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Anatomy & Physiology: Special Senses - Eye, Ear, Taste, and Smell

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  • What are the accessory structures of the eye?

    Eyebrows, eyelids, eyelashes, conjunctiva, lacrimal apparatus, and extrinsic eye muscles.

  • What is the function of the conjunctiva?

    A thin mucous membrane that covers the anterior surface of the eye and lines the eyelids, protecting and lubricating the eye.

  • Name the muscles that control eye movement and their cranial nerves.

    Lateral rectus (VI), medial rectus (III), superior rectus (III), inferior rectus (III), superior oblique (IV), inferior oblique (III).

  • What are the main layers of the eyeball?

    Sclera (outer fibrous), choroid (vascular), and retina (inner neural layer).

  • Describe the structure and function of the lens.

    Transparent, flexible, avascular; focuses light onto the retina by changing shape via ciliary muscles.

  • What is the role of the ciliary muscle in vision?

    Contracts to bulge the lens for near vision (accommodation) and relaxes to flatten the lens for distant vision.

  • Define the terms 'accommodation', 'constriction', and 'convergence' in close vision.

    Accommodation: lens bulges; constriction: pupil size decreases; convergence: eyes rotate medially to focus on close objects.

  • What wavelengths constitute visible light?

    Electromagnetic radiation with wavelengths from 400 to 700 nanometers.

  • What is the primary refractory structure of the eye?

    The cornea provides the majority of the eye's refractive power; the lens provides adjustable refractive power.

  • What are photoreceptors and their types?

    Cells in the retina that detect light: rods (dim light) and cones (color and bright light).

  • What is rhodopsin and where is it found?

    A visual pigment in rod cells' outer segments that changes shape in response to light, initiating phototransduction.

  • How does phototransduction work in rods?

    Light changes rhodopsin shape, activating transducin, which activates phosphodiesterase to reduce cGMP, closing Na+ channels and hyperpolarizing the cell.

  • What is the difference between light and dark adaptation?

    Light adaptation: rods turn off, cones adjust to bright light; dark adaptation: cones stop, rhodopsin regenerates to improve night vision.

  • What structures make up the olfactory epithelium?

    Olfactory sensory neurons, supporting cells, and olfactory stem cells located in the roof of the nasal cavity.

  • What characteristics must an odorant have to be detected?

    Must be volatile and soluble to bind to olfactory receptors and generate receptor potentials.

  • Describe the olfactory pathway from receptor to brain.

    Olfactory neurons → olfactory bulbs (glomeruli) → mitral cells → olfactory cortex.

  • What are the main types of papillae on the tongue and their taste bud distribution?

    Fungiform (few taste buds), vallate (many taste buds), foliate (many taste buds, decrease with age).

  • What are the five basic taste sensations and their typical stimuli?

    Sweet (organic substances), sour (acids), salty (metal ions), bitter (alkaloids), umami (glutamate/aspartate).

  • How do salty and sour tastes depolarize gustatory cells?

    Salty: direct Na+ influx; sour: H+ ions open depolarizing channels.

  • What is the role of gustducin in taste?

    A G protein activated by bitter, sweet, and umami receptors to initiate metabotropic signaling pathways.

  • What are the three main parts of the ear and their functions?

    External ear (collects sound), middle ear (transmits vibrations), internal ear (hearing and balance).

  • What structures are involved in hearing within the cochlea?

    Scala vestibuli, scala media, scala tympani, basilar membrane, spiral organ with hair cells.

  • How is pitch and loudness perceived in the cochlea?

    Pitch: location of stimulation on basilar membrane; loudness: amplitude of waves causing more neurotransmitter release.

  • What is the vestibular apparatus and its components?

    Structures for equilibrium: semicircular canals, utricle, saccule, and their sensory receptors.

  • What do the maculae and crista ampullaris detect?

    Maculae detect linear acceleration; crista ampullaris detects rotational movement.

  • What causes conduction deafness and sensorineural deafness?

    Conduction: sound cannot reach inner ear fluids; sensorineural: damage to hair cells or neural pathways.

  • What is tinnitus?

    Perception of ringing or buzzing without external stimuli, often due to hair cell damage.