New Recording 45

Photoreceptors and Visual Processing

• Rekita and Photoreceptors

  • Photoreceptors in Rekita are sensitive to light.

  • When light hits photoreceptors, they convert light energy into electrical energy and send impulses to the brain.

  • The visual cortex in the occipital lobe interprets these impulses, allowing us to see different objects.

Retina Structure

• The retina contains:

  • Ganglionic cells

  • Bipolar cells

  • Photoreceptors

    • Rods: Most numerous; sensitive to low light but do not detect color.

    • Cones: Sensitive to color; fewer in number compared to rods.

      • Types of cones:

        • Sensitive to blue light

        • Sensitive to green light

        • Sensitive to red light

  • Fovea Centralis:

    • Area of the retina with the highest concentration of cones for maximum visual acuity.

    • Important for reading and distinguishing fine details.

Function of Rods and Cones

• Rods:

  • Operate best in dim light.

  • Enable black, white, and gray vision, making colors invisible in low-light conditions.

• Cones:

  • Function optimally in bright light and enable color vision.

  • Require sufficient light to operate effectively.

Visual Pathway

• Signals from photoreceptors via neurons:

  • Signals crisscross at the optic chiasma, allowing both eyes to share visual information.

  • After the chiasma, signals travel along the optic tracts to the thalamus and then to the visual cortex for processing.

Eye Disorders

• Myopia (Nearsightedness):

  • Caused by an elongated eyeball, where images focus in front of the retina.

  • Corrective lenses: concave lenses help focus distant images clearly.

• Hyperopia (Farsightedness):

  • Typically results from a short eyeball or non-flexible lens, causing difficulty focusing on nearby objects.

  • Requires convex lenses for correction.

• Presbyopia:

  • Age-related vision condition causing difficulty in focusing on close objects.

  • Common after age 40, often requiring reading glasses.

• Astigmatism:

  • Caused by irregular cornea or lens curvature, leading to blurred vision.

  • Correction often done with specialized lenses.

• Cataracts:

  • Cloudy lens due to aging or conditions like diabetes.

  • Treatment often involves lens replacement surgery.

• Glaucoma:

  • Increased intraocular pressure leading to optic nerve damage.

  • Requires prompt treatment to prevent vision loss.

Hearing and Balance

• Ear Anatomy:

  • External Ear: Auricle and external auditory canal.

  • Middle Ear: Contains tympanic membrane and ossicles (malleus, incus, stapes) that amplify sound.

  • Inner Ear:

    • Cochlea (hearing) and semicircular canals (balance).

Sound Processing and Hearing Loss

• Sound waves vibrate the tympanic membrane, causing ossicles to amplify and transmit vibrations to the inner ear.

• Organ of Corti:

  • Located in the cochlea; contains hair cells that convert mechanical sound vibrations into electrical signals sent to the brain.

• Hearing Loss Types:

  • Conductive Hearing Loss: Due to outer or middle ear issues.

  • Sensorineural Hearing Loss: Results from inner ear or neural damage, often irreversible.

Taste and Smell

• Taste (Gustatory Receptors):

  • Taste buds on the tongue detect sweet, salty, sour, and bitter flavors.

  • Bitter tastes often indicate toxins and are biologically unfavorable.

• Smell (Olfactory Receptors):

  • Located in the nasal cavity; essential for flavor perception as taste and smell work together.

Key Exam Insights

• Class Preparation:

  • Review lecture recordings and notes.

  • Create flashcards for key topics.

• Exam Structure:

  • Understand grading policies and retake procedures for assessments, focus on essential concepts.