CHAPTER 3.5 (How Do Neurons Work)

Question 1

Definition:

resting potential

Answer 1

The electrical charge of a neuron when it is at rest.

Question 2

How does a neuron create its resting potential?

Answer 2

The key elements are the relative imbalance of positively and negatively charged ions inside versus outside the neuron, the semi-permeable nature of the cell membrane, electrostatic pressure and concentration gradients,m and the sodium-potassium pump.

Question 3

Definition:

ions

Answer 3

Charged atoms or molecules in intra/extracellular fluid.

Question 4

What surrounds a neuron?

Answer 4

A semi-permeable membrane.

Question 5

What do ion channels do?

Answer 5

Allow selective ion passage.

Question 6

What are the 3 key ions in resting/action potential?

Answer 6

• A⁻ (negatively charged proteins)
• Na⁺ (sodium ions)
• K⁺ (potassium ions)

Question 7

Where is K⁺ concentrated at rest?

Answer 7

Inside the neuron.

Question 8

Where is Na⁺ concentrated at rest?

Answer 8

Outside the neuron.

Question 9

Why are ion concentrations unequal?

Answer 9

Due to semi-permeable membrane and closed channels.

Question 10

Definition:

ion channels

Answer 10

Pores in the cell membrane that can open and close to allow certain ions into and out of the cell.

Question 11

What spans the semi-permeable membrane?

Answer 11

Ion channels.

Question 12

What do ion channels regulate?

Answer 12

Flow of ions in and out of the neuron.

Question 13

What is the state of Na⁺ channels at rest?

Answer 13

Mostly closed.

Question 14

What is the state of K⁺ channels at rest?

Answer 14

Some are open, allowing limited movement.

Question 15

Where are A⁻ proteins found?

Answer 15

Inside the neuron; they cannot pass through the membrane.

Question 16

What causes the inside of the neuron to be negative at rest?

Answer 16

Presence of A⁻ proteins and ion distribution.

Question 17

Definition:

electrostatic pressure

Answer 17

The force that drives ions that are of a similar charge away from one another or attracts two ions of apposite charges toward each other.

Question 18

Definition:

concentration gradient

Answer 18

The difference in concentration of sodium ions inside and outside of the neuron.

Question 19

Where is Na⁺ concentrated during resting potential?

Answer 19

Outside the neuron.

Question 20

Why can’t Na⁺ enter the neuron at rest?

Answer 20

Na⁺ channels are closed.

Question 21

What attracts Na⁺ to the inside of the cell?

Answer 21

Electrostatic pressure from internal negativity.

Question 22

What is a concentration gradient?

Answer 22

Ions move from high to low concentration.

Question 23

What two forces drive Na⁺ inward?

Answer 23

Electrostatic pressure and concentration gradient.

Question 24

Where is K⁺ concentrated during resting potential?

Answer 24

Inside the neuron.

Question 25

Why doesn’t all K⁺ leave the cell?

Answer 25

Electrostatic pressure pulls it back in.

Question 26

What maintains the resting membrane potential?

Answer 26

Imbalance of K⁺, Na⁺, and A⁻ proteins; typically around –65mV to –70mV.

Question 27

# Definition: sodium-potassium pump

Answer 27

Protein molecules in the membrane of cells that push out sodium ions and push in potassium ions.

Question 28

What ions does the pump move?

Answer 28

3 Na⁺ out, 2 K⁺ in.

Question 29

What does the pump help maintain?

Answer 29

The neuron’s negative polarization (resting potential).

Question 30

What does this process consume?

Answer 30

A large portion of the brain’s glucose energy.

Question 31

# Definition: action potential

Answer 31

A sudden positive change in the electrical charge of a neuron's axon, also known as a spike or firing; action potentials are rapidly transmitted down the axon.

Question 32

What causes current flow in neurons?

Answer 32

Ions moving down electrostatic pressure and concentration gradients.

Question 33

What happens when Na⁺ and K⁺ channels open?

Answer 33

Ions move freely, changing the electrical charge inside the neuron.

Question 34

What does the electrode record during ion movement?

Answer 34

A brief positive value inside the neuron.

Question 35

# Definition: threshold

Answer 35

The point at which the relative influence of other neurons succeeds in causing a neuron to initiate an action potential.

Question 36

# Definition: absolute refractory period

Answer 36

A very brief period of time after an action potential, during which a neuron is completely unable to fire again.

Question 37

# Definition: relative refractory period

Answer 37

A brief period just after the absolute refractory period during which a neuron can fire if it receives a stimulus stronger than its usual threshold level.

Question 38

What triggers an action potential?

Answer 38

Membrane reaches –40 mV threshold at the axon hillock.

Question 39

What is repolarization?

