Chapter 49
description
Transcript of Chapter 49
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Chapter 49
Sensory and Motor Mechanisms
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Types of Sensory Receptors
– Mechanoreceptors
– Chemoreceptors
– Electromagnetic receptors
– Thermoreceptors
– Pain receptors
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Connectivetissue
Heat
Strongpressure
Hairmovement
Nerve
Dermis
Epidermis
Hypodermis
Gentletouch
Pain Cold Hair
Mechanoreceptors- sense physical deformation caused by stimuli such as pressure, stretch, motion, and sound
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Chemoreceptors
• General chemoreceptors transmit information about the total solute concentration of a solution
• Specific chemoreceptors respond to individual kinds of molecules
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(a) Rattlesnake
(b) Beluga whales
Eye
Infraredreceptor
Electromagnetic Receptors- detect electromagnetic energy such as light, electricity, and magnetism
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Thermoreceptors, Pain Receptors
• Thermoreceptors- respond to heat or cold
• Pain Receptors- respond to excess heat, pressure, or chemicals released from damaged or inflamed tissues
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Auditorycanal
EustachiantubePinna
Tympanicmembrane
Ovalwindow
Roundwindow
Stapes
Cochlea
IncusMalleus
Semicircularcanals
Auditory nerveto brain
Skullbone
Outer earMiddle
ear Inner ear
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Hearing
• Vibrating objects create percussion waves in the air that cause the tympanic membrane to vibrate
• Hearing is the perception of sound in the brain from the vibration of air waves
• The three bones of the middle ear transmit the vibrations of moving air to the oval window on the cochlea
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• These vibrations create pressure waves in the fluid in the cochlea that travel through the vestibular canal
• Pressure waves in the canal cause the basilar membrane to vibrate, bending its hair cells
• This bending of hair cells depolarizes the membranes of mechanoreceptors and sends action potentials to the brain via the auditory nerve
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Axons ofsensory neurons
Vibration
Basilar membrane
Apex
Ovalwindow Vestibular
canal
Stapes
BaseRoundwindow
Tympaniccanal Fluid
(perilymph)
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Basilar membrane
Apex
Flexible end ofbasilar membrane
500 Hz(low pitch)
16 kHz(high pitch)
Base(stiff)
8 kHz
4 kHz
2 kHz
1 kHz
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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
Taste
Receptor cells for taste are modified epithelial cells organized into taste buds
Five taste perceptions: sweet, sour, salty, bitter, and umami (elicited by glutamate)
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Smell
• Olfactory receptor cells are neurons that line the upper portion of the nasal cavity
• Binding of odorant molecules to receptors triggers a signal transduction pathway, sending action potentials to the brain
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Olfactorybulb
Odorants
Bone
Epithelialcell
Plasmamembrane
Odorantreceptors
Odorants
Nasal cavity
Brain
Chemo-receptor
Cilia
Mucus
Action potentials
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Vision
– Iris: regulates the size of the pupil
– Retina: contains photoreceptors
– Lens: focuses light on the retina
– Optic disk: a blind spot in the retina where the optic nerve attaches to the eye
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• Light is focused by changing the shape of the lens
• The retina contains two types of photoreceptors: rods and cones
– Rods are light-sensitive but don’t distinguish colors
– Cones distinguish colors but are not as sensitive to light
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Opticnerve
Fovea (centerof visual field)
Lens
Vitreous humorOptic disk(blind spot)
Central artery andvein of the retina
Iris
RetinaChoroidSclera
Ciliary body
Suspensoryligament
Cornea
Pupil
Aqueoushumor
Animation: Near and Distance Vision
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Rightvisualfield
Righteye
Leftvisualfield
Lefteye
Opticchiasm
Primaryvisual cortexLateral
geniculatenucleus
Optic nerve
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Skeletal Muscle
• Characterized by a hierarchy of smaller and smaller units
• A skeletal muscle consists of a bundle of long fibers, each a single cell, running parallel to the length of the muscle
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• Each muscle fiber is itself a bundle of smaller myofibrils arranged longitudinally
• The myofibrils are composed to two kinds of myofilaments:
– Thin filaments consist of two strands of actin and one of regulatory protein
– Thick filaments are staggered arrays of myosin molecules
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• Striated muscle- the regular arrangement of myofilaments creates a pattern of light and dark bands
• Sarcomere- the functional unit of a muscle, separated by Z lines
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Bundle ofmuscle fibers
Muscle
Single muscle fiber(cell)
Nuclei
Z lines
Plasma membrane
Myofibril
Sarcomere
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TEM
Thickfilaments(myosin)
M line
Z line Z line
Thinfilaments(actin)
Sarcomere
0.5 µm
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The Sliding-Filament Model of Muscle Contraction
• Filaments slide past each other longitudinally, producing more overlap between thin and thick filaments
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ZRelaxedmuscle
M Z
Fully contractedmuscle
Contractingmuscle
Sarcomere0.5 µm
ContractedSarcomere
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Types of Skeletal Muscle Fibers
• Skeletal muscle fibers can be classified
– As oxidative or glycolytic fibers, by the source of ATP
– As fast-twitch or slow-twitch fibers, by the speed of muscle contraction
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Oxidative fibers- rely on aerobic respiration to generate ATP
• Many mitochondria, a rich blood supply, and much myoglobin
• Myoglobin is a protein that binds oxygen more tightly than hemoglobin does
Glycolytic fibers- use glycolysis as their primary source of ATP
• Less myoglobin than oxidative fibers, and tire more easily
In poultry and fish, light meat is composed of glycolytic fibers, while dark meat is composed of oxidative fibers
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Slow-twitch fibers- contract more slowly, but sustain longer contractions
• All slow twitch fibers are oxidative
Fast-twitch fibers- contract more rapidly, but sustain shorter contractions
• Fast-twitch fibers can be either glycolytic or oxidative
Most skeletal muscles contain both slow-twitch and fast-twitch muscles in varying ratios
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Skeletal systems transform muscle contraction into locomotion
• Skeletal muscles are attached in antagonistic pairs, with each member of the pair working against the other
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GrasshopperHuman
Bicepscontracts
Tricepscontracts
Forearmextends
Bicepsrelaxes
Tricepsrelaxes
Forearmflexes
Tibiaflexes
Tibiaextends
Flexormusclerelaxes
Flexormusclecontracts
Extensormusclecontracts
Extensormusclerelaxes