing sound waves towards inner ear
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Middle ear component
Auditory ossicles
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3 auditory ossicles:
- Malleus
- Incus
- Stapes
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Malleus:
Attached to tympanic membrane and articulates with incus
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Incus
Articulates with stapes
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Stapes
Covers an opening, the oval window, leading into the inner ear where the sound waves will be transduced into a neural signal
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Eustachian tube
Allows the middle ear to connect to the pharynx and helps quilibrate air pressure across tympanic membrane
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Inner ear
Described as a bony labyrinth
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2 regions of the inner ear and function
- Cochlea
- Vestibule
- Responsible for audition and equilibrium
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Pathway of audition (3)
- Impulse travels along vestibulocochlear nerve which synapses with neuron in medulla oblongata
- Auditory processing continues on to midbrain, thalamus, and primary auditory cortex in temporal lobe
- Location of sound can be determined by comparing information arriving at both ears
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Sensorineural deafness
Problem within the cochlea or the neural pathway to the auditory cortex. (sound wave may reach inner ear but not ultimately perceived)
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Oval window
Connective tissue membrane located at the end of the middle ear and the beginning of the inner ear.
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Scala vestibuli
Runs ALONG and ABOVE cochlear duct (scala media), the central cavity of cochlea containing neurons
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Perilymph filled tube/scala tympani
Returns to the base of cochlea travelling UNDER cochlear duct
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Round window
Where the scala tympani ends and is covered by a membrane containing fluid within scala
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How do vibrations travel in oval window
The fluid of the scala vestibuli and scala tympani move in a wave like motion. The frequency of the fluid waves match frequencies of the sound waves within membrane covering the round window
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Vestibular membrane
Separates the scala vestibuli and the cochlear duct
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Basilar membrane
Separates the scala tympani and cochlear duct
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Cochlear duct
Fluid filled cavity containing endolymph and contains organs of corti that transduce wave motion of the two scalae into neural signals
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Organs of corti
Lie on top of basilar membrane along length of cochlear duct and contain hair cells (stereocilia) extending from cell's apical surfaces
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Stereocilia
Hair cells that extend to the overlying gel-like tectorial membrane. When the pressure waves of endolymph in cochlear duct vibrate the basilar membrane, the hair cells move as well.
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What causes ion channels to open regarding stereocilia
When the stereocilia bend towards the tallest member of the array, tension in the protein tethers and opens ion channels further depolarizing cell membrane and triggering nerve impulses
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What causes ion channels to close regarding stereocilia
When the stereocilia bend towards shortest member of their array, tension on the tether slackens and ion channels close
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What part of the ear responsible for balance (equilibrium)
Inner ear is responsible for encoding information about the sense of balance (equilibrium)
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Hair cell balance (equilibrium) function
Sense head position, head movement, and weather body is in motion
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Head position and static equilibrium
(linear acceleration) Sensed by utricle and saccule
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Rotational movement
(dynamic equilibrium) sensed by semicircular duct
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Utricle and saccule
Composed of macula tissue
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Macula
Composed of hair cells surrounded by support tissue
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Otolithic membrane
The membrane serves to determine if the body or the head is tilted, in addition to the linear acceleration of the body.
