The General and Special Senses The General and Special Senses.
The General & Special Senses
description
Transcript of The General & Special Senses
The General & Special Senses
Chapter 10
Introduction
• Senses – our perception of what is “out there”– 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
General Senses
• Includes senses that are associated with skin– Temperature, pressure, touch, pain, vibration,
proprioception• Pass information along the spinal nerves
and pathways to specific areas of the cerebral cortex
Special Senses
• Olfaction, gustation, equilibrium, hearing, & vision
• Found within complex sense organs• Pass information along the cranial nerves to
specific areas of the cerebral cortex.
Receptors
• Sensory receptors are transducers – Change stimuli into electro-chemical impulses – Specific receptors can transduce only certain
types of stimuli
Interpretation of Sensory Information
• Occurs in cerebral cortex• Depends on the area of the cerebral cortex
that receives the information
Central Processing and Adaptation
• Sensory adaptation – the loss of sensitivity after continuous stimulation– Tonic receptors are always active– Phasic receptors only relay changes in the
conditions they are monitoring• Role – prevents brain from being
overloaded with unimportant information
Receptors of the General Senses
Nociceptors
• Detect pain– Referred pain– Phantom pain
Mechanoreceptors
• Respond to pressure & touch– Tactile receptors– Baroreceptors– Proprioreceptors– Thermoreceptors
Tactile Receptors• Found in the dermis
Baroreceptors• Monitor changes in pressure
Chemoreceptors• Detect chemicals in solution
– Blood composition
The Special Senses
Olfaction (the nose)• Olfactory receptors
– Can detect at least 50 different primary smells– Located in the epithelium of roof of nasal cavity
Olfactory Receptors• Molecules dissolve
in the mucus of the epithelium
• Olfactory neurons pass through the roof of the nasal cavity and synapse in the olfactory bulb
• Olfactory tracts go directly to the cerebral cortex
Gustation (the tongue)
• Taste receptors are in the taste buds
• 6 primary tastes– Sweet, sour,
salty, bitter, water, umami
Gustatory Receptors
• Located in papillae on the surface of the tongue
• Contain the gustatory receptors– Molecules dissolve
in saliva
Gustatory Receptors
Pathway of Gustatory Sense
• Cranial nerves relay sensory impulses to the cerebral cortex– All pass through the
medulla & thalamus
Equilibrium & Hearing (the ear)• External ear
– The auricle directs sound waves into the external auditory meatus to the tympanic membrane
The Middle Ear• Contains the auditory ossicles• Separated from the external ear by the tympanic
membrane– Malleus– Incus– Stapes
• Connected to the throat by the eustachian tube
The Inner Ear• Separated from the middle ear by the oval window
The Inner Ear
• Consists of a series of canals filled with fluid
The Inner Ear
• Consists of a series of canals filled with fluid– Vestibule– Semicircular
canals– Cochlea contains
• Organ of Corti
The Vestibule
• Detects static position
• Hair cells are embedded in a gelatinous material
Otoliths at Work• Otoliths are
balanced on top of gelatinous material– Slide when
head tips– Bend hairs– Generates
nerve impulse
The Semicircular Canals• Detect dynamic
balance• Arranged at right
angles to each other• Hair cells are
embedded in gelatinous material with fluid over it
• Movement of head– Bends the hairs – Creates nerve
impulses
Semicircular Canals at Work
The Cochlea
• Divided into 3 tunnels by membranes– Tunnels connect
with the oval window and round window
– Organ of Corti
Cochlear Chambers
The Organ of Corti• Consists of hair
cells on a basement membrane
• Tips of hairs touch the tectorial membrane
• Basement membrane vibrates– Sends a nerve
impulse– Hair cells bend
Pathway of Auditory Sense
Summary of Hearing• Sound waves enter the external auditory meatus• Tympanic membrane vibrates• Auditory ossicles vibrate• Oval window vibrates• Fluid in cochlea moves• 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 apparatus– Lacrimal gland produces
tears– Lacrimal canals drain
tears into lacrimal sacs– Nasolacrimal duct drains
into the nasal cavity• Extrinsic muscles move the
eyeball
Structure of the Eye – 3 Tunics• Outer tunic
– Includes cornea & sclera
• Middle tunic
– Includes choroid coat, ciliary body, lens, iris & pupil
• Inner tunic (retina)– Contains
photoreceptors• Rods & cones
The Cavities of the Eye
• The lens separates the interior of the eye into 2 cavities– Anterior cavity
• Contains aqueous humor
• Glaucoma – Posterior cavity
• Contains vitreous humor
The Cavities of the Eye
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
The Retina• Cones allow for sharp
color vision in bright light– Contain pigments– Macula lutea – Fovea centralis
• Rods provide for vision in dim light– Contain the pigment
rhodopsin– Most dense at
periphery of retina
Photo of Posterior Eye
Human Anatomy, 3rd editionPrentice Hall, © 2001
Figure 18-22c
Pathway of Vision Sense
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