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You and Your Brain

The CNS, PNS, neurons and nerves, drugs and the brain, teenage brain, and memory

Ms Schwinge

on 11 May 2015

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Transcript of You and Your Brain

The Brain
Every animal
you can think of (mammals, birds, reptiles, fish, amphibians),
has a brain. But the human brain is unique.
and Nerves

and the Brain

You and Your Brain
Central Nervous System

central nervous system (CNS) is the control center of the body. It relays messages, processes information, and analyzes information
By definition, a
drug is any substance
(other than food)
that changes the structure or function of the body
. A number of drugs, called
stimulants, increase the actions regulated by the nervous system.
Although it's not the largest, it gives us the power to speak, imagine and problem solve.
The brain performs an incredible number of tasks
including the following:

- It controls body temperature, blood pressure, heart rate and breathing.
- It accepts a flood of information about the world around you
from your various senses
(seeing, hearing, smelling, tasting and touching).
It handles your physical movement when walking, talking, standing or sitting.
It lets you think, dream, reason and experience emotions.

All of
these tasks are coordinated, controlled and regulated by an organ
that is about
the size of a small head of cauliflower.
CNS is made up of the brain, and the spinal cord.
skull and the vertebrae
in the spinal column
protect the brain and spinal cord.
largest and most prominent region
of the
human brain is the cerebrum.
cerebrum is responsible for the voluntary (or conscious) activities of the body.
It is the
site of intelligence, learning, and judgment
. A
groove divides the cerebrum into right and left hemispheres.
hemispheres are connected by a band of tissue
called the
corpus callosum.
Folds and grooves on the surface
of each hemisphere greatly
increase the surface area of the cerebrum
The lobes are named for the skull bones that cover them.
Each half
of the cerebrum
deals mainly with the opposite side of the body. Sensations
from the
left side
of the body
go to the right hemisphere,
and those from the
right side
of the body
go to the left hemisphere.
the left hemisphere controls the body's right side, and the right hemisphere control's the body's left side.
Some studies have suggested that
right hemisphere
may be
connected with creativity and artistic ability,
whereas the
left hemisphere
may be
associated with analytical and mathematical ability
; however,
there is more crossover than differentiation.
cerebrum consists of two layers
. The
outer layer
is called the
cerebral cortex,
consists of grey matter
(which is
made up mostly of densely packed nerve cells
, and is
responsible for processing information
from the
sense organs, and controls body movements
inner layer
consists of
white matter
connects the cerebral cortex and the brain stem).
The Cerebellum
second largest region
of the
is the
. The cerebellum is
located at the back of the skull.
Although the
commands to move muscles
come from the
cerebral cortex,
is the one that
is responsible for coordinating and balancing the actions of the muscles so that the body can move gracefully and efficiently.
The Brain Stem
brain stem connects the brain and spinal cord.

Located just below the cerebellum
, the
brain stem
regulates the flow of information between the brain and the rest of the body.
Some of the
important functions (including blood pressure, heart rate, breathing, and swallowing) are controlled in the brain stem.
The Spinal Cord
The spinal cord is the main communications link between the brain and the rest of the body.
Thirty one pairs of spinal nerves
branch out from the spinal cord,
connecting the brain to all of the different parts of the body.
Certain kinds of information, including some kinds of
reflexes, are processed directly in the spinal cord.
A reflex is a quick, automatic response to a stimulus. Sneezing and blinking
are two examples of reflexes.
A reflex can also allow your body to respond to danger immediately, without spending time thinking about a response.
Einstein brain was no bigger than most, but a central sulcus was missing. This allowed the part of the brain that is the seat of mathematical and visual reasoning to grow 15% wider than normal.
of the cerebrum is
divided into regions called lobes.
Peripheral Nervous System

