Nervous System I: Ion Channels
1. What structures in the cell membrane function as ion channels? Integral Proteins
Ion channels are selective for specific ions. What three characteristics of the ions are important for this selectivity? 1.
Amount of water the ion attracts
Channels can be classified as either gated or nongated channels. A sodium channel that is always open would be classified as a/an __________nongated______________ channel.
Would sodium ions move into or out of the neuron through these channels? _______Into________
Voltage-gated potassium channels open at what voltage? ______-55____ mV
Acetylcholine (ACh) and GABA are neurotransmitters that open chemically gated channels. What ions pass into the cell when these channels are activated? a.
ACh: ______sodium_____________ ions
GABA: ___chloride_____________ ions
Ion channels are regionally located and functionally unique. List all the areas on the neuron and the type of potential dependent on the following types of ion channels: Channels
Areas on the Neuron
Type of Potential
Dendrites, Cell body, & Axon
Resting membrane potential
Dendrites & Cell body
Axon Hillock & Axons
From the quiz, place an “X” by the characteristics of voltage-gated sodium channels. _____ Always open
__X__ Found along the axon
__X__ Important for action potential
__X__ Opened and closed by gates
_____ Found on the dendrites and cell bodies
_____ Important for resting membrane potential
Name two channels (gated or nongated) through which chloride ions could pass into the cell. 1.
__Chemically Gated (GABA)___
The Japanese puffer fish contains a deadly toxin (tetrodotoxin). What type of channels does this toxin block? __Sodium-gated voltage channels__
What potential would this toxin block? _Action Potential_
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