The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS). The CNS consists of the brain and spinal cord and processes sensory input and coordinates motor output. The PNS consists of nerves that connect the CNS to the rest of the body and allows for sensation and muscle/gland control. Neurons are the basic functional units that transmit electrochemical signals and communicate via synapses. The nervous system maintains homeostasis, provides sensation, higher functions, and activates muscles and glands through a complex interplay between its various parts.

1. The Nervous System

2. Functions of the Nervous System
• Maintain homeostasis with electrical signals
• Provide for sensation
• Provide for higher mental functions and
emotions
• Activate muscles and glands

3. Roles of the Nervous System
Slide 7.1a
1. Sensory input – gathering information
To monitor changes occurring inside and
outside the body (changes = stimuli)
2. Integration –
to process and interpret sensory input
and decide if action is needed.
3. Motor output
A response to integrated stimuli
The response activates muscles or glands

4. Structural Classification of the
Nervous System
Slide 7.2
 Central nervous system (CNS)
Brain & spinal cord
Dorsal cavity
Command center
Takes in info & give instruction
 Peripheral nervous system (PNS)
Nerves outside the brain and spinal cord
Communication lines

5. Functional Classification of the
Peripheral Nervous System
Slide 7.3a
 Sensory (afferent) division
Nerve fibers that carry information to the
central nervous system
Figure 7.1

6. Functional Classification of the
Peripheral Nervous System
Slide 7.3b
 Motor (efferent) division
Nerve fibers that carry impulses away from
the central nervous system
Figure 7.1

7. Functional Classification of the
Peripheral Nervous System
Slide 7.3c
 Motor (efferent) division
Two subdivisions
 Somatic nervous system = voluntary
 Autonomic nervous system = involuntary
Figure 7.1

8. Organization of the Nervous
System
Slide 7.4
Figure 7.2

9. Neuroglia vs. Neurons
• Neuroglia divide.
• Neurons do not.
• Most brain tumors are “gliomas.”
• Most brain tumors involve the neuroglia
cells, not the neurons.
• Consider the role of cell division in
cancer!

10. Support Cells of the PNS
Slide 7.7b
 Schwann cells
Form myelin sheath in the peripheral
nervous system
Figure 7.3e

11. Nervous Tissue: Neurons
Slide 7.8
 Neurons = nerve cells
Cells specialized to transmit messages
Major regions of neurons
Cell body – nucleus and metabolic center
of the cell
Processes – fibers that extend from the
cell body (dendrites and axons)

12. Neuron Anatomy
Slide 7.9b
 Cell body
Nucleus
Large
nucleolus
Figure 7.4a

13. Neuron Anatomy
Slide 7.10
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Extensions
outside the cell
body
 Dendrites –
conduct
impulses toward
the cell body
 Axons – conduct
impulses away
from the cell
body (only 1!)
Figure 7.4a

14. Axons and Nerve Impulses
Slide 7.11
 Axons end in axonal terminals
 Axonal terminals contain vesicles with
neurotransmitters
 Axonal terminals are separated from the
next neuron by a gap
Synaptic cleft – gap between adjacent
neurons
Synapse – junction between nerves

15. Nerve Fiber Coverings
Slide 7.12
 Schwann cells –
produce myelin
sheaths in jelly-roll
like fashion
 Nodes of Ranvier –
gaps in myelin
sheath along the
axon
Figure 7.5

16. Application
• In Multiple Scleroses the myelin sheath is
destroyed.
• The myelin sheath hardens to a tissue called
the scleroses.
• This is considered an autoimmune disease.
• Why does MS appear to affect the muscles?

