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The Nervous System
M. Trotter 2011
Color
•
The famous "Stroop Effect" is named after J. Ridley Stroop who discovered
this strange phenomenon in the 1930s. Here is your job: name the colors of
the following words. Do NOT read the words...rather, say the color of the
words. For example, for the word BLUE, you should say "RED". Say the colors
as fast as you can. It is not as easy as you might think!
Phineas Gage
Phineas Gage
A system that controls all of the activities of the body.
The nervous system is made of:
The brain
The nerves
The spinal cord
The senses
The nervous system also allows you to react to a stimulus.
A stimulus is a change in the environment.
Example: A hot stove
Or… tripping over a rock
Your reactions are automatic.
Automatic means that you do not have to think about your reactions.
Example: If a bug flies by your eye,
you will blink.
The Nervous System
Can also be
thought of as the
central processing
unit
7
Nervous System
Parts of the Nervous System
• Central Nervous System (CNS): brain and spinal
cord
• Peripheral Nervous System (PNS): craniospinal
nerves
• Autonomic Nervous System (ANS): nerves that
control vital organs: heart, lungs, brain, etc.
9
Neurons: nervous system cells
• All neurons have:
one axon
one cell body
one or more
dendrite(s)
10
Basic nerve cell structure
Types of Neurons
type
connected to
carry
impulses
from
sensory
receptors (eyes,
ears, other sense
organs)
other neurons
sense organs spinal cord
and brain
(efferent)
effectors (muscles
and glands)
other neurons
spinal cord
and brain
muscles
and glands
connector
other neurons
other
neurons
other neurons
(afferent)
motor
(interneuron)
carry
impulses
to
12
3 main types of nerve cells
sensory
neurone
relay
neurone
motor
neurone
Sensory neurons
Carries impulses from receptors e.g pain
receptors in skin to the CNS( brain or spinal
cord)
Relay neuron
Carries impulses from sensory nerves to
motor nerves.
Motor neuron
Carries impulses from CNS to effector e.g.
muscle to bring about movement or gland to
bring about secretion of hormone e.g ADH
Transmission of signals
The Synapse
Receptors
(eyes, ears, other sense
organs)
change information from outside
the body ( for example, light
waves) into electrical
impulses.
19
Thermo-receptors
 Location:
 Skin
 Hypothalamus
 Body Core
 Function:
 Sensation of hot and
cold
 Detects change in
body core temp.
Mechano-receptors
• Location:
– Skin
– Skeletal muscle
– Inner ear
• Function:
–
–
–
–
–
Touch
Pressure
Muscle movement
Motion
Sound
Chemo-receptors
• Location:
– Nose
– Tongue (taste buds)
– Blood vessels
• Function:
– Smell
– Taste
– Detects levels of CO2 in
blood
Photo-receptors
 Location:
 Eyes
 Function:
 Allow vision thru detection of light
Pain-receptors
Location:
Everywhere, except the
brain
Function:
Sensation of pain
Detects chemicals
released by damaged
cells
Neurons
• What is grey matter?
– Collective cell bodies and
dendrites of all neurons
• What is white matter?
– Myelinated nerve fibers
– Axons of all neurons
– Can be approximately
one meter in length
White matter
Gray matter
What is a Nerve?
• Bundle of axons
held together by
connective tissue.
• What color is
a nerve?
• White!
• Why?
• Because axons
are white matter
and they compose
nerves
How are nerves held together?
• Connective tissue
• What is this connective
tissue called?
• Neuroglial cells (nerve glue)
• Approximately half of the
volume of the brain is composed
of neuroglial cells
• Most brain tumors develop in
mesoglial cells – NOT neurons
What do neuroglial cells do?
• Support the axons
• Insulate the electrical impulses
• Like electrical tape insulates
electric wires this prevents “leaking”
of electric signals
An example of a neuroglial cell
•
•
•
•
•
•
Schwann cell
This wraps around the axon in multiple layers
It is composed of a fatty material called…
Myelin
Regular breaks in the myelin sheath are called…
Node of Ranvier
•
•
•
Impulse speed
Some neurons are fast, good conductors of
impulses
Other neurons are slow, poor conductors of
impulses
What distinguishes these
two types?
1. Diameter of the axon
2. Myelination
Fastest axons have a large diameter and are
myelinated. How much faster?
Up to 100 times faster! (Reflexes are this type)
The Nerve Impulse
• How are messages (impulses)
carried by the nervous system?
• As electrical and chemical
signals.
