Dr. Gossett – BSC 1309 / BSC 1409 Chapter 8 pt. 2 of 2 The Nervous System.

The limbic system is a term
for a group of structures
that help to produce
emotions and memory.
The limbic system is defined
on the basis of function,
rather than anatomy.
So it includes several
brain structures
that produce
emotions and memory.
The hippocampus converts
short term memories
to long term memories.
The amygdala also has
effects on long term memory,
by associating memories gathered
through different senses
and linking them to emotions,
such as the olfactory transmits
information about odors
to the limbic system.
Because as we've
studied, olfaction
is the major sense that
brings up emotions.

The limbic system
allows individuals
to experience countless
emotions, such as rage, pain,
fear, sorrow, joy,
even sexual pleasure.
And from this image,
you can see where
that olfactory bulb leading
from smell, the senses,
leads into the limbic system.
The storage and
retrieval of information
take place in two stages,
in short term and long term
memory.
Short term memory– a
small amount of information
is held for a few seconds, such
as looking up a phone number.

Long term memory
stores limitless
amounts of information
for hours, days or years.
And the hippocampus
and the amygdala
are involved in the
long term memory.

Short term memories can
be converted to long term
memories, but not all
short term memories
will be converted to
long term memories.
The reticular activating
system, abbreviated RAS,
is an activating center.
Consciousness only occurs when
the reticular activating system
stimulates the cerebral cortex.
Sleep occurs when
the RAS is inhibited
by other regions of the brain.
Conscious activity in
the cerebral cortex
can also stimulate the
RAS, such as thinking
about a problem that keeps
us up awake at night.
The RAS is an extensive
network of neurons
that runs through the
medulla and projects
to the cerebral cortex.
So the RAS, or the
reticular activating system,
filters sensory input and
keeps the cerebral cortex
in an alert state.

The spinal cord– its structure
is a tube of neural tissue.
The central canal
is contained within.
It's protected by stacked
vertebra, the vertebral column.
White matter is myelinated axons
that are grouped into tracts.
The ascending tracts carry
information to the brain,
while the descending
tracts carry information
from the brain to a nerve
leaving the spinal cord.
The gray matter
of the spinal cord
is located on the interior
region and houses interneurons,
those association neurons
we've studied about
and cell bodies of motor
neurons involved in reflexes.
Its function is to conduct
these messages between the brain
and body.
And so it serves
as a reflex center.
So this shows the back
view, the spinal nerves
that conduct the
sensory and motor
information between the
central nervous system
and a specific
region of the body.
It shows your nerves
that you have that leave
through openings
between the vertebrae.

This image shows the anatomy
0 of a nerve, surrounded
by connective tissue.
Of course, it has
a blood supply,
must have a blood supply, to
deliver nutrients and oxygen.
And it contains the axons that
we've studied in Chapter 7,
within.
A reflex is an
automatic response
to a stimulus in a prewired
circuit called a reflex arc.
It contains several parts of
this circuit– a receptor,
a sensory neuron that
brings information
from the receptors towards
the central nervous system,
an interneuron, at least one.
These are those association
neurons, also referred to.
Motor neuron that
brings information
from the central nervous system
toward an effector, which just
means a gland or a
muscle, and an effector,
either a muscle or a gland.
Spinal reflexes are
essentially decisions
made by the spinal cord
that are beneficial when
a speedy reaction's important
to a person's safety.

This just shows an image–
auto-reflex arc in step one.
A stimulus, such as
stepping on a glass,
initiates a pain sensation.
Sensory neurons detect
this, carry this information
to the spinal cord,
via sensory neuron.
The interneurons, integrated
within the spinal cord,
take this information
from the sensory neuron,
stimulate the
appropriate motor neuron.
The motor neurons stimulate the
appropriate muscle to contract.
And the leg muscles
contract, causing
them to lift the
foot off the pain.
The peripheral nervous
system includes spinal nerves
and cranial nerves.
The spinal nerves originate
from the spinal cord,
and the cranial nerves
originate from the brain.
The nerves and ganglia of
the peripheral nervous system
carry information between
the central nervous system
and the rest of the body.
There's 31 pairs
of spinal nerves,
and each pair serves a
specific region of the body.
All 31 pairs carry both
sensory and motor fibers.
Sensory fibers enter the dorsal
side, dorsal being posterior
side, of the spinal cord in a
bundle called the dorsal root.
Axons of the motor neurons
leave the ventral side,
meaning the front side, of the
spinal cord in a bundle called
the ventral root.
And this just shows
different nerves.
It shows the white matter,
which are the myelinated,
and the gray matter, which
are typically unmyelinated.