17. Neuron Cell Body Location
Slide 7.13
 Most are found in the central nervous
system
Gray matter – cell bodies and unmylenated
fibers
Nuclei – clusters of cell bodies within the
white matter of the central nervous system
 Ganglia – collections of cell bodies
outside the central nervous system

18. Classification of Neurons (based
on fxn.
Slide
7.14a
 Sensory (afferent) neurons
Carry impulses from the sensory receptors
Motor (efferent) neurons
Carry impulses from the central nervous
system to muscles and glands

19. Functional Classification of
Neurons
Slide
7.14b
 Interneurons (association neurons)
Found in neural pathways in the central
nervous system
Connect sensory and motor neurons

20. Neuron Classification
Slide 7.15
Figure 7.6

21. How Neurons Function
(Physiology)
Slide 7.17
 Irritability – ability to respond to stimuli
 Conductivity – ability to transmit an
impulse
 The plasma membrane at rest is
polarized
Fewer positive ions are inside the cell than
outside the cell

22. Starting a Nerve Impulse
Slide 7.18
 Depolarization – a
stimulus depolarizes the
neuron’s membrane
 A depolarized
membrane allows
sodium (Na+) to flow
inside the membrane
 The exchange of ions
initiates an action
potential in the neuron
Figure 7.9a–c

23. The Action Potential
Slide 7.19
 If the action potential (nerve impulse)
starts, it is propagated over the entire
axon
 Potassium ions rush out of the neuron
after sodium ions rush in, which
repolarizes the membrane
 The sodium-potassium pump restores
the original configuration
This action requires ATP

24. Nerve Impulse Propagation
Slide 7.20
 The impulse
continues to move
toward the cell body
 Impulses travel
faster when fibers
have a myelin
sheath
Figure 7.9c–e

25. All-or-None Response
• Greater intensity of the stimulation does not
produce a stronger impulse but rather more
impulses are sent
• Remember this from the muscular system??

26. Continuation of the Nerve Impulse
btwn. Neurons (Conductivity)
Slide 7.21
 Impulses are able to cross the synapse
to another nerve (electrochemical
event)
Neurotransmitter is released from a nerve’s
axon terminal
The dendrite of the next neuron has
receptors that are stimulated by the
neurotransmitter
An action potential is started in the dendrite

27. How Neurons Communicate at
Synapses
Slide 7.22
Figure 7.10

28. Ways to slow conduction
• Alcohol
• Sedatives
• Anesthetics
• Cold
• Continuous pressure

29. The Reflex Arc
Slide 7.23
 Reflex – rapid, predictable, and
involuntary responses to stimuli
 Reflex arc – direct route from a sensory
neuron, to an interneuron, to an effector
Figure 7.11a

30. Simple Reflex Arc
Slide 7.24
Figure 7.11b, c

31. • The knee-jerk reflex is an example of a 2-
neuron reflex arc (sensory receptor, afferent
neuron, efferent neuron, efferent organ)
• What would be the componeets of a 3-
neuron reflex arc?

32. Types of Reflexes and Regulation
Slide 7.25
 Autonomic reflexes
Smooth muscle regulation
Heart and blood pressure regulation
Regulation of glands
Digestive system regulation
 Somatic reflexes
Activation of skeletal muscles

33. Central Nervous System (CNS)
Slide 7.26
 CNS develops from the embryonic
neural tube
The neural tube becomes the brain and
spinal cord
The opening of the neural tube becomes
the ventricles
Four chambers within the brain
Filled with cerebrospinal fluid

34. Regions of the Brain
Slide 7.27
 Cerebral
hemispheres
 Diencephalon
 Brain stem
 Cerebellum Figure 7.12

35. Cerebral Hemispheres (Cerebrum)
Slide
 Paired (lf & rt)
superior parts of
the brain=
hemispheres
 Include more
than half of the
brain mass
 Largest & most
complex area of
the brain
Figure 7.13a

36. Cerebral Hemispheres (Cerebrum)
Slide
 The surface
is made of
ridges (gyri)
and grooves
(sulci)
Figure 7.13a

37. Lobes of the Cerebrum
Slide
 Fissures (deep grooves) divide the
cerebrum into lobes
 Longitudinal fissure – separates
hemispheres
 Lobes of the cerebrum
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe

38. Lobes of the Cerebrum
Slide
Figure 7.15a

39. Lobes of the brain
Slide 7.30
 Frontal Lobe
Primary motor area – sends impulses
to skeletal muscles
Broca’s area – involved in our ability
to speak
Intellectual and psychic functions

