sensory systems chapter 50. five senses touch taste smell sound vision
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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)
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
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
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
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
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
Rods/cones
Retina
Retina
Photoreceptors
Light
Optic nerve
Light
Tobrain
Choroid
NeuronsCone Rod
Ganglioncell
Opticnerveaxons
Amacrinecell Horizontal
cell
Bipolarcell
Pigmentedepithelium
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
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