• How does the impulse develop?
• Charged particles (ions) move
across the cell membrane
• A neuron is ready to transmit an
impulse when it is in the resting state.
• Resting membrane potential is -70 mV
Resting Membrane Potential
• The inside of the cell has a
negative charge as compared
to the outside of the cell
membrane.
• How does this charge
difference develop?
• There are more Na+ (sodium)
ions outside and fewer K+
(potassium) ions inside.
The Nerve Impulse
• How does the impulse begin?
• The neuron is stimulated by
another neuron or by stimuli from
the environment.
The Nerve Impulse
• If the stimulus is
strong enough, it
reaches threshold
level.
• This stimulates an
impulse.
• If the stimulus is not
strong enough, no
impulse occurs (allor-none principal)
The Nerve Impulse
• What happens if threshold is reached?
• An action potential (nerve impulse)
begins
• What is an action potential?
• Rapid reversal of membrane potential
in response to a stimulus
• How does this happen?
• Sodium channels open allowing
Na+ to flood into the cell.
• The membrane potential rises to +30
mV (rising phase) as inside of cell
becomes more positive
The Nerve Impulse
• Please, please, tell us what happens
next…
• When the membrane potential
reaches +30 mV, the sodium channels
close.
• Potassium channels open and K+ flows
out of the cell.
• This causes the membrane
potential to become more
negative again
(falling phase).
The Nerve Impulse
• What happens when the action potential
passes down the axon?
• The resting potential is restored via the
sodium/potassium pump.
• Now the membrane is ready to transmit
another impulse.
K+
extracellular fluid
Na+
ATP
cytoplasm
ADP
The Nerve Impulse
• What happens when the impulse reaches the axon
terminal?
• It must pass thru
the synapse.
• What is a synapse?
• It is the gap between two
neurons, or between a neuron
and organ (effector).
• Why is there a gap?
• So the neurons don’t short each other out!!
The Synapse
• How do neurons pass the impulse
across the synapse?
• Using chemicals called
neurotransmitters
• What do neurotransmitters do?
• Stimulate the dendrites of other
neurons or membranes of other cells.
• If a dendrite is stimulated, it sends its
message to the cell body and the
message is passed on
• If a muscle or gland is stimulated, a
reaction occurs in that organ.
The Synapse
The Synapse
Model of the
Synapse
synaptic vesicles
Axon of
presynaptic cell
Glycoprotein
(ligands)
neurotransmitters
synaptic cleft
receptors for
neurotransmitters
receptors for
glycoprotein
The Synapse
More nerve terms
nerve fibers
Dendrites and axions
nerve
A bundle of dendrites and axions
nucleus
A group of neuron cell bodies INSIDE the brain
and spinal cord
(plural: nucleii)
ganglion
(plural: ganglia)
A group of neuron cell bodies OUTSIDE the
brain and spinal cord
synapse
The space connecting one neuron to another
neurotransmitter
A chemical which transmits an electrical impulse
from one neuron to the next
43
The CNS includes:
White matter:
bundles of axions and dendrites
Gray matter:
masses of nerve cell bodies
The brain:
The spinal cord:
inside the cranium
inside the vertebral column
(the “backbone”)
44
The meninges: three membranes
envelop the entire CNS
(central nervous system)
dura mater
The outer, hardest, toughest
arachnoid
The middle, web like
pia mater
The inner, thinner
45
Spaces between the meninges
Dura mater
Subdural space
Subarachnoid space
Arachnoid
Pia mater
BRAIN
46
Spaces between the meninges .
47
What if a cell dies?
• Neurons cannot reproduce.
• Once a nervous system
connection is broken, it is broken
forever.
48
The Brain
49
Parts of the Brain
•
•
•
•
brainstem
cerebellum
diencephalon
cerebrum
50
Parts of the brainstem
• pons: connects the medulla oblongata, the
cerebellum, and cerebrum
• midbrain: contains auditory (hearing), visual (sight),
and muscle control centers.
• medulla oblongata: lowest and most posterior
(at the back of the brain)
The hindbrain includes the pons and the
medulla.
51
The brainstem
www.daviddarling.info/images/brainstem.jpg
52
The pons (the bridge)
Connects the medulla oblongata,
cerebellum, and cerebrum
Associates with sensory nerves: taste, hearing,
and balance.
Controls muscles of the face.
53
The medulla oblongata
controls
alertness
heart action
respiration (breathing)
blood pressure
connects the CEREBRUM with the SPINAL CORD
the RIGHT side of the brain controls the LEFT side of the body.
the LEFT side of the brain controls the RIGHT side of the body.
