CHAPTER 28 Nervous Systems
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Transcript of CHAPTER 28 Nervous Systems
BIOLOGYCONCEPTS & CONNECTIONS
Fourth Edition
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
From PowerPoint® Lectures for Biology: Concepts & Connections
CHAPTER 28Nervous Systems
Modules 28.1 – 28.9
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Three interconnected functions
– Sensory input (sensory neurons)
– Integration (interneurons)
– Motor output (motor neurons)
28.1 Nervous systems receive sensory input, interpret it, and send out appropriate commands
NERVOUS SYSTEM STRUCTURE AND FUNCTION
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Figure 28.1A
Sensory receptor
SENSORY INPUT
INTEGRATION
MOTOR OUTPUT
Effector
Peripheral nervoussystem (PNS)
Central nervoussystem (CNS)
Brain and spinal cord
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• NS: 2 divisions
– CNS: brain & spinal cord
– PNS: nerves that carry info into and out of CNS
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Figure 28.1B
Brain
1 Sensoryreceptor 2 Sensory neuron
3
4
Ganglion
Motorneuron Spinal
cord
Interneuron
CNS
Nerve
PNS
Quadricepsmuscles
Flexormuscles
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• Neurons - cells transmit nervous impulses
• Made of
– a cell body
– dendrites (highly branched fibers)
– an axon (long fiber)
28.2 Neurons are the functional units of nervous systems
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• Supporting cells protect, insulate, and reinforce neurons
• Myelin sheath - insulating material in vertebrates
– Made of Schwann cells linked by nodes of Ranvier
– Speeds up signal transmission
– Multiple sclerosis (MS) involves the destruction of myelin sheaths by the immune system
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Figure 28.2
Signal direction Dendrites
Cellbody
Cell body
Nucleus
Axon
Schwann cell
Signalpathway
Myelin sheath
Nodes ofRanvier
Synaptic knobs
Node of Ranvier
Myelin sheath
Schwann cell
Nucleus
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• Resting potential
• (+) outside and (- 70 mv) inside
28.3 A neuron maintains a membrane potential across its membrane
NERVE SIGNALS AND THEIR TRANSMISSION
Plasmamembrane
Microelectrodeinside cell
Axon
Neuron
Microelectrodeoutside cell
Voltmeter
–70 mV
Figure 28.3A
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• Stimulus changes permeability of part of plasma membrane
– Ions pass through plasma membrane, changing membrane’s voltage
– Causes nerve signal (electrical) to be generated
28.4 A nerve signal begins as a change in the membrane potential
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• Action potential - nerve signal
– Electrical change in plasma membrane voltage (charge) from the resting potential to maximum level and back to resting potential
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Ions and channels involved
• Sodium (Na+) outside, Potassium (K+) inside
• Voltage gated (Na+) and (K+) channels where specific ions go through are found in EACH node
• Change in voltage opens channels, and ions go from hi-lo concn
• Sodium/Potassium pump restores resting potential
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Figure 28.4
Resting state: voltage gated Na+
and K+ channels closed; restingpotential is maintained.
1
2
3
4
A stimulus opens some Na+channels; if threshold is reached,action potential is triggered.
Additional Na+ channels open,K+ channels are closed; interior ofcell becomes more positive.
5 The K+ channels closerelatively slowly, resulting In REFRACTORY periodWhere the node is unable To be stimulated
Na+ channels close andinactivate. K+ channelsopen, and K+ rushesout; interior of cell morenegative than outside.
