Somatic and Special Senses

Chapter 10

Introduction

• Sensory Receptors- detect environmental changes and trigger nerve impulses that travel on sensory pathways into the CNS for processing and interpretation

http://michaeldmann.net/pix_4b/gust_receptors.gif

2 large types of sensory receptors

• 1. Somatic senses: touch, pressure, temperature, and pain

• 2. Special senses: smell, taste, hearing, equilibrium, and vision

http://www.medicalook.com/systems_images/Somatic_senses.gif

Receptors and Sensations

• Receptors are distinct to a type of environmental change

• This selective response distinguishes the senses

• 5 kinds

1. Chemoreceptors

• Stimulated by changes in the chemical concentration of substances

2. Pain Receptors

• Stimulated by tissue damage

https://courses.cit.cornell.edu/psych396/student2006/the_biology_of_pain/receptor2.jpg

3. Thermoreceptors

• Stimulated by changes in temperature

http://resource.rockyview.ab.ca/t4t/bio30/images/m1/b30_m1_022_l.jpg

4. Mechanoreceptors

• Stimulated by changes in pressure or movement

http://bdml.stanford.edu/twiki/pub/Haptics/ProjectOverview/mechanoreceptors.jpg

5. Photoreceptors

• Stimulated by light energy

http://thebrain.mcgill.ca/flash/d/d_02/d_02_m/d_02_m_vis/d_02_m_vis_1a.jpg

Sensation

• Sensation-a feeling that occurs when the brain interprets sensory impulses

• Impulse is read depending on what area of the brain receives it

• One area may be sound and one area may be touch

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Projection

• Projection-process where the cerebral cortex causes a feeling to stem from a source

• It allows a person to pinpoint the region of stimulation (eyes & ears)

Sensory Adaptation

• Sensory adaptation-sensory receptors stop sending signals when they are repeatedly stimulated

• Can only be triggered if stimulus strength changes again

• Think smell (phasic)

http://www.cyndan.com.au/Portals/0/Media/F/Farm%20Mate%20cow.jpg

Somatic Senses

• 1. Sensory Nerve Fibers– Common in epithelial tissues

– Are associated with touch and pressure

http://www.exploringnature.org/graphics/anatomy/sensory%20organs.jpg

• 2. Meissner’s Corpuscles– Small masses of connective tissue

– Located in hairless portions of the skin (lips, fingertips, palms, soles, nipples, external genitalia)

– Interpret light touch

http://www.exploringnature.org/graphics/anatomy/sensory%20organs.jpg

• 3. Parcinian Corpuslces – Large structures of connective tissue

– Located in deep tissue layers like ligaments and tendons

– Respond to heavy pressure

Temperature Senses

• 1. Warm Receptors - nerve endings that respond to warmer temperatures (sensitive above 77°, unresponsive above 113°F)

• 2. Cold Receptors - nerve endings that respond to colder temperatures (sensitive between 50°F and 68°F)

http://herkules.oulu.fi/isbn9514259882/html/graphic22.png

Sense of Pain

• These protect the body because tissue damage stimulates them

• Usually unpleasant and signals the person to remove the stimulation

• Pain is persistent and doesn’t go away

• Four types

1. Visceral Pain

• Occurs in visceral tissues such as heart, lungs, intestine

http://wehelpwhathurts.homestead.com/visceral-somatic_referral_patterns_resize_smaller.jpg

2. Referred Pain

• Feels as though it is coming from a different part (heart pain may be felt as pain in arm or shoulder)

• Caused from Nerves passing through the same area

http://www.merckmanuals.com/media/home/figures/NEU_referred_pain.gif

3. Acute Pain

• Originates from skin, usually stops when stimulus stops (needle prick)

https://courses.cit.cornell.edu/psych396/student2006/the_biology_of_pain/receptor2.jpg

4. Chronic Pain

• Dull aching sensations

http://criticalscience.com/wp-content/uploads/2011/08/pain-map_alphachimp_com.jpg

Regulation of pain

• Pain is interpreted by the Cerebral Cortex in the brain.

• Three types of neuropeptides that inhibit pain: serotonin, enkephalins, endorphins.

• Natural brain chemicals can be mimicked by drugs such as morphine.

