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 Cell body: The “regular” part (contains nucleus and other organelles) Axon: Sends signals to the synapse Dendrites: Receive signals from other synapses Dendrites Cell body Axon 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) Dendrites Cell body Axon Muscle fibers Synapses 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

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 Coral snake venom blocks ACh receptors ACh cannot bind; no signals get through synapse Muscle becomes paralyzed Venom

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 signal 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 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? signal Axons