The General & Special Senses Chapter 18. Introduction Senses – our perception of what is “out there” 2 groups –General senses Includes senses that are.

The General & Special Senses

Chapter 18

Introduction

• Senses – our perception of what is “out there”• 2 groups

– General senses• Includes senses that are not specific

• Pass information through spinal nerves

– Special senses• Found within complex sense organs to cerebral cortex

• Pass information through cranial nerves to cerebral cortex

Receptors

• Sensory receptors are transducers – Change stimuli into electro-chemical impulses – Specific receptors can transduce only certain

types of stimuli

Human Anatomy, 3rd editionPrentice Hall, © 2001

Figure 18-01

Receptors

Interpretation of Sensory Information

• Occurs in cerebral cortex

• Depends on the area of the cerebral cortex that receives the information

Central Processing and Sensory Adaptation

• Sensory adaptation – the loss of sensitivity after continuous stimulation– Occurs in some types of receptors

• Role – prevents brain from being overloaded with unimportant information

Receptors of the General Senses

• Pain– Referred pain– Phantom pain

• Thermoreceptors detect changes in temperature• Mechanoreceptors respond to pressure & touch• Chemoreceptors detect chemicals in solution

– Blood composition– (Smell) – (Taste)


Figure 18-02

Referred Pain

The Special Senses

Olfaction (the nose)

• Olfactory receptors– Can detect at least 50 different primary smell– Located in the roof of nasal cavity– Molecules dissolve in the mucus or lipids of the

epithelium – Olfactory neurons pass through the roof of the

nasal cavity and synapse in the olfactory nerve– Olfactory tracts go directly to the cerebral

cortex


Figure 18-06a

Olfactory Receptors


Figure 18-06b

Olfactory Receptors

Taste (the tongue)

• Taste receptors are in the taste buds– Can detect 4 primary tastes

• Sweet, sour, salty, bitter

– Located in papillae on the surface of the tongue – Taste buds contain the taste receptors– Molecules dissolve in saliva– Cranial nerves relay sensory impulses to the

cerebral cortex


Figure 18-07a

Taste Areas of the Tongue


Figure 18-07b

Taste Buds


Figure 18-07c

Taste Bud

Equilibrium & Hearing (the ear)

• External ear– The auricle directs sound waves into the external

auditory meatus to the tympanic membrane

• Middle ear– Contains the auditory ossicles

• Malleus, incus, stapes

– Connected to throat by the eustachian tube

• Inner ear

Human Anatomy, 3rd edition

Prentice Hall, © 2001

Figure 18-09

The Ear


Figure 18-10b

The Middle Ear

The Inner Ear

• Separated from the middle ear by the oval window

• Consists of a series of canals filled with fluid

The Inner Ear

– Semicircular canals• Contains receptors for head position

– Cochlea • Contains the organ of Corti, the organ of hearing


Figure 18-12b

The Inner Ear

The Semicircular Canals

• Detects balance

• Arranged at right angles to each other

• Contain hair cells are embedded in gelatinous material with fluid over it

• Detect movement of the head – Bends the hairs, creating nerve impulses


Figure 18-12c

Hair Cells in the Semicircular Canals

The Organ of Corti

• Detects sound waves

• Consists of hair cells on a basement membrane

• Tips of hairs touch the tectorial membrane

• When the basement membrane vibrates, the hair cells are bent, sending a nerve impulse


Figure 18-16d

Organ of Corti


Figure 18-16e

Organ of Corti

Summary of Hearing

• Sound waves enter the external auditory meatus• Tympanic membrane vibrates• Auditory ossicles vibrate• Oval window vibrates• Fluid in inner ear vibrates• Basement membrane moves• Hairs rub against the tectorial membrane• Nerve impulse is sent along the auditory nerve to

the brain

Vision (the eye)

• Accessory structures– Eyelids protect the eye

• Conjunctiva lines the eyelid

• Lacrimal gland produces tears

– Extrinsic muscles move the eyeball


Figure 18-18b

The Eye

Structure of the Eye

• Consists of 3 tunics (layers)– Outer tunic – outermost layer

• Includes the cornea & sclera

– Middle tunic • Includes the choroid coat, ciliary body, and lens,

iris & pupil

– Inner tunic (retina) – inner layer• Contains the rods & cones (photoreceptors)• Includes the optic disc (blind spot),


Figure 18-20b

The Eye


Figure 18-20a

Tunics of the Eye


Figure 18-22c

Inner Tunic

The Cavities of the Eye

• The lens separates the interior of the eye into 2 cavities– Anterior cavity in front of the lens

• Contains aqueous humor– Glaucoma

– Posterior cavity behind the lens• Contains vitreous humor

Cavities of the Eye


Figure 18-23

The Vascular Tunic

• Contains many blood vessels & nerves

• The iris controls the size of the pupil

• Suspensory ligaments attach the lens to the ciliary body– Controls the shape of the lens

• Allows focusing on near & distant objects

• Cataract


Figure 18-20c

The Pupil

The Retina

• Cones allow for sharp color vision in bright light– 3 types, each with a different pigment

The Retina

• Rods provide for vision in dim light– Most dense at the periphery of the retina– Contain the pigment rhodopsin


Figure 18-22a1

Visual Receptors

Summary of Vision

• Light rays enters through the pupil

• Light rays cross in the lens

• Retina receives reversed & upside down image

• Rods & cones are stimulated

• Optic nerve carries impulse to the brain

Abnormal Vision

• Myopia

• Hyperopia

• Presbyopia

• Astigmatism

The General & Special Senses Chapter 18. Introduction Senses – our perception of what is “out there” 2 groups –General senses Includes senses that are.

Documents

tongue slide

fluid slide

middle ear slide

cerebral cortex slide

taste bud slide

organ of corti slide

organ of hearing slide

referred pain slide