Transcript Slide 1

The Senses

The Senses

Sensory Receptors

General senses of touch

 Temperature  Pressure  Pain 

Special senses:

Equilibrium Taste, Sight, Hearing Smell,

Types of Receptors


Pain receptors or nociceptors




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

Touch and Pressure

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


 free nerve endings, widely distributed,stimulated by tissue damage,do not adapt 

Acute pain fibers:

impulses rapidly thin, myelinated, conduct 

Chronic pain fibers :

impulses more slowly thin, unmyelinated, conduct

Regulation of Pain

  


 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-


. Leu-enkephalin has Tyr-Gly-Gly-Phe-


. serotonin endorphins

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


 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????




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)



 The ear houses 2 senses hearing and equilibrium.

 mechanoreceptors  3 Sections    External Middle Inner  Functions to collect and translate vibration in the air

The Ear

External Ear


external auditory meatus

tympanic membrane-

Middle Ear

tympanic cavity

auditory ossicles-

malleus, incus, and stapes


oval window-

stapes vibrates against it to move fluids in inner ear

eustachian tube or Auditory-

ear to throat: connects middle 

Inner Ear

osseous labyrinth-

filled with perilymph bony canal in temporal bone 

membranous labyrinth-

tube within osseous labyrinth filled with endolymph


3 Parts of Labyrinths


  functions in hearing

semicircular canals

  functions in equilibrium


 functions in equilibrium


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

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

Overview of Hearing


 Equilibrium has two functional parts  Static equilibrium   

Static Maculae

– receptors in the vestibule  Report on the position of the head  Dynamic equilibrium 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

Dynamic Equilibrium

 

Crista ampullaris

receptors in the semicircular canals –  Tuft of hair cells 

Action of angular head movements

 The cupula stimulates the hair cells 


(gelatinous cap) covers the hair cells An impulse is sent via the vestibular nerve to the cerebellum

Eye Muscles

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

Eye Structure and Function


layers- outer fibrous tunic, middle vascular tunic, inner nervous tunic 

1. Outer- Cornea

- anterior portion transparent, light transmission, light refraction


- posterior portion, opaque, protection 

2. Middle



- 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.


Transparent, lies behind iris, largely composed of lens fibers, elastic, held in place by suspensory ligaments of ciliary body


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

– blind spot

vitreous humor

– thick gel that holds retina flat against choroid coat

How We See



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 


- 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


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

 Microsoft Encarta Encyclopedia 2004