2. The Nervous System
Two Organ Systems Control All the Other Organ Systems:
Nervous System characteristics
Rapid response
Brief duration
Endocrine System characteristics
Slower response
Long duration

3. The Nervous System Two Anatomical Divisions:
Central Nervous System (CNS)
Brain
Spinal cord
Peripheral Nervous System (PNS)
All the neural tissue outside CNS
Afferent division (sensory input)
Efferent division (motor output)
Somatic nervous system (controls skeletal muscle)
Autonomic nervous system (controls smooth & cardiac muscle)

4. CENTRAL NERVOUS SYSTEM
Information
Processing
PERIPHERAL
NERVOUS
SYSTEM
Sensory information
within
afferent division
Motor commands
within
efferent division
includes
Somatic
nervous
system
Autonomic
nervous system
Parasympathetic
division
Sympathetic
division
Receptors
Effectors
Smooth
muscle
Somatic sensory
receptors (monitor
the outside world
and our position
in it)
Visceral sensory
receptors (monitor
internal conditions
and the status
of other organ
systems)
Skeletal
muscle
Cardiac
muscle
Glands
Adipose
tissue

5. Neural Tissue Organization
Two Classes of Neural Cells:
Neurons
For information transfer, processing, and storage
Neuroglia
Supporting framework for neurons
Contain imbedded phagocytes

6. Neural Tissue Organization
Three Classes of Neurons:
Sensory neurons
Deliver information to CNS
Motor neurons
Stimulate or inhibit peripheral tissues
Interneurons (association neurons)
Located between sensory and motor neurons
Analyze inputs, coordinate outputs

7. Neural Tissue Organization
Neuron Anatomy:
Cell body
Nucleus
Mitochondria, RoughER, other organelles
Dendrites
Several branches
Signal receptors (inward)
Axon
Signal propagation (outward)

8. Anatomy of a Typical Neuron

9. Neural Tissue Organization
Structural Classes of Neurons:
Unipolar
Dendrite, axon continuous, cell body off to one side
Sensory neurons
Multipolar
Many dendrites, one axon
Most common class of neuron
Motor Neurons
Bipolar
One dendrite, one axon
Very rare, found in sense organs

10. Structural Classification of Neurons

11. Neural Tissue Organization
Types of Neuroglia (glia):
Astrocytes
Part of blood-brain barrier
Oligodendrocytes
Responsible for myelination(protective covering) around axons
Microglia
Phagocytic defense cells
Ependymal cells
Lining of brain, spinal cord cavities
Source of cerebrospinal fluid

12. Neuroglia in the CNS

13. Neural Tissue Organization
Two Types of Neuroglia in the PNS:
Satellite cells
Surround cell bodies
Schwann cells
Surround all peripheral axons
Form myelin sheath on myelinated axons

14. Schwann Cells & Peripheral Axons

15. Neural Tissue Organization
Key Note:
Neurons perform all of the communication, information processing, and control functions of the nervous system.
Neuroglia outnumber neurons and have functions essential to preserving the physical and biochemical structure of neural tissue and the survival of neurons.

16. Neural Tissue Organization
Anatomic Organization of CNS Neurons:
Center—Collection of neurons with a shared function
Nucleus—A center with a discrete anatomical boundary
Neural cortex—Gray matter covering of brain portions
White matter—Bundles of axons (tracts) that share origins, destinations, and functions

17. Neural Tissue Organization
Anatomic Organization of PNS Neurons:
Ganglia—Groupings of neuron cell bodies
Nerve—Bundle of axons supported by connective tissue
Spinal nerves
To/from spinal cord
Cranial nerves
To/from brain

18. Neural Tissue Organization

19. Neural Tissue Organization
Pathways in the CNS:
Ascending pathways
- Carry information from sensory receptors to processing centers in the brain
Descending pathways
- Carry commands from specialized CNS centers to skeletal muscles

20. Neuron Function The Membrane Potential Resting potential
Excess negative charge inside the neuron
Created and maintained by Na-K ion pump
Negative voltage (potential) inside
-70 mV (0.07 Volts)

21. Cell Membrane at the Resting Potential

22. Neuron Function
A membrane potential exists across the cell membrane because:
the cytosol and the extracellular fluid differ in their ionic composition, and
(2) the cell membrane is selectively permeable to these ions.
The membrane potential can quickly change, as the ionic permeability of the cell membrane changes, in response to chemical or physical stimuli.