peripheral nervous system (PNS)
lies outside the central nervous system, and
consists of all the nerves and associated cells that are not part of the brain and spinal cord.
Included here are the
cranial nerves that pass through openings in the skull and stimulate regions of the head and neck, spinal nerves, and collections of nerve cell bodies.
can be divided into the
sensory division, and the motor division.
sensory division
of the peripheral nervous system
transmits impulses from sense organs to the central nervous system.
The motor division transmits impulses from the central nervous system to the muscles or glands.
motor division
is further
divided into the somatic nervous system and the autonomic nervous system.
The Somatic Nervous System
The somatic nervous system regulates activities that are under conscious control
(like the movement of our skeletal muscles).
Every time you lift your finger or wiggle your toes, you are using the motor neurons of the somatic nervous system.
Some somatic nerves
are also involved with
reflexes and can act with or without conscious control.
The Autonomic Nervous System
Reflexes, or rapid responses
, are possible because
receptors in your skin stimulate sensory neurons, which carry the impulse to your spinal cord.
Even before the information is relayed to your brain,
a group of neurons in your spinal cord automatically activates the appropriate motor neurons.
autonomic nervous system regulates activities that are automatic, or involuntary
, which means that the
of the autonomic nervous system
control functions of the body that are not under conscious control.
For instance, when you are
, the
nervous system
speeds up your heart rate

and the
blood flow to the skeletal muscles, stimulates the sweat and adrenal glands, and slows down the contractions of the smooth muscles in the digestive system.
There are
parts of the
autonomic nervous system:
1.) The
sympathetic nervous system
2.) The
parasympathetic nervous system
parasympathetic nervous systems have opposite effects on the same organ system
, and these opposing effects help
maintain homeostasis.
sympathetic nervous system prepares you to fight or run away
when faced with danger, while the
parasympathetic nervous system lets you "rest and digest."
We know now that the
brain and nervous system controls and coordinates functions
throughout the body and
responds to internal and external stimuli
. But how?
message carried by the nervous system are electrical signals called impulses
. The
cells that transmit these impulses are called neurons.
can be classified into
types according to the
in which an impulse travels.
Sensory neurons carry impulses from the sense organs to the spinal cord and brain.
Motor neurons carry impulses from the brain and spinal cord to muscles and glands.
Interneurons connect sensory and motor neurons, and carry impulses between them.
Although neurons come in all different shapes and sizes, they have certain features in common.
largest part
of a typical
is the
cell body.
cell body contains the nucleus and much of the cytoplasm
, and is responsible for much of the
metabolic activity
of the cell.
Spreading out
from the cell body
are short, branched extensions called dendrites. Dendrites carry impulses from the environment or from other neurons TOWARD the cell body.
The long fiber that carries impulses AWAY from the cell body is called the axon.
ends in a series of
small swellings called axon terminals
(located some distance from the cell body).
Neurons may have dozens of dendrites, but usually have only one axon.
In some neurons, the axon is surrounded by an
insulating membrane known as the myelin sheath. The gaps between the myelin sheath,
where the node is exposed, are called
As an impulse moves along an axon, it jumps from one node to the next, which increases the speed at which the impulse can travel.
The Nerve Impulse
nerve impulse
is similar to the
flow of electrical current
through a metal wire.
neuron remains in its resting state
(when it's not transmitting an impulse),
until it receives a stimulus large enough to start a new nerve impulse.
An impulse begins when it is stimulated by another neuron, or by the environment.
Once it begins,
the impulse travels down the axon away from the cell body and toward the axon terminal.
nerve impulse is self-propagating
, which means that
an impulse at any point causes an impulse at the next point
(like falling dominoes).
The strength of an impulse is always the same (even though the strength of a stimulus may vary). Either there is an impulse in response to a stimulus or there is not.
minimum level of a stimulus that is required to activate a neuron is called the threshold
. Any stimulus that is
stronger than the threshold will produce an impulse
, while any stimulus that is
weaker will not produce an impulse
(it's "all or nothing").
The Synapse
At the
end of the neuron
, the impulse reaches an
axon terminal
. Usually the
neuron makes chemical contact with another cell's dendrite at this location.
neuron may pass the impulse along to the second cell.
For example,
motor neurons pass their impulses to muscle cells.
location at which a neuron can transfer an impulse

