MJK Tutoring Workshop 3 answers PDF

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1. Circle which of the type(s) of synaptic transmission is being described (more than one option may be used for each answer): M = Metabotropic, I = Ionotropic, E = Electrical Transmission is bidirectional

M

I

E

Depends on extracellular Ca2+

M

I

E

Presynaptic hyperpolarization results in a postsynaptic signal

M

I

E

Synaptic transmission requires GTP

M

I

E

Neurotransmitters directly open ion channels

M

I

E

2. You think you have discovered a new ionotropic receptor for acetylcholine that is only permeable to Na+. A. You perform a gain-of-function experiment to test the above hypothesis by exogenously expressing the receptor in a cell that normally does not express it and then applying acetylcholine while recording the cell’s electrical activity. If your hypothesis is correct, what would you expect to observe? A depolarization in response to the acetylcholine

3. Rank the following types of synaptic transmission from fastest to slowest: metabotropic, ionotropic, electrical Fastest 1.electrical

2. ionotropic

3. metabotropic

Slowest

4. When you activate a newly discovered G-protein-coupled receptor, you see that the membrane potential changes from -65mV to -75mV. When you remove the ligand, the membrane goes back to -65mV within a few minutes. You know that ENa = +62mV, EK = -80mV, ECl = -65mV. What type of channel do you think is being opened by your new G-protein-coupled receptor? Na+ channels K+ channels

Cl- channels



5. Consider the diagram of the single postsynaptic neuron with one dendrite. The neuron is receiving 4 inputs: 3 excitatory (E1, E2, and E3) and one inhibitory (I). Make the following assumptions: Vm = -65 mV

Erev of the receptors at the excitatory synapses is 0mV 

Erev of the receptors at the inhibitory synapses is -75mV 

  a.

Assume all three excitatory synapses are active at the same time, and cause the postsynaptic neuron to fire an action potential. This is an example of: (circle one) Spatial summation Temporal summation Shunting

b.

If you are recording from the cell soma and all three excitatory synapses have the same number of receptors and release the same amount of neurotransmitter, which of the following statements would be true and why? (circle one and then explain in 1 sentence) i.

An EPSP from all three excitatory synapses would have the same amplitude at the cell soma.

ii. An EPSP from E1 would have a smaller amplitude than E2 or E3 at the cell soma.



iii. An EPSP from E3 would have a smaller amplitude than E2 or E1 at the cell soma. Explanation: Because E1 is furthest from the soma (1pt), an EPSP from E1 will decay more than EPSPs from the other two synapses as it travels to the soma (1pt) 6. You are trying to discover novel treatments for epilepsy, a disease where there is uncontrolled, excessive firing of action potentials. Would you want to inhibit or activate the following channels or receptors to treat epilepsy, assuming physiologic ion concentrations? (Circle one per line.) a. GABA receptor: inhibit

activate

b. AMPA receptor: inhibit

activate

+ c. Voltage-gated Na channels: inhibit

activate

+ d. Voltage-gated K channels: inhibit

activate...