SBI4U: Nervous System Signaling
Neuron Resting Potential
• Uneven concentrations of ____________________ and __________________ on either
side of neuron membrane results in the ____________________________________
than the outside
• A _____________________________________________________- after ions “leak”
down their concentration gradient
• _____________ are actively pumped ______ while ___________ ions are pumped ____
Action Potential
• ___________________ are transmitted by _____________________ that are abrupt,
pulse-like ___________________________ that last a few ten thousandths of a second.
• Action potentials can be divided into ___________ phases: the ____________________
________, _______________, and ________________
• The amplitude of an action potential is nearly constant and is not related to the size of
the stimulus, so action potentials are ________________________
Now it’s your turn to discover! Complete the action potential web quest worksheet using the
online animation on action potentials!
Terminology
• Synapse
– Region at which ___________________________________________________.
(neuron or effector organ)
• Synaptic Cleft
– ___________________ (at a synapse)
– Impulses can not propagate across a cleft
• Synaptic Vesicle
– __________________________ in _________________ neuron
• Presynaptic Neuron
– ___________________________ (before the synapse)
• Postsynaptic Neuron
– ____________________________ (after the synapse)
Neurotransmitters
5 General Criteria:
1) _______________________________
2) released at the nerve terminal in a 'chemically identifiable' form
3) the chemical should _________________________________________________
4__________________________________ by competitive antagonist based on concentration
5) active mechanisms to stop the function of the neurotransmitter


Classical transmitters _______________________________________________
Non-classical transmitters can be _____________________________________
5 Steps of Neurotransmission
1) _____________________ of the neurotransmitter
 precursors and enzymes should be in the correct place
2) storage of neurotransmitter OR precursor
 ___________________________________________
3) release of the neurotransmitter
 generally by vesicle fusion
4) binding to target receptor
 ionotropic receptors open ion channels
 metabotropic receptors modulate other signals
5) termination of the signal
 active termination caused by reuptake or chemical breakdown
Using the website http://outreach.mcb.harvard.edu/animations/synaptic.swf answer the
following questions:
1. After the action potential has traveled down the axon what signals the neurotransmitter
vesicles to migrate toward the presynaptic membrane?
2. What happens to the post-synaptic neuron when neurotransmitter binds to the postsynaptic receptors?
3. What happens to neurotransmitters when they are released from the post-synaptic
neuron receptors?
Using the following website http://outreach.mcb.harvard.edu/animations/synapse.swf
choose 2 drugs and explain what effect they have on synaptic transmission in your brain.
Write an explanation for the 2 drugs in the space below.