Part II: Neuron Function In the space below detail the steps involved in the communication of a signal between two neurons, starting with the first step of the action potential and ending with neurotransmitter release from the presynaptic terminal. Note which ion channels are open and which are closed and which directions the particular ions are moving (into or out of the cell) at each step along the way. Use the figure to help you along. Please number your steps according to the numbers in the figure. +30 0 -55 -70 Membrane potential (mV) Time
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**Resting state**: At the resting state, the neuron is at its resting membrane potential, which is typically around -70 mV. Voltage-gated sodium (Na+) channels and potassium (K+) channels are closed. The neuron is more permeable to K+ ions due to the presence of Show more…
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Part B: Nervous System II: Events at the Synapse 1. What channels in the presynaptic neuron open up in response to an action potential? 2. The presence of what ion inside the cell causes the synaptic vesicles to fuse with the membrane? 3. a. What is the name for the chemicals stored in the synaptic vesicles? b. What is the name of the space between the presynaptic neuron and the postsynaptic neuron? c. Where are the receptors located? 4. What type of channels are opened by the neurotransmitters? 5. Name two pathways for the neurotransmitters once they dissociate from the receptor. 1. 2.
Sri K.
3. Neuron Physiology a. Write the terms that complete the sentences in the spaces at the right. In a resting neuron, 1 ions are actively pumped out, which causes the membrane to be 2 with an excess of positive ions 3 the membrane and an excess of negative ions 4 the neuron. A threshold stimulus makes the membrane permeable to 5 ions that rapidly diffuse into the neuron, which depolarizes the membrane forming a nerve 6 . An impulse is conducted as a 7 wave passes along a neuron. A depolarized membrane is repolarized when 8 ions diffuse out of the neuron and replace the 9 ions that entered the neuron. Impulse conduction is more rapid in 10 nerve fibers. In synaptic transmission, an impulse reaching a synaptic knob causes the release of a 11 into the 12 . The 13 binds with 14 on the postsynaptic neuron, causing an 15 to be formed. An enzyme quickly breaks down the 16 and restores the synapse to its resting state.
Adi S.
The figure above shows a synapse through which electrical signals are transmitted from one neuron to another via messenger molecules called . When an action potential reaches the of a presynaptic neuron, these messenger molecules inside the are released out of the presynaptic neuron to the . Then they bind to the present on dendrites of the postsynaptic neuron, causing them to open up. Once they are opened, specific ions depending on the type of the channel flow in or out of the postsynaptic neuron via diffusion. The membrane potential of the postsynaptic neuron changes, either increases or decreases. ligand-gated ion channels neurotransmitters leak channels voltage-gated ion channels electrical synaptic cells synaptic cleft nucleus axon terminals synaptic vesicles chemical cell body
Shyam P.
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