This document provides an overview of the structure and function of the nervous system. It describes how the nervous system is composed of neurons and glial cells. It explains the basic parts and functions of neurons, including dendrites, cell bodies, axons, and myelin sheaths. It also outlines the main classes of neurons and how nerve impulses are conducted. Key concepts covered include the resting membrane potential, action potentials, synaptic transmission, and the roles of the central and peripheral nervous systems.

1. Nervous System
Part 1
Chapter 17

2. Nervous System
Control System

3. Also a
Communication System
3/24/2011 NS 3

4. Pattern Of Control
stimulus - response
input - integration - output
3/24/2011 NS 4

5. Pattern Of Control
stimulus response
input - integration - output
3/24/2011 NS 5

6. 3/24/2011 NS 6

7. Neurons
• the nervous system is made up of
two types of cells:
• neurons - irritable (responsive),
conductive
• glial cells - protective, supportive
& nourishing
3/24/2011 NS 7

8. Neuron Structure
3 main parts:
• dendrites - receiving area
• cell body - integrating area
• axon & terminals - sending area
3/24/2011 NS 8

9. Neuron Structure
3/24/2011 NS 9

10. Neuron Structure
• the nerve impulse or action potential is
the information sent from one nerve to
another
• it travels from the dendrites to cell
body to axon
3/24/2011 NS 10

11. Neuron Structure
• some neurons are “myelinated” and
some are not (unmyelinated)
• myelinated neurons have a fatty
myelin sheath around the axon
3/24/2011 NS 11

12. Neuron Structure
• myelinated axon
• myelin sheath
• node of Ranvier
3/24/2011 NS 12

13. Myelin Sheath
3/24/2011 NS 13

14. Classes Of Neurons
sensory (afferent) -
carry information
from sense organs
(eyes, ears) to CNS
3/24/2011 NS 14

15. 3/24/2011 NS 15

16. Classes Of Neurons
e.g. optic nerve
auditory nerve
neurons carrying temperature
& pain sensations
• short axons
• long dendrites
3/24/2011 NS 16

17. Classes Of Neurons
• interneurons (association)
carry information between other
neurons inside the CNS
they often form tracts
3/24/2011 NS 17

18. Classes Of Neurons
e.g. corpus callosum,
spinal cord tracts
• short dendrites
• long or short
axons
3/24/2011 NS 18

19. Classes Of Neurons
• motor neurons (efferent)
carry information from the
CNS to the effector organs
(muscles & glands)
3/24/2011 NS 19

20. Classes Of Neurons
e.g. nerves to skeletal
muscles, viscera & glands
• short dendrites
• long axons
3/24/2011 NS 20

21. Impulse Or Action Potential
• neurons carry information
• neurons are arranged in pathways
• impulses travel along the pathways
from one neuron to another neuron
3/24/2011 NS 21

22. 3/24/2011 NS 22

23. 3/24/2011 NS 23

24. Resting Membrane Potential
• electrical event
• difference in charge across the resting
cell axon membrane (- 60 to -70mv
inside)
3/24/2011 NS 24

25. Resting Membrane Potential
3/24/2011 NS 25

26. Resting Membrane Potential
• +ve sodium ions outside
• +ve potassium &
-ve proteins inside
3/24/2011 NS 26

27. Resting Membrane Potential
• Na/K pump keeps ion balance
3/24/2011 NS 27

28. Resting Membrane Potential
3/24/2011 NS 28

29. Ion Movements Across
Resting Neuron Membrane
3/24/2011 NS 29

30. Action Potential
• stimulus to nerve causes
• an electrical change which travels down
the axon due to
• Na+ moving in then
• K+ moving out
3/24/2011 NS 30

31. Action Potential
• Depolarization – change in charge
across neuron membrane from –60
mv to + 40 mv inside
• Repolarization – restoration of
membrane back to resting level of
– 60 mv inside
• Threshold Potential – level of
depolarization that must be
reached to trigger an action
potential
3/24/2011 NS 31

32. Action Potential
4
3/24/2011 NS 32

33. Resting Membrane Potential
3/24/2011 NS 33

34. Depolarization Begins
3/24/2011 NS 34

35. Depolarization Ends
Repolarization Begins
3/24/2011 NS 35

36. Repolarization Complete
3/24/2011 NS 36

37. Action Potential
• Action Potential
3/24/2011 NS 37

38. Action Potential
3/24/2011 NS 38

39. Action Potential
2 parts:
upswing down swing
depolarization repolarization
3/24/2011 NS 39

40. Action Potential
2 parts:
upswing down swing
Na+ inflow K+ outflow
depolarization repolarization
3/24/2011 NS 40

41. Action Potential
• Na+/K+ pump in membrane
• pumps the Na+ out & the
• K+ in after the action potential is over
3/24/2011 NS 41

42. Action Potential
• the depolarization at one point of the
membrane acts as a
• stimulus for the next point on the
membrane which then depolarizes
and so on down the membrane
3/24/2011 NS 42

43. Refractory Period
• the period following one stimulus when
the neuron cannot respond to another
stimulus
• so each action potential is a separate
event
3/24/2011 NS 43

44. Action Potential
• the action potential is
ALL OR NONE - it either happens fully
or not at all
- it cannot be partial
3/24/2011 NS 44

45. Nerve Conduction Speed
• larger, myelinated axons conduct
faster by
• “saltatory conduction” where action
potential jumps from node to node
3/24/2011 NS 45

