Sensory systems

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Sensory systems

• Chapter 50

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Five senses

• Touch
• Taste
• Smell
• Sound
• Vision

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Sensory systems

• Sensory info is received
• Nerve impulse or action potential
• All or nothing response
• Response depends on part of brain that receives
  the info

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Sensory information

• Sensory info to CNS
• 1. Sensory reception
• 2. Transduction
• Graded potential
• Ion channels open or close
• Receptor potential
• Change in membrane potential
• Depolarization

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Sensory information

• 3. Transmission
• Goes to CNS via afferent pathway
• 4. Interpretation
• Perception by the brain

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Sensory receptors

• Nerve endings
• Specialized neurons or epithelial cells
• Associated with sensory organs -eyes
• All stimuli is a form of energy

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Sensory receptors

• Stimuli-outside body
• Heat, light, pressure chemicals
• Stimuli-inside body
• BP, body position, body temperature

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Types of sensory receptors

• Mechanoreceptors
• Pressure, stretch, touch
• Chemoreceptors
• chemicals
• Electromagnetic receptors (photoreceptors)
• Nociceptors (pain)
• Thermoreceptors

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Receptors

• Cutaneous receptors
• Skin
• Heat, cold, pressure, pain touch
• Thermoreceptors
• Heat/Cold
• Hypothalamus
• Regulates temp of blood (core temp)

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Receptors

• Mechanoreceptors
• Touch
• Close to surface of skin
• Hair follicle receptors
• Pressure
• Deeper

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skin
Cold
Hair
Heat
Gentletouch
Pain
Epidermis
Dermis
Hypodermis
Hairmovement
Connectivetissue
Strongpressure
Nerve
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Receptors

• Nociceptors
• Pain
• Severe temperature change
• Tissue damage
• Free nerve endings (naked dendrites)
• Located in the epidermis

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PAIN
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Receptors

• Proprioceptors
• Give info on animals body parts
• Position
• Movement
• Stretch receptors on muscle
• Prevent over stretch

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Receptors

• Baroreceptors
• Detect tension or stretch in blood vessel walls
• Internal carotids
• Aortic arch
• Drop in BP
• Stimulation to increase HR vasoconstriction

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Receptors

• Chemoreceptor
• Aorta carotid
• Medulla oblongata
• pH (blood CSF)
• Slow breathing
• Increased CO2
• Lowers pH
• Causes an increased respiration rate

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Taste

• Taste buds
• Collections of receptor cells
• Epithelial cells
• Papillae
• Raised areas on tongue
• Taste buds located

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Taste

• Taste buds contain 50-100 taste cells
• Food dissolves in saliva
• Contact taste cells
• Taste salty, sweet, sour, bitter

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Taste

• Chemoreceptors
• Salt Na1
• Sour H1
• Directly through ion-channel
• Sweet receptor proteins for sugar
• Bitter Kchannels are closed by receptor proteins

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Papilla
Papillae
Tastebuds
Tongue
(a) The tongue
Sweet
Taste bud
Salty
Sour
Bitter
Umami
Tastepore
Foodmolecules
Sensoryreceptorcells
Sensoryneuron
(b) A taste bud
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Sweet
Sugar molecule
G protein
Sweetreceptor
Tongue
Phospholipase C
SENSORYRECEPTORCELL
Sugarmolecule
Taste pore
PIP2
Sensoryreceptorcells
Tastebud
IP3(secondmessenger)
Sodiumchannel
Sensoryneuron
IP3-gatedcalciumchannel
Nucleus
ER
Ca2(secondmessenger)
Na
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Smell

• Olfactory receptors
• Chemoreceptors
• Located upper portions of nasal passages
• Dendrites are in cilia
• Axon goes directly to cerebral cortex
• Odorant or odorous substance binds proteins
• Second messenger response in receptor cell

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Smell

• Opens membrane to Ca Na
• Causes impulse (action potential)
• Distinguish thousands of odors
• Very accurate
• Single odorant molecule

