1. Chapter 48
Nervous Systems

2. Figure 48.2 Organization of some nervous systems
Nerve net
Nerve ring
Radial nerve
Eyespot
Brain
Nerve cord
Transverse nerve
Segmental ganglion
Ventral nerve cord
Segmental ganglia
Anterior nerve ring
Longitudinal nerve cords
Ganglia
Sensory ganglion
Spinal cord
(dorsal nerve
cord)
(d) Leech (annelid)
(c) Planarian (flatworm)
(b) Sea star (echinoderm)
(a) Hydra (cnidarian)
(e) Insect (arthropod)
(f) Chiton (mollusc)
(g) Squid (mollusc)
(h) Salamander (chordate)

3. Figure 48.3 Overview of information processing by nervous systems
Sensor
Effector
Motor output
Integration
Sensory input
Peripheral nervous system (PNS)
Central nervous system (CNS)

4. Figure 48.4 The knee-jerk reflex
Sensory neurons from the quadriceps also communicate
with interneurons in the spinal cord.
The interneurons inhibit motor neurons that supply the hamstring (flexor) muscle. This inhibition prevents the hamstring from contracting,
which would resist the action of the quadriceps.
The sensory neurons communicate with
motor neurons that supply the quadriceps. The
motor neurons convey signals to the quadriceps,
causing it to contract and jerking the lower leg forward. 4 5 6
The reflex is
initiated by tapping
the tendon connected
to the quadriceps
(extensor) muscle. 1
Sensors detect
a sudden stretch in
the quadriceps. 2
Sensory neurons
convey the information
to the spinal cord. 3
Quadriceps muscle
Hamstring muscle
Spinal cord (cross section)
Gray matter
White matter
Cell body of sensory neuron in dorsal root ganglion
Sensory neuron
Motor neuron
Interneuron
Figure 48.4 The knee-jerk reflex

5. Figure 48.5 Structure of a vertebrate neuron
Dendrites
Cell body
Nucleus
Axon hillock
Axon
Signal direction
Synapse
Myelin sheath
Synaptic terminals
Presynaptic cell
Postsynaptic cell

6. Figure 48.6 Structural diversity of vertebrate neurons
Axon
Cell body
Dendrites
(a) Sensory neuron
(b) Interneurons
(c) Motor neuron

7. Figure 48.8 Schwann cells and the myelin sheath
Nodes of Ranvier
Schwann
cell
Nucleus of Schwann cell
Axon
Layers of myelin
Node of Ranvier
0.1 µm

9. Figure 8.15 The sodium-potassium pump: a specific case of active transport

10. Figure 48.12 Graded potentials and an action potential in a neuron
+50
–50
–100
Time (msec)
 4  5 6
Threshold
Resting potential
Hyperpolarizations
Depolarizations
Membrane potential (mV)
Stimuli
Stronger depolarizing stimulus
Action potential
(a) Graded hyperpolarizations produced by two stimuli that increase membrane permeability to K+. The larger stimulus produces a larger hyperpolarization.
(b) Graded depolarizations produced by two stimuli that increase membrane permeability to Na+. The larger stimulus produces a larger depolarization.
(c) Action potential triggered by a depolarization that reaches the threshold.

11. Figure 48.14 Conduction of an action potential– +
Na+
Action potential K+
Axon
An action potential is generated as Na+ flows inward across the membrane at one location. 1 2
The depolarization of the action potential spreads to the neighboring region of the membrane, re-initiating the action potential there. To the left of this region, the membrane is repolarizing as K+ flows outward. 3
The depolarization-repolarization process is repeated in the next region of the membrane. In this way, local currents of ions across the plasma membrane cause the action potential to be propagated along the length of the axon.

12. Figure 48.17 A chemical synapse
Presynaptic cell
Postsynaptic cell
Synaptic vesicles containing neurotransmitter
Presynaptic membrane
Postsynaptic membrane
Voltage-gated Ca2+ channel
Synaptic cleft
Ligand-gated ion channels
Na+ K+
Ligand- gated ion channel
Neuro- transmitter 1
Ca2+ 2 3 4 5 6

13. Figure 48.19 The vertebrate nervous system
Central nervous
system (CNS)
Peripheral nervous
system (PNS)
Brain
Spinal cord
Cranial
nerves
Ganglia
outside
CNS
Spinal

14. Figure 48.21 Functional hierarchy of the vertebrate peripheral nervous system
Somatic
nervous
system
Autonomic
Sympathetic
division
Parasympathetic
Enteric

15. Parasympathetic division Action on target organs:
Figure 48.22 The parasympathetic and sympathetic divisions of the autonomic nervous system
Parasympathetic division
Sympathetic division
Action on target organs:
Location of
preganglionic neurons:
brainstem and sacral
segments of spinal cord
Neurotransmitter
released by
acetylcholine
postganglionic neurons:
in ganglia close to or
within target organs
Constricts pupil
of eye
Stimulates salivary
gland secretion
Constricts
bronchi in lungs
Slows heart
Stimulates activity
of stomach and
intestines
of pancreas
Stimulates
gallbladder
Promotes emptying
of bladder
Promotes erection
of genitalia
Cervical
Thoracic
Lumbar
Synapse
Sympathetic
ganglia
Dilates pupil
Inhibits salivary
Relaxes bronchi
in lungs
Accelerates heart
Inhibits activity of
stomach and intestines
Inhibits activity
Stimulates glucose
release from liver;
inhibits gallbladder
adrenal medulla
Inhibits emptying
Promotes ejaculation and
vaginal contractions
Sacral
thoracic and lumbar
some in ganglia close to
target organs; others in
a chain of ganglia near
spinal cord
norepinephrine

16. Unnumbered figure page 1029

17. Unnumbered figure page 1030

18. Unnumbered figure page 1031

19. Figure 48.27 The human cerebral cortex
Frontal lobe
Temporal lobe
Occipital lobe
Parietal lobe
Frontal
association
area
Speech
Smell
Hearing
Auditory
Vision
Visual
Somatosensory
Reading
Taste
Somatosensory cortex
Motor cortex