Download The Sympathetic Nervous System

The Nervous
System
Anatomically, the nervous system can
be divided into:
1. The central nervous system
(CNS), which includes the brain and
spinal cord
2. The peripheral nervous system
(PNS), which includes cranial and
spinal nerves that carry messages to
and from parts of the body.
Functionally, the nervous system can be divided into:
1. The somatic nervous system, which includes
voluntary control of the skeletal muscles.
2. The autonomic nervous system (sometimes called
visceral nervous system) which includes the involuntary
control of smooth muscle, cardiac muscle, and glands.
The autonomic nervous system (ANS) can be
divided into:
A. The sympathetic nervous system
(stress, fight or flight)
B. The parasympathetic nervous system
(maintain homeostasis, rest, digest)
Basic
Anatomy
of the
Nervous
System
Neurons and Their Functions
A neuron is:
•A nerve cell
•Carries nerve impulses between the CNS and the
body tissues
•Bundles of neurons in the PNS are called nerves
•Bundles of neurons in the CNS are called tracts
The neuron consists of:
•Cell body
•Dendrites
•Axon
•Myelin Sheath
(Schwann Cells)
•Nodes of Ranvier
•Synapses
The cell body of the neuron contains the nucleus
and organelles. The axon and dendrites branch off
of the cell body.
illustration from wikipedia.com
The function of the dendrites is to serve as
receptors.
They recieve stimuli from the body or from other neurons
along a neural pathway.
The axon is the neruon fiber that conducts nerve impulses
away from the cell body.
The nerve impulse may be delivered to another neuron, to a muscle, or to a gland.
The axons are covered with myelin, which insulates the
fiber and helps nerve impulses to travel down the length of
the axon.
Schwann cells wrap around the axon and produce layers of
myelin.
There are tiny gaps in between myelin sheaths. These gaps
are called nodes.
This creates a faster nerve impluse.
The axon terminals, at the ends of the axon, send the
nerve impulse from its neuron, to the dendrites of
another neuron.
Nerve impulses can also be sent to muscle cells or
glands.
This junction is called a synapse.
How does a nerve impulse travel?
The cell membrane of a resting neuron carries an electric charge.
At rest, the inside of the membrane is negative and the outside is positive. This state is said
to be polarized (ready for action!).
A nerve impulse starts when a stimulus causes a reversal in the electrical charge (action
potential), which travels down the membrane like an electric current.
When the reversal of electric charges occurs, the membrane is depolarized.
When the membrane returns back to its resting state, it is repolarized, and ready for
stimulation again.
What happens at a synapse?
In the terminal branches at the end of a neuron, there are
small vesicles (called butons) that contain chemicals.
These chemicals are called neurotransmitters.
When the nerve impulse reaches the butons, the
neurotransmitter is released, and acts as a chemical
signal, stimulating the next cell.
The target cells, such as muscles or
glands, that carry out responses from
the neurotransmitters, are called
effectors.
•Open the "forms" tab.
•On your paper, answer questions 1-10,
answers only.
This is individual work,
not group work.
•This is an assessment of your understanding
of the material thus far.
•I want to know what YOU understand, not
what you can copy from your neighbor.
•Please turn in your answers to the review
questions when you finish.
Bell Ringer: Use your computer and books to
research and write about the following, in complete
sentences. Write your name on your Bell Ringer and
turn it in when you finish.
What is Shingles?
What virus causes shingles?
What are the signs and symptoms of
shingles?
How can shingles be identified?
Why is shingles considered a disorder of the
nervous system?
Moving right
along..... The
Spinal Cord and
Spinal Nerves!
The spinal cord
sits protected
inside the
vertebrae, and
stretches from
the skull to the
end of the
sacrum.
The brain and spinal cord are both protected
by bones, and by three meninges (protective
membrane layers)
The outer layer is
very tough, and is
called the dura
mater ("tough
mother")
The middle layer,
the arachnoid
mater, is avascular
connective tissue.
The innermost
layer, the pia mater
("soft mother") is
highly vascularized
and very thin.
The spinal nerves
originate in the
spinal cord, and
each one
innervates a
different area of the
body.
