Neurons --- Building a Biocomputer

Question 1

Neuron

Answer 1

The basic cellular unit of the nervous system.

Question 2

Soma
(cell body)

Answer 2

In neuroscience, the CELL BODY of a neuron.

Question 3

Dendrite

Answer 3

A branching, threadlike extension of the cell body that increases the receptive surface of a neuron.

Question 4

Axon

Answer 4

The long, thin, hollow, cylindrical extension of a neuron that normally carries a nerve impulse away from the cell body.

Question 5

Terminal button

Answer 5

A small bulge at the end of an axon that stores and releases neurotransmitters. It forms junctions with other neurons, allowing for communication between them.

Question 6

Myelin

Answer 6

The substance that forms the insulating sheath around the axons of many neurons. It consists mainly of phospholipids, with additional myelin proteins, and accounts for the whitish color of white matter.

Question 7

Ion channel

Answer 7

A group of proteins forming a channel that spans a cell membrane, allowing the passage of ions between the extracellular environment and the cytoplasm of the cell.

Question 8

Neuropeptide

Answer 8

Brain chemicals that regulate the activity of neurons.

Question 9

Receptor site

Answer 9

A region of specialized membrane on the surface of a cell (e.g., a neuron) that contains receptor molecules that receive and react with particular messenger molecules (e.g., neurotransmitters).

Question 10

Synapse

Answer 10

The specialized junstion through which neural signals are transmitted from one neuron (the presynaptic neuron) to another (the postsynaptic neuron).

Question 11

Neurotransmitters

Answer 11

Any of a large number of chemicals that can be released by neurons to mediate transmission of nerve signals across the junctions (synapses) between neurons. When triggered by a nerve impulse, the neurotransmitter is released from the terminal button, travels across the synaptic cleft, and binds to and reacts with receptor molecules in the postsynaptic membrane.

Question 12

Why are there so many neurotransmitters?

Answer 12

Some neurotransmitters are used by specifc “pathways” that interlink regions of the brain. It is as if different pathways speak different languages. Perhaps this helps prevent confusing “crosstalk” or intermixing of messages.

Question 13

Do neurotransmitterrs always trigger an action potential in the next neuron?

Answer 13

No, but they do change the likelihood of an action potential in the next neuron. Some neurotransmitters excite the next neuron, others inhibit it.

Question 14

Excitatory neurotransmitter

Answer 14

Exerts a facilitatory or activating downstream effect on postsynaptic neurons. That is, it depolarizes the postsynaptic neurons, resulting in a greater likelihood of an action potential.

Question 15

Inhibitory neurotransmitter

Answer 15

Hyperpolarizes the postsynaptic
neurons—thereby making the intracellular space more negative, and hence, requiring a greater positive charge to overcome—resulting in a smaller likelihood of an action potential.

Question 16

Ion

Answer 16

An atom or molecule that has acquired an electrical charge by gaining or losing one or more electrons. They are either negatively or positively charged.

Question 17

What kind of molecules located inside and outside the neuron?

Answer 17

“Plus” charges exist outside the neuron.
“Minus” charges exist inside the neuron.

Question 18

Saltatory Conduction

Answer 18

A type of conduction of nerve impulses that occurs in myelinated fibers, in which the impulses skip from one node of Ranvier to the next. This permits much faster conduction velocities compared with those of unmyelinated fibers.

Question 19

What kind of impulse occurs between neurons?

Answer 19

Electrical

Question 20

What kind of communication occurs
between neurons?

Answer 20

Chemical

Question 21

Resting potential

Answer 21

The electric potential across the plasma membrane of a neuron when it is in the nonexcited, or resting, state. - 60 — -70 millivolts.

Question 22

When does the neuron reach its threshold?

Answer 22

If the ectrical charges rise to about -50 milivolts, the neuron will reach its threshold.

Question 23

Threshold

Answer 23

The minimum intensity of a stimulus that is necessary to evoke a response; An excitatory threshold is the minimum stimulus intensity that triggers an action potential in
a neuron.

Question 24

Depolarization

Answer 24

A reduction in the electric potential across the plasma membrane of a cell, especially a neuron, such that the inner surface of the membrane becomes less negative in relation to the outer surface. Depolarization occurs when the membrane is stimulated and sodium ions (Na+) flow into the cell. If the stimulus intensity exceeds the excitatory threshold of the neuron, an action potential is created and a nerve impulse propagated.