Morphine

http://recoverylife.com/resources/gallery_photo/morphine60.jpg

Special Senses

• Smell: olfactory organs

• Taste: taste buds

• Hearing equilibrium: Ears

• Sight: Eyes

http://www.exploringnature.org/graphics/anatomy/poster_special_senses_small.jpg

Sense of Smell

• The sense of smell is associated with complex sensory structures in the upper region of the nasal cavity

http://www.umm.edu/graphics/images/en/8689.jpg

Olfactory Receptors

• Chemoreceptors that are stimulated by chemicals that are dissolved in liquid

• Aid in food selection because smell and taste are closely related

http://www.yalescientific.org/wp-content/uploads/2011/05/fulllengths-olfaction-2.jpg

Olfactory Organs

• Contain the olfactory receptors which are masses that cover the upper parts of the nasal cavity

http://www.medicalook.com/systems_images/Olfactory_sense.gif

Olfactory Receptor Cells

• Bipolar neurons surrounded by epithelial cells

• Covered in cilia which have receptor proteins that the odor chemicals bind to

http://openwetware.org/images/b/ba/Olfactory_System_2.jpg

Olfactory Bulbs

• Receive the nerve impulses from the receptor cells (located in the brain)

http://lynlaukimdak.wikispaces.com/file/view/42.jpg/219698964/42.jpg

Olfactory Tracts

• Located inside the olfactory bulbs and interpret the nerve impulses

http://www.medicalook.com/systems_images/Olfactory_sense.gif

Smell Video

10.6 Sense of Taste (258-260)

http://1.bp.blogspot.com/_JUfBbVlJk-s/TOB1pd-ZqVI/AAAAAAAABhM/BoQ04mSXNWI/s1600/tongue.jpg

The special organs of taste; papillae

http://thesalience.files.wordpress.com/2013/05/taste-buds-fungiform-papillae-vallate-papilla-gustatory-hairs-stratified-squamous-epithelium-of-tongue-taste-fibers-of-cranial-nerves.jpg

Gustatory cells; 50 to 150 receptor cells

The chemical must dissolve in the watery fluid surrounding the taste buds that are

produced by the salivary glands.

http://oldenaplesperio.com/wp-content/uploads/2013/05/salivary-glands.jpg

1. Sweet—table sugar2. Sour—lemon

3. Salty—table salt4. Bitter—caffeine or quinine

http://www.zecuppa.com/images/primary-tastes.jpg

It detects monosodium glutamate (MSG), used as a flavor enhancer in many

prepared foods

http://insidescoopsf.sfgate.com/files/2013/03/umamiBUB.jpg

10.7 Sense of Hearing (260-264)

http://www.mhhe.com/biosci/esp/2001_saladin/folder_structure/in/m4/s5/assets/images/inm4s5_1.jpg

Auricle (pinna)—outer ear; External Auditory meatus

http://www.infovisual.info/03/img_en/049%20External%20middle%20internal%20ear.jpg

malleus, incus, stapes - transmit vibrations and amplify the signal

http://upload.wikimedia.org/wikipedia/commons/b/b0/Illu_auditory_ossicles.jpg

Eustachian tube; Connects the middle ear to the throat; Helps maintain air

pressure

http://3.bp.blogspot.com/-AcDUnUFGUAQ/T2P-qSzTfbI/AAAAAAAAAE0/UoQmO3yBy9M/s1600/Middle-Ear-Pressure2.gif

Labyrinth, semicircular canals, cochlea, round window, and organ of

Corti

http://www.brainhq.com/media/49/download/middle-inner-ear_0.jpg

Labyrinth: communicating chambers and tubesOsseous Labyrinth and Membranous Labyrinth

Perilymph and Endolymph (fluids within the labyrinth)

http://www.positivehealth.com/img/image-article/Issue%20166/Articles/Inner%20Ear.gif

Semicircular Canals: sense of equilibrium

http://www.daviddarling.info/images/semicircular_canals.jpg

Cochlea: sense or hearing

http://upload.wikimedia.org/wikipedia/commons/thumb/a/a6/Cochlea.svg/490px-Cochlea.svg.png

Organ of Corti: contains hearing receptors, hair cells detect vibrations

http://www.nature.com/nature/journal/v405/n6783/images/405130aa.2.jpg

Hair cells

http://www.neurophys.wisc.edu/auditory/johcfig2.jpg

10.8 Sense of Equilibrium (264-267)

http://classes.midlandstech.edu/carterp/Courses/bio110/chap09/Slide17.JPG

It senses the position of the head and maintains stability and posture

http://people.emich.edu/pbogle/PHED_200/overheads/ch10_art/10_11.jpg

It balances the head during sudden movements; Semicircular canals

http://faculty.spokanefalls.edu/InetShare/AutoWebs/GaryB/AP%20242/Unit%204/Anatomy%20of%20the%20ear-Equilibrium_files/slide0007_image011.jpg

It interprets impulses from the semicircular canals and maintains overall

balance and stability

http://nh-chs-anatomy.pbworks.com/f/1390421610/Cerebellum-6%5B1%5D.jpg