Ligand Gated Channels- Lecture 16

Question 1

What is excitatory stimuli?

Answer 1

one that depolarizes the membrane, either by activating an inward current or reducing an outward current

Question 2

What does an excitatory channel do?

Answer 2

carries inward currents

Question 3

What is an inhibitory stimuli?

Answer 3

stimuli that hyperpolarize the membrane by increasing a K+ conductance or (in the case of ligand gated channels) by activating a Cl- conductance (though this will have little effect on Vm)

Question 4

Give two examples of cys-loop channels.

Answer 4

nicotinic acetylcholine receptor

GABA-A receptor

Question 5

What is a nicotinic acetylcholine receptor?

Answer 5

non-selective cationic permeability (primarily Na+ in and K+ out but sometimes Ca2+ and Mg2+); depolarizes the membrane (excitatory effect); when both binding sites are bound to acetylcholine, the M2 helices twist away from center, permitting flow

Question 6

What is GABA-A receptor?

Answer 6

main inhibitory response in the brain; permeable to anions (Cl-); inhibitory effect due to membrane hyperpolarization and decrease in total membrane resistance; when both binding sites are bound to GABA, the M2 helices twist away from center, permitting flow

Question 7

What are glutamate receptors?

Answer 7

activated by excitatory neurotransmitter glutamate; permeable to Na+ and K+ (AMAP-type) and sometimes Ca2+ (NMDA-type); mediate fast synaptic transmission in the brain

Question 8

What characterizes cys-loop receptors?

Answer 8

large loop in the extracellular N-terminal domain formed by cross-linked cysteines; contain 4 membrane-spanning helices and a large intracellular loop between M3-4; two binding sites per receptor (both required for opening)

Question 9

What is the pathway of interaction between AMPA and NMDA receptors?

Answer 9

presynaptic neuron activity releases glutamate into the synapse –> glutamate binds and activates AMPA receptors on the postsynaptic neuron, depolarizing it as well as the NMDA receptors –> NMDA channels gates open, but Mg2+ still blocks it –> if the presynaptic neurons are very active and do depolorize the cell via the AMPA-type channels the MG2+ ions are expelled from the NMDA channels –> Ca2+ flows into the postsynaptic neuron through the NDMA channels –> enzymes and producing long-lasting changes in the efficiency of communication between the pre and post synaptic neuron activated