Science Section 3 - additional Flashcards
What is the vestibular system?
the sensory system comprised of components in the inner ear that provides the brain with information about motion and position; creates the sense of balance and spatial orientation
Sensory transduction
process of translating light, sound, or pressure into electrochemical signals
What is proprioception?
the sense of where your body is in a space
Receptive field
region where a sensory receptor can detect a stimulus (specific to each sensory receptor)
What is the retina?
the thin layer at the back of the eyeball where there are rods and cones for phototransduction to take place
Cornea
the front, transparent layer of the eye where refraction of light takes place
What is refraction?
bending or focusing
What is the iris?
the circular, pigmented muscle that controls the size of the pupil in the eye
When does the pupil/iris dilate?
in dim or low light
When does the pupil/iris contract to reduce its size?
in bright lights
What is the function of the lens in the eye?
further refracts light to focus the image on the retina by changing its shape
Reduction to the len’s flexibility becaues of aging causes what?
farsightedness
What is myopia?
Nearsightedness; occurs when the distance between the retina and cornea is too long so the image focus falls in front of the retina
Function of photoreceptors
to receive and transduce light in the retina
Pigmented epithelium
a pigmented cell layer just outside the retina that works to support the function of photoreceptors, for example, by absorbing excess light and getting rid of broken photoreceptor cells
What is the choroid?
network of blood vessels outside the pigmented epithelium layer that brings oxygen and nutrients to the photoreceptor cells
Fovea
center of the retina where vision is the most acute or sharpest
Function of rods
used for peripheral and low light vision as they have more disks and are located outside of the center of the retina
Function of cones
Respond to bright lights and are located in the fovea
What are opsins?
pigments that absorb different wavelengths of color
What type of opsins do rods use?
rhodopsin
Short waves of light are usually what color?
blue
Medium wavelengths of light are usually what color?
green
Long wavelengths of light are usually what color?
red
How many types of cones are there?
3 with each responding to one of the certain colors (red, green, or blue), trichromatic theory
What is absorption spectra?
refers to different opsin in cone receptors that will respond to different wavelengths of light
When light hits the opsin the cell is depolarized or hyperpolarized?
Hyperpolarized
The cell is ___________ in the absence of light
depolarized
Describe the process when light is absorbed by the opsin
1). The molecules shape inside changes, activating opsin 2). Which encounters a G-protein that will then eventually activate enzyme phosophodiesterase. This enzyme then breaks down cGMP that leads to there not being enough of it to bind to the ion channels, leading them to close and stop the influx of sodium and calcium that makes the membrane potential more positive
What is the function of cGMP?
aka cyclic guanosine monophosphate; a molecule that keeps certain ion channels open
Describe the process when there is an absence of light
The photoreceptor cells release glutamate that will bind to receptors on the bipolar cells which will then synapse on retinal ganglion cells whose axons exit the eyes as the optic nerve
Bipolar cells
connect photoreceptor cells to ganglion cells in the retina
Amacrine cells
distribute info. from one bipolar cell to many ganglion cells
Horizontal cells
form connections between one central rod or cone to many distant photoreceptors and several bipolar cells
What happens if a photoreceptor depolarizes a horizontal cell?
the horizontal cell inhibits the distant bipolar cells (aka lateral inhabitation)
What is lateral inhabitation?
the capacity of excited neurons to reduce the activity of their neighbors
Center-surround receptive fields
a visual receptive field with a circular center region and a surround region; stimulation of the center has the opposite effect on surrounding areas
Purpose of lateral inhabitation/center-surround receptive fields
to sharpen the edges and enhance the contrast in images by amplifying edges and borders
What allows for highly acute vision in the fovea?