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How do hair cells depolarize and repolarize
The moving otolithic membrane bending the stereocilia
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Calcium carbonate crystals and otoliths
Found on top of otolithic membrane that make the membrane top heavy
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Semicircular canals
3 ring like extensions of vestibule filled with perilymph, containing an additional compartment called semicircular duct within each canal
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Semicircular ducts
Filled with endolymph and specialized for the detection of angular accelerations (eg. Bending, rotation of head)
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Ampulla
Enlarged region with the base of each semicircular canal. Contains sense organ of balance (crista ampullaris)
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Crista ampullaris
Sense organ of balance containing hair cells with stereocilia on the apical side and respond to rotational movement
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Cupula
Jelly like structure that attach to top of ampulla
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Vestibular system
Where balance is coordinated and carries information from utricle, saccule, semicircular duct
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Medulla oblongata
Where axons terminate and project axons in brain stem
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Cerebellum
Another region where axons project directly
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Reticular formation
Respiratory and cardiovascular functions in relation to body movements
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Spinal cord
Spinal reflexes involved with posture and balance
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Vision
Special sense of sight based on transduction of light stimuli received through eye
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Orbit
Where the eyes are located within
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Bony orbits
Surrounds eyeballs protecting them and anchoring soft tissues of eyes
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Eyelids and lash function
Help protect eyes from abrasion by blocking particles that may land on the surface of the eye
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Palpebral conjunctiva
Thin membrane on inner surface of eye lid extending over the white areas of the eye (sclera) connecting the eyelids to the eyeball
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Lacrimal gland
Tear production located beneath lateral edges of the nose and each side of nose. Tears flow through lacrimal duct to medial corner of eye washing away foreign particles
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Sclera
White areas of eye
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How is movement of the eye achieved
Contraction of 6 extraocular muscles originating from bones of the orbit and insert into surface of eyeball
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6 extraocular muscles moving the eye:
- Levator palpebrae superioris
- Superior rectus
- Inferior rectus
- Medial rectus
- Lateral rectus
- Inferior oblique
- Superior oblique
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Eyes
Hollow sphere composed of 3 layers of tissue (tunics)
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3 layers of the tissue (tunics):
- Fibrous tunic
- Vascular tunic
- Neural tunic
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Fibrous tunic
Outermost layer including white sclera and clear cornea
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Vascular tunic
Middle layer composed of choroid, ciliary body, iris
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Neural tunic
Innermost layer containing nervous tissue for photoreception
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Sclera
Accounts for 5/6 of surface of the eye, most of which is not visible
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Cornea
Covers anterior tip of the eye and allows light to enter eye
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Choroid
Layer of highly vascularized connective tissue that provides blood supply to eyeball (posterior to ciliary body)
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Ciliary body
Muscular structure attached to lens by zonule fibers (suspensory ligaments). They bend the lens allowing it to focus light on the back of the eye
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What 2 structures of the eye allow lens to bend
Ciliary body and zonule fibers
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Iris
Colored part of eye
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2 smooth muscles in iris:
- Sphincter pupillae
- Radical dilator pupillae
- They open and close the pupil
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Pupil
Hole at the center of the eye that allows light to enter
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How does the iris regulate amount of light reaching retina
Iris constricts the pupil in response to bright light and dilates the pupil in response to dim light
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2 cavities of the eye:
- Anterior cavity: space between cornea and lens, filled with watery fluid called aqueous humor
- Posterior cavity: space behind lens; filled with viscous fluid called vitreous humor
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Retina
Composed of several layers and contains specialized cells for the initial processing of visual stimuli. Turns light energy into 3 dimensional images and is a layer of photoreceptors and glial cells
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Bipolar cell in retina
Connects photoreceptor to ganglion cell in the inner synaptic layer
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Optic disc and optic nerve
Axons of the ganglion cells collect at the optic disk and leave the eye as optic nerves
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Blind spot explanation
Because axons pass through the retina, there are no photoreceptors at the very back of the eye, where the optic nerve begins; this creates a "blind spot" in the retina and a corresponding blind spot in the visual field
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Macula lutea
Exact center of the retina containing small depression in the middle called fovea
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Fovea
Region where retina lacks supporting cells and blood vessels and only contain photoreceptors so there is least amount of incoming light so it is the sharpest vision
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2 parts of photoreceptor cells:
- Inner segment
- Outer segment
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Inner segment
Contains nucleus, organelles
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Outer segment
Specialized region in which photoreception takes place
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2 types of photoreceptors:
- Rods
- cones
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Rods
Contain stack of membrane bound discs containing the pigment rhodopsin
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Cones
Detect different colors and require brightly lit environments
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Opsins
3 cone photopigments that are each sensitive to a particular wavelength of light
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Pigments in human eye
Red, green, blue
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Focusing light on retina (3):
- Contraction and relaxation of muscles and the accommodation of lens
- Muscles allow for greater or less convergence of eyeballs so that both eyeballs can be directed at same point in space
- Closer the object, the greater degree of convergence
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How is accommodation done
Accomplished by contraction or relaxation of circulatory ciliary muscle to which the suspensory ligaments are attached
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Ciliary muscle contraction
Allows suspensory ligaments to loosen and the lens to bulge
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Ciliary muscle relaxation
Pulls suspensory ligaments taut, pulling the lens flat
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Visual sensory pathway (3):
- The left field of view of each eye is processed on the right side of the brain
- The right field of view of each eye is processed on the left side of the brain
- (optic chiasm)
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Optic tract
Axons of the visual system
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3 major targets of optic tract:
- Two in diencephalon
- One in midbrain
- Superior colliculi (visual reflex center in midbrain)
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Where are most of the connections of the optic tract to
Thalamus
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Visual cortex
Located in the occipital lobe of the cerebrum where axons are projected
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Optic disc
Blind spot
