Mini Exam 2 Review worksheet Key PDF

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Review worksheet answers for discussion section
Psych 330- Behavioral Neuroscience with Professor Lori Astheimer ...

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Discussion Section 3 Worksheet: Mini-Exam 2 Review 1. Label the following diagram of a resting neuron’s membrane with the following information: a. Relative concentration of ions inside and outside the cell b. Arrows showing the direction that the force of diffusion is pushing each ion type c. Arrows showing the direction that electrostatic pressure is pushing each ion type d. Leak channels for specific ion types e. The overall voltage of the resting membrane potential -65 to 70 mV

“Leak channels” 2. Complete the following chart summarizing the key types of ion channels involved in neuronal communication What type of Location on the What makes it What makes it Ion Channel Type potential does it neuron open? close? influence most? Everywhere N/A (always open) N/A Resting Leak Chemically-gated Voltage-gated

Dendrites, soma Axon

Neurotransmitter binds Voltage reaches threshold

NT dissociates

Post-synaptic

Time-dependent (about 1 ms)

Action

3. Describe the effects of opening each of following ion channels, using de- and hyperpolarize terminology as well as the type of potential produced: a. Chemically-gated Na+ channel: Depolarize (EPSP) as Na+ comes into the cell b.

Chemically-gated Cl- channel: Hyperpolarize (IPSP) as Cl- comes into cell.

c.

Chemically-gated K+ channel: Hyperpolarize (IPSP) as K+ leaves the cell

4. Why is the refractory period of voltage-gated ion channels so important to the conduction of an action potential? a. The refractory period keeps the action potential moving forward along the axon by preventing the depolarization from activating previous ion channels and spreading backwards

Discussion Section 3 Worksheet: Mini-Exam 2 Review b. The refractory period also gives the axon time to “recover” from each action potential so that each AP is a separate, discrete signal. This limits the maximum number of action potentials that can be generated at any given point. 5.

In a myelinated axon, the action potential is only regenerated at _____Node of Ranvier______. What happens to the signal underneath the myelin sheath?

Under the myelin sheath, conduction is mostly passive. Passive conduction is decremental (fading) but very rapid, because myelin insulates the decremental conduction until it can be regenerated at the next node of Ranvier (i.e., insulation prevents K+ leakage out of the cell). Therefore, the action potential “jumps” from node to node via a process called saltatory conduction. This process is much faster in myelinated versus unmyelinated axons, since neurons don’t have to open each voltage-gated ion channel across the axon to regenerate the AP.

C +40 Membrane,potential,(mV)

6. Describe in as much detail as possible what is happening at each of the labeled points along the following action potential graph: a. Voltage-gated Na+ channels open, Na+ rushes into the cell b. Na+ continues to rush in as voltage-gated K+ channels open and K+ leaves cell c. Na+ channels enter refractory state d. K+ continues to leave cell e. K+ channels are closed, but excess K+ has accumulated just outside cell. f. Excess K+ diffuses away, returning cell to resting potential. g. Label the stages of depolarization (A-C), repolarization (C-E), and hyperpolarization (E) on the graph (see brackets)

B

D

A F 470

E Threshold,of excitation

Note: Another great way to study this is to ask yourself WHY each of these things is happening snldelwnlq 7. Synaptic Transmission Recap: a. What type of ion channel is most directly responsible for the release of neurotransmitters via exocytosis? ______ Voltage-gated calcium _______ b. NT vesicles fuse with the cell membrane in an area of the axon terminal called the __ release/active zone _____, which is directly across from the __ post-synaptic density ____ on the postsynaptic cell. c. During exocytosis, NTs are released through an opening called a ___fusion pore ____, and the remnants of the fused vesicles are called ___“omega” figures ___.

8. How would the amount of NT released at a synapse be influenced if you… a. Blocked voltage-gated Ca++ channels on the presynaptic cell? NT release would not start b. Blocked the action of the Ca++ pump? Increased NT release

Discussion Section 3 Worksheet: Mini-Exam 2 Review c. Added an inhibitory neuron that formed an axoaxonic synapse at the terminal bouton? Decreased NT release d. Added a drug that blocks autoreceptor function on the presynaptic cell? Increased NT release 9. Compare and contrast ionotropic and metabotropic receptors: Compare: • Both are transmembrane proteins • Both involve interactions with NT • Both lead to changes in the post-synaptic cell Contrast: • Ionotropic o fast effect o cause small changes in membrane potential (EPSP and IPSP) • Metabotropic o Longer-lasting effects o G-protein coupled receptor § NT activates G-protein complex which opens other ion channels or second messenger pathways 10. What is the difference between NT reuptake and deactivation, and why are both processes important for neural communication? NT reuptake brings whole NT back into the presynaptic neuron via a transporter protein, and deactivation uses enzymes to break down NT right in the synaptic cleft. Both mechanisms eliminate NT from the synaptic cleft, and this level of NT control is important for neuronal signaling, as it limits the stimulation one signal can produce (lessening the chances of overstimulation). Both processes also allow for NTs to be recycled: after reuptake, NTs can be directly repackaged into vesicles, and after deactivation, the constituent parts can still be taken into the presynaptic neuron and reassembled to make new neurotransmitters, so both mechanisms allow for a continual supply of neurotransmitter....