Each area that is
innervated by a
spinal nerve is
called a
dermatome.
The functions of the
spinal cord:
Carries information from the peripheral
nervous system, up to the brain
Carries information from the brain to the
peripheral nervous system
Plays a role in spinal reflexes and stretch
reflexes, which do not require the brain to
process sensory information, and create a
quick response
A diagram of a stretch reflex
Sensory information enters the dorsal horn of the spinal cord, and
travels upward to the brain in the ascending tracts.
Motor impulses traveling down from the brain are carried in
descending tracts, and exit through the ventral (anterior) horn of
the spinal cord.
Sensory neurons are referred to as "afferent" neurons, and enter the spinal
cord at the dorsal horn.
Motor neurons are referred to as "efferent" neurons, and enter the spinal
cord at the ventral horn.
Sensory = Afferent = Dorsal Root, Dorsal = Afferent. Ventral = Efferent.
SAD DAVE
The Autonomic Nervous System
Remember the ANS is responsible for regulating
glands, and controlling the function of smooth
muscle (organs and blood vessels) and heart
muscle.
There are two functional divisions of the ANS:
•The Parasympathetic Nervous System (PNS)
•The Sympathetic Nervous System (SNS)
The Sympathetic Nervous System
Most organs are supplied by both
sympathetic and parasympathetic
nerve fibers.
The SNS acts on organs to help us
deal with a stressful situation
(think of being chased by an animal).
The SNS increases heartrate
Increases blood pressure
Dilates (opens up) blood vessels that supply skeletal muscles
Dilates bronchial tubes to increase oxygen intake
Stimulates the adrenal glands to produce hormones such as epinephrine
Increases metabolism
Dilates the pupil
Fight or Flight!
Because blood flow is increased to your skeletal
muscles, there is less blood flow to other organs
such as the stomach and intestines.
What do you think happens to digestion during
a sympathetic response?
The Parasympathetic Nervous System
The PNS works to reverse the stress response and maintain homeostasis in
the body.
Blood flow to the digestive organs is increased
Digestive glands (pancreas, liver) are stimulated
Heart rate and blood pressure decrease
Bronchi of lungs constrict
The PNS is responsible for our "rest and digest" actions.
Recap Questions:
1. What division of the autonomic nervous
system mediates the "fight or flight"
response?
2. What division of the autonomic nervous
system mediates the "rest and digest"
response?
3. Describe the basic "spinal reflex."
4. Differentiate between "afferent" and
"efferent" neurons.
The Brain and
Cranial
Nerves
The brain occupies
the cranial cavity,
and is coverd by the
same meninges of
the spinal cord (dura
mater, arachnoid
mater, and pia
mater).
The brain is
surrounded by
cerebrospinal fluid,
which also circulates
within the brain itself.
• Meningitis is an inflammation of the meninges,
usually caused by viruses, bacteria, or fungi. It
is diagnosed by lumbar puncture and collection
of cerebrospinal fluid.
• Meningitis can be treated with antibiotics, but
left untreated, can be deadly.
• Vaccines can help prevent some cases of
meningitis.
The cerebrospinal fluid (CSF) provides a cushion to
the brain and spinal cord, and carries nutrients and
wastes.
The CSF is produced in the four ventricles of the
brain.
Hydrocephalus is a condition that is caused when there is an
obstruction to the flow of CSF.
In the infant, hydrocephalus results in cranial enlargement.
In the adult, the bones are fused and cranial enlargement
cannot occur.
What do you think happens when CSF builds up in the adult
brain?
Hydrocephalus can be treated by placing a shunt in the
ventricle of the brain. The shunt drains excess CSF into
either the peritoneal cavity (belly) or into the atrium of the
heart. The body will absorb and eliminate the extra fluid if
needed.
The Structure of the Brain
There are two cerebral hemispheres.
Each cerebral hemisphere can be divided into four lobes:
The frontal, parietal, temporal, and occiptal.
• The frontal lobe is relatively large in
humans. This lobe contains the motor
area, and an area important for speech.
