General and Special Senses Ch. 49 AP Biology Ms. Haut.

General and Special Senses

Ch. 49Ch. 49

AP BiologyAP Biology

Ms. HautMs. Haut

Classification of Sensory System Classification of Sensory System by structural Complexityby structural Complexity

General SensesGeneral Senses– NocioreceptorsNocioreceptors– ThermoreceptorsThermoreceptors– MechanoreceptorsMechanoreceptors– ChemoreceptorsChemoreceptors

Special SensesSpecial Senses– OlfactionOlfaction– VisionVision– HearingHearing– TasteTaste– EquilibriumEquilibrium

Sensory Receptors

Gather information and Gather information and pass it on to the CNS.pass it on to the CNS.

Specialized cells or cell processes monitoring conditions in/outside body

Specific for a certain type of stimulus → “receptor specificity”

Sensory Transduction

Sensory transduction– Conversion by sensory

receptors of stimuli into electrical signals.

Receptor potentials– Changes in membrane

potentials caused by sensory stimuli.

– Vary in intensity, depending on the strength of the stimulus.

Receptor potential transmitted to CNS

Receptor potentials are integrated through Receptor potentials are integrated through summationsummation

In sensory adaptation,In sensory adaptation,– Some sensory receptors become less Some sensory receptors become less

sensitive when they are stimulated sensitive when they are stimulated repeatedly.repeatedly.

– Make wearing clothing uncomfortable Make wearing clothing uncomfortable without itwithout it

Sensory Integration

Free nerve ending

Encapsulated nerve ending

Specialized receptor cells

Complexity Range of ReceptorsComplexity Range of Receptors

Types of Sensory Receptors

MechanoreceptorsMechanoreceptors ChemoreceptorsChemoreceptors Electromagnetic receptorsElectromagnetic receptors ThermoreceptorsThermoreceptors Nocioreceptors (pain receptors)Nocioreceptors (pain receptors)

Sensory Receptors

– A section of human A section of human skinskin

Reveals why the Reveals why the surface of our body is surface of our body is sensitive to such a sensitive to such a variety of stimuli.variety of stimuli.

Mechanoreceptors Respond to physical distortion of cell membrane

(pressure, touch, stretch, motion, and sound)

– Baroreceptors Sensitive to internal pressures: blood pressure, lung stretch, digestive tract tension

– Proprioceptors monitors of muscle stretch

– Tactile receptors - touch, pressure, vibration Unencapsulated: free nerve endings, Merkels dics -

fine touch Encapsulated: Meissners corpuscles - fine touch;

Pacinian corpuscles - deep pressure

Chemoreceptors Respond to small

concentration changes of specific molecules (chemicals)

Internal chemoreceptors monitor blood composition (e.g. Na+, pH, pCO2 )

Found within aortic and carotid bodies

Very important for homeostasis

http://ecc-book.com/assets/images/carotid_and_aortic_bodies.jpg

Electromagnetic Receptors

Detect various forms of electromagnetic Detect various forms of electromagnetic energy (visible light, electricity, magnetism)energy (visible light, electricity, magnetism)

Photoreceptors—detect visible lightPhotoreceptors—detect visible light Snakes have infrared receptors—detect body Snakes have infrared receptors—detect body

heatheat Some fishes use electroreceptors—locate Some fishes use electroreceptors—locate

objects and preyobjects and prey Birds, salmon, sea turtles use Earth’s Birds, salmon, sea turtles use Earth’s

magnetic field for migrationmagnetic field for migration

Thermoreceptors

Respond to changes in temperature

In dermis, skeletal muscles, liver and hypothalamus

Free nerve endings

– Cold receptors

– Warm receptors

http://lpc1.clpccd.cc.ca.us/lpc/zingg/anat/alecture/alect_stud/ach18_s.ppt.

Nocioreceptors (Pain Receptors) Respond to heat, mechanical Respond to heat, mechanical

stress and chemicals associated stress and chemicals associated with tissue damagewith tissue damage

– Most concentrated in skinMost concentrated in skin– Function is protection against Function is protection against

further tissue damagefurther tissue damage– Generally do not adapt to Generally do not adapt to

continual stimuli. continual stimuli.