23. Transmembrane potential (mV)
Activation of voltage-
regulated sodium channels
and rapid depolarization
Depolarization to threshold
Sodium ions
Local
current
Potassium ions
Inactivation of sodium
channels and activation of
voltage-regulated
potassium channels
+30
DEPOLARIZATION
REPOLARIZATION 3 2
Transmembrane potential (mV)
The return to normal
permeability and resting state _
Threshold 60 _ 1 70 4
Resting
potential
REFRACTORY PERIOD 1 2 3
Time (msec)

24. Neuron Function Key Note:
“Information” travels within the nervous system primarily in the form of propagated electrical signals known as action potentials. The most important information (e.g., vision, balance, movement), is carried by myelinated axons.

25. Neural Communication Synapse Basics Intercellular communication
Axon terminal receives electrical signal from cell body
Input to next cell
Chemical signaling to cross synapse
Neurotransmitter release

26. Neural Communication Structure of a Synapse: Presynaptic components
Axon terminal
Synaptic knob
Synaptic vesicles
Synaptic cleft
Postsynaptic components
Neurotransmitter receptors

27. The Structure of a Typical Synapse
Neural Communication
The Structure of a Typical Synapse

28. Neural Communication Synaptic Function and Neurotransmitters
Cholinergic synapses
Release neurotransmitter acetylcholine
Enzyme in synaptic cleft (acetylcholinesterase) breaks it down
Adrenergic synapses
Release neurotransmitter norepinephrine
Dopaminergic synapses
Release neurotransmitter dopamine

29. Neural Communication An action potential arrives and
depolarizes the synaptic knob
Extracellular Ca2+ enters the synaptic
cleft triggering the exocytosis of ACh
PRESYNAPTIC
NEURON
Action potential
Synaptic vesicles
EXTRACELLULAR
FLUID
ACh ER
Synaptic
knob
Synaptic
cleft
Ca2+
Ca2+
AChE
Chemically regulated
sodium channels
POSTSYNAPTIC
NEURON
CYTOSOL
ACh is removed by AChE
(acetylcholinesterase)
ACh binds to receptors and depolarizes
the postsynaptic membrane
Initiation of
action potential
if threshold
is reached
Propagation of
action potential
(if generated)
Na2+
Receptor
Na2+
Na2+
Na2+
Na2+

30. Neural Communication Neuronal pools Divergence Convergence
Groups of interconnected neurons with specific functions
Divergence
Spread of information from one neuron to several others
Convergence
Several neurons send information to one other

31. Two Common Types of Neuronal Pools
Neural Communication
Two Common Types of Neuronal Pools

32. Neural Communication Key Note:
A synaptic terminal releases a neuro-transmitter that binds to the postsynaptic cell membrane. The result is a brief, local change in the permeability of the postsynaptic cell.
Many drugs affect the nervous system by stimulating neurotransmitter receptors and thus produce complex effects on perception, motor control, and emotions.

33. The Central Nervous System
Meninges—Layers that surround and protect the brain and spinal cord (CNS)
Dura mater (“tough mother”)
Tough, fibrous outer layer
Epidural space above dura of spinal cord
Arachnoid (“spidery”)
Subarchnoid space
Cerebrospinal fluid
Pia mater (“delicate mother”)
Thin inner layer

34. The Meninges

35. The Meninges

36. The Central Nervous System
Spinal Cord Basics:
Relays information to/from brain
Processes some information on its own (reflexes)
Divided into 31 segments
Each segment has a pair of:
Dorsal root ganglia
Dorsal roots
Ventral roots
Gray matter appears as horns
White matter organized into columns

37. Anatomy of the Spinal Cord

38. Anatomy of the Spinal Cord

39. Sectional Anatomy of the Spinal Cord

40. Sectional Anatomy of the Spinal Cord

41. The Central Nervous System
Key Note:
The sensory and motor nuclei (gray matter) of the spinal cord surround the central canal. Sensory nuclei are dorsal, motor nuclei are ventral. A thick layer of white matter consisting of ascending and descending axons covers the gray matter. These axons are organized into columns of axon bundles with specific functions. This highly organized structure often enables predicting the impact of particular injuries.