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NOSE
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Nose
Brain
Action potentials
Olfactorybulb
Odorants
Nasal cavity
Bone
Epithelialcell
Odorantreceptors
Chemo-receptor
Plasmamembrane
Cilia
Odorants
Mucus
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Hearing

• Outer ear
• Pinna, canal
• Middle ear
• Tympanic membrane (ear drum)
• Eustachian tube
• Small bones (malleus, incus, stapes)
• Inner ear
• Cochlea, auditory nerve

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Figure 50.10a
Middle ear
Outer ear
Inner ear
Skull bone
Stapes
Semicircularcanals
Incus
Malleus
Auditorynerve to brain
Cochlea
Ovalwindow
Auditorycanal
Eustachiantube
Pinna
Tympanicmembrane
Roundwindow
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Ear
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Hearing

• Vibrations move in canal
• Cause eardrum to move
• Vibrations pass through the bones
• Stapes pass vibration to inner ear
• Causes pressure waves in fluid in cochlea
• Basilar membrane of the cochlea vibrates

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Hearing

• Hair cells on membrane vibrate
• Leads to change in membrane potentials in sensory
  neurons
• Sound interpreted
• Humans hear 20-20,000 hertz
• Age decreases higher frequencies
• Dogs hear sounds at 40,000 hertz

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Ears

• Inner ear
• Body position balance
• Two chambers near the cochlea
• Utricle saccule
• Filled with fluid
• Hair cells in chambers respond to changes in head
  positions

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Ears

• Utricle horizontal motion
• Saccule vertical motion
• Different movement causes different sensory
  neurons to be stimulate
• Labyrinth system
• Spin around become dizzy

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Equilibrium
Semicircular canals
Flow of fluid
Vestibular nerve
Cupula
Hairs
Haircells
Axons
Vestibule
Utricle
Body movement
Saccule
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Eye

• Sclera
• White outer layer of connective tissue
• Conjunctiva
• Epithelial layer
• Covers outer surface of sclera
• Under surface of the eyelid
• Cornea
• Clear part of sclera, light passes through

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Eye

• Choroid
• Pigmented layer under the sclera
• Iris
• Color part of eye formed by the choroid
• Pupil
• Opening at the center of the iris
• Controlled by iris
• Lens
• Behind the pupil, held in place by ligaments

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Eye

• Retina
• Back of eye where image is focused
• Optic nerve
• Sensory neurons
• Vitreous humor
• Jellylike substance behind the lens
• Aqueous humor
• Thinner fluid
• Fills smaller chamber in front of the lens

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EYE
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Choroid
Sclera
Retina
Suspensoryligament
Fovea
Cornea
Iris
Optic nerve
Pupil
Aqueoushumor
Lens
Centralartery andvein ofthe retina
Optic disk
Vitreoushumor
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Eye

• Light enters eye through cornea
• Passes through pupil to lens
• Lens focuses images on retina
• Photoreceptor cells of retina transduce light
  energy
• Action potentials pass via sensory neurons in the
  optic nerve

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Eye

• Rods cones
• Photoreceptors of eyes
• Rods black and white vision in dim light
• Cones high visual acuity color vision
• Located in center of retina

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EYE
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Rods/cones
Retina
Choroid
Photoreceptors
Neurons
Retina
Cone
Rod
Light
Tobrain
Optic nerve
Light
Ganglioncell
Amacrinecell
Horizontalcell
Opticnerveaxons
Bipolarcell
Pigmentedepithelium
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Figure 50.17ba
Rod
Disks
Synapticterminal
Outersegment
Cellbody
Cone
Rod
Cone
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Eyes

• Binocular vision
• Axons of ganglion cells form optic nerves
• Optic 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 versa
• Thalamus
• Cortex

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Vision
Rightvisualfield
Opticchiasm
Righteye
Lefteye
Leftvisualfield
Optic nerve
Primaryvisual cortex
Lateralgeniculatenucleus
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Near and Distance Vision
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Eyes

• Nearsightedness longer eyeball
• Farsightedness shorter eyeball
• Asitgmatism problems with lens or cornea
• Light rays converge unevenly
• Colorblindness inherited lack of one or more
  types of cones