Small receptive fields; the horizontal cell connects fewer retinal ganglion cells to a single photoreceptor
Receptive fields in the ________ parts of the retina are larger and provide _______ sharp vision
peripheral, less
What is the retinofugal pathway?
connects the retina to the visual cortex through the lateral geniculate nucleus
The name for the retinofugal pathway comes from
the Latin word “fugit” which means “fleeing”
Optic chiasm
point where axons from both eyes come together; only the axon close to the nose (inner) crosses to the other side while the outer axon comes out the same side
Optic tract
continuation of the optic nerve; the axons that bring visual info. to V1 after the optic chiasm
What is binocular vision?
vison that incorporates vision input from both eyes into a single image, done by comparing how an object’s appearance differs from the left and right eye to calculate depth perception
What is the LGN of the thalamus?
aka lateral geniculate nucleus that is specialized for processing visual input
Describe the LGN
Information from both eyes are not mixed and cells that are specialized for detecting fine detail and color, for example, are separated into distinct layers. Cells do use lateral inhibitation and maps out the same way as the retina.
Another important function of the LGN of the thalamus
Receiving info. from the eyes and other areas of the brain, it decides how to send information to the occipital love. For example, it may inhibit background info. if it is not what you are focusing on (figure-ground) or it won’t send info. if you are asleep
How many layers does the primary visual cortex have?
six
Input to what goes to layer four of the primary visual cortex?
the cerebral cortex
Most input goes to what layer of layer four in the V1?
4C
What type of neurons are found in layer 4C of the V1?
Spiny stellate neurons whose dendrites are covered in spines to maximize the number of synapses it has
Pyramidal cells
are found in other layers of V1 that have one long axon and dendrite to send inputs across longer distances
What is another names for the primary visual cortex?
striate cortex
Does binocular or monocular information from the LGN enter layer 4C of the V1?
Monocular. Information from the two eyes begin to mix once the info. moves beyond layer 4C
Other ways neurons in V1 are depolarized?
by specific orientations of light, direction, and color orientation
What is the retinotopic map?
a map of visual information from the retina onto neurons in the visual cortex and LGN. The central part is represented in the back and peripheral regions are represented further forward
The left side of the visual cortex represents?
the right half of the visual field (and vice versa)
The image in V1 is _______ and ________
upside down, backward
What is corticol magnification?
refers to the fact that the number of neurons in the visual cortex responsible for processing an object of a given size in the visual field varies as a function of the location of the stimulus in the visual field; items appear larger in the center of field (imaged on the fovea and are processed by a larger amount of neurons) and objects to the side are smaller and processed by fewer neurons in V1
Where does visual input go after being processed by V1?
Extrastriate cortex
What is the extrastriate cortex?
a region of the occipital lobe surrounding the primary visual cortex that is involved in high resolution vision and object recognition
Visual information about location and motion is sent from V1 to?
Top or dorsal parts of the occipital and parietal lobe that specialize in processing aspects of vision including spatial orientation, depth perception, and location/velocity/direction of an object. The dorsal stream of info. processes info. about the “where” of visual stimuli
What is area MT?
region of cortex in the parietal lobe that deals with motion perception
Direction-selective neurons
these neurons in area MT fire action potentials maximally when they detect movement in a particular direction
What happens if area MT is damaged on both sides of the brain?
It can lead to akinetopsia (motion blindness). People with this condition see moving objects are rapidly shifting still frames, similar to a flip book
Bottom (ventral) regions of the occipital and parietal lobe receive what type of information from V1?
color, shape, and form. These regions deal with the recognition of faces, objects, symbols, text, and visual objects. Process the “what” of stimuli
Damage to the ventral visual stream can result in
difficulty recognizing visual objects
What is visual agnosia?
impairment with recognizing objects via only vision and is caused by damage to areas of the temporal lobe that deal with object recognition
What is prosopagnosia?
face blindness; patients cannot recogonize others by facial features
What is parallel processing?
the ability of the brain to simultaneously process incoming stimuli, including
color, motion, shape, and depth, separately by different cells at all levels of the visual system
The ear is also known as
pinnae
What is sound and how does it vary?
