1. Figure 11.2 Schematic of levels of organization in the nervous system.
Central nervous system (CNS)
Peripheral nervous system (PNS)
Brain and spinal cord
Cranial nerves and spinal nerves
Integrative and control centers
Communication lines between the
CNS and the rest of the body
Sensory (afferent) division
Motor (efferent) division
Somatic and visceral sensory
nerve fibers
Motor nerve fibers
Conducts impulses from the CNS
to effectors (muscles and glands)
Conducts impulses from
receptors to the CNS
Somatic sensory
fiber
Somatic nervous
system
Autonomic nervous
system (ANS)
Skin
Somatic motor
(voluntary)
Visceral motor
(involuntary)
Conducts impulses
from the CNS to
skeletal muscles
Conducts impulses
from the CNS to
cardiac muscles,
smooth muscles,
and glands
Visceral sensory fiber
Stomach
Skeletal
muscle
Motor fiber of somatic nervous system
Sympathetic division
Parasympathetic
division
Mobilizes body
systems during activity
Conserves energy
Promotes house-
keeping functions
during rest
Sympathetic motor fiber of ANS
Heart
Structure
Function
Sensory (afferent)
division of PNS
Parasympathetic motor fiber of ANS
Bladder
Motor (efferent)
division of PNS

2. (a) Astrocytes are the most abundant CNS neuroglia.
Figure 11.3a Neuroglia.
Capillary
Neuron
Astrocyte
(a) Astrocytes are the most abundant CNS neuroglia.

3. (b) Microglial cells are defensive cells in the CNS.
Figure 11.3b Neuroglia.
Neuron
Microglial
cell
(b) Microglial cells are defensive cells in the CNS.

4. (c) Ependymal cells line cerebrospinal fluid-filled cavities.
Figure 11.3c Neuroglia.
Fluid-filled cavity
Ependymal
cells
Brain or
spinal cord
tissue
(c) Ependymal cells line cerebrospinal fluid-filled cavities.

5. Myelin sheath Process of oligodendrocyte Nerve fibers
Figure 11.3d Neuroglia.
Myelin sheath
Process of
oligodendrocyte
Nerve
fibers
(d) Oligodendrocytes have processes that form myelin sheaths around CNS nerve fibers.

6. (forming myelin sheath)
Figure 11.3e Neuroglia.
Satellite
cells
Cell body of neuron
Schwann cells
(forming myelin sheath)
Nerve fiber
(e) Satellite cells and Schwann cells (which form myelin) surround neurons in the PNS.

7. Figure 11.4 Structure of a motor neuron.
Dendrites
Cell body
Neuron cell body
(receptive
regions)
(biosynthetic center
and receptive region)
Nucleolus
Axon
(a)
Dendritic
spine
(impulse
generating
and conducting
region)
Nucleus
Impulse
direction
Nissl bodies
Node of Ranvier
Axon terminals
(secretory
region)
Axon hillock
Schwann cell
(one inter-
node)
Neurilemma
(b)
Terminal
branches

8. Figure 11.4a Structure of a motor neuron.
Neuron cell body
(a)
Dendritic spine

9. Figure 11.4b Structure of a motor neuron.
Dendrites
(receptive regions)
Cell body
(biosynthetic center
and receptive region)
Nucleolus
Axon
(impulse generating
and conducting region)
Impulse
direction
Nucleus
Node of Ranvier
Nissl bodies
Axon
terminals
(secretory
region)
Axon hillock
Schwann cell
(one inter-
node)
Neurilemma
(b)
Terminal
branches

10. Figure 11.5a Nerve fiber myelination by Schwann cells in the PNS.
plasma membrane
Schwann cell
cytoplasm
A Schwann cell
envelopes an axon. 1
Axon
Schwann cell
nucleus
The Schwann cell then
rotates around the axon,
wrapping its plasma
membrane loosely around
it in successive layers. 2
Neurilemma
The Schwann cell
cytoplasm is forced from
between the membranes.
The tight membrane
wrappings surrounding
the axon form the myelin
sheath. 3
Myelin sheath
(a) Myelination of a nerve fiber (axon)

11. Figure 11.5b Nerve fiber myelination by Schwann cells in the PNS.
sheath
Schwann
cell
cytoplasm
Axon
Neurilemma
(b) Cross-sectional view of a myelinated axon (electron micrograph 24,000X)

12. Figure 11.10 The spread and decay of a graded potential.
Stimulus
Depolarized region
Plasma
membrane
(b) Spread of depolarization: The local currents (black arrows) that are created depolarize adjacent membrane areas and allow the wave of depolarization to spread.
(a) Depolarization: A small patch of the membrane (red area) has become depolarized.
Active area
(site of initial
depolarization)
–70
Resting potential
Distance (a few mm)
(c) Decay of membrane potential with distance: Because current is lost through the “leaky” plasma membrane, the voltage declines with distance from the stimulus (the voltage is decremental). Consequently, graded potentials are short-distance signals.

13. Figure 11.11 Action Potential (1 of 2)
The big picture 1
Resting state 2
Depolarization 3
Repolarization 3
Membrane potential (mV)
Action
potential 4
Hyperpolarization 2
Threshold 1 1 4
Time (ms)
The AP is caused by permeability changes in the
plasma membrane 3
Action potential
Relative membrane
permeability
Na+ permeability 2
Membrane potential (mV)
K+ permeability 1 1 4
Time (ms)

14. Axodendritic synapses Dendrites Axosomatic synapses Cell body
Figure 11.16a Synapses.
Axodendritic
synapses
Dendrites
Axosomatic
synapses
Cell body
Axoaxonic synapses
(a)
Axon

15. Figure 11.17 Chemical Synapse (1 of 3)
Presynaptic
neuron
Presynaptic
neuron
Postsynaptic
neuron
Action potential
arrives at axon terminal. 1
Voltage-gated Ca2+
channels open and Ca2+
enters the axon terminal. 2
Mitochondrion
Ca2+
Ca2+
Ca2+
Ca2+
Ca2+ entry causes
neurotransmitter-
containing synaptic
vesicles to release their
contents by exocytosis. 3
Synaptic
cleft
Axon
terminal
Synaptic
vesicles
Neurotransmitter
diffuses across the synaptic
cleft and binds to specific
receptors on the
postsynaptic membrane. 4
Postsynaptic
neuron

16. Figure 11.22a Types of circuits in neuronal pools.

17. Figure 11.22b Types of circuits in neuronal pools.

18. Figure 11.22c-d Types of circuits in neuronal pools.

19. Figure 11.22e Types of circuits in neuronal pools.

20. Figure 11.22f Types of circuits in neuronal pools.

21. Figure 11.23 A simple reflex arc.
Stimulus
Interneuron 1
Receptor 2
Sensory neuron 3
Integration center 4
Motor neuron 5
Effector
Spinal cord (CNS)
Response

22. Table 11.2 Comparison of Action Potentials with Graded Potentials (4 of 4)