RA CH 10 Senses notes PDF

Preview

Summary

teacher Virginia turner, at Harper college, Online class...

Description

CH 10- Senses 10.1 introduction Receptors vary greatly 2 major categories General senses- touch, pressure, temp, pain Special senses- taste, smell, hearing, sight

10.2 receptors, sensations and perception 

   

5 types according to sensitivities o Chemoreceptors- stimulatd by changes in concentration of certain chemicals o Pain receptors- by tissue damage o Thermoreceptors- by changes in temp o Mechanoreceptors- by changes in pressure/ movement o Photoreceptors- by light Sensation- when receptors reach threshold and resulting actioncause brain to be aware of stimulis Perception- brain interprets sensory impulses Projection- brain causes a sensation to seem it comes from the stimulated receptor Sensory adapotation- nervous system is less responsive to maintained stimulus

10.3 General Senses 



 

3 kinds of receptors, touch/ pressure receptors o Free nerve endings- epithelial tissue, dentaries branch and extend between epithelial cells.  Itching o Tactile corpuscles- oval masses of flattened connective tissue, 2 + sensory nerve fibers, abundant in hairless areas- lips, fingertips, palms, soles o Lamellated corpuscles- large, deeper dermal and subQ tissues, respond to heavy pressure Senses of pain o Consist of free nerve endings respond to painful stimuli, widely distributed throughout skin and internal tissues, except in nerv tiss. In brain o Protect body- tissue damage stimulates pain receptors Referred pain- pain comes from another place than stimulated area Slow pain fibers- unmyelinated- conduct impulses slowly = delayed, dull, aching sensation

10.4 Special senses 

Special senses, receptors are in large complex sensory organs in head o Smell – olfactory organs o Taste – taste buds o Hearing/ equilibrium- ears o Sight – eyes 10.5 sense of smell

 

Olfactory – smell receptors and taste = are chemoreceptors (chemicals dissolved in liquids stimulate them) Olfactory organs – yellow/brown masses of epithelium, stamp size, cover upper parts of nasal cavity, superior nasal conchae and part of nasal septum o Contain olfactory receptor cell- bipolar neurons o Stimulated olfactory cells send impulses along axons which synapse with neurons in olfactory bulbs (impulses are processed, and additional impulses are conducted along olfactory tracts 10.6 Sense of taste

  



Taste buds- special organs of taste A particular chemical must dissolve in watery fluid for it to be tasted o Salivary glands provide it 5 taste sensations o Sweet o Sour o Salty o Bitter o Umami – delicious UNDERGOES ADAPTATION RAPIDLY

10.7 Sense of Hearing  



Ear has outer, middle and inner o Sense of hearing + equilibrium OUTER EAR o 3 parts  Auricle- external ear, funnel like  External acoustic meatus- s shape tube  Eardrum- tympanic membrane o Sound waves that enter external acoustic meatus change pressure on eardrum- which vibrates in response, reproduces vibrations of source MIDDLE EAR o Tympanic cavity

o

o

o o

o

Air filled space in temporal bone  3small bones , Auditory ossicles  Malleus- attaches to eardrum causes incus to vibrate  Incus- passes movement to stapes  Stapes Bones bridge eardrum and inner ear Oval ligament holds stapes to opening in wall of cavity called – OVAL WINDOW- leads to inner ear  Vibration of stapes at window moves fluid in the inner ear, which stimulates the hearing receptors Auditory tube- connects middle ear to nasal cavity  Pushes eardrum in/out at pressure changes INNER EAR  Communicating chambers and tubes- labyrinth  Perilymph- fluid in space between membranous and boney labyrinths  Endolymph- fluid in membranous labyrinth  Labyrinth has  3 membranous semicircular ducts within  3 Semicircular canals houses receptors for dynamic equilibrium  A cochlea- with hearing receptors Spiral organ- contains hearing receptors, on upper surface of basilar membrane 10.8 Sense of Equilibrium







2 senses o Static equilibrium- balance when head and body is still o Dynamic equilibrium – balance when head and body are suddenly moved/ rotated STATIC EQUILLIBRIUM o Organs  vestibule- bony chamber between the semicircular canals and cochlea  Utricle  Saccule o Utricle and saccule have macula DYNAMIC EQUILLIBRIUM o 3 semicircular canals in labyrinth o Detect motion of head, aid in balance during sudden movement o Canals lie at right angle to each other 10.9 Sense of sight





Visual receptors – in eye + accessory organs o Eyelids- 4 layers o Lacrimal apparatus o Extrinsic muscles Secretion by lacrimal gland moistens eye and lids

 

 



  

Tears have enzyme – lysozyme- kills bacteria Eye is a hollow, spherical structure, 2.5 cm in diameter o 3 layers  Outer – fibrous  Middle- vascular  Inner – nervous Cornea is continuous with sclera- white portion of eye, opaque because of collagenous and elastic fibers, protects eye and serves as an attachment for muscles Ciliary muscle and suspensory ligaments enable lens to adjust shape to focus -accommodation o Lens is enclosed by clear capsule of elastic fibers, keeps lens under constant tension, keeps globular shape o When tension on ligaments relaxes- capsule rebounds and lens capsule rebounds, lens surface become more convex- focused for seeing closer objects Iris- thin diaphragm of connective + smooth muscle fibers, is colored from outside, extends from periphery of ciliary body and lies between cornea and lens o Controls size of pupil Retina- inner layer of the wall of the eye, contains the visual receptor cells (photoreceptors) Optic disc- nerve fibers exit, medial to fovea centralis, blind spot of the eye Rods and cones o Rods- 100x more sensitive to light provides vision in dim lights, without color o Cones- detect color, less sensitive, do not respond in dim light...