54
The midbrain
controls
vision
hearing
muscles
55
The cerebellum
coordinates muscle activity.
has three parts:
the vermis
the right cerebellar hemisphere
the left cerebellar hemisphere
56
The diencephalon
is located between the midbrain
and the cerebrum
has three parts:
the thalamus: receives sensory
information and sends it to the
cerebral cortex.
the epithalamus: contains the
pineal body and olfactory centers.
the hypothalamus: connects the
endocrine and nervous systems.
http://www.daviddarling.info/encyclopedia/A/anatomy_and_physiology.html
57
The hypothalamus
connects the endocrine and nervous
systems.
controls
the autonomic nervous system
body temperature
carbohydrate and fat metabolism
appetite
emotions
www.brainexplorer.org
58
The cerebrum
is divided into two cerebral hemispheres
has an outer surface,
or CORTEX,
made of “gray matter”
www.laskerfoundation.org
59
The cerebral cortex
is divided into parts called lobes:
1. the frontal lobe
2. the parietal lobe
3. the temporal lobe
4. the occipital lobe
www.colorado.edu
60
The frontal lobe
is the center for voluntary movement
is called the “motor area” (movement)
includes the prefrontal area,
for intelligence, creativity, memory, and
ideas.
61
The parietal lobe
Collects, recognizes, and organizes
sensations:
feelings of
pain
temperature
touch
position
movement
62
The temporal lobe
• processes auditory (hearing)
information
• stores auditory (hearing) and
visual (seeing) memories
• includes Broca’s speech area
63
The occipital lobe p. 282
is at the back of the cerebral
hemisphere
involves
vision
visual memory
eye movements
64
Side to side?
- The right
hemisphere
controls the left
side of the body!
The left
hemisphere
controls the right
side of the body!
65
The limbic system p. 282
The limbic system
controls emotions and
memory
67
Cerebrospinal fluid
• Cerebrospinal fluid: watery liquid
is found inside the brain, spinal
cord, and subarachnoid space
supports the brain’s weight
protects and cushions the brain
and the spinal cord
68
PNS: Peripheral Nervous System
• Includes all the nerves and
ganglia outside the brain and
spinal cord
cranial nerves: 12 pairs of nerves
connected directly to the brain
spinal nerves: 31 pairs of nerves
connected to the spinal cord
69
Nerve Pathways
Somatic (body) motor pathways
carry impulses from the CNS
(central nervous system) to
skeletal muscles
• pyramidal pathways carry
impulses that control voluntary
actions that involve thought
• extrapyramidal pathways carry
impulses that control automatic
movements, such as walking
70
Reflexes
• A reflex is an action that:
occurs below the brain, within in
the spinal cord
is an automatic reaction
is not conscious (voluntary)
can be inborn (a baby has it at birth,
such as sucking, swallowing,
urinating)
can be learned (such as
talking,walking, driving)
71
More reflexes
• INBORN
knee jerk reflex
pupillary reflex
Babinski
swallowing
coughing
blinking
• LEARNED
reading
typing
swimming
dancing
skating
playing football
72
Important reflexes
• knee jerk: lower leg jerks when
knee is tapped
• Babinski: toes curl up when sole
of foot is stroked
• pupillary: pupils of eyes contract
in bright light
73
The Autonomic Nervous System
controls
• involuntary, smooth, and cardiac
(heart) muscles and glands.
• systems that work automatically:
digestive, circulatory, respiratory,
urinary, and endocrine.
74
The Autonomic Nervous System
has two parts
• the sympathetic system
• the parasympathetic system
These parts work together to
maintain homeostasis: normal
balance of the systems in the
body.
