Chapter 9: Nervous System
-allows feeling, thinking, moving,
and awareness
-coordinates all body functions to
maintain homeostasis and enables
the body to respond to changing
conditions
1. Nerve cells are also known as
_neurons, which are the structural
and functional units of the nervous
system.
2. Neurons transmit information by
electrochemical changes_ called nerve
impulses to other neurons and cells.
3. Bundles of axons are known as
nerves__.
4. Nervous system support cells are
_neuroglial cells____________,
which function to support, insulate,
and provide nutrients__.
5. Organs of the central nervous
system are brain and spinal cord.
6. Peripheral nervous system is
composed of nerves that connect
CNS to body parts.
7. Function of two nervous systemssensory, integrative, and motor
8. Function of sensory receptors—
gather info by detecting changes
inside and outside the body, monitor
external environ. factors (such as
light and sound), and conditions of
the body’s internal environ. (such as
temp and O2 level)
9. Describe motor functions use
peripheral neurons to carry impulses
to effectors (muscles or
glands=Action)
10. Responsive structures—what are
they and what do they do—
Effectors—muscles and glands—
respond to signal from sensory
receptors
11. Describe the two categories of
motor functions—Somatic—
consciously controlled (muscles),
Autonomic –involuntary (heart,
smooth muscle, glands)
12. Neuroglial cells produce the fatty
lipoprotein __myelin______.
13. List the four types of neuroglial
cells (of CNS) and their functions.
a. Microglial- support neurons and
phagocytize bacteria and debris
b. Oligodendrocytes-provide myelin
around axons
c. Astrocytes-structure, joint parts,
help regulate chem. concentrations,
form scar tissue
d. Ependymal- form membranes of
specialized brain parts, inner linings
of spaces of brain and spinal cord
14. What are Schwann cells? Cells of
PNS that form myelin sheath around
axons
15. Section 9.4: Sketch a neuron,
describing the dendrites, axon,
myelin.
Myelinated- found
in CNS—white
matter
Unmyelinatedfound in CNS are
gray matter
16. Draw each type of neuron and
describe their locations.
a. Multipolar-many processes from
body (one axon) in brain and spinal
cord
b. Bipolar-two processes (one axon,
one dendrite) in specialized parts of
eye, nose, ears
c. Unipolar-single process that
divides into two (one is dendrite,
other enters brain or spinal cord)
17. List the three ways neurons are
grouped and describe.
a. Sensory-Carry impulses from
body parts to brain or spinal cord—
receive signal from receptor
b. Interneurons -In brain or spinal
cord-transmit impulses from one
part to another—direct impulses
from sensory to motor
c. Motor-Carry impulses from brain
or s.c. to effectors, causing muscle
contraction or gland secretion
18. Read 9.5 –What forms a nerve
impulse? A change in neuron
membrane polarization and return
to resting state (action potential)
19. Describe the resting potential.
The undisturbed potential
difference in electrical charge
between the inside and the outside
of the membrane—Higher
Potassium inside, Sodium outside
20. What conditions can affect the
resting potential? Stimuli such as
changes in temperature, light, or
pressure occurring outside the
body
21. The change in the potential is
directly proportional to – the
intensity of the stimulation
22. 9.6 Describe how a nerve
impulse occurs.—Action potential
(permeability changes cause
sodium to rush into the cell,
causing a depolarization until
Potassium diffuses out) causes a
bioelectric current to flow to the
adjacent nerve cell membrane,
which triggers another action
Events leading to conduction of nerve
impulse (brown box P. 213)
1. Neuron membrane maintains
resting potential
2. Threshold stimulus is received
3. Sodium channels open
4. Sodium ions diffuse inward,
causing depolarization
5. Potassium opens, diffusing
outward
6. Action potential that results
causes a bioelectric current that
stimulates adjacent portions of
membrane
7. Wave of action potentials
travels axon as nerve impulse
ACTION
POTENTIALS
OCCUR AT NODES
OF RANVIER
23. What is a synapse? Junction
between two communicating
neurons (no direct contact)
24. When a nerve impulse reaches
a synaptic knob, some of the
synaptic vesicles release a
neurotransmitter, which reacts
with receptors on the next neuron
25. 2 excitatory neurotransmitters
are (increase sodium ion
permeability which may trigger
nerve impulses) Acetylcholine,
Norepinephrine
9.8
26. Facilitation-neuron is more
excitable to incoming stimulation
because it received excitatory input.
Convergence-Axons originating
from different parts of NS but
leading to the same neuron
Divergence-impulses leaving a
neuron and passing into several
other neurons
9.9
27. Sensory fibers-bring sensory
info to CNS
Motor fibers-carry info from CNS to
effectors
Nerves do the same
9.10 Nerve Pathways
28. What are they? The paths a
nerve impulse follows as it travels
through the nervous system
29. A reflex arc makes up the
simplest nerve pathway (only a few
neurons).
30. What are reflexes? Involuntary,
automatic subconscious responses to
change (stimuli) within or outside
the body—maintain homeostasis by
controlling involuntary processes
(hr, br, bp, digestion) and carry out
auto. Actions such as swallowing,
sneezing, coughing and vomiting
31. How does the knee jerk reflex
occur? Patellar ligament is struck,
causing a pull on the quad. femoris
muscle, stimulating stretch receptors
in this muscle, receptors trigger
impulses that move along sensory
neurons to the spinal cord, then
impulse travels back to the quad.
femoris, which contracts in response
and the leg kicks
32. How many neurons are
involved? Only two—a sensory
communicating with a motor
33. How does the withdrawal reflex
occur? Skin receptors send the
message (you’re hurting yourself
stupid) through sensory receptors to
the spinal cord, impulses travel
through interneurons to motor
neurons, which signal the flexor
muscles to contract and move,
extensor muscles are inhibited---
Other Interneurons send sensory
impulses to brain to feel pain (don’t
hurt yourself more, stupid)
34. How is the withdrawal reflex
protective? Protects the body from
further tissue damage