More Related Content Similar to Nervous System.ppt Similar to Nervous System.ppt (20) More from LeaCamillePacle More from LeaCamillePacle (20) Nervous System.ppt1. Essentials of Human Anatomy & Physiology
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Seventh Edition
Elaine N. Marieb
Chapter 9
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
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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
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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
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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
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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
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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
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Schwann cells
Form myelin sheath in the peripheral
nervous system
Figure 7.3e
11. Nervous Tissue: Neurons
Slide 7.8
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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)
13. Neuron Anatomy
Slide 7.10
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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
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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
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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
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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
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Sensory (afferent) neurons
Carry impulses from the sensory receptors
Motor (efferent) neurons
Carry impulses from the central nervous
system to muscles and glands
21. How Neurons Function
(Physiology)
Slide 7.17
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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
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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
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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
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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
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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
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Figure 7.10
28. Ways to slow conduction
• Alcohol
• Sedatives
• Anesthetics
• Cold
• Continuous pressure
29. The Reflex Arc
Slide 7.23
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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
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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
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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
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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
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Cerebral
hemispheres
Diencephalon
Brain stem
Cerebellum Figure 7.12
35. Cerebral Hemispheres (Cerebrum)
Slide
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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
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
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Figure 7.15a
39. Lobes of the brain
Slide 7.30
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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
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Figure 7.14
41. Slide
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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
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Interpretation areas of the cerebrum
Speech/language region
Language comprehension region
General interpretation area
43. Specialized Area of the Cerebrum
Slide
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Figure 7.13c
44. Layers of the Cerebrum
Slide
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Gray matter
Outer layer
Composed
mostly of neuron
cell bodies
Initiates
thoughts &
voluntary actions
Figure 7.13a
45. Layers of the Cerebrum
Slide
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White matter
Fiber tracts
inside the gray
matter
Example:
corpus callosum
connects
hemispheres
Figure 7.13a
46. Diencephalon
Slide
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Sits on top of the brain stem
Enclosed by the cerebral heispheres
Made of three parts
Thalamus
Hypothalamus
Epithalamus
47. Thalamus
Slide 7.35
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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
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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
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Houses the pineal body (an endocrine
gland) – sexual maturity and growth
Includes the choroid plexus – forms
cerebrospinal fluid
50. Brain Stem
Slide
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Attaches to the spinal cord
Parts of the brain stem
Midbrain
Pons
Medulla oblongata
Size your thumb (~ 3 inches)
51. Midbrain
Slide 7.39
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Mostly composed of tracts of nerve
fibers
Reflex centers for vision and hearing
52. Pons
Slide 7.40
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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
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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
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Two hemispheres with convoluted
surfaces
Functions in balance and coordination
Provides involuntary coordination of
body movements
56. Protection of the Central Nervous
System
Slide
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Scalp and skin
Skull and vertebral column
Meninges
Figure 7.16a
57. Protection of the Central Nervous
System
Slide
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Cerebrospinal fluid
Blood brain barrier
Figure 7.16a
58. Meninges
Slide
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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
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Arachnoid layer
Middle layer
Web-like
Pia mater
Internal layer
Clings to the surface of the brain
60. Cerebrospinal Fluid
Slide 7.46
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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
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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
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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
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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
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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
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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
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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
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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
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73. Anatomy of the Autonomic Nervous
System
Slide 7.73
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Figure 7.25
74. Autonomic Functioning
Slide
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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
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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
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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
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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