75
Autonomic Nervous System
• http://faculty.washington.edu/ch
udler/auto.html
Organization of Nervous System
Related Terms: Central
Nervous System
(CNS)
• The part of the nervous system
that includes:
the brain
the spinal cord
78
Related Terms:
Autonomic System
part of the peripheral nervous
system
serves automatic systems
cannot be controlled voluntarily
includes:
parasympathetic system
peripheral system
79
Related Terms:
Peripheral System
part of the nervous system
includes nerves and ganglia outside the
spinal cord and brain:
cranial nerves
spinal nerves
autonomic nervous system
80
•
•
•
•
•
Anatomy
Related Terms:
cerebellum: second largest part
of the brain
cerebrum: largest part of the
brain
cerebral cortex: outer part of the
cerebrum; contains gray matter
cerebrospinal fluid: watery fluid
in the brain and spinal cord
convolution: fold in the surface of
the cerebrum
81
Related Terms:
Anatomy
• corpus callosum: connection
between the two hemispheres
(halves) of the cerebrum
• dura mater: membrane
surrounding the brain and spinal
cord
• fissure: deep groove on the
surface of the brain
• foramen magnum: hole in the
back of the cranium through
which the spinal cord passes
82
Related Terms:
anatomy
• hemisphere: either the right or
the left side of the brain
• hippocampus: memory center of
the brain, may be related to
learning and memory problems
• lateral ventricle: open space in
each hemisphere of the brain
• limbic system: the “emotional
brain”
83
Related terms:
Anatomy
• lobes (parts) of the cerebrum
occipital (in the back)
frontal (in the front)
temporal (on top)
parietal (on the sides)
84
Related terms:
Anatomy
• medulla oblongata: posterior part
of the brain connected to the
spinal cord
• meninges: three membranes
surrounding the central nervous
system:
dura mater
pia mater
arachnoid
• midbrain: upper part of the
brainstem
85
Related Terms:
Spinal Nerves
• spinal cord: lowest part of the
central nervous system (CNS);
extends from the medulla
oblongata to the base of the
spine
• subarachnoid: space between the
pia mater and the arachnoid
• subdural space: space between
the dura mater and the
arachnoid.
86
Nerve Structures and Related Terms
• myelinated nerves: nerves covered with
white fatty material called myelin
• neuron: single nerve cell; has a cell body,
axon, and dendrites
• neurotransmitters: chemicals that stimulate
(start) or prohibit (prevent) the
transmission of nervous impulses
87
Nerve Structures and Related Terms
• plexus: network of spinal nerves
• reflex: an action done without a
person’s control, such as blinking
• sensory neurons: nerves that
carry information from the sense
organs to the spinal cord
• synapse: space between two
neurons, across which an impulse
is transmitted (passed)
88
Related Terms: Cranial Nerves
There are 12 pairs of cranial nerves.
Here are a few of them:
• acoustic (also called auditory):
hearing
• facial: facial muscles and taste
• olfactory: sense of smell
89
Related Terms: More Cranial Nerves
• opthalmic: forehead, nose, and
eye
• optic: retina (back) of the eye
• trigeminal: eye and upper and
lower jaws
• vagus: most of the trunk of the
body
90
Cranial Nerves
Cranial Nerve
Mnemonic 1 (nerves)
Mnemonic 2
(alternate)
Mnemonic
3*(Sensory vs.
Motor)
I. Olfactory
On
Oh
Some*
II. Ocular
Old
Oh
Say
III. Oculomotor
Olympus'
Oh
Marry*
IV. Trochlear
Towering
To
Money
V. Trigeminal
Tops
Touch
But*
VI. Abducens
A
And
My
VII. Facial
Fin
Feel
Brother
VIII. Vestibulocochlear/Acoustic
And
A
Says
IX. Glossopharyngeal
German
Good
Big
X. Vagus
Viewed
Vein
Business
XI. Accessory (Spinal Accessory)
Some
Ah
Makes
XII. Hypoglossal
Hops
Heaven
Money
Cranial Nerves
• http://www.pitt.edu/~anat/Neur
o/CranialNerves/CN.htm
Related Terms: Spinal Nerves
There are many spinal nerves.
Spinal nerves are identified by numbers and letters.
