1A. Define Resting Potential and State Its Value in Millivolts

Section #9.2 Electrochemical Impulse

Textbook Guided Reading

1a. Define resting potential and state its value in millivolts.

1b. Define action potential and state its value in millivolts.

2a. Why is it that negative ions do little to change a membrane?

2b. Which positively charged ions most commonly move across the membrane in a nerve cell?

2c. The resting membrane is 50x more permeable to ______consequently more ______ions diffuse out of the nerve cell than ______ions diffuse into the nerve cell.

2d. What controls the movement of ions across the cell membrane?

3a. Upon excitation, the nerve cell membrane becomes more permeable to ______than ______. This rapid inflow of ______ions causes depolarization. The charge on the membrane is now ______.

3b. What is the role of the Na – K pump?

3c. What is the ratio of the Na:K being exchanged?

3d. What is the period called as the membrane is being restored to a charge of -70mV?

4.In a sentence, what happens during an action potential?

5.Define threshold level.

6.Define synapse.

7a.Acetylcholine is an example of what type of a neurotransmitter?

7b.What effect does an excitatory neurotransmitter have?

7c. How is the acetylcholine prevented from continually triggering an action potential?

7d. How might an inhibitory neurotransmitter work?

7e. name 4 other neurotransmitters found in the CNS?

7f. Name a neurotransmitter found in the CNS and PNS?

7g. Copy Figure 12 and label neurotransmitters as excitatory or inhibitory.

8. Explain summation.

ANSWERS

6. Snyapse: regions between neurons or between neurons and effectors (muscles).

7a. Acetylcholine is an example of a excitatory neurotransmitter.

7b. Excitatory neurons cause the sodium channels to open on the post synaptic neuron. When the sodium channels open, sodium ions rush in and cause a depolarization of the post-synaptic neuron ( action potential).

7c. The acetylcholine is prevented from continually triggering an action potential because an enzyme called cholinesterase is released from the membrane of the postsynaptic neuron, cholinesterase destroys acetylcholine. Once acetylcholine is destroyed, the sodium channels close and the neuron returns being a polarized membrane, or resting potential.

7d. Inhibitory neurotransmitters work by making the post-synaptic neuron more permeable to potassium. By opening even more potassium gates, the potassium ions inside follow the concentration gradient and diffuse out of the cell, causing the number of positive ions outside the cell to increase, making the relative charge outside of the cell even more positive. This means the neuron is said to be hyperpolarized.

7e. Serotonin, dopamine, gamma-aminobutyric acid (GABA), and glutamic acid in the CNS.

7f. Also, norepinephrine (noradrenaline) in CNS and PNS.

7g. Nueron C releases inhibitory neurotransmitters.

8. Summation: effect produced by the accumulation of neurotransmitters from two or more neurons.