40. Sensory and Motor Areas of the
Cerebral Cortex
Slide 7.31
Figure 7.14

41. Slide
 Temporal Lobe
Gustatory, auditory, olfactory area
 Occipital Lobe
Visual areas
 Parietal Lobe
Sensations; pain; hot & cold; touch; speech
& reading

42. Specialized Area of the Cerebrum
Slide
 Interpretation areas of the cerebrum
Speech/language region
Language comprehension region
General interpretation area

43. Specialized Area of the Cerebrum
Slide
Figure 7.13c

44. Layers of the Cerebrum
Slide
 Gray matter
Outer layer
Composed
mostly of neuron
cell bodies
Initiates
thoughts &
voluntary actions
Figure 7.13a

45. Layers of the Cerebrum
Slide
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 White matter
Fiber tracts
inside the gray
matter
Example:
corpus callosum
connects
hemispheres
Figure 7.13a

46. Diencephalon
Slide
 Sits on top of the brain stem
 Enclosed by the cerebral heispheres
 Made of three parts
Thalamus
Hypothalamus
Epithalamus

47. Thalamus
Slide 7.35
 The relay station for sensory impulses
 Transfers impulses to the correct part of
the cortex for localization and
interpretation
 Ability to concentrate
 Degree of wakefulness
 Pleasantness & unpleasantness

48. Hypothalamus
Slide
Helps regulate body temperature
Controls water balance
Regulates metabolism
Appetite and thirst
An important part of the limbic system
(emotions)
The pituitary gland is attached to the
hypothalamus

49. Epithalamus
Slide 7.37
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Houses the pineal body (an endocrine
gland) – sexual maturity and growth
 Includes the choroid plexus – forms
cerebrospinal fluid

50. Brain Stem
Slide
 Attaches to the spinal cord
 Parts of the brain stem
Midbrain
Pons
Medulla oblongata
 Size your thumb (~ 3 inches)

51. Midbrain
Slide 7.39
 Mostly composed of tracts of nerve
fibers
Reflex centers for vision and hearing

52. Pons
Slide 7.40
 The bulging center part of the brain
stem
 Mostly composed of fiber tracts
 Includes nuclei involved in the control of
breathing

53. Medulla Oblongata
Slide 7.41
 The lowest part of the brain stem
 Merges into the spinal cord
 Contains important control centers
Heart rate control
Blood pressure regulation
Breathing
Swallowing
Vomiting

54. Cerebellum
Slide
 Two hemispheres with convoluted
surfaces
 Functions in balance and coordination
 Provides involuntary coordination of
body movements

55. Cerebellum
Slide
Figure 7.15a

56. Protection of the Central Nervous
System
Slide
 Scalp and skin
 Skull and vertebral column
 Meninges
Figure 7.16a

57. Protection of the Central Nervous
System
Slide
 Cerebrospinal fluid
 Blood brain barrier
Figure 7.16a

58. Meninges
Slide
 Dura mater
Double-layered external covering
Periosteum – attached to surface of the
skull
Meningeal layer – outer covering of the
brain
Folds inward in several areas

59. Meninges
Slide
 Arachnoid layer
Middle layer
Web-like
 Pia mater
Internal layer
Clings to the surface of the brain

60. Cerebrospinal Fluid
Slide 7.46
 Similar to blood plasma composition
 Forms a watery cushion to protect the
brain
 Circulated in arachnoid space,
ventricles, and central canal of the
spinal cord
 Changes in composition help diagnose
disorders

61. Nervous System disorders
• Meningitis – inflammation of the meninges;
serious threat to the brain b/c of bacterial or
viral types may spread into central nervous
tissue
• Encephalitis – inflammation of the brain
• Hydrocephalus – “water on the brain;” CSF
cannot drain and pressure is exerted on the
brain

62. Blood Brain Barrier
Slide 7.48
 Includes the least permeable capillaries
of the body
 Excludes many potentially harmful
substances
 Useless against some substances
Fats and fat soluble molecules
Respiratory gases
Alcohol
Nicotine
Anesthesia