cell is called a
Neurons are able to transmit these impulses across a synapse to another cell
through the use of special
chemicals called neurotransmitters.
When an impulse arrives at an axon terminal, the neurotransmitters diffuse across to the neighboring cell to create a stimulus.
nervous system
performs its regulatory functions through the
transmission of information
along pathways from one part of the body to another, and
synapses are key relay stations
along the way.
nervous system
depends on
neurotransmitters to bridge the gap between neurons
. A
interferes with
the action of
neurotransmitters can disrupt the functioning of the nervous system.
Stimulants increase heart rate, blood pressure, and breathing rate.
In addition, they
increase the release of neurotransmitters at some synapses
in the brain.
This release leads to a feeling of
energy and well-being.
when the effects of stimulants wear off, the brain's supply of neurotransmitters has been depleted.
The user quickly falls into
fatigue and depression.
Long term use can cause
circulatory problems, hallucinations, and psychological dependence.
Even stronger effects are produced by drugs that act on neurons in the pleasure centers of the brain.
effects of cocaine
, for example, are so
that they produce an
uncontrollable craving for more
of the drug.
Cocaine causes
the sudden
release of a neurotransmitter
in the brain.
this compound is
released when a basic need, such as hunger or thirst, is fulfilled.
By fooling the brain into releasing dopamine, cocaine produces intense feelings of pleasure and satisfaction.
so much dopamine is released when the drug is used that the brain's supply of dopamine is depleted when the drug wears off.
Users quickly discover that they feel
sad and depressed without the drug
, which leads to
psychological dependence.
also acts as a
powerful stimulant, increasing heart rate and blood pressure.
The stimulation can be
so powerful that the heart is damaged, or the brain hemorrhages.
People who use
go through similar
neurotransmitter depletion
. Since their
brain becomes flooded with dopamine and serotonin while on the drugs
they "use up" all of their reserves.
This means that
once they come down
from the high, they are
hit with a very strong wall of depression.
Some drugs, called
depressants, decrease the rate of functions regulated by the brain.
Depressants slow down heart rate and breathing rate, lower blood pressure, relax muscles, and relieve tension.
Some depressants
enhance the effects of neurotransmitters that prevent some nerve cells from firing.
parts of the
sense fear,
and therefore
the individual. However, as a result, the
user can come to depend on
the drug to relieve the anxieties of everyday life.
When depressants are used with alcohol
(a double depressant dose), the results are often fatal because that combination can
depress the activity of the central nervous system until breathing stops.
Alcohol slows down reflexes and reaction times, disrupts coordination, and impairs judgment.
Heavy drinking
fills the blood with so much alcohol that the CNS cannot function properly
, which can lead to
alcohol poisoning.
Excessive alcohol
use can also cause
damage to the liver,
which is
where alcohol is broken down.
liver cells die
and scar tissue is formed, the
liver becomes less able to handle alcohol or complete its normal functions.
Eventually, a heavy drinker may die from liver failure.
is another
slows down the central nervous system.
Its active ingredient is known as
and is
damaging to lung tissue as well as pre-frontal lobe development in adolescents.
Opiates mimic natural chemicals
in the brain known as
which normally
help to overcome sensations of pain.
The opium poppy produces a powerful class of
drugs called
The first doses of these drugs produce
strong feelings of pleasure and security, but the body quickly adjusts to the higher level of endorphins, and begins to expect that level.
Once this happens, the
body can't do without the drug
, and a user who tries to stop will suffer from
uncontrollable pain and sickness because the body cannot produce enough of the natural endorphins.
Teenage Brain

