SENSES Flashcards
Classification of Senses
*All sense organs regardless of type, size, or location, function by being able to detect a new stimulus or change in the intensity of a particular environmental stimulus
Sense Receptors
Receptor cells may be encapsulated (covered) or unencapsulated (without covering).
Special sense cells can be classified by stimuli that activate them:
-Photoreceptors: light
-Chemoreceptors: chemicals (taste, smell)
-Mechanoreceptors: movement or pressure
-Thermoreceptors: temperature changes
-Proprioceptors: body position, muscle tension.
What are the common functional characteristics of all sense organs?
-All sense organs detect stimuli and convert them into nerve impulses.
-Impulses are sent to the brain (central nervous system), where they are interpreted as sensations.
General Sense Organs
-Free nerve endings: detect pain, temperature, discriminative touch.
-Tactile (Meissner) corpuscles: detect fine touch and low-frequency vibration.
-Lamellar (Pacini) corpuscles: detect deep pressure, high-frequency vibration.
-Proprioceptors (Golgi tendon and muscle spindles): detect muscle tension and length.
SCLERA
White of the eye, provides protection.
CHOROID
Vascular layer; prevents light scattering.
RETINA
Contains rods (night vision) and cones (color vision).
CONJUNCTIVA
The mucous membrane that covers the sclera and lines the eyelids.
LENS
Focuses light onto the retina.
Explain the Visual Pathway
-Light enters through the cornea and is focused by the lens onto the retina.
-Impulses travel through the optic nerve to the brain’s visual cortex.
-Vision is processed in the brain, not directly in the eye.
Hearing and Equilibrium
-External ear: auricle, external auditory canal, tympanic membrane.
-Middle ear: ossicles (malleus, incus, stapes) amplify sound vibrations.
-Inner ear: cochlea (hearing), semicircular canals (balance), filled with fluid (perilymph and endolymph).
-Balance: sensed by hair cells in the semicircular canals and vestibule
Explain the Hearing Pathway
- Sound waves enter the external ear and vibrate the tympanic membrane.
- Ear ossicles amplify the vibrations, transferring them to the oval window.
- Movement of perilymph triggers vibrations in endolymph, stimulating hair cells in the cochlea.
- Nerve impulses are sent to the brain via the cochlear nerve.
Taste (Gustation)
*Receptors: taste buds (chemoreceptors) located on the tongue, palate, and lining of the mouth.
*Cranial nerves VII and IX carry taste impulses to the brain.
*Four primary tastes: sweet, sour, salty, bitter (also umami, metallic).
Smell (Olfaction)
-Receptors are in the nasal cavity (olfactory mucosa).
-Chemicals are dissolved in mucus and detected by olfactory receptors.
-Smell is linked to the limbic system, which explains its association with memory and emotions.
Integration of Senses
*Senses are processed in the brain, not directly at the receptor site.
*Sensory information can be processed subconsciously.
*Aging may cause a decline in sensory perception.
