1. Module#7 The Nervous System
Functions:
Communication
Coordination
Control
Gathering information

2. Differences between
human and animal NS:
1. Language
2. Judgment
3. Problem solving
4. Creativeness
5. Passing along heritage

3. Two Divisions of the NS
1.Central nervous system (CNS)
• the brain and spinal cord
• is encased in bone (skull and
vertebral column)

5. Two Divisions of the NS
2. Peripheral nervous system
(PNS)
•nerves and ganglia that branch
from the CNS and go to body.

7. Nerves – bundles of axons and
their sheaths which extend
from the CNS
Ganglia – collections of neuron
cell bodies which are outside
of the CNS

8. CNS
1. Brain
•protected by cranium
•high level thought
•major organ of the NS
•Message center
•Uses info to formulate ideas
•Makes decisions
•Communicates with body

9. CNS
1. Brain
2. Spinal Cord
Thick bundle nerve fibers
within spinal cavity
How brain communicates
with most of body
Ends at first lumbar

10. Peripheral NS
1. Cranial nerves
Nerves that come from brain
12 pairs
Branch from brain stem
Transmit from/to eyes, ears,
mouth, face and scalp

12. Peripheral NS
1. Cranial nerves
2. Spinal Nerves
Nerves that come from spinal
cord
31 pairs
Transmit signals to and from
the rest of the body

13. Spinal nerves

14. Two divisions of Peripheral NS:
1. Afferent
 sensory pathways - involves the
sensory organs like eyes, ears..
Neurons carry action potential
from sense organs to CNS
Also called sensory division

15. Two divisions of Peripheral NS:
1. Afferent
2. Efferent
Motor pathways - system that
innervates muscles, effector
organs, and glands.
Also called motor division

17. Action potential –
electrical signal that
travels along a neuron.

18. Divisions of the Efferent Nervous System:
1. Somatic Motor Nervous
System (SMNS)
transmits action potential
from CNS to skeletal muscles
conscious, voluntary control

19. Divisions of the Efferent Nervous System:
1. Somatic Motor Nervous System (SMNS)
2. Autonomic NS
 carries stimulus from the
CNS to the smooth
muscles, cardiac muscles, and
glands
Involuntary, unconscious

20. Divisions of the autonomic system:
1. Sympathetic system
•prepares body for physical activity
•increases heart rate, blood
pressure, blood glucose levels
•Prepares for “flight or fight”

21. Divisions of the autonomic system:
1. Sympathetic system
2. Parasympathetic:
Regulates resting and nutritionally
related functions
Includes
digestion, urination, defecation
Slows down heart, etc. after “Fight
or Flight” response

23. NS at a Cellular level:
2 types of cells:
1. Neurons = functioning cell

24. Three parts of neurons (nerve cells):
A. cell body
 contains the nucleus of cell
B. dendrites –
short, branched extensions of cell
body
receive nerve impulses and conduct
them toward the cell body

25. Three parts of neurons (nerve cells):
A. cell body
B. dendrites
C. axon
one long extension which carries
impulses away from cell body to other
cells
hillock where the cell body ends and
axon begins

26. Axon continued:
Is wrapped in a substance called
myelin produced by neuroglial cells
myelin speeds up impulsed
Myelin is called Schwann in PNS
and oligodendrocyte in CNS
Gaps in myelin called nodes of
Ranvier

27. Axon continued :
Axons vary in length
Axon splits into collateral
axons and then end in
presynaptic terminals

28. Nerve impulses
travel from the
dendrite to
body to axon.
Collateral Axons

29. Mature neurons can
not undergo mitosis.
They are parenchyma
permanent cells!!
TAKE CARE of
them!!

30. But, Mrs. Crawford
how can I take care of
them?
Get plenty of
sleep, avoid lots of
TV, avoid
caffeine, alcohol, drug

31. Well, how many
neurons do I have?
It is believed you have
around 100 billion,
some will die just due
to natural causes
(about 7,000/day)

32. NS at a Cellular level continued
Can classify neurons based on
their structure - how many
processes they have
(dendrites and axons):

33. 1.Unipolar –one process with a
cell body that hangs off to the
side
2.Bipolar – two processes an
axon and a single dendrite
with the cell body in middle
3. Multipolar –only one axon
with many dentrites.

34. Bipolar
multipolar
unipolar

35. NS at a Cellular level continued
oWhat in the world is a
association neuron Mrs.
Crawford?
A neuron that conducts
action potentials for
one neuron to another.
(interneurons)

36. NS at a Cellular level:
2 types of cells:
1. Neurons = functioning cell
2. Neuroglia
Binds, protects and insulates
neurons
Is the majority of cells in
the NS.
They do carry on mitosis!!

37. Types of Neuroglia :
1.Schwann cells – insulate axons of
PNS
2. Oligodendrocytes – insulate
axons of CNS
3. Microglia – white blood cells of
brain

38. Types of Neuroglia :
4. Astrocytes – form blood-brain
barrier regulating what can enter
the brain and what cannot. (Some
toxins pass through such as alcohol
toxins)

39. Types of Neuroglia :
5. Ependymal cells – two types
a. non – ciliated – secrete
cerebrospinal fluid
b. ciliated – move cerebrospinal
fluid around

40. Wrappings of the Nerve:
Epineurium – wraps the nerve –
white, shiny
Perineurium – wraps the fascicles
Endoneurium – wraps the
Schwann cells of axons
Fascicles are bundles of axons

42. Nerve anatomy:
Run along with veins and
arteries
Medium sized = shoe string
Sciatic nerve –
largest, thickness of index
finger

44. 3 Types of Nerves:
1. Sensory – carries sensory
messages only (optic
nerve)
2. Motor – carries messages
to the muscles (eye
muscles)
3. Mixed – carries both

45. Healing in Nervous
System:
•Neurons cannot undergo
mitosis.
•Nerve healing occurs
under certain conditions.

46. Conditions of nerve
healing:
•Axon is wrapped in Schwann
cells which means only in
PNS
• Axon ends are close and
pointed in right direction

47. Conditions of nerve
healing
No healing in CNS, spinal
cord or brain
Can be surgically aided

48. Why are Schwann cells able
to aide in healing and
oligodendrocytes not?
There are many Schwann
cells per axon in PNS, but
many axons per
oligodendrocyte in the CNS.