Neuroninterior
Actionpotential
Thresholdpotential
Resting potential
1
2
3
4
5
Na+
Na+
Na+
Na+
1 Return to resting state.
1
Neuroninterior
K+
K+
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Polarized / Depolarized / Repolarized / Hyperpolarized
• POLARIZED
resting potential – opposite sides of membranes have opposite charges ( - inside / + outside)
• DEPOLARIZED
when membrane reaches threshold – 50 mV, Na+ gates open and Na+ rush in, changing inside to +++
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Polarized / Depolarized / Repolarized / Hyperpolarized
• REPOLARIZED
Na+ gates close, K+ gates open and K+ rush out, making inside membrane (-) again
• HYPERPOLARIZED
K+ gates stay open longer; more K+ rush out and cell becomes – 90 mV = REFRACTORY PERIOD (node is temp unstimulatable)
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HYPERPOLARIZED -> RESTING POTENTIAL
• Na+ / K+ pump pumps Na+ out and K+ in to restore RP (-70 mV)
• Some Na+ move to next node to change charge if reach – 50 mV, next Na+ gate opens
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Figure 28.4
RESTING POTENTIAL1
2
3
4
REACHING THRESHOLD
DEPOLARIZATION
5 HYPERPOLARIZATIONRefractory Period
REPLORIZATION
Neuroninterior
Actionpotential
Thresholdpotential
Resting potential
1
2
3
4
5
Na+
Na+
Na+
Na+
1 Return to resting state.
1
Neuroninterior
K+
K+
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28.5 The action potential propagates itself along the neuron
Figure 28.5
1
2
3
Axon
Action potential
Axonsegment
Action potential
Na+
Na+
K+
K+
Action potential
Na+
K+
K+
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• Action potential: all-or-none event
– Stronger the stimulus = more AP coming through nodes (instead of stronger AP)
ex. Tap on finger versus hammer hitting finger
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• Synapse:
– Space between two neurons or between a neuron and target (muscle) cell
• Synapses - either electrical or chemical
– Electrical: Action potentials pass between cells w/o neurotransmitter
– Chemical: neurotransmitters cross synaptic cleft to bind to receptors on surface of the receiving cell
28.6 Neurons communicate at synapses
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Figure 28.6
1
Actionpotentialarrives
2
Vesicle fuses with plasma membrane
3
Neurotransmitteris released intosynaptic cleft
Axon ofsendingneuron
Vesicles
SENDINGNEURON
Synapticknob SYNAPSE
SYNAPTICCLEFT
RECEIVINGNEURON
Ion channels
Neurotransmittermolecules
4
Neuro-transmitterbinds to receptor
Receivingneuron
5 Ion channel opens
Receptor
Ions
Neurotransmitter
6 Ion channel closes
Neurotransmitter brokendown and released
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• Excitatory NT: open Na+ gates for AP to move forward
• Inhibitory NT: open Cl- gates = decrease next cell’s ability to develop AP
• Summation: total excitation and inhibition determines whether or not next cell will move signal forward (AP go forward)
28.7 Chemical synapses make complex information processing possible
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• Neuron receiving input from 100s other neurons
Figure 28.7
Dendrites Synaptic knobs
Myelinsheath
Receivingcell body
AxonSynapticknobs
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• Radially symmetrical animals = nerve net
– Example: Hydras
28.10 Nervous system organization usually correlates with body symmetry
NERVOUS SYSTEMS
Figure 28.10A
A. Hydra (cnidarian)
Nervenet
Neuron
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• Most bilaterally symmetrical animals exhibit– Cephalization:concentration of nervous
system in head region
– Centralization: presence of CNS
Figure 28.10B-E
B. Planarian (flatworm)
Eye
Brain
Nervecord
Transversenerve
C. Leech (annelid)
Brain
Ventralnervecord
Segmentalganglion
D. Insect (arthropod)
Brain
Ventralnervecord
Ganglia
Brain
Giantaxon
E. Squid (mollusk)
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28.11 Vertebrate nervous systems are highly centralized and cephalized
Figure 28.11A
CENTRAL NERVOUSSYSTEM (CNS)
PERIPHERALNERVOUSSYSTEM (PNS)
Brain
Spinal cord
Cranialnerve
Spinalnerves
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• The brain and spinal cord contain fluid-filled spaces
Figure 28.11B
BRAIN Meninges
Ventricles
Central canalof spinal cord
Spinal cord
White matter
Gray matterDorsal rootganglion(part of PNS)
Central canal Spinal nerve(part of PNS)
SPINAL CORD(cross section)
