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AP Biology
The
Nervous
System
2003-2004
Overview
 The Nervous System controls and
coordinates all the functions of the
body.
 The Nervous System consists of two
main sub-divisions:


Central Nervous System (CNS)
Peripheral Nervous System (PNS)
• The Peripheral Nervous System is
divided into two sub-divisions:


Somatic- voluntary
Autonomic- involuntary
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http://inside.salve.edu/walsh/cns_pns.jpg
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Structure and Function of the Neuron
 Neuron is the scientific name for a Nerve
Cell.
 Neurons consist of 3 basic structures:



Cyton, or cell body.
Dendrites- receive messages, impulses, and
send them to the cell body.
Axons- send messages away from the cell
body.
• Nerve impulses travel from one neuron to
another across synapses, or spaces in
between the cells.
• The “jumping across” the synapse is
facilitated (helped) by chemicals called
Neurotransmitters. ex: dopamine, serotonin
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Parts of the Neuron
 Dendrites – Branched
parts of a neuron that
receive impulses from
other neurons.
 Cyton (Cell Body)
Contains cytoplasm and
the nucleus. Impulses
pass through here to the
axon.
 Axon- Single long fiber
that carries impulses
away from the cell body.
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 A Neuron
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Myelin Sheath
signal
direction
 Axon coated with insulation
made of myelin cells (Fatty,
protein substance)
speeds signal
 330 mph vs. 11 mph

myelin coating
Multiple Sclerosis
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 immune system (T cells) attacks myelin coating
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 loss of signal
Synapse
Junction between nerve cells


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1st cell releases chemical, called
Neurotransmitter, to trigger next
cell
drugs affect the nervous system at
this junction
synapse
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Synapses
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Drugs and Natural Neurotransmitters
According to the American Society of Addiction Medicine: Opiates affect the body’s natural
neurotransmitters, Dopamine, Serotonin, GABA and Endorphin.
So what do they do for you?
•
•
•
•
•
Serotonin regulates sleep and appetite.
Dopamine is the feel good chemical, plays an important role in mood, energy, attitude, motivation.
GABA acts as your calming neurotransmitter, helping you relax.
Acetylcholine for processing information and memory.
Endorphins are feel good chemicals our bodies release under extreme pain. They are considered the
bodies own opiates.
When opioids, heroin and other prescription pain relievers are abused your brain stops producing these
neurotransmitters.
And here’s why: Opiates release 2 to 10 times the amount of dopamine that natural rewards do.
What do you do if the volume is too loud? You turn it down, right? Well our brain does that same thing
when it adjusts to the overwhelming surges of dopamine (and other neurotransmitters) sent from abusing
drugs.
To compensate for these surges your brain begins to automatically produce much less natural dopamine and
other key neurotransmitters, which in turn can cause a myriad of opioid withdrawal symptoms and health
problems.
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Nerve impulses, Na+ K+ pump
When a nerve fiber
is conducting a
nerve impulse,
which is also known
as the action
potential , a change
in polarity flows
along the axon’s
membrane. A
protein carrier
pumps Na+ out of
the axon and K+
into the axon.
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Types of Neurons
Neurons can also be classified by the direction
that they send information:
･Sensory (or afferent) neurons: send
information from sensory receptors (e.g., in
skin, eyes, nose, tongue, ears) TOWARD the
central nervous system.
･Motor (or efferent) neurons: send information
AWAY from the central nervous system to
muscles or glands.
･Interneurons: send information BETWEEN
sensory neurons and motor neurons. Most
interneurons are located in the central
nervous system.
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Reflexes
 Stimulus- a change
in the environment.
 Response/Reactionhow the body reacts
to a stimulus.
 Reflex Arc- the
pathway that an
impulse follows to
illicit a response to a
stimulus.
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Reflex Arc...

1.
2.
3.
4.
5.
When you touch a hot object you automatically pull your hand away without a conscious effort. Such automatic reflex
actions are governed by a simple combination of neurons called reflex arcs. Usually there are five (5) parts of a reflex arc
(see text):
Receptor - sense organ in skin, muscle, or other organ
Sensory neuron - carries impulse towards CNS
Interneuron - carries impulse within CNS
Motor neuron - carries impulse away from CNS
Effector - structure by which animal responds (muscle, gland, etc).

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Parts of the Central Nervous System
 The Brain
 Spinal cord
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The Brain




Coordinates body activities
Made up of approximately 100 billion neurons
Uses 20% of bodies oxygen and energy
Divided into three major parts


the Cerebrum
the Cerebellum
the Brain Stem (Medulla Oblongata, Pons)
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Cerebrum
 Largest part of the brain
 Thinking
 Memory is stored
 Movements are controlled
 Impulses from the senses are
interpreted.
 Has 2 hemispheres, right and left
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What are YOU?
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Cerebrum specialization
 Regions specialized for different functions
 Lobes

