Sensory systems Chapter 50. Five senses Touch Taste Smell Sound Vision.

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Sensory systems Chapter 50

Transcript of Sensory systems Chapter 50. Five senses Touch Taste Smell Sound Vision.

Sensory systems

Chapter 50

Five senses

TouchTaste SmellSoundVision

Sensory systems

Sensory info is receivedNerve impulse or action potential All or nothing responseResponse depends on part of brain that receives the info

Sensory information

Sensory info to CNS1. Sensory reception 2. TransductionGraded potentialIon channels open or closeReceptor potentialChange in membrane potentialDepolarization

Sensory information

3. TransmissionGoes to CNS via afferent pathway4. InterpretationPerception by the brain

Sensory receptors

Nerve endingsSpecialized neurons or epithelial cells Associated with sensory organs -eyesAll stimuli is a form of energy

Sensory receptors

Stimuli-outside bodyHeat, light, pressure & chemicalsStimuli-inside bodyBP, body position, body temperature

Types of sensory receptors

Mechanoreceptors– Pressure, stretch, touch

Chemoreceptors – chemicals

Electromagnetic receptors (photoreceptors) Nociceptors (pain)Thermoreceptors

Receptors

Cutaneous receptors: SkinHeat, cold, pressure, pain & touchThermoreceptorsHeat/Cold Hypothalamus – Regulates temp of blood (core temp)

Receptors

MechanoreceptorsTouchClose to surface of skinHair follicle receptorsPressure Deeper

skin

Connectivetissue

Heat

Strongpressure

Hairmovement

Nerve

Dermis

Epidermis

Hypodermis

Gentletouch

Pain Cold Hair

Receptors

Nociceptors:PainSevere temperature changeTissue damageFree nerve endings (naked dendrites)Located in the epidermis

PAIN

Receptors

ProprioceptorsGive info on animal’s body parts Position MovementStretch receptors on musclePrevent over stretch

Receptors

Baroreceptors:Detect tension or stretch in blood vessel wallsInternal carotids Aortic archDrop in BP Stimulation to increase HR & vasoconstriction

Receptors

Chemoreceptor Aorta & carotidMedulla oblongatapH (blood & CSF)Slow breathingIncreased CO2

Lowers pHCauses an increased respiration rate

Taste

Taste budsCollections of receptor cellsEpithelial cellsPapillaeRaised areas on tongue Taste buds located

Taste

Taste buds contain 50-100 taste cellsFood dissolves in saliva Contact taste cellsTaste salty, sweet, sour, bitter

Taste

ChemoreceptorsSalt: Na+1

Sour: H+1

Directly through ion-channel Sweet: receptor proteins for sugarBitter: K+channels are closed by receptor proteins

Papillae

Papilla

TastebudsTongue

(a) The tongue

Taste bud

Sensoryneuron

Sensoryreceptorcells

SweetSaltySourBitterUmami

(b) A taste bud

Tastepore

Foodmolecules

Sweet

G proteinSugar molecule

Phospholipase C

Tongue

Sodiumchannel

PIP2

Na+

IP3

(secondmessenger)

Sweetreceptor

ER

Nucleus

Taste pore

SENSORYRECEPTORCELL

Ca2+

(secondmessenger)

IP3-gatedcalciumchannel

Sensoryreceptorcells

Tastebud

Sugarmolecule

Sensoryneuron

Smell

Olfactory receptorsChemoreceptors Located upper portions of nasal passagesDendrites are in ciliaAxon goes directly to cerebral cortexOdorant or odorous substance binds proteins Second messenger response in receptor cell

Smell

Opens membrane to Ca & Na Causes impulse (action potential)Distinguish thousands of odorsVery accurateSingle odorant molecule

NOSE

Nose

Olfactorybulb

Odorants

Bone

Epithelialcell

Plasmamembrane

Odorantreceptors

Odorants

Nasal cavity

Brain

Chemo-receptor

Cilia

Mucus

Action potentials

Hearing

Outer ear:Pinna, canalMiddle ear:Tympanic membrane (ear drum)Eustachian tubeSmall bones (malleus, incus, stapes)Inner ear:Cochlea, auditory nerve

Figure 50.10a

Outer ear Middle ear Inner ear

Skullbone

Malleus

Incus

Stapes

Auditorycanal

Tympanicmembrane

Ovalwindow

Roundwindow

Cochlea

Eustachiantube

Semicircularcanals

Auditorynerve to brain

Pinna

Ear

Hearing

Vibrations move in canalCause eardrum to moveVibrations pass through the bonesStapes pass vibration to inner earCauses pressure waves in fluid in cochleaBasilar membrane of the cochlea vibrates

Hearing

Hair cells on membrane vibrateLeads to change in membrane potentials in sensory neuronsSound interpretedHumans hear 20-20,000 hertzAge decreases higher frequenciesDogs hear sounds at 40,000 hertz

Ears

Inner earBody position & balanceTwo chambers near the cochleaUtricle & sacculeFilled with fluidHair cells in chambers respond to changes in head positions

Ears

Utricle: horizontal motionSaccule: vertical motionDifferent movement causes different sensory neurons to be stimulateLabyrinth systemSpin around become dizzy

Equilibrium

Vestibular nerve

Semicircular canals

Saccule

Utricle Body movement

Hairs

Cupula

Flow of fluid

Axons

Haircells

Vestibule

Eye

Sclera: White outer layer of connective tissueConjunctiva: Epithelial layerCovers outer surface of sclera Under surface of the eyelidCornea: Clear part of sclera, light passes through

Eye

Choroid Pigmented layer under the scleraIrisColor part of eye formed by the choroidPupilOpening at the center of the irisControlled by irisLensBehind the pupil, held in place by ligaments

Eye

RetinaBack of eye where image is focusedOptic nerve Sensory neuronsVitreous humorJellylike substance behind the lensAqueous humorThinner fluid Fills smaller chamber in front of the lens

EYE

ScleraChoroid

Retina

Fovea

Optic nerve

Centralartery andvein ofthe retina

Optic disk

Vitreoushumor

Lens

Aqueoushumor

Pupil

Iris

Cornea

Suspensoryligament

Eye

Light enters eye through cornea Passes through pupil to lensLens focuses images on retinaPhotoreceptor cells of retina transduce light energyAction potentials pass via sensory neurons in the optic nerve

Eye

Rods & conesPhotoreceptors of eyesRods: black and white vision in dim lightCones: high visual acuity & color visionLocated in center of retina

EYE

Rods/cones

Retina

Retina

Photoreceptors

Light

Optic nerve

Light

Tobrain

Choroid

NeuronsCone Rod

Ganglioncell

Opticnerveaxons

Amacrinecell Horizontal

cell

Bipolarcell

Pigmentedepithelium

Figure 50.17ba

Rod

Rod

Cone

Cone

Synapticterminal

Cellbody

Outersegment

Disks

Eyes

Binocular visionAxons of ganglion cells form optic nervesOptic nerves meet at the optic chiasm (base of the cerebral cortex)Visions from the right visual field go to the left side of the brain and vise versaThalamusCortex

Vision

Rightvisualfield

Righteye

Leftvisualfield

Lefteye

Opticchiasm

Primaryvisual cortex

Lateralgeniculatenucleus

Optic nerve

Near and Distance Vision

Eyes

Nearsightedness: longer eyeballFarsightedness: shorter eyeballAsitgmatism: problems with lens or cornea Light rays converge unevenlyColorblindness: inherited lack of one or more types of cones