Answer 39

K⁺ exits the cell, restoring negative charge.

Question 40

What is hyperpolarization?

Answer 40

Cell becomes more negative than resting potential.

Question 41

What moves the signal down the axon?

Answer 41

Sequential opening/closing of Na⁺ and K⁺ channels.

Question 42

# Definition: myelin

Answer 42

A fatty, white substance formed from glial cells that insulates the axons of many neurons.

Question 43

What is neural coding?

Answer 43

Information conveyed by patterns and timing of spikes.

Question 44

What are nodes of Ranvier?

Answer 44

Gaps in myelin where Na⁺ channels open.

Question 45

What is saltatory conduction?

Answer 45

Action potential jumps node to node, speeding transmission.

Question 46

What analogy explains saltatory conduction?

Answer 46

Like a cellphone signal boosted at each tower.

Question 47

# Definition: synapses

Answer 47

Tiny spaces between the axon terminal of one neuron and the nuron through which chemical communication occurs. | A tiny gap (~20nm) between neurons,

Question 48

# Definition: neurotransmitters ## Footnote Function?

Answer 48

Specialized chemicals that travel across synapses to allow communication between neurons. ## Footnote Carry signals to the postsynaptic neuron.

Question 49

# Definition: synaptic vesicles

Answer 49

Membrane-bound spheres in the axon terminals of neurons in which neurotransmitters are stored before their release.

Question 50

What is the presynaptic terminal?

Answer 50

The axon terminal of the sending neuron.

Question 51

How are neurotransmitters released?

Answer 51

Vesicles bind to the presynaptic membrane and release contents into the synaptic cleft.

Question 52

What is the synaptic cleft?

Answer 52

The space between the presynaptic and postsynaptic neurons.

Question 53

# Definition: neurotransmitter receptors

Answer 53

Proteins in the membranes of neurons that bind to neurotransmitters.

Question 54

What are the 6 common neutransmitters?

Answer 54

* Glutamate * GABA * Acetylcholine (ACh) * Dopamine * Serotonin * Norepinephrine

Question 55

# Definition: glutamate | Function ## Footnote Associated drug(s)

Answer 55

Learning and memory, movement, emotions, cognition. ## Footnote Ketamine

Question 56

# Definition: GABA (Gamma-Amino Butyric Acid) | Function ## Footnote Associated drug(s)

Answer 56

Learning, anxiety regulation. ## Footnote Valium (diazepam - used to relieve anxiety, muscle spasms), Ambien (Zolpidem - used to treat insomnia)

Question 57

# Definition: acetylcholine (ACh) | Function ## Footnote Associated drug(s)

Answer 57

Learning, attention, movement of muscles. ## Footnote Nicotine

Question 58

# Definition: dopamine | Function ## Footnote Associated drug(s)

Answer 58

Movement, reward learning, addiction. ## Footnote Cocaine; heroin; methamphetamine.

Question 59

# Definition: serotonin | Function ## Footnote Associated drug(s)

Answer 59

Mood regulation, sleep, memory. ## Footnote Exstasy (MDMA); LSD (hallucinogens); monoamine oxidase inhibitors (MAOIs), selective serotonin reuptake inhibitors (SSRIs; antidepressants).

Question 60

# Definition: norepinephrine | Function ## Footnote Associated drug(s)

Answer 60

Attention, arousal. ## Footnote Adderall (a stimulant made up of dextroamphetamine and amphetamine)

Question 61

# Definition: postsynaptic potentials

Answer 61

Electrical events in postsynaptic neurons that occur when a neurotransmitter binds to one of its receptors.

Question 62

# Definition: depolarization

Answer 62

What occurs when the inside of the neuron membrane becomes less negative relative to the outside.

Question 63

# Definition: hyperpolarization

Answer 63

What occurs when the inside of the neuron membrane becomes more negative relative to the outside.

Question 64

What triggers a postsynaptic potential?

Answer 64

Neurotransmitter binding to a receptor.

Question 65

What are the two types of postsynaptic potentials?

Answer 65

Excitatory (EPSP) and Inhibitory (IPSP).

Question 66

What happens during an EPSP? ## Footnote Which neurotransmitter is linked to EPSPs?

Answer 66

Na⁺ enters, causing depolarization (less negative inside). ## Footnote Glutamate.

Question 67

What happens during an IPSP? ## Footnote Which neurotransmitter is linked to IPSPs?

Answer 67

Cl⁻ enters, causing hyperpolarization (more negative inside). ## Footnote GABA.

Question 68

What happens during an IPSP?

Answer 68

Cl⁻ enters, causing hyperpolarization (more negative inside).

Question 69

# Definition: neuroplasticity

Answer 69

The brain's ability to create new neural pathways as a result of experience or following an injury.