Lecture 15/ Neuro I

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known ionic composition. It is possible to measure small changes resulting from ions moving across the membrane under different conditions.

This technique has been applied to many systems; here is a piece of plant cell membrane showing that blue light is able to stimulate the transport of H⁺across the membrane.

Q. What cell type do you think the piece of membrane is from? - guard cell protoplasts

Microelectrodes can also be used to apply a current across the membrane patch to mimic a change in membrane potential.

In this patch from a neuron, decreasing the membrane potential (known as depolarization) causes Na+ ions to flow across the membrane from the "outside" to the "inside".

This shows that neurons have special voltage-gated ion channelsthat open in response to electrical activity. Most channels are either "open" and "closed" (rather than varying by degree); when "open" over a million ions can cross per second.

B. Neuron resting potential 48.5
An unstimulated neuron is much like other animal cells. It has a concentration gradient for several ions:

Ion
Na⁺K⁺Cl^-other anions*

Inside
15 mM 150 mM
10 mM 100 mM

Outside 150 mM
5 mM 120 mM

*(these are amino acids, proteins, sulfates, phosphates that don't cross membrane)

This situation is created by the concerted action of several transport proteins.

1. Na+/K+ pump8.14 The majorelectrogenic pumpin animal cells is the Na+/K+ pump. It uses energy from ATP hydrolysis to move Na⁺out of the cell and K⁺in. However, the exchange is not equal; 3 Na+ leave for every 2 K+ that enter.


known ionic composition. It is possible to measure small changes resulting from ions moving across the membrane under different conditions. This technique has been applied to many systems; here is a piece of plant cell membrane showing that blue light is able to stimulate the transport of H⁺across the membrane. Q. What cell type do you think the piece of membrane is from? - guard cell protoplasts Microelectrodes can also be used to apply a current across the membrane patch to mimic a change in membrane potential. In this patch from a neuron, decreasing the membrane potential (known as depolarization) causes Na+ ions to flow across the membrane from the "outside" to the "inside". This shows that neurons have special voltage-gated ion channelsthat open in response to electrical activity. Most channels are either "open" and "closed" (rather than varying by degree); when "open" over a million ions can cross per second. B. Neuron resting potential 48.5 An unstimulated neuron is much like other animal cells. It has a concentration gradient for several ions:
Ion Na⁺K⁺Cl^-other anions*	Inside 15 mM 150 mM 10 mM 100 mM	Outside 150 mM 5 mM 120 mM
*(these are amino acids, proteins, sulfates, phosphates that don't cross membrane) This situation is created by the concerted action of several transport proteins. 1. Na+/K+ pump8.14 The majorelectrogenic pumpin animal cells is the Na+/K+ pump. It uses energy from ATP hydrolysis to move Na⁺out of the cell and K⁺in. However, the exchange is not equal; 3 Na+ leave for every 2 K+ that enter.