Vestibular System & Visual System Flashcards
What are the functions of the vestibular system?
Balance, equilibrium posture, head, body, eye movement
What is the signaling Mechanism of the Vestibular Sacs?
The calcium crystals (otoliths) move gelatinous cap upon head movement or linear head acceleration. The embedded stereocilia of the hair cells move and change the polarization and rate of action potentials
What do the semicircular canals respond to? How do they do this?
Signal head’s rotational acceleration; The inertial resistance of the endolymph fluid induces bending of the Cupula and stereocilia
What is the central vestibular pathway?
Hair cells –> Scarpas’a Ganglia –> Vestibularcochlear Nerve –> Vestibular Nuclei (brainstem) –> Thalamus (VP)–> Somatosensory cortex, Cranial Nerves, Cerebellum
What is the Vestibulo-Ocular Reflex
Fixed line of sight (as your head moves left, your eyes move right to keep on point of focus)
What are the 3 characteristics that determine perceived color?
Hue (wavelength/color), Brightness (Amplitude), Saturation(“purity” of wavelength)
What is the cell in the retina that fires action potentials?
Ganglion Cells
What is the direct pathway in the retina?
Photoreceptors –> Bipolar Cells –> Ganglion Cells
What do horizontal cells do?
Receive input from photoreceptors and project to other photoreceptors and bipolar cells
What do Amacrine cells do?
Receive input from bipolar cells and project to ganglion cells, bipolar cells, and other amacrine cells
What are the 2 main types of photorecptors?
Rods and Cones
What are the characteristics of the peripheral retina?
High ratio of rods to cones, high ratio of photoreceptors to ganglion cells, more sensitive to light
What is the fovea? What are the characteristics?
Pit in retina where outer layers are pushed aside; 1:1 ratio of photoreceptors to ganglion cells, all cones
What is the dark current?
Rod outer segments are depolarized in the dark because of steady influx of Na+
What happens to photoreceptors in response to light?
Hyperpolarize
What is the main function of rods?
To detect overall level of light
What is the main function of cones?
Color vision
What is the receptive field?
Area of retina that, when stimulated with light, changes a cell’s membrane potential
What kind of receptors do Off bipolar cells have? What happens in the dark?
Ionotrophic recepotrs; Depolarize in the dark
What kind of receptors do on bipolar cells have? What do they do in response to light?
Metabotrophic receptors; Depolarize in light
What happens in response to light on the center of an on-center bipolar cell?
Depolarization
What happens in response to light on the surround of an on-center bipolar cell?
Hyper polarization
What are the responses to light of an off-center bipolar cell?
Opposite of the on-center cells
What are the types of ganglion cells? How do they differ?
M-type (large), P-type (small)
How does the red-green color opponents work?
Red on center = lots of action potentials
Red on center & surround = some action potentials
Red on center & green on surround = few action potentials
What is the optic pathway to the brain?
Retina –> optic nerve –> optic chaism –> Supra chiasmatic nucleus (brainstem) –> LGN (thalamus) –> optic radiations –> Occipital Lobe
If you cut the left optic tract, what will happen?
Lose field of vision in left side of both eyes
What does the superior colliculus do?
Orients the eyes in response to new stimuli
What layer is the recipient of major LGN inputs?
Laver IV C
What are the orientation selective cells?
outside layer IV C, simple cortical cells
What are complex cells?
Direction specific, guide movements (dorsal stream)
What is the dorsal stream of visual information?
Analysis of visual motion and the visual control of actions
What is the ventral stream of visual information?
Perception of the visual world and the recognition of objects
