Chapter 4: Neuron's Use of Electrical Signals to Transmit Information

Question 1

Electrical stimulation

Answer 1

passage of electrical current from an uninsulated tip of an electrode through tissue, resulting in changes of the electrical activity of the tissue

Question 2

Electroencephalogram (EEG) and a discovery by them

Answer 2

graph that records electrical activity of the brain and indicates graded potentials of many neurons; shows that the activity is too slow to be actual electricity –> it is a wave of charge of ions

Question 3

Oscilloscope

Answer 3

device that serves as a sensitive voltmeter by registering changes in voltage over time

Question 4

Microelectrodes

Answer 4

microscopic insulated wire or salt water-filled glass tube whose uninsulated tip is used to stimulate or record from neurons; can be on outside, inside or suctioned to it

Question 5

Diffusion

Answer 5

movement from an area of higher concentration to lower

Question 6

Concentration gradient

Answer 6

relative abundance of a substance in space or solution

Question 7

Voltage gradient

Answer 7

difference in charge between 2 regions

Question 8

How Ion movement produces electrical charges

Answer 8

difference of chloride on the 2 sides of a membrane produces a difference in charge or voltage; at equilibrium the concentration gradient and voltage gradient are equal

Question 9

Resting potential

Answer 9

store of potential energy produced by a greater negative charge on the intracellular relative to extracellular side (-70mv)

Question 10

Maintaining resting potential (3)

Answer 10

1) Proteins stay in the cell
2) K+ and Cl- flow more freely across the membrane. Na+ more restricted
3) Na+-K+ pumps extrude Na+ and inject K+ (3 Na for 2 K)

Question 11

Maintaining resting potential inside the cell

Answer 11

K+ inside in large numbers to counteract the negative charge of A-; not all K+ goes in because of the concentration gradient of inside vs outside so the inside stays a bit negative relative to outside

Question 12

Maintaining resting potential outside the cell

Answer 12

a few K+ outside to contribute to relative negative charge of the inside; 10x Na+ outside; Cl- contributes little to the potential (12x Cl- outside)

Question 13

Graded potentials

Answer 13

small voltage fluctuation across cell membrane

Question 14

Hyperpolarization

Answer 14

increase in electrical charge across a membrane, usually due to the inward flow of Cl- or Na+ or outward flow of K+; Ex. -70 to -73

Question 15

Depolarization

Answer 15

decrease in electrical charge across a membrane, usually due to inward flow of Na+; Ex. -70 to -65

Question 16

3 Channels for Graded Potentials

Answer 16

1) K+ channels: efflux of them causes hyperpolarization
2) Cl- channels: influx of Cl- hyperpolarizes
3) Na+: influx of sodium depolarizes

Question 17

Action Potential

Answer 17

large brief reversal in polarity of the axon membrane; lasts 1ms; Na+ flows in, shortly after K+ flows out; from -70 to -50 to +30 to -100 then slowly to -70 again

Question 18

Threshold potential

Answer 18

voltage on a neural membrane when action potential is triggered (usually -50mv)

Question 19

Voltage sensitive channel

Answer 19

gated protein channel that opens or closes at certain voltages

Question 20

Absolutely refractory

Answer 20

state of an axon in the repolarizing period, new action potential cannot be elicited (some exceptions), because gate 2 of the Na+ channels, which are not voltage sensitive, are closed

Question 21

Relatively refractory

Answer 21

more stimulation needed for action potential because it is hyperpolarized; K+ channels still open

Question 22

Nerve impulse

Answer 22

propagation of an action potential on the membrane of an axon; each action potential propagates another on an adjacent part of the membrane (all or none)

Question 23

Saltatory (jumping) conduction

Answer 23

fast propagation of an action potential at successive nodes of Ranvier

Question 24

Nodes of Ranvier

Answer 24

part of an axon not covered by myelin; these allow for less energy to be used and for the nerve impulse to travel faster

Question 25

What happens during an Excitatory Post Synaptic Potential (EPSP)?

Answer 25

Na+ channels open; results in a brief depolarization of a neuron membrane in response to stimulation, the neuron is more likely to produce an action potential

Question 26

What happens during an Inhibitory Post Synaptic Potential (IPSP)?

Answer 26

K+ channels open or Cl- open; results in a brief hyperpolarization of a neuron membrane in response to stimulation, as a result is less likely to produce an action potential

Question 27

What is the Initial Segment and why is it significant in transmitting neural impulses?

Answer 27

it is the area near or overlapping the axon hillock that is rich in voltage sensitive channels; because of this it is the area where the action potential begins (usually); dendrites closest to the initial segment influence it more

Question 28

Temporal Summation

Answer 28

it is the addition of one graded potential to another that occur close in time

Question 29

Spatial Summation

Answer 29

the addition of one graded potential to another that occur close in space on the membrane

Question 30

What is back propagation and what process does it play a role in?

Answer 30

the reverse movement of an action potential into the soma and the dendritic field of a neuron; perhaps it plays a role in plastic changes critical in learning as it lets the dendrites know when an action potential has occured down the axon

Question 31

Optogenetics

Answer 31

a transgenic technique that combines genetics and light to excite or inhibit targeted cells in living tissue

Question 32

Where does the conduction of information begin?

Answer 32

ion channels

Question 33

Stretch sensitive channels

Answer 33

an ion channel on a tactile sensory neuron that respond to the stretching of a membrane, activating a nerve impulse

Question 34

What is an end plate and what neurotransmitter does it receive?

Answer 34

a receptor-ion complex on a muscle that is activated by the release of the neurotransmitter acetylcholine from the terminal of a motor neuron

Question 35

What are transmitter sensitive channels, why are they important and where are they located?

Answer 35

a receptor complex that has both a receptor site for a chemical and a pore through which ions can flow; it is important because acetylcholine attaches to it and allows for the flow of Na+ and K+ through the same pore that leads to the contraction of muscles; located on the end plate

Question 36

Mysathenia Gravis

Answer 36

acetylecholine receptors are blocked and muscles cannot depolarize (slow eye opening example)

Question 37

At resting potential each ion is: (3)

Answer 37

1) Na+: driven in by electrostatic forces and concentration gradient 2) K+: driven in by electrostatic forces and out by concentration gradient 3) Cl- driven out by electrostatic and by concentration gradient