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28.12 The peripheral nervous system of vertebrates is a functional hierarchy
Figure 28.12A
Peripheralnervous system
Sensorydivision
Motordivision
Sensingexternal
environment
Sensinginternal
environment
Autonomicnervous system
(involuntary)
Somaticnervous system
(voluntary)
Sympatheticdivision
Parasympatheticdivision
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• Motor division of the PNS
– Autonomic nervous system: involuntary control over the internal organs
– Somatic nervous system: voluntary control over skeletal muscles
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• Autonomic NS:
– Parasympathetic division: resting / digesting
– Sympathetic division: fight / flight
28.13 Opposing actions of sympathetic and parasympathetic neurons regulate the internal environment
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Figure 28.13
PARASYMPATHETIC DIVISION SYMPATHETIC DIVISION
Brain
Constrictspupil
Stimulatessalivaproduction
Constrictsbronchi
Slowsheart
Stimulatesstomach,pancreas,and intestines
Stimulatesurination
Spinalcord
Eye
Salivaryglands
Lung
Heart
LiverStomach
Adrenalgland
Pancreas
Intestines
Bladder
Dilatespupil
Inhibitssalivaproduction
Relaxesbronchi
Acceleratesheart
Stimulatesepinephrineand norepi-nephrine release
Stimulatesglucoserelease
Inhibitsstomach,pancreas,and intestines
Inhibitsurination
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Figure 28.15A
Forebrain
Cerebrum
Thalamus
Hypothalamus
Pituitary gland
Midbrain
Hindbrain
Pons
Medullaoblongata
Cerebellum
Spinal cord
Cerebralcortex
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• Hemisphere – left/right
Figure 28.15B
Left cerebralhemisphere
Right cerebralhemisphere
Corpuscallosum
Basalganglia
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• Cerebral cortex: voluntary motion; higher function (memory and creativity); conscious mind; speech; problem solving; sensations – smell, sights, temperature, etc
• Olfactory lobe: smell
• Thalamus: relay sensory input and distribute to appropriate part of cerebral cortex
• Hypothalamus: body homeostasis – hormone level, temperature, hunger, thirst, pain, etc
28.16 Parts of CNS / Brain
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• Pons: relay center cerebellum
• Medulla (oblongata): vital functions – breathing, heart rate, CO2 level
• Cerebellum: muscle movement and balance
• Spinal cord: brain to body – reflex arc
BIOLOGYCONCEPTS & CONNECTIONS
Fourth Edition
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
From PowerPoint® Lectures for Biology: Concepts & Connections
CHAPTER 29The Senses
Modules 29.1 – 29.3
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Sensation
– Awareness of sensory stimuli
• Perception
– Brain’s full integration of sensory data
29.1 Sensory inputs become sensations and perceptions in the brain
Figure 29.1
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• Sensory receptors (sight, touch, sound, smell, taste)
29.2 Sensory receptor cells convert stimuli into electrical energy
SENSORY RECEPTION
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Figure 29.2A
Taste bud anatomy1
2 Sugarbinding
Tongue Taste pore
Taste bud
Sugarmolecule
Sensoryreceptorcells
Sensory neuron
Receptor cellmembrane
Sugar molecule
Ionchannels
Ion
3 Receptorpotential
4 Synapse
Sensoryreceptorcell
Neuro-transmittermolecules
Sensoryneuron
Action potential
5 Action potentials
No sugar Sugar present
mV
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• Action potentials transmitted to CNS via sensory neurons
• Brain distinguishes different types of stimuli
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Figure 29.2B
Sugarreceptor
BRAIN
Interneurons
Saltreceptor
Sensoryneurons
TASTEBUD
No salt
Increasing sweetness Increasing saltiness
No sugar
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• Pain receptors
– Sense dangerous stimuli
• Thermoreceptors
– Detect heat or cold
• Mechanoreceptors
– Respond to mechanical energy (touch, pressure, and sound)
29.3 Specialized sensory receptors detect five categories of stimuli
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Figure 29.3A
Heat Lighttouch
Pain Cold (Hair) Lighttouch
Epidermis
Dermis
Nerve Touch Strongpressure
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• Stretch receptors and hair cells are two types of mechanoreceptors
Figure 29.3B
“Hairs” ofreceptor cell
Neurotransmitterat synapse