46. Saltatory Conduction
3/24/2011 NS 46

47. Synapse
• information passes from one neuron
to another
• across synapses using
• chemical transmitters
• synapses are one way only
3/24/2011 NS 47

48. Synapse
• a synapse can be between
• 2 neurons or between a
• neuron & its effector organ
• it is at synapses that mood
altering drugs affect
the nervous system
3/24/2011 NS 48

49. Synapse
• neuron -
neuron
synapse
• axon terminal
3/24/2011 NS 49

50. 3/24/2011 NS 50

51. Summation & Integration
• all sensory input to the neuron cell body
at any time is added together or
“summated”
• if there is enough stimulation an action
potential will be triggered
3/24/2011 NS 51

52. Neurotransmitters
• acetyl choline (ACh) -
destroyed by cholinesterase
• nor-adrenaline
(nor- epinephrine) - destroyed by
monoamine oxidase (MAO)
3/24/2011 NS 52

53. Neurotransmitters
3/24/2011 NS 53

54. Neurotransmitters
• low nor- epinephrine (adrenaline) levels
• are linked with
3/24/2011 NS 54

55. Neurotransmitters
• can be
excitatory e.g. ACh, norepinephrine,
serotonin or
inhibitory e.g. GABA & glycine
3/24/2011 NS 55

56. Neurotransmitters
• there are also naturally occurring
• painkillers or opiates - such as
those which give a “runner’s
high”
3/24/2011 NS 56

57. Nervous System - Structure
2 regions:
• central nervous system
- brain & spinal cord
• peripheral nervous system
- everything else…..
3/24/2011 NS 57

58. Organization Of The Nervous
System
CNS PNS
brain cranial nerves*
(12 pairs)
spinal spinal nerves*
cord (31 pairs)
* and associated ganglia
3/24/2011 NS 58

59. Ganglia & Nuclei
Collections of neuron cell bodies in the:
• CNS - nuclei (gray matter)
3/24/2011 NS 59

60. Ganglia & Nuclei
• PNS - ganglia (spinal ganglia &
autonomic ganglia)
3/24/2011 NS 60

61. Spinal Cord
• central canal filled with CSF
• outer white matter - myelinated tracts
• inner gray matter - cell bodies &
unmyelinated tracts
3/24/2011 NS 61

62. Spinal Cord Functions
• reflex centre part of the spinal reflex
arc
• communication between the brain &
the peripheral nervous system
(many tracts )
3/24/2011 NS 62

63. Spinal Cord
• spinal reflex
dorsal
root
ventral
root
interneuron
3/24/2011 NS 63

64. Brain
• ventricles
• white matter (tracts)
• gray matter ( nuclei & tracts)
• different functions in different areas
3/24/2011 NS 64

65. Brain - Cerebrum
Prefrontal
lobe
3/24/2011 NS 65

66. Brain
3/24/2011 NS 66

67. Brain & Spinal Cord
• hollow - filled with
cerebrospinal fluid
(CSF)
• covered with 3
membranes –
• meninges
• both are protective
& supportive
3/24/2011 NS 67

68. Parts Of The Brain
(from highest to lowest)
• cerebral hemispheres
(4 lobes)
• diencephalon
(thalamus/hypothalamus)
• limbic system
• cerebellum
3/24/2011 NS 68

69. Parts Of The Brain
(from highest to lowest)
brain stem
• midbrain
• pons
• medulla oblongata
• reticular formation
(in brain stem)
3/24/2011 NS 69

70. Structure Of Cerebrum
• 2 hemispheres joined by the corpus
callosum
• basal ganglia help control skeletal
muscles
3/24/2011 NS 70

71. Structure Of Cerebrum
4 lobes
1) frontal
2) parietal
3) temporal
4) occipital
3/24/2011 NS 71

72. Brain Functions
4 lobes
3/24/2011 NS 72

73. Cerebral Cortex
• outer layer of the
cerebrum = the cortex
• gray matter
• motor, sensory and
association areas
3/24/2011 NS 73

74. Cerebral Cortex
3/24/2011 NS 74

75. Brain Functions
1) frontal - motor control &
highest mental functions
2) parietal - skin senses
e.g. pain, touch, temperature
3/24/2011 NS 75

76. Brain Functions
3) temporal - sound & smell,
sensory interpretation
4) occipital - sight
3/24/2011 NS 76

77. Brain Functions
Cerebrum (cerebral
hemispheres)
• highest functions
e.g. memory, learning,
perception, awareness
3/24/2011 NS 77

78. Brain Functions
Diencephalon
• thalamus - sensory filter
• hypothalamus - homeostasis
(many functions)
e.g. hunger, body temperature
3/24/2011 NS 78

79. Brain Functions
Cerebellum
• balance , posture
3/24/2011 NS 79

80. Brain Functions
Brain Stem –
sensory & motor tracts, reticular
formation
• midbrain - nuclei e.g. (balance)
• pons - respiratory centres
• medulla - vital centres
3/24/2011 NS 80

81. Brain Functions
• reticular formation
network which contains the
• Reticular Activating System
which controls alertness/sleep
3/24/2011 NS 81

82. Chapter 17: Part 1
Internet Resources:
• http://yucky.kids.discovery.com/noflash/body/
pg000136.html
• http://users.tpg.com.au/users/amcgann/body/
nervous.html
• http://faculty.washington.edu/chudler/introb.ht
ml
• http://users.rcn.com/jkimball.ma.ultranet/Biolo
gyPages/C/CNS.html
• http://www.bartleby.com/107/183.html
3/24/2011 NS 82