Download PPT and questions for class today.

Today in class
• Notes
• Writing assignment
• Vocabulary Activity
• Reminder – quiz tomorrow
• Reminder – candy neuron
tomorrow – bring candy
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Neurons and Neuronal Communication:
The Structure of a Neuron
There are billions of neurons
(nerve cells) throughout the body.
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Action potential:
a neural impulse that travels down an
axon like a wave
Just as “the wave” can flow to
the right in a stadium even
though the people only move
up and down, a wave moves
down an axon although it is
only made up of ion exchanges
moving in and out.
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When does the cell send
the action potential?...
when it reaches a
threshold
The neuron
receives
signals from
other
neurons;
some are
telling it to
fire and some
are telling it
not to fire.
 When the
threshold is
reached, the
action potential
starts moving.
 Like a gun, it
either fires or it
doesn’t; more
stimulation does
nothing.
 This is known as
the “all-ornone” response.
How neurons communicate
(with each other):
The action
potential
travels down
the axon
from the cell
body to the
terminal
branches.
The signal is
transmitted
to another
cell.
However, the
message
must find a
way to cross
a gap
between
cells. This
gap is also
called the
synapse.
The threshold is reached when
excitatory (“Fire!”) signals
outweigh the inhibitory (“Don’t
fire!”) signals by a certain amount.
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The Synapse
The synapse is a
junction between the
axon tip of the
sending neuron and
the dendrite or cell
body of the receiving
neuron.
The synapse is
also known as the
“synaptic
junction” or
“synaptic gap.”
5
Neurotransmitters
Neurotransmitters
are chemicals
used to send a
signal across the
synaptic gap.
6
Reuptake:
Recycling Neurotransmitters [NTs]
Reuptake:
After the neurotransmitters
stimulate the receptors on
the receiving neuron, the
chemicals are taken back up
into the sending neuron to
be used again.
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Neural Communication:
Seeing all the Steps Together
8
Roles of Different Neurotransmitters
Some Neurotransmitters and Their Functions
Neurotransmitter Function
Problems Caused by Imbalances
Serotonin
Affects mood, hunger,
sleep, and arousal
Undersupply linked to depression;
some antidepressant drugs raise
serotonin levels
Dopamine
Influences movement,
learning, attention, and
emotion
Oversupply linked to schizophrenia;
undersupply linked to tremors and
decreased mobility in Parkinson’s
disease and ADHD
Acetylcholine
(ACh)
Enables muscle action,
learning, and memory
ACh-producing neurons deteriorate as
Alzheimer’s disease progresses
Norepinephrine
Helps control alertness
and arousal
Undersupply can depress mood and
cause ADHD-like attention problems
GABA (gammaaminobutyric acid
A major inhibitory
neurotransmitter
Undersupply linked to seizures,
tremors, and insomnia
Glutamate
A major excitatory
neurotransmitter;
involved in memory
Oversupply can overstimulate the brain,
producing migraines or seizures; this is
why some people avoid MSG
(monosodium glutamate) in food 9
Serotonin
pathways
Networks of neurons that
communicate with serotonin
help regulate mood.
Dopamine
pathways
Networks of neurons that
communicate with dopamine are
involved in focusing attention
and controlling movement.
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Hearing the message
How Neurotransmitters Activate
Receptors
When the
key fits,
the site is
opened.
11
Keys that almost fit:
Agonist and Antagonist Molecules
An agonist molecule fills
the receptor site and
activates it, acting like the
neurotransmitter.
An antagonist molecule
fills the lock so that the
neurotransmitter cannot
get in and activate the
receptor site.
12
Recap
The Structure of the Neuron
• Basic Building block of the nervous system
• Consist of cells specialized for rapidly
Part communicating
Function
information
DENDRITES
RECEIVE INFORMATION FROM ADJOINING NEURONS
SOMA (CELL BODY)
RECEIVES AND STORES INFORMATION WITHIN THE CELL
NUCLEUS
GOVERNS AND DIRECTS ACTION OF THE CELL
AXON
TRANSMITS NEURAL IMPULSE DOWN LENGTH OF CELL
TERMINAL BUTTONS
BRANCHING AT END OF AXON; CONTAINS
NEUROTRANSMITTERS
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TYPES OF NEURONS
• Sensory neurons – bring information from
outside world to your brain
• Motor neurons – transmit responses from
brain to muscles and glands
• Interneurons
– Connect neurons to other neurons
– Join sensory and motor neurons in spinal cord
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Synapses
• What are synapses – part of the structure of the
Neuron
• What is the purpose of synapses?
–They are the chemical (neurotransmitter)
connections between ALL neurons
So can you describe the structure of
the Neuron? No, not yet.
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Next Question…
• What is the purpose of Glial cells?
– Fact – most numerous cells within the nervous
system
– Fact – Like glue – holding neurons together
– Fact – assist and support activity of neurons
– Fact – forms the myelin sheath (covering of the
axon)
–The myelin sheath – what is the myelin
sheath?
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Myelin Sheath
• Fatty, protective covering on neuron axons
• Forms over time, usually by age of 12
• Nodes of Ranvier (gaps in myelin sheath) –
neural impulse may jump from node to node
• Fact – Multiple sclerosis (MS) – a condition
that occurs from the destruction of myelin
sheath
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How Neurons Communicate
• Ions involved: sodium, potassium, and
chloride
• Resting potential – neuron not activated; cell
has slightly negative charge
• Depolarization – stimulation leads sodium to
enter cell; electrical charge now changed from
negative to positive
• Action Potential – neuron fires down length of
axon; called a neural impulse
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Importance of Neurotransmitters
• Synapse is tiny gap between one neuron and
the next
• At synapse, the impulse changes from
electrical to chemical
• Neurotransmitters are these chemical
messengers across synapse
• Chemicals from adjacent neurons may either
excit or inhibit cell firing
List 5 Neurotransmitters and explain what they
do.
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Can you do the following? Do you
need your outline to do it?
Take out a sheet of paper and do it.
• 1. Describe the structure of a neuron.
• 2. Describe the process by which an action
potential is triggered.
• 3. Describe how nerve cells communicate, and
discuss the importance of neurotransmitters for
human behavior.
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