• The parietal lobe contains the
sensory area, and assists with estimation
of sizes, shapes, and distances.
• The temporal lobe contains the
olfactory area and the autidorty area
• The occipital
visual area
lobe contains the
The corpus callosum is located
between the hemispheres, and
permits impulses to cross from
the right side to the left side of the
brain.
The basal ganglia are masses of
gray matter that help regulate
body movement and facial
expressions. The
neurotransmitter dopamine is
secreted in the basal ganglia.
In the innermost part of the brain, near
the corpus callosum and basal ganglia,
the thalamus and hypothalamus are
located.
The thalamus functions to sort and
route information to different parts of the
cerebral cortex (like a post office of
sorts).
The hypothalamus maintains
homeostasis by controlling body
temperature, water balance, sleep,
appetite, and some primal emotions.
The limbic system is
involved in emotional states
and behavior.
In the limbic system lies the
amygdala, a mass of ganglia that
control feelings of fear (sympathetic
nervous system)
The hippocampus is involved in
learning, the formation of long term
memory, and spatial navigation.
The Cerebellum
•The cerebellum aids in the coordination of
voluntary muscles,
•helps to maintain balance by processing messages
from the inner ear, tendons and muscles,
•And aids in maintaining muscle tone to ready the
body for quick changes if necessary.
The brain stem connects the brain with the spinal cord, and is a
very primitive portion of our brain.
The midbrain acts as a relay center for some eye and ear
reflexes, and gives rise to cranial nerves III and IV.
The pons lies just under the midbrain. The pons
is an important connective link between the
cerebellum and the rest of the nervous system.
Some reflexes and involuntary actions (breathing)
are controlled with help from the pons.
The pons also gives rise to cranial nerves V, VI, VII,
and VIII.
The Medulla Oblongata
The medulla oblongata is located between the pons and
the spinal cord.
The respiratory center in the medulla controls the muscles
of respiration.
The cardiac center helps regulate the rate and force of
cardiac contractions.
The vasomotor center regulates the contraction of smooth
muscle in the blood vessel walls (thus controlling blood
pressure).
Cranial nerves IX, X, XI, and XII originate in the medulla.
The Brain Made Simple
Somethin' Wrong With
His Medulla Oblongata
No, Colonel Sanders,
YOU'RE wrong!
Mama Said the medulla
oblongatta controls
respirations, blood
pressure, and cardiac
contractility.
Disorders of the Brain
1. Cerebrovascular Accident (abbreviated CVA) is also known as a stroke.
2. Cerebral hemorrhage, or bleeding within the brain, can be caused by a
ruptured blood vessel (such as from an arteriovenous malformation,
aneurysm, or an injury to the head) and can lead to brain damage or stroke
in some cases.
3. Cerebral Palsy, as disorder caused by brain damage occuring during or
before birth, and can lead to muscular disorders.
4. Epilepsy, an abnormality of the electrical activity of the brain, leads to
seizures.
5. Tumors
6. Alzheimers disease, caused by degeneration of the cerebral cortex and
hippocampus.
7. Parkinson's disease
Answer the following review questions and turn them in...
1. What lobe of the brain is responsible for higher-order thinking, such as
reasoning, planning, and personality?
2. What part of the brain helps us to form long term memories?
3. What is the structure that connects the right hemisphere to the left
hemisphere?
4. What is the tough outer meninge of the brain called?
5. What brain disorder is characterized by difficulty controlling speech and
movement due to a lack of the neurotransmitter dopamine?
6. What parts of the brain degenerate in someone with Alzheimer's?
7. What are the symptoms of Alzheimer's?
8. What part of the brain controlls respirations, the heart, and the
dilation/constriction of blood vessels?
9. What is the function of the amygdala?
10. If the cerebellum is damaged, what symptoms might a person experience?
11. Research this: Has there ever been a person born without a cerebellum, and
survive? Explain what you find in your research.
12. What part of the brain recieves visula stimuli and processes it?
13. In what lobe of the brain is the auditory processing area?
14. How many ventricles are in the brain?
15. What is the result of a buildup of cerebrospinal fluid in and around the brain?