(PHE 127) SENSE ORGANS

SENSE ORGANS

(READ TILL THE END)

Sense organs are specialized structures in the body that detect and respond to external and internal stimuli, allowing organisms to interact with their environment. They transmit sensory information to the brain, which interprets the signals, enabling perception.

Each sense organ contains specialized receptors that convert stimuli into electrical signals sent to the brain via sensory nerves.

Humans have five primary sense organs:

1. Eyes (Vision)

2. Ears (Hearing & Balance)

3. Nose (Smell)

4. Tongue (Taste)

5. Skin (Touch, Temperature, Pressure, Pain)


1. Eyes (Vision)




 Structure & Function:

  •  Cornea: Transparent outer layer that refracts light.
  •  Iris: Colored part controlling pupil size to regulate light entry.
  •  Lens: Focuses light onto the retina.
  •  Retina: Contains photoreceptors (rods for dim light, cones for color vision).
  •  Optic Nerve: Transmits visual signals to the brain.

 Process of Vision:

1. Light enters through the cornea and pupil.

2. The lens focuses light onto the retina.

3. Photoreceptors convert light into electrical signals.

4. The optic nerve sends signals to the brain for interpretation.

 Common Disorders:

  •  Myopia (nearsightedness)
  •  Hyperopia (farsightedness)
  •  Cataracts (cloudy lens)
  •  Glaucoma (optic nerve damage)

 

2. Ears (Hearing & Balance)



 Structure & Function:

  •  Outer Ear (Pinna & Ear Canal): Collects sound waves.
  •  Middle Ear (Eardrum & Ossicles): Amplifies vibrations.
  •  Inner Ear (Cochlea & Vestibular System):
  •    Cochlea: Converts sound vibrations into nerve impulses.
  •    Semicircular Canals & Otolith Organs: Maintain balance.

 Process of Hearing:

1. Sound waves enter the ear canal.

2. The eardrum vibrates, moving ossicles (malleus, incus, stapes).

3. Cochlear hair cells convert vibrations into electrical signals.

4. The auditory nerve sends signals to the brain.

 Common Disorders:

  •  Conductive hearing loss (blockage/middle ear damage)
  •  Sensorineural hearing loss (inner ear/nerve damage)
  •  Tinnitus (ringing in the ears)
  •  Vertigo (balance disorder)


 3. Nose (Smell Olfaction)

 Structure & Function:

  •  Olfactory Epithelium: Contains smell receptors.
  •  Olfactory Bulb: Processes odor signals.
  •  Olfactory Nerve: Transmits signals to the brain.

 Process of Smell:

1. Odor molecules bind to olfactory receptors.

2. Signals travel via the olfactory nerve to the brain.

3. The brain identifies the smell.

 Common Disorders:

  •  Anosmia (loss of smell)
  •  Hyposmia (reduced smell sensitivity)
  •  Sinus infections affecting olfaction


 4. Tongue (Taste Gustation)


 Structure & Function:

  • Taste Buds: Contain chemoreceptors for five basic tastes:Sweet, Sour, Salty, Bitter, Umami (savory).
  •  Papillae: Small bumps on the tongue housing taste buds.

 Process of Taste:

1. Food chemicals dissolve in saliva.

2. Taste receptors send signals via cranial nerves.

3. The brain interprets taste.

 Common Disorders:

  •  Ageusia (loss of taste)
  •  Dysgeusia (altered taste perception)


 5. Skin (Touch, Temperature, Pressure, Pain Somatosensation)


 Structure & Function:

  • Epidermis & Dermis: Contain sensory receptors:
  • Meissner’s Corpuscles: Light touch.
  • Pacinian Corpuscles: Deep pressure.
  • Free Nerve Endings: Pain & temperature.

 Process of Touch Sensation:

1. Receptors detect stimuli.

2. Sensory nerves transmit signals to the spinal cord and brain.

 Common Disorders:

  •  Neuropathy (nerve damage causing numbness/pain)
  •  Burns affecting touch sensitivity

 

This note provides the skeletal overview of the five primary sense organs, their functions, and related disorders. More Detailed explanation will be done in the class.

(Copy the note with the diagrams)

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