Muscle Effects
What is acetylcholine, and what role does it normally play at the neuromuscular junction?
Acetylcholine is a neurotransmitter that binds to receptors on the muscle cell membrane and triggers depolarization, which starts muscle contraction.
What do cone snails inject into their prey?
Cone snails inject conotoxins into the bloodstream.
Where are cone snails typically found?
Cone snails are marine snails found in warm oceans.
What is the main role of the presynaptic terminal?
The presynaptic terminal releases neurotransmitters into the synapse.
What happens to a muscle fiber if acetylcholine cannot bind to its receptors?
The muscle fiber cannot depolarize, so it will not contract.
What is the general effect of conotoxins on the prey’s body?
They block nerve signaling, causing the prey to become rapidly paralyzed.
How do cone snails hunt their prey?
They use a harpoon-like tooth to inject potent venom into their prey.
What happens when neurotransmitters reach the postsynaptic terminal?
They bind to receptors, which causes ion channels to open or close and produces a postsynaptic response.
How does conotoxin’s disruption at the neuromuscular junction lead to paralysis in the prey?
Conotoxin prevents acetylcholine from activating muscle fibers, so the muscles cannot depolarize or contract, causing paralysis.
How do conotoxins interfere with nerve and muscle cell communication?
They disrupt ion channels, such as sodium and calcium channels, which are necessary for nerve signals to be sent.
What is the purpose of the cone snail’s venom?
The venom is used to paralyze prey so it cannot escape.
How does an action potential in the presynaptic neuron lead to neurotransmitter release?
The action potential causes depolarization, which opens voltage-gated calcium channels. Calcium enters the axon terminal and triggers vesicles to release neurotransmitters into the synaptic cleft.
Explain why preventing muscle cell depolarization stops muscle contraction.
Depolarization is required to trigger the release of calcium inside the muscle cell, which is necessary for muscle fibers to shorten. Without depolarization, this process does not occur.
Why does blocking sodium and calcium ion channels prevent nerve signals from traveling?
These ion channels are required to create and transmit electrical signals in nerve and muscle cells. When they are blocked, the electrical impulses cannot form or move along the cells.
Why is being highly venomous an advantage for cone snails in the ocean?
Being highly venomous allows cone snails to quickly immobilize prey, making it easier to capture food and survive.
Why are calcium ions essential for synaptic transmission?
Calcium ions cause synaptic vesicles to move to the membrane and release neurotransmitters into the synapse, allowing the signal to be passed to the next neuron.
Predict how the prey’s nervous and muscular systems are affected overall when conotoxin blocks acetylcholine signaling, and explain why this gives the cone snail a survival advantage.
Nerve signals can no longer cause muscles to contract, so the prey becomes unable to move. This paralysis prevents escape, allowing the cone snail to easily capture its prey.
Explain how interference with ion channels leads to paralysis and why this benefits the cone snail.
Without functioning ion channels, nerve cells cannot communicate with muscles, so muscles cannot contract. This causes paralysis, preventing the prey from escaping and allowing the cone snail to capture it.
Considering that some cone snail species are dangerous to humans, what does this suggest about the strength and biological role of their venom?
It suggests that cone snail venom is extremely potent and targets important biological systems like nerves and muscles, showing how powerful and effective it is for both hunting and defense.
Predict what would happen to synaptic transmission if the calcium channels in the presynaptic terminal did not open.
Calcium would not enter the axon terminal, vesicles would not release neurotransmitters, and the postsynaptic neuron would not receive the signal, so the nerve impulse would stop.