Visceral Pain: Visceral Pain: – Only visceral receptors that Only visceral receptors that

produce sensations;produce sensations;– Stretch receptors are Stretch receptors are

stimulated by pressure stimulated by pressure and/or a decrease in oxygen and/or a decrease in oxygen levelslevels

– May feel as if its coming from May feel as if its coming from another area of the body = another area of the body = referred painreferred pain. . http://lpc1.clpccd.cc.ca.us/lpc/zingg/anat/alecture/

alect_stud/ach18_s.ppt.

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Pain Management

Prostaglandins increase pain by sensitizing Prostaglandins increase pain by sensitizing receptorsreceptors

Aspirin and Ibuprofin reduce pain by inhibiting Aspirin and Ibuprofin reduce pain by inhibiting prostaglandin synthesisprostaglandin synthesis

Special Senses

HearingHearing

EquilibriumEquilibrium

VisionVision

OlfactionOlfaction

TasteTaste

Hearing

The ear is composed of three regions:The ear is composed of three regions:– The outer ear, the middle ear, and the The outer ear, the middle ear, and the

inner earinner ear

Ear Structure and Function

The outer earThe outer ear– Consists of the Consists of the pinnapinna

and the and the auditory auditory canalcanal..

– Collects sound Collects sound waves and passes waves and passes them to the eardrum, them to the eardrum, a sheet of tissue that a sheet of tissue that separates the outer separates the outer ear from the middle ear from the middle ear.ear.http://www.lhsc.on.ca/cochlear/images/sound2.jpg


When sound waves When sound waves strike the eardrum,strike the eardrum,– It vibrates and It vibrates and

passes the sound passes the sound waves to three small waves to three small bones.bones.

http://www.hawkeyecollege.edu/faculty/cdostal/A&P%20Powerpoints/Special%20Senses.ppt#287,34,Slide 34


The inner earThe inner ear– Consists of fluid-filled Consists of fluid-filled

channels in the channels in the bones of the skull.bones of the skull.

Semicircular canals—Semicircular canals—equilibriumequilibrium

Cochlea—hearing Cochlea—hearing

http://lpc1.clpccd.cc.ca.us/lpc/zingg/anat/alecture/alect_stud/ach18_s.ppt.


Organ of Corti

Actual hearing organActual hearing organ

– Is found within the cochlea.Is found within the cochlea.

– Consists of hair cells, the receptor cells of the Consists of hair cells, the receptor cells of the ear.ear.

Hearing

When sound waves are collected by the outer ear,When sound waves are collected by the outer ear,– They are transmitted eventually to the cochlea.They are transmitted eventually to the cochlea.– Hair cells in the organ of Corti bend, which Hair cells in the organ of Corti bend, which

triggers nerve cells to send signals to the brain.triggers nerve cells to send signals to the brain.

Auditory Pathway

Cochlear branch of CN VIII

To inferior colliculus of opposite side of midbrain

To cochlear nucleus of medulla

To thalamus

To auditory cortex

Louder soundsLouder sounds– Cause greater movement of the hair cells Cause greater movement of the hair cells

and more action potentials.and more action potentials.


Deafness, the loss of hearing, can be caused by infections, injury, Deafness, the loss of hearing, can be caused by infections, injury, or overexposure to loud noises.or overexposure to loud noises.– Conduction hearing lossConduction hearing loss– Sensorineurial hearing lossSensorineurial hearing loss

Hearing Problems

Conduction Hearing Loss

Caused by anything that interferes with the Caused by anything that interferes with the transmission of sound from the outer to the inner ear. transmission of sound from the outer to the inner ear. – Middle ear infections (otitis media). Middle ear infections (otitis media). – Blockage of the outer ear, most commonly by wax. Blockage of the outer ear, most commonly by wax. – Otosclerosis—ossicles of the middle ear harden —ossicles of the middle ear harden

and become less mobile. and become less mobile. – Damage to the ossicles, for example by serious Damage to the ossicles, for example by serious

infection or head injury. infection or head injury. – Perforated eardrum, caused by an untreated ear Perforated eardrum, caused by an untreated ear

infection, head injury or a blow to the ear, or from infection, head injury or a blow to the ear, or from poking something in your ear. poking something in your ear.