42. The Central Nervous System
Brain Regions
Cerebrum
Diencephalon
Midbrain
Pons
Medulla oblongata
Cerebellum

43. The Brain

44. The Brain

45. The Brain

46. The Central Nervous System
Brain—The four hollow chambers in the center of the brain filled with cerebrospinal fluid (CSF)
CSF produced by choroid plexus
CSF circulates
From ventricles and central canal
To subarachoid space
Accessible by lumbar puncture
To blood stream

47. Ventricles of the Brain

48. Circulation of Cerebrospinal Fluid

49. The Central Nervous System
Functions of the Cerebrum:
Conscious thought
Intellectual activity
Memory
Origin of complex patterns of movement
Anatomy of Cerebral Cortex:
Highly folded surface
Elevated ridges (gyri)
Shallow depressions (sulci)

50. The Central Nervous System
Functions of the Cerebral Cortex
Hemispheres serve opposite body sides
Primary motor cortex (precentral gyrus)
Directs voluntary movement
Primary sensory cortex (postcentral gyrus)
Receives somatic sensation (touch, pain, pressure, temperature)
Association areas
Interpret sensation
Coordinate movement

51. Surface of Cerebral Hemispheres

52. The Central Nervous System
Hemispheric Lateralization
Categorical hemisphere (usually left)
General interpretative and speech centers
Language-based skills
Representational Hemisphere (usually right)
Spatial relationships
Logical analysis

53. Hemispheric Lateralization

54. (Electroencephalogram)
Brain Waves
(Electroencephalogram)

55. The Central Nervous System
The Basal Nuclei
Lie deep within central white matter of the brain
Responsible for muscle tone
Coordinate learned movements
Coordinate rhythmic movements (e.g., walking)

56. The Basal Nuclei

57. The Central Nervous System
Functions of the Limbic System
Establish emotions and related drives
Link cerebral cortex intellectual functions to brain stem autonomic functions
Control reflexes associated with eating
Store and retrieve long-term memories

58. The Limbic System

59. The Central Nervous System
The Diencephalon
Switching and relay center
Integration of conscious and unconscious motor and sensory pathways
Components include:
Epithalamus
Choroid plexus
Pineal body
Thalamus
Hypothalamus

60. The Central Nervous System
The Diencephalon and Brain Stem
Figure 8-24(a)

61. The Central Nervous System
Functions of the Thalamus
Relay and filter all ascending (sensory) information
Relay a small proportion to cerebral cortex (conscious perception)
Relay most to basal nuclei and brain stem centers
Coordinate voluntary and involuntary motor behavior

62. The Central Nervous System
Functions of the Hypothalamus
Produce emotions and behavioral drives
Coordinate nervous and endocrine systems
Secrete hormones
Coordinate voluntary and autonomic functions
Regulate body temperature

63. The Central Nervous System
Anatomy and Function of the Brain Stem
Midbrain
Process visual, auditory information
Generate involuntary movements
Pons
Links to cerebellum
Involved in control of movement
Medulla oblongata
Relay sensory information
Regulate autonomic function

64. The Central Nervous System
Functions of the Medulla Oblongata
Links brain and spinal cord
Relays ascending information to cerebral cortex
Controls crucial organ systems by reflex
Cardiovascular centers
Respiratory rhythmicity centers

65. The Central Nervous System
Anatomy and Function of the Cerebellum
Oversees postural muscles
Stores patterns of movement
Fine tunes most movements
Links to brain stem, cerebrum, spinal cord
Communicates over cerebellar peduncles

66. The Central Nervous System
Key Note:
The brain, a large mass of neural tissue, contains internal passageways and chambers filled with CSF. The six major regions of the brain have specific functions. As you ascend from the medulla oblongata to the cerebrum, those functions become more complex and variable. Conscious thought and intelligence are provided by the cerebral cortex.

67. The Peripheral Nervous System
PNS Basics
Links the CNS with the body
Carries all sensory information and motor commands
Axons bundled in nerves
Cell bodies grouped into ganglia
Includes cranial and spinal nerves

68. The Peripheral Nervous System
The Cranial Nerves
12 Pairs
Connect to brain not the cord
Olfactory (CN I)
Sense of smell
Optic (CN II)
Sense of vision
Oculomotor (CN III)
Eye movement

69. The Peripheral Nervous System
The Cranial Nerves (continued)
Trochlear (CN IV)
Eye movement
Trigeminal (CN V)
Eye, jaws sensation/movement
Abducens (CN VI)
Facial (CN VII)
Face, scalp, tongue sensation/movement
Vestibulocochlear (CN VIII)
Hearing, balance

70. The Peripheral Nervous System
The Cranial Nerves (continued)
Glossopharyngeal (CN IX)
Taste, swallowing
Vagus (CN X)
Autonomic control of viscera
Accessory (CN XI)
Swallowing, pectoral girdle movement
Hypoglossal (CN XII)
Tongue movement

71. The Cranial Nerves

72. The Cranial Nerves

73. The Peripheral Nervous System
Key Note:
The 12 pairs of cranial nerves are responsible for the special senses of smell, sight, and hearing/balance, and control movement of the eye, jaw, face, tongue, and muscles of the neck, back, and shoulders. They also provide sensation from the face, neck, and upper chest and autonomic innervation to thoracic and abdominopelvic organs.

