The Eye
What are the parts of the Eyes?
Pupil, iris, cornea, sclera, optic nerve, optic disk, macula, the fovea, aqueous humor, lens, and the vitreous humor.
Whats the difference in P cells and M cells, both function and structure wise?
M cells have larger receptive fields, they conduct action potentials rapidly in the opticnerve, and they are more sensitive to low-contrast stimuli. M cells respond to stimulation of there receptive field center with a transient Burt of action potentials.
P cells respond with a sustained discharger as long as the stimulus is on
What are the Sensory systems?
Vestibular system: Head and body location, body movements.
What are the Basic Tastes?
Saltiness, Sourness, Sweetness, Bitterness, and Umami.
Monocular: Layer IVC--> similar to LGN cells, Layer IVC(Alpha)-->insensitive to the wavelength, Layer IVC(Beta)--> center-surround color opponency.
Binoculare: Most neurons in layer superficial to IVC are binoculars. Two receptive fields--> one for each eye.
What is color opponent in Ganglion cells?
Color-opponent cells reflecting the fact that the response to one color in the receptive field center is canceled by showing another color in the receptive field surround. There are two types of opponent, red vs green and yellow vs blue.
Red light bathes the receptive field center the neuron responds with a strong burst of action potential.
Red light covers both the center and the surround of the receptive field, the neurons is still excited but much less.
The red ON center responses is canceled by the green OFF surround response.Whats the Auditory Pathway?
1. Sound wave moves the tympanic membrane.
2. Tympanic membrane moves the ossicles.
3. Ossicles move the membrane at the oval window.
4. Motion at the oval window moves fluid in the cochlea
5. Movement of fluid in the cochlea casques a response in sensory neurons.
The Organs of taste?
Papillae: Foliate Papillae, Vallate papillae, Fungiform papillae.
Each papilla has from one to several hundred taste bud. Each Tates bud has taste receptor cells (taste cells), basal cells and gustatory afferent axons.
What is a Simple cell receptive field?
Simple cells: is Binocular and sensitive to stimulus orientation, has an ON- center or OFF-center region flanked on one or both sides by an antagonistic surround. The response of a simple cell to optimally oriented bars of light at different location in the receptive field, for this the neuron, the middle location gives an ON response and the two flanking locations give OFF responses.
Photoreceptors respond to light, and they influence the membrane potential of the bipolar cells.
The ganglion cells fire action potential in response to light that propagate along the optic nerve to the brain
Horizontal cells receive input from the photoreceptors and project neurites laterally to influence surrounding bipolar cells and photoreceptors
Amacrine cells receive input from bipolar cells and project laterally to influence surrounding ganglion cells, bipolar cells, and other amacrine cells.
What is Retinofugal projection?
What is the sound force amplification by Ossicles?
The process by which an environmental stimulus causes an electrical response in a sensory receptor cell is Called transduction. Transduction press: Taste stimuli (tastings) may:
Pass directly through ion channels (salt and sour).
Bind to and block ion channels (sour).
Bind to G-protein-coupled receptors and activate second messenger to open ion channels (bitter, sweet and umami).
What is the Transduction Pathway by hair cells?
a stiff filament called a tip link connects each channel to the upper wall of the adjacent cilium.
The Displacement of the cilia in one direction increase tension on the tip link, increasing the rate of channel opening and the amount of inward K+ current. Displacement in the opposite direction relieves tension on the tip link, thereby causing the channel to spend more time closed, reducing inward K+ movement.
what is the phototransduction pathway in rods?
1. light activated (bleaches) rhodopsin
2. Transducin, the G-protein, is stimulated
3. Phosphodiesterase (PDE), the effector enzyme, is activated
4. PDE activity reduces the cGMP level.
5. Na+ channels close, and the cell membrane hyperpolarizes
What is Binocular vision?
This is when the central portion of both visual hemifields is viewed by both retinas. The left visual hemifield is "view" by the right hemisphere and the right visual hemifield is "viewed" by the left hemisphere. The Ganglion cell axons from the nasal retina cross at the optic chasm.
At rest, the hair cells are held between the reticulate lamina and the basilar membrane, and the tips of the outer hair cell stereo cilia are attached to the tectorial membrane. When sound causes the basilar membrane to deflect upward, the reticulate lamina moves up and inward towards the modulus, causing the stereo cilia to bend outward.
What is the transduction mechanisms of vertebrate olfactory receptor cells.
1. odorants bind to membrane odorant receptor proteins
2. stimulate G-protein (Golf)
3. Activate adenylyl cyclase form cAMP
4. Bind cAMP to a cyclist nucleotide-gate cation channel.
5. Open cation channels and allow influx of Na+ and Ca2+
6. Open Ca2+ activated Cl- channels the cause current flow and membrane depolarization (receptor potential)
Explain what happen when a dark spot hits the center of a ganglion cell receptive field.
Dark spot in the center of the receptive field causes the cell to depolarize, whereas dark in the surround causes the cell to hyperpolarize.
In uniform illumination, the center and surround cancel to yield some low level of response.
The edge enters the surround region of the receptive field without encroaching on the center, the dark area hyperpolarizing the neurons, decreased firing.
The dark area begins to include the center, however, the partial inhibition by the surround is overcome, and the cell response increases.
When the dark area finally fills the entire surround, the center response is canceled
What happens when the left side of the optic nerve is cut?
Vision will be lost completely int eh left eye, the blindness is only in the monocular portion of the left hemifield because the right eye still sees most of the left visual field.
The cochlear amplifier: outer hair cells amplify the movement of the basilar membrane during low-intensity sound stimuli.
Prestin: protein required for outer hair cell movements
Motor protein change the length of outer hair cells, and outer hair cells respond to sound with both a receptor potential and a change in length.
Explain the central Olfactory pathways.
Axons of olfactory receptor cells penetrate the cribriform plate and enter the olfactory bulb. After multiple branching, each olfactory axon synapses upon second-order neurons within a spherical glomerulus. The second-order neurons send axons through the olfactory tract further into the brain.