RC

ITP - Topic 7

Chapter 7: Sensation and Perception

Learning Objectives

  • Explain the relationship of sensation and perception

  • Discuss mechanism of sense organs and their functions in the body

  • Explore different kinds of perception

  • Understand the importance of maintaining a healthy sensory system

  • Identify and explain different extrasensory perceptions

Introduction to Sensation and Perception

  • Sensation: Process by which sensory receptors and nervous system receive stimulus energy from the environment.

  • Perception: Process of organizing and interpreting sensory information to recognize meaningful objects and events.

  • The brain interprets sensory input to give meaning to experiences.

Processing Sensory Information

  • Bottom-up Processing: Assembling and integrating sensory information to perceive stimuli.

  • Top-down Processing: Applying models, ideas, and expectations to interpret sensory information.

Mechanism of Sensation

Steps of Sensation

  1. Reception: Stimulation of sensory receptor cells by energy (sound, light, heat, etc.)

  2. Transduction: Conversion of cell stimulation into neural impulses.

  3. Transmission: Delivery of neural information to the brain for processing.

Understanding Stimuli

  • Stimulus: Any environmental factor that elicits a sensation.

  • Classification of Stimuli:

    • Intensity:

      • Threshold

      • Subliminal

      • Terminal (pain-causing)

    • Nature: Describes physical characteristics of stimuli (light waves, sound waves, etc.)

Sensory Thresholds

  • Absolute Threshold: Minimum stimulus intensity needed to detect a stimulus 50% of the time.

  • Examples of Sensory Thresholds:

    • Vision: Candle flame at 30 miles on a dark night

    • Hearing: Tick of a watch at 20 ft in silence

    • Taste: One teaspoon of sugar in 2 gallons of water

    • Smell: One drop of perfume in a 3-room apartment

    • Touch: Wing of a bee falling on a cheek from 1 cm

Sensory Receptors

  • Biological structures excitable to stimuli.

  • Each sensation has specific receptor cells.

Vision

Mechanism of Vision

  • Receptor: Eye

  • Pathway of Light: Light through cornea → pupil → lens → retina

  • Photoreceptors:

    • Rods: Function in dim light, peripheral vision, no color detection.

    • Cones: Responsible for color vision in bright light.

Color Vision Theories

Trichromatic Theory

  • Proposes three types of color receptors (cones) sensitive to red, green, and blue.

  • Colors created by combining light waves of these three colors.

Opponent-Process Theory

  • Each of the three cone types corresponds to two opposing wavelengths (red-green, blue-yellow, black-white).

Common Vision Problems

  • Cataracts: Clouding of lens affecting visual acuity and color.

  • Retinopathy: Damage to blood vessels causing blurred vision and floaters.

  • Glaucoma: Increased fluid pressure damaging optic nerve.

  • Macular Degeneration: Distorted central vision.

  • Myopia: Difficulty in seeing distant objects (nearsightedness).

  • Hyperopia: Difficulty in seeing close objects (farsightedness).

Auditory Sense

Mechanism of Hearing

  • Receptor: Ear

  • Path of Sound: Sound waves → outer ear (pinna) → auditory canal → eardrum → ossicles → oval window → cochlea

  • Hair Cells: Sensory receptors for hearing located in the cochlea.

Types of Hearing Loss

  • Conduction Deafness: Issues with mechanical systems transmitting sound.

  • Nerve Deafness: Damage to receptors in the inner ear or auditory nerve.

Olfactory Sense

  • Receptor: Nose

  • Mechanism: Inhaled gaseous substances stimulate olfactory cells generating neural impulses.

Gustatory Sense

  • Receptor: Tongue

  • Taste Buds: Approximately 9,000 taste receptors located on the tongue.

Cutaneous Sense

  • Receptor Organ: Skin

  • Sensation Types: Pressure, warmth, cold, pain.

Perception and Grouping

  • Gestalt Principles: Refers to perceiving patterns or wholes that are more than just their parts.

  • Primary laws of perceptual organization:

    • Law of Proximity

    • Law of Continuity

    • Law of Closure

    • Law of Similarity

  • Figure-Ground: Distinction of an object (figure) from its background (ground).