1. The Senses

2. The Senses Sensory Receptors General senses of touch Temperature
Pressure
Pain
Special senses: Taste, Sight, Hearing Smell, Equilibrium

3. Types of Receptors Chemoreceptors Pain receptors or nociceptors
Thermoreceptors
Mechanoreceptors
Photoreceptors

4. Somatic or Body Senses
associated with skin, muscles, joints, and viscera
three groups
exteroceptive senses – senses associated with body surface; touch, pressure, temperature, pain
proprioceptive senses – senses associated with changes in muscles and tendons
visceroceptive senses – senses associated with changes in viscera

5. Touch and Pressure

6. Sensitivity to Temperature
Warm receptors
temperatures above 25 C (77 F)
unresponsive to temperature above 45 C (113 F)
Cold receptors
temperature between 10 C (50 F) and 20 C (68 F)
Pain receptors
below 10 C
above 45 C

7. Pain
free nerve endings, widely distributed,stimulated by tissue damage,do not adapt
Acute pain fibers: thin, myelinated, conduct impulses rapidly
Chronic pain fibers: thin, unmyelinated, conduct impulses more slowly

9. Regulation of Pain Thalamus aware of pain Cerebral Cortex
judges intensity of pain
locates source or pain
produces motor response to pain
produces emotions to pain
Pain Inhibiting Substances
enkephalins-Met-enkephalin is Tyr-Gly-Gly-Phe-Met. Leu-enkephalin has Tyr-Gly-Gly-Phe-Leu.
serotonin
endorphins

10. Stretch Receptors Found in muscles and tendons:
Can shut down contraction if it endangers the body.
Can also be turned off during fight or flight response

11. Smell Olfactory receptors are in the roof of the nasal cavity
Neurons with long cilia
Chemicals must be dissolved in mucus for detection
Impulses are transmitted via the olfactory nerve
Interpretation of smells is made in the cortex
Contain 1000 genes that code for the sense of smell, but only a few hundred are active????
WHY

12. Olfaction

13. Taste
Taste Buds: organs of taste, located on papillae of tongue, roof of mouth, linings of cheeks and walls of pharynx
The tongue is covered with projections called papillae
Taste buds are found on the sides of papillae
Gustatory cells are the receptors (Chemoreceptor)
Have gustatory hairs (long microvilli)
Hairs are stimulated by chemicals dissolved in saliva
Sensory impulses from taste receptors travel along cranial nerves; facial nerve, glossopharyngeal nerve, and vagus nerve, to medulla oblongata then to the thalamus and to the gustatory cortex (for interpretation)

14. Taste

15. Hearing Functions to collect and translate vibration in the air
The ear houses 2 senses hearing and equilibrium.
mechanoreceptors
3 Sections
External
Middle
Inner
Functions to collect and translate vibration in the air

16. The Ear External Ear Auricle external auditory meatus
tympanic membrane-
Middle Ear
tympanic cavity
auditory ossicles- malleus, incus, and stapes

17. Cont…….
oval window- stapes vibrates against it to move fluids in inner ear
eustachian tube or Auditory- connects middle ear to throat:
Inner Ear
osseous labyrinth- bony canal in temporal bone filled with perilymph
membranous labyrinth- tube within osseous labyrinth filled with endolymph

18. Cont… 3 Parts of Labyrinths cochlea functions in hearing
semicircular canals
functions in equilibrium
vestibule

21. Cochlea Scala vestibuli- upper compartment,
Scala tympani- lower compartment,
Cochlear duct- membranous labyrinth in cochlea
Vestibular membrane- separates cochlear duct from scala vestibuli
Basilar membrane- separates cochlear duct from scala tympani

23. Organ of Corti group of hearing receptor cells (hair cells)
on upper surface of basilar membrane
different frequencies of vibration move different parts of basilar membrane
particular sound frequencies cause hairs of receptor cells to bend
nerve impulse generated

25. Overview of Hearing

26. Equilibrium Equilibrium has two functional parts Static equilibrium
Dynamic equilibrium
Static
Maculae – receptors in the vestibule
Report on the position of the head
Send information via the vestibular nerve
Anatomy of the maculae
Hair cells are embedded in the otolithic membrane
Otoliths (tiny stones) float in a gel around the hair cells
Movements cause otoliths to bend the hair cells

28. Dynamic Equilibrium
Crista ampullaris – receptors in the semicircular canals
Tuft of hair cells
Cupula (gelatinous cap) covers the hair cells
Action of angular head movements
The cupula stimulates the hair cells
An impulse is sent via the vestibular nerve to the cerebellum

29. Extrinsic Eye Muscles Six skeletal muscles that move the eyeball
Superior rectus- rotates eye up and medially
Inferior rectus- rotates eye down and medially
Medial rectus- rotates eye medially
Lateral rectus- rotates eye laterally
Superior oblique- rotates eye down and laterally
Inferior oblique- rotates eye up and laterally

31. Eye Structure and Function
3 layers- outer fibrous tunic, middle vascular tunic, inner nervous tunic
1. Outer- Cornea- anterior portion transparent, light transmission, light refraction Sclera- posterior portion, opaque, protection
2. Middle- Iris- anterior, pigmented, controls light intensity Ciliary body- anterior, pigmented, holds lens, moves lens for focusing Choroid coat- provides blood supply, pigments absorb extra light
Anterior of eye filled with aqueous humor.
Lens-Transparent, lies behind iris, largely composed of lens fibers, elastic, held in place by suspensory ligaments of ciliary body

33. Cont.. contains visual receptors continuous with optic nerve
3. Inner- retina
contains visual receptors
continuous with optic nerve
ends just behind margin of the ciliary body
composed of several layers
fovea centralis –produces sharpest vision
optic disc – the raised disk on the retina at the point of entry of the optic nerve, lacking visual receptors and so creating a blind spot.
vitreous humor – thick gel that holds retina flat against choroid coat

34. How We See Photoreceptors:
Rods- long, thin projections, contain light sensitive pigment called rhodopsin, hundred times more sensitive to light than cones, provide vision in dim light, produce colorless vision, produce outlines of objects
Cones- short, blunt projections, contain light sensitive pigments called erythrolabe(Red Light), chlorolabe(Green Light), and cyanolabe(Blue Light), provide vision in bright light, produce sharp images, produce color vision

36. References Jack Brown M.S. Biology
Shier,David, Jackie Butler, Ricki Lewis: Hole’s Human Anatomy and Physiology 10th edition: 2004: McGraw-Hill
Marieb, Elaine: Essentials of Human Anatomy and Physiology 7th edition. 2003: Pearson Education Inc: Benjamin Cummings pub.
Microsoft Encarta Encyclopedia 2004