C = A nerve connected to one of the cervical (neck) vertebrae
T = A nerve connected to one of the thoracic (upper body)
vertebrae
L = A nerve connected to one of the lumbar ( middle body)
vertebrae
S = A nerve connected to one of the sciatic (lower body)
vertebrae
EX: L4 means the fourth lumbar vertebra
93
Related Terms: Infections
encephalitis: inflammation of the
brain
herpes zoster: infection caused by
herpes virus; characterized by
small blisters on the skin; also
called “shingles”
meningitis: inflammation of the
brain and meninges
myelitis: inflammation of the spinal
cord
94
Related Terms: Infections
• Poliomyelitis (“polio”): virus infection
of the spinal cord, caused by a polio
virus
• Polyneuritis: inflammation of a large
number of spinal nerves at the same
time
• Rabies: infection of the CNS and
salivary glands, transmitted by animal
bite
• Tetanus: acute bacterial infection
caused by a bacterium found in soil,
dust, or animal or human wastes
95
Related Terms: Hereditary and Congenital
Disorders
• hereditary: inherited from a
parent
• congenital: a disorder a child has
at birth
• developmental: a disorder that
appears as a child grows
96
Related Terms: Hereditary and Congenital
Disorders
• anencephaly:
congenital (a child is born with
it)
bones of cranium are
defective
brain and spinal cord do not
develop
• cephalocele: part of the contents
of the cranium protrude through
a hole in the cranium
97
Related Terms: Hereditary and Congenital
Disorders
• epilepsy
nervous system disorder
inherited or the result of trauma
(injury)
patient may have convulsions of four
types:
grand mal
petit mal
psychomotor
focal
98
Related Terms: Hereditary and Congenital
Disorders
• hydrocephalus: enlarged head because of fluid
accumulating inside the cranium
• meningocele: the meninges protrude (stick out)
through a defect in the cranium or spine
• microcephaly: a baby is born with a very small
head
• spina bifida: a baby is born with defective
vertebrae
99
Related Terms: Circulatory Disturbances
• cerebral hemorrhage: bleeding
into the cerebrum
• CVA (cerebrovascular accident)
also called stroke or apoplexy
bleeding in the brain due to
ruptured artery
symptoms: headache, nausea,
vomiting, confusion
100
Related Terms: Circulatory Disturbances
• epidural hematoma: collection of
blood outside the dura mater
• intracranial hemorrhage: bleeding
inside the cranium
• subdural hemorrhage or
hematoma: bleeding between the
dura mater and the arachnoid
membrane
101
Related Terms: Other Organic Abnormalities
• Alzheimer’s disease: progressive
brain disease, mainly of the
elderly (people over 65)
• ALS (amytrophic lateral sclerosis):
progressive nervous system
disease of the spinal cord with
muscle weakness and twitching.
• Aphasia: loss of the ability to
speak or write
• Ataxia: loss of muscle
102
Related Terms: Other Organic Abnormalities
• Alzheimer’s disease: progressive
brain disease, mainly of the
elderly (people over 65)
• ALS (amytrophic lateral sclerosis):
progressive nervous system
disease of the spinal cord with
muscle weakness and twitching.
• aphasia: loss of the ability to
speak or write
• ataxia: loss of muscle
103
Related Terms: Other Organic Abnormalities,
• aura: before an epileptic seizure,
a patient sees, smells, hears, or
feels something unusual.
• Bell’s palsy: weakness on one side
of the face
• cerebral palsy: brain damage
affecting control of muscles
• chorea: nervous disease with
involuntary jerky movements.
104
Related Terms: Other Organic Abnormalities
• coma: patient is unconscious, can’t be
awakened
• delirium: patient has hallucinations, is
excited, restless, and incoherent ( talking in
an illogical way)
• dementia: brain deteriorates because of
disease
• dyskinesia: patient’s movements are
incomplete or uncontrolled, because of
disease
105
Related Terms: Other Organic Abnormalities
• dysphasia: patient doesn’t speak
clearly
• hemiplegia: one side of the body is
paralyzed
• Jacksonian seizures: seizures that start
in a distant part of the body, such as
the fingers, and spread towards the
center of the body
• multiple sclerosis: progressive disorder
of brain and spinal cord, starting early
in life, resulting in tremors, lack of
106
Related Terms: Other Organic Abnormalities
• narcolepsy: patient suddenly falls
asleep
• neuralgia: pain in a nerve
• palsy: paralysis
• paralysis: loss of ability to move a
part of the body
• paraplegia: paralysis of lower
body and legs
• paresis: a form of paralysis
107
Related Terms: Other Organic Abnormalities
• Parkinson’s disease: nervous
system disease of late life
• amnesia: loss of memory
• syncope: fainting
108
Related Terms: Oncology
• glioma: any tumor (cancer) of the
nervous system
109
Surgical Procedures
•
•
•
•
•
craniectomy: removing part of the skull
cranioplasty: repairing the skull
crainotomy: surgical opening of the skull
lobectomy: removing a lobe of the brain
lobotomy: cutting into the frontal lobe of the
brain
• neuroplasty: repair of a nerve
110
Laboratory tests
• brain scan: using a scanner to diagnose defects of
the brain
• cerebrospinal fluid tests: check for blood,
infection,and other abnormalities
• echoencephalogram: using ultrasound to check
the brain for abnormalities
• electroencephalogram (EEG) using a machine to
check for abnormal electrical activity in the brain
• myelography: x-ray of the spinal cord
111