63. Traumatic Brain Injuries (TBI)
Slide 7.49
 Concussion
 Slight or mild brain injury
 Bleeding & tearing of nerve fibers happened
 Recovery likely with some memory loss
 Contusion
 A more severe TBI
 Nervous tissue destruction occurs
 Nervous tissue does not regenerate
 Cerebral edema
 Swelling from the inflammatory response
 May compress and kill brain tissue

64. Cerebrovascular Accident (CVA)
Slide 7.50
 Commonly called a stroke
 The result of a ruptured blood vessel
supplying a region of the brain
 Brain tissue supplied with oxygen from
that blood source dies
 Loss of some functions or death may
result

65. Alzheimer’s Disease
Slide 7.51
 Progressive degenerative brain disease
 Mostly seen in the elderly, but may
begin in middle age
 Structural changes in the brain include
abnormal protein deposits and twisted
fibers within neurons
 Victims experience memory loss,
irritability, confusion and ultimately,
hallucinations and death

66. Spinal Cord
 Extends from medulla
oblongata to T12 region
 31 pairs of nerves
 Fxn is to conduct nerve
impulses& serve for
spinal reflex centers
 Spinal tap – withdrawal
of CSF (2-3 ml);
decreases pressure
and can diagnose
problems

67. Peripheral Nervous System
Slide 7.55
 Nerves and ganglia outside the central
nervous system
 Nerve = bundle of neuron fibers
 Neuron fibers are bundled by
connective tissue

68. Classification of Nerves (PNS)
Slide 7.57
 Mixed nerves – both sensory and motor
fibers
 Afferent (sensory) nerves – carry
impulses toward the CNS
 Efferent (motor) nerves – carry impulses
away from the CNS

69. PNS Structure
1. Sensory (afferent) division – nerve fibers
that convey impulses to the CNS from
sensory receptors
a. Somatic sensory fibers – impulses from skin,
skeletal muscles, and joints
b. Visceral sensory fibers – impulses from
visceral organs

70. PNS structure (cont.)
2. Motor (efferent) division – caries impulses
from the CNS to organs, muscles and
glands; causes a response
a. (somatic ( voluntary) nervous system – allows
voluntary contraction of skeletal muscles
b. Autonomic ( involuntary ) nervous system –
regulates involuntary actions, such as glands,
cardiac, and muscles

71. Autonomic Nervous System
Slide 7.67
 The involuntary branch of the nervous
system
 Consists of only motor nerves
 Divided into two divisions
Sympathetic division
Parasympathetic division

72. Comparison of Somatic and
Autonomic Nervous Systems
Slide 7.69
Figure 7.24

73. Anatomy of the Autonomic Nervous
System
Slide 7.73
Figure 7.25

74. Autonomic Functioning
Slide
 Sympathetic – “fight-or-flight”
Response to unusual stimulus
Takes over to increase activities
Remember as the “E” division = exercise,
excitement, emergency, and
embarrassment

75. Autonomic Functioning
Slide
 Parasympathetic – housekeeping
activities
Conserves energy
Maintains daily necessary body functions
Remember as the “D” division - digestion,
defecation, and diuresis

76. Development Aspects of the
Nervous System
Slide
7.75a
 The nervous system is formed during
the first month of embryonic
development
 Any maternal infection can have
extremely harmful effects
 The hypothalamus is one of the last
areas of the brain to develop

77. Development Aspects of the
Nervous System
Slide
 No more neurons are formed after birth,
but growth and maturation continues for
several years (new evidence!)
 The brain reaches maximum weight as
a young adult
 However, we can always grow
dendrites!

78. Nervous System Disorders
1. Cerebral palsy – neuromuscular disability
where voluntary muscles are poorly controlled;
causes by a temporary lack of oxygen to motor
areas of the brain during delivery
2. Spina bifada – results when vertebrae from
incompletely; part of the spinal cord is
functionless
3. Parkinson’s disease – disorder in the ganglia
characterized by shaking

79. Nervous System Disorders
4. Orthostatic hypertension – type of low blood
pressure resulting from changes in body position
(sympathetic)
5. Brain shrinkage – common but sped up in
boxers and alcoholics (both groups exhibit signs
of dementia unrelated to aging)
6. Epilepsy – characterized by seizures – caused
by sudden bursts of irregular electrical activity
in the brain

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