chapter 11 senses

Senses Overview

• Chapter 11/ MT Pages 280-286

• Types of Senses:

  • Sight

  • Smell

  • Hearing

  • Taste

  • Touch

Learning Objectives - Lesson 11.1: Sense Organs

• Classify sense organs as special or general.

• Explain the basic differences between these two groups.

• Discuss how a stimulus is converted into a sensation.

• Describe general sense organs and their functions.

• Discuss the structures of the eye, ear, tongue, and nose and their functions.

Overview of Sensory Perception

• Millions of sense organs throughout the body located in skin, muscles, and internal organs.

• Referred to as sensory receptors; respond to stimuli like touch, pressure, pain, and temperature.

• Essential for homeostasis; can detect changes in both internal (e.g., pain sensation) and external environments (e.g., auditory).

• Classified as General senses (widely distributed) or Special senses (localized and complex organs).

General Sense Organs

• Exist as individual cells or receptor units, distributed widely.

• Found in skin, muscles, tendons, joints, and internal organs.

• Responsible for sensations such as pain, temperature, touch, pressure, and body position.

• Distinct from special sense organs, which are complex groupings of receptors.

Special Sense Organs

• Consist of receptors grouped in specific areas facilitating smell, taste, vision, hearing, and equilibrium.

• Grouped within complex structures enhancing their function.

Sensory Receptor Types

Structural Classification

• Encapsulated: Covered by a capsule, located in the skin.

• Unencapsulated: "Free" or "naked" receptors.

Functional Classification

• Photoreceptors: Change in light intensity/color (Vision)

• Chemoreceptors: Presence of chemicals (Taste/Smell)

• Pain receptors: Physical injury (Injury)

• Thermoreceptors: Changes in temperature

• Mechanoreceptors: Mechanical stimuli causing position/shape changes

• Proprioceptors: Position of body parts/changes in muscle length or tension.

Sensory Pathways

• Reaction to stimulus occurs almost instantaneously.

• Sensory pathway involves action potentials from receptors through the spinal cord:

  • Pathway to thalamus (skin receptors) or cerebellum (proprioceptors).

  • Impulses sent to specific cerebral cortex areas for conscious interpretation.

• All sense organs share functional characteristics in stimuli detection and impulse conversion.

General Sense Organs Distribution

• Widespread, with receptors concentrated in skin.

• Types of skin receptors:

  • Free Nerve Endings: Pain, touch, tickle, temperature.

  • Tactile (Meissner) Corpuscle: Fine touch and vibration.

  • Bulbous (Ruffini) Corpuscle: Touch and pressure.

  • Lamellar (Pacini) Corpuscle: Pressure and vibration.

  • Bulboid (Krause) Corpuscle: Touch.

Modes of Sensation

• Can detect: Vibration, deep pressure, light pressure, pain, stretch, temperature.

• Muscle receptors stimulated by stretch provide information on body part position and movement (Proprioception).

• Deep general sensory receptors in internal organs include mechanoreceptors and chemoreceptors that signal fullness and regulate vital functions.

Special Senses Overview

• Vision, Hearing, and Equilibrium, Taste, Smell.

The Eye

Structure

• Fibrous Layer: Tough outer layer consisting of sclera (white of the eye) and cornea (transparent front).

• Vascular Layer: Contains the choroid, iris, pupil, lens, and ciliary muscle.

• Inner Layer: Retina contains rods (night vision) and cones (color vision).

Eye Components

• Rods respond to dim light; cones respond to bright light with color sensitivity (red, green, blue).

• Retinal Blood Vessels provide blood to retinal neurons.

Eye Fluids

• Aqueous humor: Watery fluid in anterior cavity.

• Vitreous humor: Gel-like fluid in posterior cavity.

Visual Pathway

• Light enters the eye through the pupil, passing through various parts until it reaches the retina.

• Nerve impulses generated in rods and cones activate and travel through optic nerve to the visual cortex for interpretation.

Disorders of the Eye

• Refraction Disorders: Farsightedness, nearsightedness, astigmatism, cataracts, conjunctivitis.

• Retina Disorders: Diabetic retinopathy, glaucoma, age-related macular degeneration.

• Color Blindness: X-linked genetic disorder affecting the cones.

Learning Objectives - Lesson 11.2: The Ear, Taste, and Smell Receptors

• Discuss anatomy and sensory function of the ear in hearing and equilibrium.

• Describe the anatomy of the tongue in relation to taste.

• Discuss the nasal cavity's anatomy and function in smell.

• Understand integration of senses in the brain.

The Ear

General Information

• Sense organ for hearing and balance utilizing mechanoreceptors.

• Divided into External, Middle, and Inner Ear.

External Ear

• Comprises auricle (pinna) and external acoustic canal leading to the tympanic membrane.

Middle Ear

• Contains auditory ossicles (malleus, incus, stapes) transferring vibrations to the inner ear.

Inner Ear

• Composed of bony labyrinth and membranous labyrinth filled with perilymph and endolymph,

• Contains the vestibule for balance and cochlea for hearing.

Hearing Pathway

• Sound waves make tympanic membrane vibrate, and this motion is transmitted to the brain via auditory ossicles and cochlear nerve.

Equilibrium

• Mechanoreceptors in the vestibule and semicircular canals detect head movement and aid in balance.

Sense of Taste (Gustation)

• Taste receptors (gustatory cells) located in taste buds respond to chemicals in saliva.

• Primary tastes include sweet, sour, bitter, and salty.

Smell (Olfaction)

• Chemoreceptors in the nasal cavity detect odors and respond by generating nerve impulses.

• Signals adapted based on initial stimulus strength over time.

Integration of Senses

• Brain integrates sensory signals for perception, affecting taste and smell based on external factors like aging and health.

Review Questions

• White of the eye: A. Choroid, B. Cornea, C. Sclera, D. Retina.

• Colored part of the eye: A. Retina, B. Cornea, C. Pupil, D. Iris.

• Retina contains: A. Lens and conjunctiva, B. Rods and cones, C. Pupil and optic nerve, D. Iris and sclera.

• External ear consists of: A. Auricle and Acoustic canal, B. Labyrinth, C. Corti and Cochlea, D. Tympanic membrane.

• Fluid in front of lens: A. Vitreous Humor, B. Optic nerve, C. Macula, D. Aqueous Humor.