IB Bio Topic 6.5 - Neurons and Synapses

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31 Terms

1

Neuron

another term for a nerve cell that transmits signals as electrical impulses

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2

Myelin Sheath

An insulating layer surrounding the axons of some neurons. They speed up the transmission of a nerve impulse

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3

Schwann Cells

Cells of mostly lipids (with some proteins). They are responsible for making the myelinated sheath.

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4

Axon

The part of a neuron along which the nerve signal travels (toward the terminal)

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5

Node of Ranvier

The gap between adjacent Schwann cells

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6

Saltatory Conduction

Refers to myelination speeding up the rate at which signals travel across a neuron by forcing them to jump between nodes of Ranvier.

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7

Continuous Conduction

Refers to the form of conduction for nerve signals on neurons that are not myelinated. It is slower than saltatory conduction.

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8

Cell Body

where the nucleus of the neuron is located

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9

Resting Potential

the resting electrical imbalance between the inside and outside of a neuron resulting from the gradient of sodium and potassium ions across its membrane. There are more sodium ions outside the neuron and more potassium ions inside the neuron

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10

Membrane Potential

the broad term for the electrical difference across the membrane of a cell. In resting nerve cells, this value is -70 mV because the membrane is more permeable to potassium ions (K) and also pumps out three Na+ ions per two K+ ions for each turn of the sodium potassium pump.

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11

Depolarization

refers to stimulated dendrites causing voltage-gated Na+ (sodium ion) channels to open in a neuron, resulting in the rapid diffusion of sodium ions down a concentration gradient into the neuron

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12

Repolarization

refers to the opening of voltage-gated K+ (potassium ion) channels opening when the membrane potential reaches +30 mV

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13

Hyperpolarization

refers to a brief period after repolarization where the membrane potential is at a lower value than the resting potential

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14

Refractory Period

refers to a period following hyperpolarization where a neuron’s Na+ channels are deactivated, preventing the cell from being depolarized

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15

Action Potential

the membrane potential of a neuron during depolarization and repolarization. It notably peaks at +30 mV

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16

Oscilloscope

a device that registers electrical voltages and displays them on a screen as time passes

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17

Threshold Potential

the minimum level to which a membrane potential must be depolarized to trigger an action potential. It varies between -55 mV and -40 mV

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18

All or Nothing Principle

The principle that aneuron MUST be depolarized to reach above around -50 mV for action potential to be initiated. Otherwise, nothing happens.

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19

Synapse

a structure connecting a neuron to a gland, muscle, sensory cell (receptor), or another neuron

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20

Presynaptic Neuron

Refers to the neuron before the synapse

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21

Postsynaptic Neuron

Refers to the neuron after the synapse

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22

Neurotransmitters

chemicals that diffuse from the presynaptic neuron to the postsynaptic neuron. They may cause action potentials in postsynaptic neurons, allowing nerve signals to travel between multiple neurons

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23

Postsynaptic Potentials

the possible changes in the membrane potential of a postsynaptic neuron due to neurotransmitters

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24

Excited

Refers to when neurotransmitters cause a cell’s membrane potential to increase (depolarized)

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25

Inhibited

Refers to when neurotransmitters cause a cell’s membrane potential to decrease (hyperpolarized)

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26

Acetylcholine

a neurotransmitter often found in synapses connecting nerves and muscle fibers. It is notable for its secretion ensuring action potential is propagated to the postsynaptic neuron.

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27

Choline Acetyltransferase (Choline Acetyl Transferase)

An enzyme that combines an acetyl group with choline to form acetylcholine, which is stored in vesicles in presynaptic neurons

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28

Acetylcholinesterase

An enzyme that breaks down acetylcholine into acetyl and choline after it is secreted from the presynaptic neuron, so they can be reabsorbed and reused.

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29

Modulation

refers to synapses’ function of controlling the intensity and duration of the nerve signals they send

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30

Neonicotinoids

a group of compounds that are widely used as insecticides due to their ability to prevent nerve signals of insects from being propagated to their postsynaptic nerves

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31

Cholinergic Synapses

any synapse that uses acetylcholine as its neurotransmitter

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