Overview of Sensory Organs

Overview of Sensory Organs and Functions

• Humans rely on senses to perceive the world: sight, hearing, taste, and smell.
• Sensory organs consist of specialized receptors that convert external stimuli into signals understandable by the brain, a process termed sensory transduction.

Eye

• The eye contains photoreceptors located in the retina that convert light waves into neural signals.
• Photoreceptors include rods (sensitive to low light) and cones (responsible for color vision).

Ear

• The ear uses mechanoreceptors to transform sound waves into neural signals, essential for hearing.
• Auditory processing involves various structures, including the cochlea and auditory cortex.

Types of Sensory Receptors

• Thermoreceptors: Detect temperature changes.
• Pain receptors: Respond to potentially harmful stimuli.
• Mechanoreceptors: Sensory cells for detecting mechanical pressure or distortion.
• Chemoreceptors: Respond to chemical stimuli for taste and smell.
• Electromagnetic receptors: Detect light and other electromagnetic waves.

Sensory Transduction Process

• Each sensory receptor generates an electrical signal called receptor potential.
• The strength of the external stimulus influences the amplitude of receptor potential; a stronger stimulus yields a larger receptor potential.

Taste

• Taste buds involve signal transduction pathways that facilitate taste perception.
• Different receptors in taste buds respond to specific taste modalities like sweet and salty.

Smell

• The olfactory system uses multiple odorant receptors (100-200 types) to discern a wide range of scents through combinations of activated receptors.

Vision

• Color perception is based on three types of cone cells that correspond to red, green, and blue wavelengths.
• Position, object recognition, and movement are processed by complex visual systems beyond just color detection.

Hearing

• Sound properties, such as pitch and loudness, are encoded via neural signals produced by auditory receptors.
• Action potentials generated by these signals follow an "all or none" principle; stimulating a greater receptor potential releases more neurotransmitters, leading to a higher rate of action potential firing in sensory neurons.

Encoding Sensory Information

• Intensity of the sensory stimulus correlates with receptor potential amplitude.
• Different stimuli types are encoded by distinct receptor cells, allowing discrimination of various sensory inputs.