It is a series of pressure changes in the air and vary in frequency (pitch) and intensity (volume)
What is the tympanic membrane?
a membrane at the end of the
auditory canal that moves in response to variations in air pressure caused by soundwaves; also called the ear
drum
What is the middle ear?
transfers and magnifies sound waves from
the ear canal and ear drum to the inner ear, where the sound waves are transduced
What are the ossicles?
the small bones found in the middle ear that
act like a series of levers to transfer and magnify the sound waves from the ear drum to the cochlea of the inner ear
What connects the middle ear with the back of the throat?
eustachian tube
Name the three ossicles
hammer (malleus), anvil (incus), and stirrup (anvil)
Function of the cochlea (inner ear)
transduces sound
Cochlea is Latin for
“snail” because of its spiral shape
Function of the semicircular canals (inner ear)
as a major part of the vestibular system, they allows us to know where we are in a space and are critical for balance (along w/the utricle and saccule structures)
What protects/encases the structures of the inner ear?
the labyrinth which is a bony and hollow structure
What is the oval window?
outside of the cochlea that transfers the physical movement created by a sound wave on the tympanic membrane via the ossicles to the liquid inside the membrane that’ll travel inside the cochlea before bulging out the round window to relieve pressure
What are the 3 fluid filled cavities in the cochlea?
the scala vestibuli at the top, the scala tympani at the bottom, and the scala media in the middle. Each of which are separated by a membrane
What hollow cavities of the cochlea does the basilar membrane separate?
scala tympani (bottom) and scala media (middle
How does the width/stiffness of the basilar membrane change?
it is stiffer/narrower at the outside of the spiral (where the cochlea is the widest) and floppier/wider at the center (apex) of the spiral where the cochlea is the narrowest
Different stiffness of the basilar membrane means?
its different regions will maximally vibrate at different frequencies of waves through the fluid
Where do high frequency sounds vibrate the basilar membrane?
oval window (near the entrance port)
Where do low frequencies sounds vibrate the basilar membrane?
farther long the membrane
How does the basilar membrane and Organ of Corti move when the stapes pushes a wave into the fluid of the scala vestibuli?
They move along with the sound wave
What is the Organ of Corti?
the structure in the cochlea of the inner
ear in which the hair cells are found and where auditory transduction takes place
What are stereocilia?
tiny hair like protrusions found on the hair cells of the Organ of Corti that are embedded in the tectorial membrane
What is the tectorial membrane?
Located above the organ of Corti
in the cochlea, in which the tips of the stereocilia of the hair cells are embedded, this membrane helps them create the back-and-forth movement of the cilia
required for sound transduction as it does not move along w/the sound waves
The hair cells and organ of Corti are bathed in what?
Endolymph, which fills the scala media and has a high ion concentration of potassium
What happens to the cilia of the inner hair cells when the Organ of Corti moves up and down?
They are bent back and forth which opens and closes small ion channels via connectors known as tiplinks. When they are bent forward, the tip links open the potassium channel which causes depolarization leading to voltage gated calcium channels to open that’ll then cause a neurotransmitter to be released at the basal end of the hair cell. If this happens, then an action potential happens in the dendrites of cochlear nerve neurons which brings auditory info. to the brain
How do hair cells differ from most other neurons?
there is a higher concentration of potassium outside the cell vs the inside
Function of outer hair cells
cells of the inner ear featuring
stereocilia, or long hair-like appendages, that can extend or contract to magnify the vibration of the basilar membrane, which helps the cochlea transduce with high sensitivity and accuracy
Auditory pathway info. vs visual pathway info.
Information from both ears are mixed together when traveling the brain while info. from the eyes is kept separate
Interaural intensity difference
your brainstem can use the sound shadow caused by head to calculate where the sound came from (if a sound originates from the left ear, it’ll sound louder on the left than the right)
Interaural time delay
ex: if a sound originates on the left side of your head, then its signal will reach the auditory nuclei in the brainstem faster than the same info. travelling from the right side
Inferior colliculus
a cluster of grey matter found in the
brainstem that forms an important relay station for auditory information on its way to the brain
Medial geniculate nucleus (MGN) of the thalamus
the region or nucleus of the
thalamus used to relay auditory information to the cerebral cortex it is thought to influence the direction and maintenance of attention
Where is the primary auditory cortex located?
found in the insular cortex which is tucked in the fold between the temporal and parietal lobes
Tonotopic mapping of A1
the map of the auditory cortex matches the mapping of the basilar membrane and organized by pitch (similar to the Organ of Corti, neurons in A1 have a particular pitch or frequency they’ll maximally respond to) and some neurons are intensity tuned (they’ll give a peak response to a particular volume)