Question 25

Action potential

Answer 25

The change in electrical potential that propagates along the axon of a neuron during the transmission of a nerve impulse or the contraction of a muscle. It is marked by a rapid, transient Depolarization of the cell’s plasma membrane, from a Resting Potential of about -70 mV (inside negative) to about + 30 mV (inside positive), and back again, after a slight Hyperpolarization, to the resting potential. Each action potential takes just a few milliseconds.

Question 26

What happens during an action
potential?

Answer 26

• All-or-nothing event (a nerve
  impulse occurs completely or not
  at all).
• An action potential begins when ion channels open and sodium ions (Na+) rush into the axon. After it passes, potassium ions (K+) flow out of the axon. This quickly renews the negative charge inside the axon so that it can fire again. Sodium ions that enter the axon during an action potential are pumped out more slowly. Removing them restores the original resting potential.

Question 27

Repolarization

Answer 27

The change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential which has changed the membrane potential to a positive value.

Question 28

Negative after-potential

Answer 28

A drop in electrical charge below the resting potential. This negative afterpotential occurs because potassium ions (K+) flow out of the neuron while the membrane gates are open.

Question 29

Hyperpolarization

Answer 29

An increase in the electric potential across the plasma membrane of a cell, especially a neuron, such that the inner surface of the membrane becomes more negative in relation to the outer surface. It occurs during the final portion of an action potential or in response to inhibitory neural messages.

Question 30

What are the steps of nerve impulse transmission?

Answer 30

1. In its resting state, axon has a negatively charged interior.
2. During an action potential, positively charged atoms (ions) rush into the axon. This briefly changes the electrical charge inside the axon from negative to positive. Simultaneously, the charge outside the axon becomes negative.
3. The action potential advances as positive and negative charges reverse in a moving zone of electrical activity that sweeps down the axon.
4. After an action potential passes, positive ions rapidly flow out of the axon to quickly restore its negative charge. An outward flow of additional positive ions returns the axon to its resting state.

Question 31

Where are the neurotransmitters are stored?

Answer 31

In tiny sacs called synaptic vesicles.

Question 32

What is the main mode of action of Acetylcholine?

Answer 32

Excitatory neurotransmitter

Question 33

What is the main mode of action of Dopamine?

Answer 33

Excitatory neurotransmitter

Question 34

What is the main mode of action of GABA?

Answer 34

Inhibitory neurotransmitter

Question 35

What is the main mode of action of Glutamate?

Answer 35

Excitatory neurotransmitter

Question 36

What is the main mode of action of Neropinephrine?

Answer 36

Excitatory neurotransmitter

Question 37

What is the main mode of action of Serotonin?

Answer 37

Inhibitory neurotransmitter

Question 38

What is the function of Acetylcholine in the brain?

Answer 38

Participates in movement, autonomic function, learning, and memory.

Question 39

What is the function of Dopamine in the brain?

Answer 39

Participates in motivation, reward, and planning of behavior.

Question 40

What is the function of GABA in the brain?

Answer 40

Major inhibitory effect in the central nervous system; participates in moods.

Question 41

What is the function of Glutamate in the brain?

Answer 41

Major excitatory effect in the central nervous system; participates in learning and memory.

Question 42

What is the function of Norepinephrine in the brain?

Answer 42

Participates in arousal and vigilance, and mood.

Question 43

What is the function of Serotonin in the brain?

Answer 43

Participates in mood, appetite, and sleep.

Question 44

What are the effects of imbalance of acetylholin?

Answer 44

Deficiency may play a role in Alzheimer’s disease.

Question 45

What are the effects of imbalance of dopamine?

Answer 45

Deficiency may lead to Parkinson’s disease, reduced feelings of pleasure; excess may lead to schizophrenia.

Question 46

What are the effects of imbalance of GABA?

Answer 46

Deficiency may lead to anxiety.

Question 47

What are the effects of imbalance of glutamate?

Answer 47

Excess may lead to neuron death and autism; deficiency may lead to tiredness.

Question 48

What are the effects of imbalance of norepinephrine?

Answer 48

Excess may lead to anxiety.

Question 49

What are the effects of imbalance of serotonin?

Answer 49

Deficiency may lead to depression and/or anxiety.

Question 50

Neural network

Answer 50

Interlinked collections of neurons that process information in the brain.

Question 51

Neuroplasticity

Answer 51

The ability of the nervous system to change in response to experience or environmental stimulation.

Question 52

Node of Ranvier

Answer 52

Any of successive regularly spaced gaps in the myelin sheath surrounding an axon. The gaps permit the exchange of ions across the plasma membrane at those points, allowing the nerve impulse to leap from one node to the next in so-called saltatory conduction along the axon.