frontal
frontal
parietal
 speech,
control of emotions

temporal
 smell, hearing

occipital
 vision

parietal
 speech, taste
reading
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temporal
occipital
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Cerebellum
 Responsible for the
coordination of
muscles and is the
center of balance
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Medulla
 Center for regulating
heart beat,
respiration, and
other involuntary
actions such as
hiccups, vomiting,
sneezing,
swallowing.
 Medula Oblongata
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Other Structures inside the Brain
 Thalamus – receives messages from
sensory receptors; relays information to
proper regions of cerebrum
 Hypothalamus - Little bean shape,
Regulates hunger, thirst, fatigue, anger,
etc… controls pituitary
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Section 35-3
Cerebrum
Thalamus
Pineal
gland
Hypothalamus
Cerebellum
Pituitary gland
Pons
Medulla oblongata
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Spinal cord
The Spinal Cord
 Extension of the brain stem
 Bundles of neurons that carry impulses
from all parts of the body to the brain
and from the brain to all parts of your
body
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The
Somatic
Peripheral Nervous
System
Your brain and
spinal
cord are
and
Autonomic
connected
to the
Systems
The
rest of yournervous
body by
peripheral
the peripheral
system
has two
nervous
system.The
major
divisions.
The PNSsystem
is made
somatic
up of 12 voluntary
pairs of
controls
nerves from
actions.
It is your
made
brain
cranial
up
of called
the cranial
nerves,
andnerves
31
and
spinal
pairsgo
from
your
that
from
the
spinal cord
called
central
nervous
spinal nerves.
system
to your
Spinal nerves
are
skeletal
muscles.
made
up of bundles
The
autonomic
of
sensory
and the
system
controls
Research
Visit
motor
neurons
involuntary
actionsGlencoe
Science
bound
together
those
not
under by
Web site
at
connective
tissue.
conscious
controltx.science.glencoe.
For
reason,
a
such
as more
your heart
comthis
for
single
spinalabout
nerve
rate,
breathing,
information
can
have impulses
digestion,
and
the nervous
system.
going
tobrochure
and
from
glandular
functions.
Make a
the
brain
at
the
These
two
outlining recent
same
time.
Some
divisions,
along
with
medical
advances.
nerves
contain
only
the
central
nervous
sensory make
neurons,
system,
up
and some
your
body'scontain
nervous
only motor neurons,
system.
but most nerves
contain both types
of neurons.
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Peripheral Nervous System
 Connects body to brain & spinal cord
 12 pairs of nerves from your brain
(cranial nerves)
 31 pairs from your spinal cord (spinal
nerves)

Bundles of sensory and motor neurons
held together by connective tissue
 Two divisions
Somatic
 Autonomic

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Divisions of the PNS:
Somatic Nervous System
 Controls voluntary actions
 Made up of the cranial and spinal
nerves that go from the central nervous
system to your skeletal muscles
Autonomic Nervous System
 Controls involuntary actions-those not
under conscious control-such as your
heart rate, breathing, digestion, and
glandular functions
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2 Divisions of Autonomic N. S.
 Sympathetic division: Important for
flight or fight responses. Stops
digestion, dilates pupils, increases
heart rate and breathing. The
neurotransmitter norepinephrine is
released.
 Parasympathetic division: promotes
internal responses in the relax state.
digestion of food, slows the heart. Uses
the neurotransmitter acetylcholine.
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http://www.christopherreeve.org/Research/Research.cfm?ID=178&c=21
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Alzheimer Disease
 Loss of reason and
memory
 Proteins start to surround
the nucleus in the
neurons.
 Plaques form in axons
 Acetylcholine, the
chemical that stimulates
neurons, seems to
decrease.
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Animals rely on two systems for homeostasis:
Nervous System is a system of nerve cells called neurons. It
consists of a central nervous system (brain and spinal cord)
and peripheral nerves. Typical responses are fast and short
lasting.
Endocrine System is a system of ductless glands that secrete
hormone into the blood. Hormones travel to target tissues.
Typical responses are slow and long lasting.
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Progesterone
Estradiol
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 End of Chapter 8 notes
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Human Endocrine
Glands
Ductless glands
transport hormones in
the blood
Duct glands are
exocrine glands that
use tubes to carry the
secretion
(salivary, tears)
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Pituitary gland and Hypothalamus serve to link the nervous
system other glands and metabolic functions.
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Thyroid and Parathyroid help regulate calcium metabolism
Feedback!
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Goiter: Iodine deficiency and feedback causes the thyroid to
enlarge
This people have a goiter, a condition
that is easily preventable with iodized
salt
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Thyroid regulates metabolism
Graves disease: hyperthyroid
feedback
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Pancreas helps regulate blood glucose
feedback
Insulin from Beta cells reduce blood sugar
Glucagon
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Biologyfrom Alpha cells increase blood sugar
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THE FIGHT OR FLIGHT MECHANISM
•Large amount of adrenaline pumped into the body to put
us in a state of increased alertness
•Blood is redirected away from the extremities to the large
muscles of the body
•The heart starts working harder to move the blood to the
large muscle groups as quickly as it can
•Increase in Respiratory Rate
•Release of red blood cells
•Release of sugar by liver
•Increase in metabolic rate
alektorophobia
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Gonads: Testes and Ovaries produce hormones that
regulate secondary sex traits
Male sex traits include
those changes that occur
during puberty
Androgens include
testosterone
feedback
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Female sex traits
include the
menstrual cycle and
the changes seen
during puberty
feedback
LH and FSH from
the pituitary
Estrogen and
progesterone from
the ovary
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Identify the Glands
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