Sensory Systems Overview

Overview

This lecture covers medical terminology related to the sensory systems, including anatomy, physiology, word parts, diseases, and related specialties for taste, smell, hearing, balance, touch, and vision.

Introduction to the Sensory Systems

• The major senses are taste, smell, touch, hearing, sight, and balance.
• Touch includes pressure, vibration, stretch, and hair-follicle position, detected by various mechanoreceptors.
• Temperature and pain are detected by thermoreceptors and nociceptors, respectively.
• Senses are classified as general (distributed, like touch and proprioception) or special (localized to specific organs).

Gustation (Taste) and Olfaction (Smell)

• Gustation is the sense of taste, involving four papillae: circumvallate, foliate, filiform, fungiform.
• Taste buds on papillae detect chemical stimuli, activating facial, glossopharyngeal, and vagus cranial nerves.
• Five main taste submodalities: sweet, salty, sour, bitter, umami, with potential for a sixth (fats).
• Olfaction is the sense of smell, with receptor neurons in the superior nasal cavity, sending signals to the olfactory cortex and hypothalamus for memory/emotion association.

Audition (Hearing), Equilibrium (Balance), and Somatosensation (Touch)

• Hearing (audition) converts sound waves to neural signals via the external, middle, and inner ear.
• The external ear includes the auricle, auditory canal, and tympanic membrane.
• The middle ear has ossicles (malleus, incus, stapes) that transmit vibrations to the cochlea.
• The inner ear includes the cochlea (hearing) and vestibule (balance), sending information via the vestibulocochlear nerve.
• The cochlea detects frequencies from 20 to 20,000 Hz, separating them using hair cells.
• Balance is sensed by otolith organs (head position) and semicircular canals (head movement) in the inner ear.
• Somatosensation includes touch, pressure, vibration, pain, temperature, and proprioception, with receptors distributed throughout skin and organs.

Vision (Sight)

• Vision is the transduction of light into neural signals by the eyes, located in the bony orbits.
• The eye has three layers: fibrous tunic (sclera, cornea), vascular tunic (choroid, ciliary body, iris), and neural tunic (retina).
• The retina contains rods (low-light vision) and cones (color vision), with highest acuity at the fovea.
• The eye has anterior (aqueous humor) and posterior (vitreous humor) cavities.
• Color vision is enabled by three types of cones sensitive to different wavelengths (blue, green, red).

Diseases and Disorders of the Sensory Systems

• Anosmia: loss of smell due to trauma, age, or drugs.
• Otitis media: middle ear inflammation, common in children.
• Otitis externa: external ear inflammation (swimmer’s ear).
• Conductive hearing loss: disruption in sound transmission in outer/middle ear.
• Sensorineural hearing loss: damage to neural components.
• Tinnitus: perception of ringing in the ears.
• Otosclerosis: hardening of ear ossicles, causing hearing loss.
• Rhinitis: nasal cavity inflammation, causing congestion.
• Blindness: severe visual disability, defined by reduced field or acuity.
• Cataract: clouding of the lens, causing blurry vision.
• Conjunctivitis: inflammation of the conjunctiva (pink eye).
• Diabetic retinopathy: retinal disease from diabetes, leading to vision loss.
• Glaucoma: progressive optic nerve degeneration from increased eye pressure.
• Macular degeneration: damage to retina's macula, causing loss of central vision.
• Nystagmus: involuntary eye movements.
• Retinal detachment: separation of retina, may lead to blindness.
• Strabismus: misalignment of eyes, can cause amblyopia (lazy eye).

Medical Specialties and Procedures

• Optometrist: examines eyes and prescribes lenses.
• Ophthalmologist: manages eye diseases and performs surgery.
• Otorhinolaryngologist (ENT): treats ear, nose, throat conditions.
• Audiologist: evaluates and manages hearing loss.
• Ophthalmic assistants and technicians provide supportive optical care.

Key Terms & Definitions

• Mechanoreceptor — sensory neuron responding to mechanical pressure.
• Thermoreceptor — neuron detecting temperature changes.
• Nociceptor — sensory neuron responding to pain.
• Proprioception — awareness of body position.
• Kinesthesia — sense of body movement.
• Visceral — pertaining to internal organs.
• Neurotransmitter — chemical messenger between neurons.
• Glossopharyngeal — relating to tongue and throat.
• Umami — savory taste.
• Olfaction — sense of smell.
• Tympanic membrane — ear drum.
• Equilibrium — sense of balance.
• Sclera — white of the eye.
• Fovea — central pit of cones in the eye.
• Visual acuity — sharpness of vision.
• Otalgia — ear pain.
• Otitis externa — swimmer’s ear.
• Floaters — spots or lines drifting in vision.

Action Items / Next Steps

• Memorize sensory system word parts (prefixes, combining forms, suffixes).
• Review videos on taste/smell, hearing/balance, and vision.
• Practice labeling activities for ear and eye anatomy.
• Study definitions and diseases of the sensory systems.