There's 12 pairs
of cranial nerves.
These 12 pairs
service the structures
of the head and
certain body parts,
including the heart
and the diaphragm.
Some of the cranial nerves
only carry sensory fibers,
others carry only
motor, and others
carry both types,
sensory and motor fibers.
Subdivisions of the
central nervous system
include the systematic
and autonomic.
The systematic governs
the conscious sensations,
the voluntary movements.
While the autonomic,
auto, covers unconscious,
involuntary,
internal activities.
The somatic nervous system sends
information about conditions
within the body to the
autonomic nervous system,
which then makes the
appropriate adjustments.
Subdivisions of the
autonomic nervous system
include the sympathetic
and parasympathetic.
The sympathetic prepares our
body for the fight or flight,
for emergency situations.
Parasympathetic adjusts
the body functions
so that energy is conserved
during restful times.
The two subdivisions
have antagonistic effects
when one innervates an organ.
Typically, a lot is
neurotransmitter-used
acetylcholine.
In the sympathetic,
you have increased
breathing rate, heart
rate, blood pressure,
increased oxygen and
glucose delivery.
It is going to occur body
cells to fuel respond.
It's going to stimulate the
adrenal glands to release
hormones such as epinephrine
and norepinephrine
into the bloodstream,
which is going
to help to prolong the effects.
So they're going to have
antagonistic effects.
We're either going to be in
restful or rest and digest.
If we're preparing
for fight or flight,
we're not really concerned
about digesting our food.
And so this just shows
the different break downs
of the parasympathetic and the
sympathetic nervous system,
so voluntary versus involuntary.
You see the parasympathetic
slows heart rate,
whereas on the opposite side,
the sympathetic increases heart
rate.
So they're antagonistic effect.
Parasympathetic
widens blood vessels.
Sympathetic narrows
blood vessels, and so on.
Increased digestive
activity on parasympathetic,
decreased in sympathetic
nervous system.
So they're going to have
antagonistic effects.

Headaches– tension
headaches, about 60% to 80%
are in response to stress,
caused by muscle contraction
to the head, face, or neck.
Migraine headaches are
caused by an imbalance
in the brain's chemistry,
possibly linked
to low levels of the
neurotransmitter serotonin.
A stroke or cerebral
vascular accident
is caused by the
interruption of blood flow
to a region of the brain,
such as nerve cells.
The extent and type of
impairment caused by a stroke
is going to depend on the
region of the brain affected.
Common cause is a blood
clot, which blocks a vessel,
or fatty deposits that
may block a blood vessel.
Factors that increase
a risk of a stroke
are high blood pressure, heart
disease, diabetes, smoking,
obesity or excessive alcohol.

There's a syndrome termed
Neglect Syndrome, wherein
damage to the right
posterior part of the brain,
the individual will behave as
if the left side of things, even
their own body
parts, don't exist,
possibly combing hair
only on the right side,
maybe only eating
on the right side.

A coma is caused by
trauma to neurons
in regions of the brain that
are responsible for stimulating
the cerebrum, that reticular
activating system that we
studied about earlier that gives
us our wake-up consciousness.
A coma can be caused
by mechanical shock,
such as a blow to the
head, tumors, infections,
drug overdose, or failure
of the kidney or liver.
During a coma, a person is
totally unresponsive to all
sensory input and
cannot be awakened.
So it differs from a deep sleep.
Spinal cord injury results
in the loss of function
below the site of injury.
And depending on which
nerve tracks are damaged,
injury may result in
paralysis, loss of sensation
or possibly both.
If the cord is
completely severed,
then there is complete
loss of sensation
and voluntary movement
below the level of the cut.
And there's several
different stages
of sleep– stage one, two,
three, four and rapid eye
movement.
Rapid eye movement is a time
when our breathing becomes more
rapid, irregular and shallow,
the eyes jerk rapidly,
limb muscles may be
temporarily paralyzed.
REM, about 50% of the time
that infants spend in REM.
As adults, we spend about 50%
in stage two, about 20% in REM.

Leave A Comment

Your email address will not be published
*