Information from: http://www.deafness-and-hearingaids.net/2007/10/25/conductive-and-sensorineural-hearing-loss/

Sensorineural Hearing Loss Due to damage to the pathway that sound impulses take from the Due to damage to the pathway that sound impulses take from the

hair cells of the inner ear to the auditory nerve and the brain. hair cells of the inner ear to the auditory nerve and the brain. – Age-related hearing loss (presbyacusis). It’s partly due to the Age-related hearing loss (presbyacusis). It’s partly due to the

loss of hair cells in the cochlea. loss of hair cells in the cochlea. – Acoustic trauma (injury caused by loud noise) can damage Acoustic trauma (injury caused by loud noise) can damage

hair cells. hair cells. – Certain viral or bacterial infections such as mumps or Certain viral or bacterial infections such as mumps or

meningitis meningitis – Certain drugs, such as some powerful antibiotics, can cause Certain drugs, such as some powerful antibiotics, can cause

permanent hearing loss. permanent hearing loss. – Acoustic neuroma. This is a benign tumor affecting the Acoustic neuroma. This is a benign tumor affecting the

auditory nerve. It needs to be observed and is sometimes auditory nerve. It needs to be observed and is sometimes treated with surgery. treated with surgery.

– Other neurological (affecting the brain or nervous system) Other neurological (affecting the brain or nervous system) conditions such as multiple sclerosis, stroke, or a brain tumor. conditions such as multiple sclerosis, stroke, or a brain tumor.

Information from: http://www.deafness-and-hearingaids.net/2007/10/25/conductive-and-sensorineural-hearing-loss/

Organs of EquilibriumOrgans of Equilibrium

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Receptor cells are in two structures

Vestibule

Semicircular canals

Figure 8.16a, b

Organs of Equilibrium


Equilibrium has two functional parts

Static equilibrium – sense of gravity at rest

Dynamic equilibrium – angular and rotary head movements

Figure 8.16a, b

Equilibrium

Inner ear detects the Inner ear detects the position of the body with position of the body with respect to gravity and respect to gravity and the motion of the body. the motion of the body.

http://www.mnstate.edu/rodenb/Human%20Biology/senses%20lec%20handout.pdf

Vision

– The human eyesThe human eyes Are able to detect a multitude of visual Are able to detect a multitude of visual

stimuli.stimuli.

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Structure of the Human Eye

Function of the Structures

ScleraSclera

– Is the outer Is the outer covering.covering.

Cornea Cornea

– Lets light into Lets light into the eye and the eye and also helps also helps focus light.focus light.


IrisIris– Regulates the size of Regulates the size of

the pupil, which lets the pupil, which lets light into the interior light into the interior of the eye.of the eye.

LensLens– Focuses light onto Focuses light onto

the retina by the retina by refracting light rays refracting light rays and changing shape.and changing shape.


Two fluid-filled Two fluid-filled chambers make up the chambers make up the bulk of the eye.bulk of the eye.– The large chamber is The large chamber is

filled with vitreous filled with vitreous humor.humor.

– The small chamber The small chamber contains aqueous contains aqueous humor.humor.

Accomodation

Accomplished by Accomplished by changing the curvature changing the curvature of the lensof the lens– For distant objects, For distant objects,

the lens needs to be the lens needs to be made flattermade flatter

– For near objects the For near objects the lens needs to be lens needs to be made thicker and made thicker and more rounded more rounded

Seeing in Color

Built into the human retinaBuilt into the human retina– Are two types of photoreceptors named for their Are two types of photoreceptors named for their

shapes.shapes.


Photoreceptors

ConesCones– Are stimulated by bright light and can distinguish color.Are stimulated by bright light and can distinguish color.

