Neurophysiology

Question 1

What are neurons uniquely structured for?

Answer 1

Communication

Neurons are specialized cells designed to transmit information.

Question 2

What is the phospholipid bilayer?

Answer 2

A barrier around the neuron that controls ion movement

It consists of hydrophilic heads and hydrophobic tails that prevent water-soluble molecules from passing.

Question 3

What are ion channels?

Answer 3

Transmembrane proteins allowing specific ions to cross the membrane

They are crucial for maintaining ion balance and communication in neurons.

Question 4

What are the types of ion channels based on how they open?

Answer 4

• Leak channels
• Voltage-gated channels
• Ligand-gated channels

Each type allows ions to flow in response to different stimuli.

Question 5

What drives ion movement across the neuronal membrane?

Answer 5

Concentration gradients, electrical gradients, and electrochemical gradients

These gradients determine the direction and flow of ions.

Question 6

What occurs at equilibrium for ions?

Answer 6

No net movement of ions occurs across the membrane

The concentration and electrical gradients balance out.

Question 7

What is the equilibrium potential for sodium (Na)?

Answer 7

+60 mV

This is the membrane voltage where sodium ions have no net movement.

Question 8

What is membrane potential?

Answer 8

The difference in electrical charge between the inside and outside of a neuron

It is crucial for neuronal communication.

Question 9

Define depolarization and hyperpolarization in neuronal terms.

Answer 9

Depolarization - membrane potential moves towards 0 mV, becomes less negative
Hyperpolarization - membrane potential moves away from 0 mV, becomes more negative

This indicates a less negative charge inside the neuron.

Question 10

What triggers excitatory postsynaptic potentials (EPSPs)?

Answer 10

Opening of sodium channels

This influx of Na+ depolarizes the neuron, increasing action potential likelihood.

Question 11

What effect do inhibitory postsynaptic potentials (IPSPs) have?

Answer 11

They hyperpolarize the neuron, making it more negative

This decreases the likelihood of firing an action potential.

Question 12

What is temporal summation?

Answer 12

Summation of EPSPs from one presynaptic neuron over time

It can help reach the action potential threshold.

Question 13

Explain spatial summation.

Answer 13

Summation of inputs from multiple presynaptic neurons

This occurs simultaneously to activate a single postsynaptic neuron.

Question 14

What is an action potential?

Answer 14

A brief, rapid change in electrical potential across the neuron’s membrane

It is an all-or-nothing response that triggers neurotransmitter release.

Question 15

What happens during the rising phase of an action potential?

Answer 15

Sodium channels open and sodium flows into the cell

This causes depolarization of the membrane.

Question 16

What is the absolute refractory period?

Answer 16

A period where no action potential can occur regardless of stimulus strength

It occurs when sodium channels are open or inactive.

Question 17

What are electrical synapses?

Answer 17

Connections between neurons that allow rapid, bidirectional signal transmission

They are formed by gap junctions and enable fast communication.

Question 18

What characterizes chemical synapses?

Answer 18

Transmission via neurotransmitters across a synaptic cleft

They allow for unidirectional communication and can produce complex effects.

Question 19

What is the role of calcium ions in neurotransmitter release?

Answer 19

Calcium influx triggers the release of neurotransmitters

This occurs when voltage-gated calcium channels open at the axon terminal.

Question 20

What types of receptors do neurotransmitters bind to?

Answer 20

• Ionotropic receptors
• Metabotropic receptors

These receptors mediate the effects of neurotransmitters on the postsynaptic neuron.

Question 21

What is the all-or-nothing principle in action potentials?

Answer 21

If the threshold is reached, an action potential is fired; otherwise, it does not occur

Action potentials are not graded and propagate fully along the axon.

Question 22

List the three major chemical categories of neurotransmitters.

Answer 22

• Amino Acids
• Amines
• Peptides

Each category includes various neurotransmitters with distinct functions.

Question 23

What are the four ways neurotransmitters are inactivated?

Answer 23

• Diffusion
• Degradation
• Reuptake
• Glial cell uptake

These mechanisms ensure neurotransmitter levels are regulated in the synaptic cleft.

Question 24

What is a neuronal membrane?

Answer 24

A barrier that goes around the neuron that controls what goes in and out of the neuron

Question 25

What is the difference between hydrophilic heads and hydrophobic tails in the phospholipid bilayer?

Answer 25

Hydrophilic heads - water-attracted parts of the cell membrane that interact with water molecules Hydrophobic tails - water-repulsed parts of the cell membrane that avoid water molecules

Question 26

What does it mean when we say that ion channels are selective?

Answer 26

Each type of ion channel only lets certain ions through

Question 27

What is the difference between chemical and electrical gradients?

Answer 27

Chemical gradients: ions move from areas of high to low concentration (through diffusion) Electrical gradients: ions move towards areas of opposite electrical charge

Question 28

Is ion movement active or passive, and what does it mean

Answer 28

Ion movement is passive; no energy is required when a pathway like an open ion channel exists

Question 29

When does equilibrium occur in ion movement?

Answer 29

Concentration gradient and electrical gradient for ion are equal in strength BUT opposite in direction

Question 30

What is the total electrochemical force in equilibrium?

Answer 30

ZERO - the ion's distribution is stable over time

Question 31

Describe the concentrations of fluid inside and outside of neurons of the following ions: - Sodium (Na+) - Chloride (Cl-) - Potassium (K+)

Answer 31

Sodium (Na) and Chloride (Cl) - Higher concentration outside the neuron (extracellular fluid - outside neurons) - Lower concentration inside the neuron (intracellular fluid - inside neurons) Potassium (K) - Higher concentration inside the neuron (intracellular fluid) - Lower concentration outside the neuron (extracellular fluid)

Question 32

Electrochemical gradients push what ions out the cell and pulls in what ions into the cell?

Answer 32

Pushes in sodium (Na+), pulls out potassium (K+)

Question 33

What is the voltage of resting potential?

Answer 33

Around -65 mV

Question 34

Is the inside of the cell more or less negative than the outside? Why?

Answer 34

Inside of the cell is more negative than the outside because the intracellular fluid has more negatively charged proteins and amino acids

Question 35

What equation calculates the equilibrium potential of an ion?

Answer 35

The Nernst Equation

Question 36

What are postsynaptic potentials?

Answer 36

Changes in membrane potential that move the neuron away from its resting potential