Quiz 2

Lateral line (fish • Cupula (stem) • Hair cells (bulb): bend in response to cupula which opens ion channels • Support cells surround hair cells • Connects to afferent fibers at bottom of bulb Statocyst (balance organ) • Ion rolls and depresses stereocilia. Brain adjusts. • Stereocilia: hair appendecis on inside of hair cells • Hair cells are connected to afferent fibers

Vision- Phototransduction Hearing- Mechanotransduction Balance (Vestibular)- Mechanotransduction Touch- Mechanotransduction Taste- Chemotransduction Smell- Chemotransduction

Inner Ear • Semicircular canals go to 2 statycyst chambers which goes to cochlea (inner ear) • Semicircular canals: One vertical, one horizontal, one diagonal. Has liquid inside–>disturbs Semicircular canal anatomy • Mechanotransduction cells • Surrounded by gelatinous mass that encapsulates and protects the rest • Stereocilia inside • Hair cell furthest inside • Connects to sensory neurons and nerve • All is surrounded by the semicircular canal fluid • When you rotate–> pressure by fluid moves the mechanotransduction cell

• Highly sensitive mechanoreceptors • Large component of Somatosensory Cortex • Similar to fish lateral line system • Aid in: navigation, prey detection and capture, eating, communication

• Pinna • External auditory canal • Tympanic membrane: eardrum. Vibration is transferred to middle ear.

• Middle ear cavity • Malleus: round • Incus: Bump to the long thing • Stapes: Hook to the inner ear (smallest)

• Semicircular canal • Cochlea

Pitch: Stimulating different portions of the cochlea Volume: Stimulating the hair cells w/in the cochlea more or less intensely.

Sound wave vibrates eardrum –> transferred to malleus–> pushes incus–>pushes stapes–>pushes inner ear • Converts sound wave to mechanical force • Converts mechanical force to fluid wave that travels into cochlea and excites Mechanosensory neurons which is transmitted via the vestibulococlear nerve • Sound wave reverberates ear drum • Moves malleus (converts auditory to mechanical force and amplifies the initial sound by 3x) • Stapes to oval window (converts mechanical force to a fluid wave)

Two branches: Vestibular branch and cochlear branch

Connects the middle ear (stapes) to the inner ear (cochlea)

Three chambers: • Upper canal • Lower canal • Cochlear duct (lots of external K) (houses the organ of corti: responsible for taking the environmental signal and converting it to action potentials and transmitting the signal to the brain) Inside Organ of Corti • Has tectorial membrane on top (upper canal pushes down) which moves resets. Then fluid wave travels to lower canal pushing stereocilia off of the ion channels–>signal transduction goes to temporal lobe • Also contains basilar membrane

Rest 1 • No sound vibrations present • Basilar membrane is immobile Activation 3 • Sound vibrations push basilar membrane upward • Hair cell stereocilia bend against the tectorial membrane, triggering the release of neurotransmitters Repolarization 2, 4 • Downward motion of basilar membrane relative to the tectorial membrane bends stereocilia in the opposite direction • Causes hair cells to repolarize

Within organ of corti within cochlea

Outside Conjunctiva/cornea: Transparent, protective Aqueous humor Iris: Opens/closes to let more/less light Pupil Lens: Focus info to fovea via ciliary muscle Ciliary muscle: On sides by lens Vitreous humor Retina Fovea: Indentation, perceive color Sclera: Protective outside covering, makes white in eyes Optic nerve Retinal blood vessels: Feeds and discards waste

Focusing on close objects • Ciliary muscles contract • Makes lens rounder and increases the bending of light rays Focusing on distant objects • Ciliary muscles relax • Makes lens flatted and reduces the bending of light rays

Form of G coupled protein Cis retinal is made in dark • When a photon hits it, it is converted to trans Trans retinal is made in light Change from cis to trans leads to change in opsin conformation Then activates the alpha subunit and it becomes phosphorylated

Sensory cells • Hyperpolarize in light (go from releasing lots of it to little neurotransmitter (glutamate)) Cone • Disc contains conopsin • Cytoplasm • Mitochondria • Nucleus • Synaptic ending • 100% Abs of light means little glutamate Rod • Disc contains rhodopsin • Cytoplasm • Mitochondria • Nucleus • Synaptic ending

CONE CELLS! • 3 Diff types (each absorb a different color) • Each cone responds to many wavelengths, not just one, and the brain compares how strongly each cone type is activated. The different “mixes” of activation create all the colors we see.

• Light stimulation of rhodopsin leads to activation of a G protein, transduction • Activated G protein activated cGMP PDE • (3cGMP hold channel open) PDE hydrolyzes cGMP to GMP, reducing its concentration • This leads to closure of Na+ channels

Epithelium Rod and cone Horizontal cell Bipolar cells Amacrine cell Ganglion cells (sensory neurons) Optic nerve

• Depolarized • Cone releases neurotransmitters to horizontal cell • On Bipolar Switch is hyperpolarized (no neurotransmitter) • Off Bipolar Switch is depolarized (produces lots of neurotransmitters) • Goes to amacrine • On Ganglion Switch is hyperpolarized (no neurotransmitter) • Off Ganglion Switch is depolarized (produces lots of neurotransmitters) OFF=FOLLOW FAITHFULLY THE POLARITY

• Hyperpolarized (shut Na channel) • Cone releases less neurotransmitters to horizontal cell • EPSP to On Bipolar Switch. Depolarized (produces lots of neurotransmitters) • IPSP to Off Bipolar Switch. Produces little neurotransmitters. • Goes to amacrine • On Ganglion Switch produces lots of neurotransmitters. • Off Ganglion Switch produces little neurotransmitters OFF=FOLLOW FAITHFULLY THE POLARITY

• Rods and cones send graded potentials to bipolar cells (on/off) • Horizontal cells clarify graded potentials to bipolar cells to sharpen the image • Two types of bipolar cells: OFF follow the rod and cone cell’s polarity. ON depolarize when rods/cones are hyperpolarized • Amacrine cells clarify graded potentials to adjust for motion or brightness • Two types of ganglion cells: OFF follow the rod and cone cell’s polarity. ON depolarize when rods/cones hyperpolarize and hyperpolarize when rods/cones depolarize • Ganglion cells are sensory neurons and send action potential via optic nerve to brain • Fovea stimulated maps to different places in optic cortex • The type of color we perceive is a function of its wavelength which stimulates R, G, and B cone cells more or less intensely depending on each’s absorptivity of that wavelength