Sensoryneuron
Actionpotentials
Moreneurotransmitter
(1) Receptor cell at rest (2) Fluid moving in one direction
Lessneurotransmitter
(3) Fluid moving in other direction
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• Electromagnetic receptors
– Respond to electricity, magnetism, and light
• Photoreceptors sense light
– They are the most common electromagnetic receptors
Figure 29.3D
Eye
Infraredreceptor
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29.5 Vertebrates have single-lens eyes
Figure 29.5
Sclera
Muscle
Ligament
Iris
Pupil
Cornea
Aqueoushumor
Lens
Vitreoushumor
Choroid
Retina
Fovea(center ofvisual field)
Opticnerve
Arteryand vein
Blind spot
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• Human eye
– Cornea and lens focus light on photoreceptor cells in the retina
– Photoreceptors most concentrated in fovea
– two eyes compensates for blind spot
– blind spot optic nerve passes through retina
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Figure 29.6
Muscle contracted
Ligaments
Light from anear object Lens
Choroid
Retina
NEAR VISION(ACCOMMODATION)
DISTANCE VISION
Muscle relaxed
Light from adistant object
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• photoreceptor cells
• Rods (contrast – black/white)
– Cones (color)
29.8 Our photoreceptor cells are rods and cones
Figure 29.8A
Cell body
Synapticknobs
Membranous discscontaining visual pigments
ROD
CONE
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Figure 29.8B
Retina
Opticnerve
Fovea
Opticnervefibers
Retina
Photoreceptors
Neurons Cone Rod
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– outer ear channels sound waves to eardrum
29.9 The ear converts air pressure waves into action potentials that are perceived as sound
HEARING AND BALANCE
Figure 29.9A
OUTER EARMIDDLE
EAR INNER EAR
Pinna Auditorycanal Eustachian
tube
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– The eardrum passes vibrations to chain of bones in middle ear
Figure 29.9B
Stirrup
Anvil
Hammer
Skull bones
Semicircular canals(function in balance)
Auditory nerve,to brain
Cochlea
EardrumOval window(behind stirrup)
Eustachian tube
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– bones transmit vibrations to fluid in cochlea, which houses organ of Corti
– Vibrations in cochlear fluid move hair cells (mechanoreceptors) against overlying membrane
– Bending hair cells trigger nerve signals to brain via the auditory nerve
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Middlecanal
Bone
Cross sectionthrough cochlea ORGAN OF CORTI
Lowercanal
Uppercanal
Auditorynerve
Hair cells
Overlying membrane
Sensoryneurons
Basilarmembrane To auditory nerve
Figure 29.9C
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• Louder sounds generate
– more action potentials are generated
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Figure 29.9D
OUTER EAR MIDDLE EAR INNER EAR
Pinna Auditorycanal
Ear-drum
Hammer,anvil, stirrup
Ovalwindow
Cochlear canal
Upper and middle Lower
Time
Organ of Cortistimulated
Amplificationin middle ear
Onevibration
Amplitude
Pre
ss
ure
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• Organs of balance located in inner ear
– Semicircular canals
29.10 The inner ear houses our organs of balance
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• Equilibrium structures in the inner ear
Figure 29.10
Semicircularcanals
Nerve
Cochlea
Utricle
Saccule
Flow of fluid
Cupula
Flowof fluid
Cupula
Hairs
Haircell
Nerve fibers
Direction of body movement
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• Smell and taste depend on chemoreceptors sending nerve signals to the brain
– Specific molecules binding to chemoreceptors determine signals
29.12 Odor and taste receptors detect categories of chemicals
TASTE AND SMELL
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• Olfactory (smell) receptors are sensory neurons that line the upper part of the nasal cavity
Figure 29.12A
BRAIN
NASAL CAVITY
Action potentials
Bone
Chemo-receptorcell
Cilia
Epithelialcell
MUCUS
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• Taste receptors - sensory neurons located in back of the throat and tongue (taste buds)
• types of taste receptors
– Sweet, sour, salty, bitter, umami
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• Insects have taste receptors located in sensory hairs on feet– can taste food
by stepping on it
Figure 29.12B
To brain
Chemo-receptorcells
Sensoryhair
Pore at tip