74. The Peripheral Nervous System
The Spinal Nerves
31 Pairs
8 Cervical
12 Thoracic
5 Lumbar
5 Sacral
Dermatome—Region of the body surface monitored by a pair of spinal nerves

75. The Peripheral Nervous System
Nerve Plexus—A complex, interwoven network of nerves
Four Large Plexuses
Cervical plexus
Brachial plexus
Lumbar plexus
Sacral plexus

76. The Peripheral Nervous System
Reflex—An automatic involuntary motor response to a specific stimulus
The 5 steps in a reflex arc
Arrival of stimulus and activation of receptor
Activation of sensory neuron
CNS processing of information
Activation of motor neuron
Response by effector (muscle or gland)

77. Reflex Action Sensation relayed to the brain by collateral Dorsal root
Arrival of
stimulus and
activation of
receptor
Activation of a
sensory neuron
REFLEX
ARC
Receptor
Stimulus
Effector
Ventral
root
Information
processing
in CNS
Response
by effector
Activation of a
motor neuron
KEY
Sensory neuron
(stimulated)
Excitatory
interneuron
Reflex Action
Motor neuron
(stimulated)

78. The Peripheral Nervous System
Examples of Reflexes
Monosynaptic reflex—Simplest reflex arc; sensory neuron synapses directly on motor neuron
Stretch reflex—Monosynaptic reflex to regulate muscle length and tension (example: patellar reflex)
Muscle spindle—Sensory receptor in a muscle that stimulates the stretch reflex

79. Stretching of muscle tendon stimulates muscle spindles Muscle spindle
(stretch receptor)
Stretch
Spinal
cord
REFLEX
ARC
Contraction
Activation of motor
neuron produces reflex
muscle contraction
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

80. The Peripheral Nervous System
Polysynaptic reflex—A reflex arc with at least one interneuron between the sensory afferent and motor efferent
Has a longer delay than a monosynaptic reflex (more synapses)
Can produce more complex response
Example: flexor reflex, a withdrawal reflex
Brain can modify spinal reflexes

81. The Flexor Reflex

82. The Peripheral Nervous System
Key Note:
Reflexes are rapid, automatic responses to stimuli that “buy time” for the planning and execution of more complex responses that are often consciously directed.

83. The Peripheral Nervous System

84. The Autonomic Nervous System
Branch of nervous system that coordinates cardiovascular, digestive, excretory, and reproductive functions
Should the lower text be 30 pt?

85. The Autonomic Nervous System
Divisions of the ANS
Sympathetic division
Preganglionic neurons in the thoracic and lumbar segments of the spinal cord
“Fight or flight” system
Parasympathetic division
Preganglionic neurons in the brain and sacral segments
“Rest and digest” system

86. The Autonomic Nervous System
Key Note:
The two divisions of the ANS operate largely without our awareness. The sympathetic division increases alertness, metabolic rate, and muscular abilities;
The parasympathetic division reduces metabolic rate and promotes visceral activities such as digestion.

87. The Sympathetic Division

88. The Autonomic Nervous System
Effects of Sympathetic Activation
Generalized response in crises
Increased alertness
Feeling of euphoria and energy
Increased cardiovascular activity
Increased respiratory activity
Increased muscle tone

89. The Parasympathetic Division

90. The Autonomic Nervous System
Effects of Parasympathetic Activation
Relaxation
Food processing
Energy absorption
Brief effects at specific sites

91. The Autonomic Nervous System
Relationship between the Two Divisions:
Sympathetic division reaches visceral and somatic structures throughout the body
Parasympathetic division reaches only visceral structures via cranial nerves or in the abdominopelvic cavity
Many organs receive dual innervation
In general, the two divisions produce opposite effects on the their target organs

92. Aging and the Nervous System
Age-Related Changes
Reduction in brain size and weight
Loss of neurons
Decreased brain blood flow
Changes in synaptic organization of the brain
Intracellular and extracellular changes in CNS neurons