Download Bite Me!

Bite Me!
Neurons, synapses,
and the venomous
creatures that take
advantage of them
The Nervous System
• The nervous system consists
of the brain, spinal cord, and
nerves
• These organs and tissues
are made of cells called
neurons
• The neurons in the nervous
system control everything
else in your body with
signals
Parts of a Neuron
Dendrites
Axon
Cell body: The “regular”
part (contains nucleus and
other organelles)
Axon: Sends signals to the
synapse
Dendrites: Receive signals
from other synapses
Cell body
Synapse
Close-Up of a Synapse
• Neurotransmitters carry
signals from a neuron’s
axon across the synapse to
another cell
• The cell across the
synapse has receptors
where neurotransmitters can
bind
• Synapses need both
neurotransmitters AND
receptors to function
Neuromuscular Junction (NMJ)
• The NMJ is just one
type of synapse,
formed by a neuron
and a muscle cell
• Neurotransmitters
from the axon send
signals to the muscle
• Synapses can form
between two neurons,
or between a neuron
and another type of
cell
Dendrites
Cell body
Synapses
Axon
Muscle fibers
Acetylcholine (ACh)
• ACh is one of many types of
neurotransmitter
• ACh is the neurotransmitter
used at the NMJ
• The unique structure of the
ACh molecule allows it to fit in
its receptor
Close-Up of the NMJ
• Neuron releases ACh
from its axon
• ACh crosses the
synapse and binds to
receptors in the
muscle cell
• Muscle responds to
ACh signal by
contracting
NMJ In Real Life…
• Where are the muscle fibers? Neurons? Synapses?
• Where are the neurotransmitters? The receptors?
Labeling NMJ Parts
(Real Science Experiment!)
Red = ACh Receptors
Green = Axon
Neurotoxins
• Proper function of the nervous
system is necessary for survival!
• Molecules that interfere with the
nervous system are called
neurotoxins
• Different neurotoxins can act on
different parts of a synapse
Neurotoxins in Nature
• Neurotoxins occur
naturally in some (not
all) animal venoms
• The animals pictured
have neurotoxic venom
• Neurotoxins in venom
can disrupt the function
of the NMJ
Coral Snake Venom
Venom
Venom
• Coral snake
venom blocks
ACh receptors
• ACh cannot bind;
no signals get
through synapse
• Muscle becomes
paralyzed
Black Widow Spider
Venom
• Black widow venom
causes the axon’s
ACh to be released
all at once
• No ACh left for
intentional
movement signals
• The muscle spasms,
then is paralyzed
Neurotoxins in Science
• Neuroscientists use
neurotoxins to study how
synapses work
• Using a neurotoxin ( ) that
blocks one neurotransmitter
( ) makes it easier to see
the effects of other
neurotransmitters ( )
• Disrupting the synapse in a
predictable way is a control
Axons
Controls in Science
Miracle-Gro
Compost
Ace Fertilizer
Which kind of fertilizer is the best at making plants grow?
Controls in Science
Miracle-Gro
CONTROL
Ace Fertilizer
Which kind of fertilizer is the best at making plants grow?
Controls in Neuroscience
Axons
• The neurotoxin controls for
the effect of the green
neurotransmitter
• If green neurotransmitter is
blocked, signals we observe
must be coming from pink
neurotransmitter
• Other experiments to try?