During the
teen years,
under the influence of massive
new hormonal messages
as well as current needs and experiences, the
teenage brain is being reshaped, and reconstructed.
Information highways are being sped up
(a process called
), and some
old routes are being closed down
(this is called
thers are
re-routed and reconnected
to other destinations.
explains why the
personality and stability
that was evident just
a year or two before adolescence lessens
and suddenly
new perspectives, and reactions take hold.
thickening in gray matter
on the
outer part of the brain
peaks at
age 11 in girls and at age 12 in boys
. Then, during the
teen years, the brain trims back excess cells and connections
so what's left is more
cells and connections used the most survive and flourish, and those not used will wither and die.
One of the
last parts
of the brain to
complete this maturation
process is the
prefrontal cortex (PFC)
, the part of the brain responsible for
planning, judgment and self-control.
This part of the brain,
when fully developed
, is in a
constant dialogue with the emotional brain
(the limbic brain). In the
adult brain, the PFC and the limbic brain are in balance,
each one inhibiting the other. For the
teenage brain
, however,
the PFC is undeveloped, and the emotional brain rules the moment.
Although your brain has reached
90% of its full size by the time you turn 6
, it does
mean that it is virtually
fully developed.
depressed teenager and a depressed adult
share some features, but they are
not the same
Adults with depression exhibit anhedonia
, which means they
lose interest in things they previously enjoyed, and can't enjoy them
even when they're offered.
, on the other hand,
may lose interest in pursuing these activities, but may still enjoy them in the moment
Adults with depression tend to be sad; for teenagers, irritability
may be more evident than sadness.
The vast majority of depressed teenagers
haven't suffered a trauma
and do not come from abusive backgrounds. The reality is that
while depression may be triggered by a setback, loss, or abuse, those events aren't always the cause
. In addition,
sadness arising from grief or demoralization does not always progress into major depression.
The truth is that we don't really know what causes depression. We know that
disrupted neurotransmitters can cause mood changes, and that parts of the brain can change in size due to depression.
Antidepressants work on stabilizing neurotransmitter
functions by
blocking the reuptake
of the feel-good chemicals.
This allows the brain to have more neurotransmitters available for brain communication.
This is what can lead to poor impulse control, difficulty concentrating, impaired judgment, and inexplicable mood changes.
Memory is the mental process of retaining and recalling information or experiences
. It is the process of
taking events, or facts, and storing them
in the brain for later use.
Once a memory is created, it must be stored
(no matter how briefly). Many experts think there are
three ways memories are stored:
1.) sensory stage
2.) short-term memory
3.) long-term memory
(for some things).
Because there is
no need
for us
to maintain everything in our brain
the different stages
of human memory function as a sort of
that helps to
protect us from the flood of information
that we're confronted with on a daily basis.
and the Brain

Memories are
established as
sequences of electrical activity that connects the brain cells
, or neurons, in several parts of the brain. These
electrical connection pathways link all your senses and sensory input to your physical and emotional response,
storing everything in memory.
Memory begins the moment the information is received through the eyes, ears, nose, skin or taste buds.
Sensory impressions
are fleeting, lasting
only a few seconds
, unless you consciously choose to remember and encode information either visually or verbally.
Important information
is gradually
transferred from short-term
memory into
The more the information is repeated or used, the more likely it is to eventually end up in long-term memory
, or to be
(That's why studying helps people to perform better on tests)
New information decays if you ignore it too long, and can "dissolve" if it becomes bombarded by too much noise and interference
. This is why listening to loud music while studying interferes with the memory process.
Unlike sensory and short-term memory, which are limited and decay rapidly,
long-term memory can store unlimited amounts of information indefinitely.
If you've
something, it may be because you
didn't encode it very effectively, because you were distracted while encoding should have taken place, or because you're having trouble retrieving it.
that occur
while you're trying to remember
something can really
get in the way of encoding
memories. It may cause you to
think you're remembering what you're doing, but you may not have effectively saved it
in your memory.
You may also
because you're simply
having trouble retrieving the memory
. If you've ever
tried to remember
something one time and
, but then
later you remember that same item
, it could be that there was a
mismatch between retrieval cues and the encoding of the information you were searching for.
encoded information is stored first in the short-term memory
(also known as
working memory
), but only for
30 seconds to a few minutes
because there is
limited capacity.
Types of Memory
Declarative Memory:
Also known as "
explicit memory
," it's used to
recall "everyday" facts and knowledge.
Non-Declarative Memory:
Also know as "
implicit memory
," it is used to remember
skills, procedures, and habits
Full transcript