1/3/15 1 The Senses • Help to maintain homeostasis • General senses – receptors located throughout the body Within the skin, organs & joints Sense of touch • Special senses – receptors in the head Sight Smell Taste Hearing Equilibrium Receptors • Receptors – specialized cells that collect info from the environment & pass info to the nervous system • Chemoreceptors – receptors for smell & taste; respond to chemicals in solution • Pain receptors (nociceptors) – • Thermoreceptors – respond to temp. • Mechanoreceptors – • Proprioceptors sense changes in tension of muscles & tendons • Baroreceptors detect changes in pressure • Stretch receptors detect changes in length or volume • Photoreceptors respond to patterns made by light; sight
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The Senses• Help to maintain homeostasis
• General senses – receptors located throughout the body
� Within the skin, organs & joints
� Sense of touch
• Special senses – receptors in the head
�Sight
�Smell
�Taste
�Hearing
�Equilibrium
Receptors• Receptors – specialized cells that collect info from
the environment & pass info to the nervous system
• Chemoreceptors – receptors for smell & taste; respond to chemicals in solution
• Pain receptors (nociceptors) –
• Thermoreceptors – respond to temp.
• Mechanoreceptors –
• Proprioceptors sense changes in tension of muscles & tendons
• Baroreceptors detect changes in pressure
• Stretch receptors detect changes in length or volume
• Photoreceptors respond to patterns made by light; sight
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Chemical Senses – Taste & Smell
• Chemoreceptors; respond to chemicals in a solution
•Chemicals dissolved in saliva & fluids in nasal membranes
• Both senses complement each other; 80% of taste depends on smell
Olfaction –• Olfactory receptors are located in the roof
of the nasal cavity
•Chemicals must be dissolved in mucus
•Sniffing intensifies smell; pulls molecules across olfactory receptor cells
•Olfactory cells surrounded by supporting cells
•Olfactory hairs increase the surface area of receptor cells
•Olfaction closely related to taste & memories
Olfaction
•Impulses are transmitted from receptor cells to the olfactory nerve
•Olfactory nerve passes thru ethmoid bone to the olfactory bulb.
•Interpretation of smells is made in the cortex but passes through the limbic system, the part of the brain that stores memories and emotions
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The Sense of Taste
• Gustation –
• Taste buds – receptor organs for taste
• Location of taste buds
• Most are on the tongue
• Hard & soft palate
• Cheeks
The Tongue and Taste• Tongue is covered w/projections called
• Taste buds are found on the sides of papillae
• Taste buds are constantly being replaced due to wear and tear
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Structure of Taste Buds• Taste buds consist of 3 types of cells;
gustatory cells, supporting cells, & basal cells
�Gustatory cells (taste cells) are the receptors
�Supporting cells surround taste cells
�Gustatory hairs (long microvilli) protrude from TASTE PORE
− Hairs are stimulated by chemicals dissolved in saliva
�Basal cells are located at the base & are the source for new taste cells
Anatomy of Taste Buds
Taste Sensations• Sweet receptors –
�Sugars, carbohydrates
• Sour receptors –
�Acids (lemon, vinegar)
• Salty receptors –
�Metal ions (NaCl)
• Bitter receptors –
�Alkaloids (aspirin), many poisons
• Umami
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Taste Pathway• Impulses are carried to the gustatory
complex by several cranial nerves because taste buds are found in different areas
• Facial nerve – transmits impulse from taste buds in anterior 2/3 of tongue
• Glossopharyngeal nerve – from taste buds in posterior 1/3 of tongue
• Vagus nerve - from the few taste buds at the base of the tongue & pharynx
The Ear
• Houses 2 senses
� Hearing
� Equilibrium
• Receptors are mechanoreceptors –respond to vibrations & movement of fluids in ear
• Different organs house receptors for each sense
Anatomy of the Ear
• The ear is divided into 3 areas
• Outer (external) ear
• Middle ear
• Inner ear
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The External Ear• Involved in hearing only
• Structures of the external ear
• Pinna (auricle) – shell shaped structure; directs sound waves into canal
• External auditory canal –w/in temporal bone external acoustic meatus
• Tympanic membrane –transfers sound waves
The External Auditory Canal
• Ceruminous glands secrete ear wax (cerumen)
• External ear ends at the tympanic membrane or eardrum
Middle Ear or Tympanic Cavity
• Air-filled cavity within the bone
• Only involved in the sense of hearing
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Middle Ear or Tympanic Cavity
• 2 tubes are associated with the middle ear
• The opening from the auditory canal is covered by the tympanic membrane
• The auditory tube or eustachian tube connects middle ear w/throat
• Allows for equalizing air pressure during yawning, swallowing or flight