Somatic and Special Senses

I. Aids to Understanding Words

Choroid: Skinlike

Example: Choroid Coat – Middle, vascular layer of the eye.

Cochlea: Snail

Example: Cochlea – Coiled tube in the inner ear.

Iris: Rainbow.

Example: Iris – Colored, muscular part of the eye.

Labrinth: Maze

Example: Labyrinth – Complex system of connecting chambers and tubes of the inner ear.

Lacri: Tears.

Example: Lacrimal Gland – Tear gland.

Macula: Spot.

Example: Macula Lutea – Yellowish spot on the retina.

Olfact: To smell.

Example: Olfactory – Pertaining to sense of smell.

Scler: Hard

Example: Sclera – Tough, outer protective layer of the eye.

Tympan: Drum.

Example: Tympanic Membrane – Eardrum.

Vitre: Glass.

Example: Vitreous Humor: Clear, jellylike substance within the eye.

10.1 Introduction

What is the function of sensory receptors?

Sensory receptors detect environmental changes and trigger impulses that travel on sensory pathways into the central nervous system.

10.2 Receptors, Sensations, and Perceptions

A. List five groups of sensory receptors.

Chemoreceptors, pain receptors, thermoreceptors, mechanoreceptors, and photoreceptors. Chemoreceptors are stimulated by changes in concentration of certain chemicals. Pain receptors are stimulated by pain receptors. Thermoreceptors stimulated by changes in temperature. Mechanoreceptors stimulated by changes in pressure/movement. Photoreceptors are caused by light.

B. The process that allows an individual to located the region of stimulation is called projection.

C. The process that makes a receptor ignore a continuous stimulus unless the strength of that stimulus is increased is sensory adaptation.

D. What is a sensation?

Sensations happen when sensory receptors reach threshold and the action potential causes the brain to become aware of the stimulus.

10.3 General Senses

Type

Structure/Location

Sense

Free Nerve Ending

  • Receptors common in epithelial tissue.

  • Sensation of itching.

Meissner’s (Tactile) Corpuscles

  • Small oval passes of flattened in connective tissue sheaths. Found in hair, skin, lips, finger tips, palms, soles, nipples, and genital organs.

  • Responds to light sensations.

  • Responds to motions that barely touch the skin.

Pacinian (Lamellated) Corpuscles

  • Large structures composed of connective tissue, fibers, and cells.

  • Common in deeper dermal and subcutaneous tissues and in muscle tendons and in joint ligaments.

  • Responds to heavy pressure and sensation of deep pressure.

Temperature Senses

  • Two types of free nerve endings: Warm receptors and cold receptors.

  • Sense of warm and cold.

Free Nerve Endings (Pain Receptors)

  • Receptors consisting of free nerve endings that respond to stimuli.

  • Widely spread through skin and internal organs.

  • Sense of pain.

10.4 Special Senses

List the special senses:

Smell – Olfactory organs.

Taste – Taste buds.

Hearing – Ears

Equilibrium – Ears

Sight – Eyes

10.5 Sense of Smell

The sense of smell supplements the sense of taste.

10.6 Sense of Taste

A. Describe the structure of taste receptors.

Taste buds have 50 to 150 modified epithelial cells which work as receptor cells. Taste buds are included epithelial supporting cells. Structure is spherical. Has opening with the taste pores. Taste hairs are sensitive parts.

B. How does saliva contribute to the perception of taste?

Particular chemicals must be dissolved in fluids around the taste buds in order to be tasted. Saliva is the fluid provided. Saliva makes tasting possible.

D1. List five primary taste sensations.

1. Sweet (table sugar)

2. Sour (lemon)

3. Salty (table salt)

4. Bitter (caffeine)

5. Umami (certain amino acids/chemical relatives)

D2. What areas of the tongue are associated with each taste?

Tip of the tongue is most sensitive to sweet stimuli.

Margin of the tongue is sensitive to sour.

Back of the tongue can detect bitterness.

Saltiness can be sensed throughout the tongue.

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