Transcript video slide

Chapter 48:
Nervous Systems
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 48.1 A functional magnetic resonance image of
brain areas activated during language processing
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Figure 48.2 Organization of some nervous systems
Eyespot
Nerve net
Brain
Brain
Nerve
cord
Transverse
nerve
Radial
nerve
Nerve
ring
Ventral
nerve
cord
Segmental
ganglion
(a) Hydra (cnidarian)
(b) Sea star (echinoderm)
(c) Planarian (flatworm)
(d) Leech (annelid)
Brain
Brain
Ventral
nerve
cord
Segmental
ganglia
(e) Insect (arthropod)
Anterior
nerve ring
Ganglia
Longitudinal
nerve cords
(f) Chiton (mollusc)
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Brain
Ganglia
(g) Squid (mollusc)
Spinal
cord
(dorsal
nerve
cord)
Sensory
ganglion
(h) Salamander (chordate)
Figure 48.3 Overview of information processing by
nervous systems
Sensory input
Integration
Sensor
Motor output
Effector
Peripheral nervous
system (PNS)
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Central nervous
system (CNS)
Figure 48.5 Structure of a vertebrate neuron
Dendrites
Cell body
Nucleus
Synapse
Signal
Axon direction
Axon hillock
Presynaptic cell
Postsynaptic cell
Myelin sheath
Synaptic
terminals
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Figure 48.6 Structural diversity of vertebrate neurons
Dendrites
Axon
Cell
body
(a) Sensory neuron
(b) Interneurons
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(c) Motor neuron
50 µm
Figure 48.7 Astrocytes
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Figure 48.8 Schwann cells and the myelin sheath
Node of Ranvier
Layers of myelin
Axon
Schwann
cell
Axon
Myelin sheath
Nodes of
Ranvier
Schwann
cell
Nucleus of
Schwann cell
0.1 µm
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Figure 48.9 Intracellular Recording
APPLICATION Electrophysiologists use intracellular recording to measure the membrane potential of
neurons and other cells.
A microelectrode is made from a glass capillary tube filled with an electrically conductive
TECHNIQUE
salt solution. One end of the tube tapers to an extremely fine tip (diameter < 1 µm). While looking through a
microscope, the experimenter uses a micropositioner to insert the tip of the microelectrode into a cell. A
voltage recorder (usually an oscilloscope or a computer-based system) measures the voltage between the
microelectrode tip inside the cell and a reference electrode placed in the solution outside the cell.
Microelectrode
–70 mV
Voltage
recorder
Reference
electrode
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Figure 48.13 The role of voltage-gated ion channels
in the generation of an action potential (layer 5)
Na+
Na+
– –
– –
– –
– –
+ +
+ +
+ +
+ +
K+
3
Na+
Na+
+ +
+ +
+ +
+ +
– –
– –
– –
– –
K+
Rising phase of the action potential
4 Falling phase of the action potential
Na+
+ +
+ +
+ +
– –
– –
+ +
– –
– –
K+
Membrane potential
(mV)
+50
Na+
3
0
2
–50
–100
2 Depolarization
Action
potential
4
Threshold
5
1
1
Resting potential
Time
Na+
Extracellular fluid
Na+
Activation
gates
Potassium
channel
+ + + + + + + +
+ +
+ +
+ +
Plasma membrane
– – – – – – – –
Cytosol
– –
– –
– –
Sodium
channel
1
K+
Inactivation
gate
Resting state
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Na+
+ +
+ +
+ +
+ +
– –
– –
– –
– –
K+
5
Undershoot
Figure 48.15 Saltatory conduction
Schwann cell
Depolarized region
(node of Ranvier)
Myelin
sheath
––
–
Cell body
+
++
+
++
–––
––
–
+
+
Axon
+
++
––
–
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Figure 48.17 A chemical synapse
Postsynaptic cell
Presynaptic
cell
Synaptic vesicles
containing
neurotransmitter
5
Presynaptic
membrane
Neurotransmitter
Postsynaptic
membrane
Ligandgated
ion channel
Voltage-gated
Ca2+ channel
1 Ca2+
4
2
Synaptic cleft
Na+
K+
3
Ligand-gated
ion channels
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Postsynaptic
membrane
6
Table 48.1 Major Neurotransmitters
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Figure 48.19 The vertebrate nervous system
Central nervous
system (CNS)
Brain
Spinal cord
Peripheral nervous
system (PNS)
Cranial
nerves
Ganglia
outside
CNS
Spinal
nerves
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Figure 48.20 Ventricles, gray matter, and white matter
Gray matter
White
matter
Ventricles
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Figure 48.25 Are mammalian biological clocks
influenced by external cues?
EXPERIMENT
In the northern flying squirrel (Glaucomys sabrinus), activity normally begins with the onset of darkness and
ends at dawn, which suggests that light is an important external cue for the squirrel. To test this idea, researchers monitored the activity
of captive squirrels for 23 days under two sets of conditions: (a) a regular cycle of 12 hours of light and 12 hours of darkness and (b)
constant darkness. The squirrels were given free access to an exercise wheel and a rest cage. A recorder automatically noted when
the wheel was rotating and when it was still.
(a) 12 hr light-12 hr dark cycle
Light
RESULTS
Dark
Light
Dark
1
Days of experiment
When the squirrels
were exposed to a regular
light/dark cycle, their wheel-turning
activity (indicated by the dark bars)
occurred at roughly the same time
every day. However, when they
were kept in constant darkness,
their activity phase began about 21
minutes later each day.
(b) Constant darkness
5
10
15
20
12
16
20
24
4
Time of day (hr)
CONCLUSION
8
12
12
16
20
24
4
Time of day (hr)
The northern flying squirrel’s internal clock can run in constant darkness, but it does so on
its own cycle, which lasts about 24 hours and 21 minutes. External (light) cues keep the clock running on a 24-hour cycle.
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8
12
Figure 48.27 The human cerebral cortex
Frontal lobe
Parietal lobe
Speech
Frontal
association
area
Taste
Reading
Speech
Smell
Somatosensory
association
area
Hearing
Auditory
association
area
Visual
association
area
Vision
Temporal lobe
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Occipital lobe
Figure 48.28 Body representations in the primary
motor and primary somatosensory cortices
Frontal lobe
Parietal lobe
Toes
Lips
Jaw
Genitalia
Tongue
Tongue
Pharynx
Primary
motor cortex
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Abdominal
organs
Primary
somatosensory cortex