3 types which distinguish red wavelengths, blue 3 types which distinguish red wavelengths, blue wavelengths, and green wavelengthswavelengths, and green wavelengths

– Contain visual pigments, photopsins, which absorb bright light.Contain visual pigments, photopsins, which absorb bright light.

http://www.medgadget.com/archives/img/retinal_layers.jpg

Photoreceptors

RodsRods– Are extremely sensitive to light and enable us to Are extremely sensitive to light and enable us to

see in dim light, though only in shades of gray.see in dim light, though only in shades of gray.– Contain a visual pigment, rhodopsin, which can Contain a visual pigment, rhodopsin, which can

absorb dim light.absorb dim light.

Photoreceptors

The fovea contains a high concentration of cones and The fovea contains a high concentration of cones and is the retina’s center of focus.is the retina’s center of focus.

Rods are concentrated in the peripheral regionsRods are concentrated in the peripheral regions

Visual Pathway

Optic chiasma - optic Optic chiasma - optic nerves partially cross (right nerves partially cross (right side of the field of each eye side of the field of each eye combining and going to the combining and going to the lateral geniculate on the lateral geniculate on the right, those from the left to right, those from the left to the left) the left)

Vision Problems and Corrections Three of the most common visual problemsThree of the most common visual problems

– Are nearsightedness, farsightedness, and Are nearsightedness, farsightedness, and astigmatism.astigmatism.

– Result from focusing problems.Result from focusing problems.– Can be helped by corrective lenses or Can be helped by corrective lenses or

surgical procedures.surgical procedures.

Nearsightedness (myopia)

Occurs when the eyeball is longer than Occurs when the eyeball is longer than normal.normal.

Farsightedness (hyperopia)

Occurs when the eyeball is shorter than normal.Occurs when the eyeball is shorter than normal.

Astigmatism

Blurred vision Blurred vision caused by a caused by a misshapen lens or misshapen lens or cornea.cornea.

Glasses and Glasses and contacts can be contacts can be used to correct used to correct problemproblem

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Chemical Senses – Taste and SmellChemical Senses – Taste and Smell


Both senses use chemoreceptors

Stimulated by chemicals in solution

Taste has four types of receptors

Smell can differentiate a large range of chemicals

Both senses complement each other and respond to many of the same stimuli

Olfaction – The Sense of SmellOlfaction – The Sense of 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

Olfaction – The Sense of SmellOlfaction – The Sense of Smell

Olfactory Pathways

Receptor neurons pass into cranium through cribiform Receptor neurons pass into cranium through cribiform plate and synapse in olfactory bulbs.plate and synapse in olfactory bulbs.

Olfactory neurons are the only neurons knownOlfactory neurons are the only neurons known1.1. to routinely replace themselves to routinely replace themselves 2.2. to reach the cerebrum without synapsing in the to reach the cerebrum without synapsing in the

thalamus thalamus

Olfactory discrimination - Although difficult to describe, Olfactory discrimination - Although difficult to describe, the number of different odors recognizable is the number of different odors recognizable is immense. immense.

The Sense of TasteThe Sense of Taste


Taste buds house the receptor organs

Location of taste buds Most are on

the tongue

Soft palate

Cheeks Figure 8.18a, b

The Tongue and TasteThe Tongue and Taste


The tongue is covered with projections called papillae

Filiform papillae – sharp with no taste buds

Fungifiorm papillae – rounded with taste buds

Circumvallate papillae – large papillae with taste buds

Taste buds are found on the sides of papillae

Structure of Taste BudsStructure of Taste Buds

Gustatory cells are the receptors– Have gustatory hairs

(long microvilli)– Hairs are stimulated

by chemicals dissolved in saliva

http://www.lrn.org/Graphics/Senses/figure%208.8.gif

Taste SensationsTaste Sensations

Slide 8.41Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Sweet receptors Sugars Saccharine Some amino acids

Sour receptors Acids

Bitter receptors Alkaloids

Salty receptors Metal ions

Gustatory Pathway Gustatory Pathway

Impulses are carried to the gustatory complex by several cranial nerves because taste buds are found in different areas– Facial nerve– Glossopharyngeal

nerve– Vagus nerve

General and Special Senses Ch. 49 AP Biology Ms. Haut.

Documents

sensory receptors of

sensory stimuli

visceral receptors

visceral pain

sensationsstretch receptors

referred pain

blood pressure

summationin sensory