Topic 2- Neurophysiology Intro & Review

Question 1

What is resting potential?

Answer 1

Resting potential is a stable, negative electrical charge across a neuron’s cell membrane when it’s not actively transmitting signals, typically around -70mV.

Question 2

What is the threshold for excitation in a neuron?

Answer 2

The threshold for excitation in a neuron is around -55mV. To initiate an action potential, the membrane potential needs to reach -55mV.

Question 3

What sets neurons apart from other cells?

Answer 3

Neurons are different from other cells because they are excitable. Their ability to change membrane potential, especially from resting potential to the threshold, allows them to respond to stimuli and transmit signals

Question 4

Membrane Potential

Answer 4

Difference in electrical charge across the cell membrane.

Question 5

What is the tendency of ions regarding concentration and voltage gradients

Answer 5

Ions tend to move down concentration and voltage gradients.

Question 6

What is the role of active transporter proteins in maintaining the membrane potential?

Answer 6

Active transporter proteins create and maintain ion gradients, ensuring that there are more positively charged ions outside the cell than inside, contributing to the membrane potential.

Question 7

What does the sodium-potassium (Na+/K+) pump do to maintain the resting membrane potential?

Answer 7

The Na+/K+ pump actively transports 3 sodium ions (Na+) out of the cell for every 2 potassium ions (K+) it pumps into the cell, contributing to the negative charge inside the cell.

Question 8

How does potassium (K+) contribute to the resting membrane potential?

Answer 8

Potassium ions leak out of the cell through potassium ion channels, allowing some positive charge to leave the cell and helping to establish the negative resting membrane potential.

Question 9

What is hyperpolarization and explain how it is inhibitory?

Answer 9

It makes the neuron’s membrane potential even more negative than its resting state, moving it farther away from the threshold needed to trigger an action potential.

Question 10

Depolarization

Answer 10

Process that makes the neuron’s electrical state more positive, which is exciting because it brings the neuron closer to the action potential threshold

Question 11

Four Types of Ion Channels

Answer 11

Leak (non-gated)
Ligand-gated
Mechanical (modality gated)
Voltage-gated

Question 12

Leaky Channels (ex. K+ ion channel)

Answer 12

Allow for passive diffusion of ions in and out of the cell (selectively permeable)

Question 13

Mechanical Channels

Answer 13

sensitive to physical changes in the cell membrane, such as stretching, pressure, or deformation.

Question 14

Voltage Gated Ion Channels

Answer 14

Membrane proteins that respond to changes in the electrical potential (voltage) across the cell membrane.

Question 15

Ligand Gated Ion Channels

Answer 15

Respond to the binding of specific chemical signaling molecules, called ligands, to their receptor sites.

Question 16

Ligand Gated ion Main Function

Answer 16

Convert chemical signal to electrical signal and play a crucial role in synaptic transmission, where neurotransmitters bind to receptors on postsynaptic neurons to initiate an electrical signal.

Question 17

Where are mechanical channels found?

Answer 17

Sensory receptors, like touch receptors, and play a role in transducing mechanical stimuli into electrical signals.

Question 18

Steps of an Action Potenital

Answer 18

1) Resting Membrane Potential
2) Depolarization
3) Rising Phase
4) Repolarization
5) Overshoot and Hyperpolarization
6) Return to Resting Potential
7) Refractory Period

Question 19

First Step: Resting Membrane Potential

Answer 19

Neurons’ resting potential is around -70 mV due to ion imbalance, with K+ inside and Na+ outside the cell.

Question 20

Second Step: Depolarization

Answer 20

When a stimulus reaches the threshold, voltage-gated Na+ channels open, causing an influx of Na+ ions and making the membrane potential more positive.

Question 21

Third Step: Rising Phase of an action potential`

Answer 21

During this phase, more Na+ ions flow into the neuron, leading to a continuous increase in membrane potential (more positive), reaching approximately +30 mV.

Question 22

4) Repolarization

Answer 22

After reaching its peak, voltage-gated Na+ channels close, and voltage-gated K+ channels open, allowing K+ ions to exit, making the membrane potential more negative.

Question 23

5) Overshoot and Hyperpolization

Answer 23

The membrane potential briefly goes below the resting level (overshoot) due to the efflux of potassium ions, followed by a temporary hyperpolarization where it becomes more negative due to open K+ channels.

Question 24

How does a neuron Return to Resting Potential after an action potential?

Answer 24

The sodium-potassium pump (Na+/K+ pump) actively moves Na+ ions out and K+ ions in, restoring the original ion balance, and resetting the membrane potential to around -70 mV

Question 25

What is the Refractory Period in an action potential?

Answer 25

It’s a period when the neuron is less responsive to stimuli. This refractory period consists of two phases: the absolute refractory period, during which another action potential cannot be triggered because voltage gated sodium channels are closed , and the relative refractory period, during which a stronger stimulus is required to initiate a new action potential.

Question 26

How can different cells can have different types of APS

Answer 26

Due to different types and densities of ion channels

Question 27

What is the function of the axon in a neuron?

Answer 27

The axon acts like a cable, transmitting the electrical signal (action potential) from the cell body to the presynaptic terminals, where communication with other cells occurs.

Question 28

Why are neuronal membranes not good insulators?

Answer 28

Neuronal membranes allow ions like sodium (Na+) and potassium (K+) to leak across them, which makes them poor insulators and challenges the maintenance of electrical signals over long distances

Question 29

How is the signal strength boosted in neurons?

Answer 29

Neurons use nodes of Ranvier along their axons. At these nodes, the action potential is regenerated or “boosted” by the opening of voltage-gated ion channels, ensuring the signal remains strong during transmissio

Question 30

What is the major challenge in neuronal communication?

Answer 30

The major challenge is speed. Neurons often need to transmit signals quickly for rapid responses. The leakiness of neuronal membranes can slow down signal propagation, but the continual regeneration of the action potential at nodes of Ranvier helps maintain signal speed.

Question 31

What are oligodendrocytes, and where are they found?

Answer 31

Oligodendrocytes are glial cells found in the central nervous system (CNS), including the brain and spinal cord.:

Question 32

What is the primary function of oligodendrocytes?

Answer 32

The primary function of oligodendrocytes is to provide insulation to axons by producing myelin, which speeds up the transmission of electrical signals in the CNS.

Question 33

What are Schwann cells, and where are they located?

Answer 33

Schwann cells are glial cells found in the peripheral nervous system (PNS), which includes nerves outside the brain and spinal cord

Question 34

What is the role of Schwann cells?

Answer 34

Schwann cells play a role in myelinating axons in the PNS, helping in rapid nerve signal transmission and supporting nerve regeneration.

Question 34

What creates the small gaps known as Nodes of Ranvier along the axon?

Answer 34

Nodes of Ranvier are small gaps where myelin-forming glial cells (oligodendrocytes in the CNS or Schwann cells in the PNS) do not cover the axon, creating spaces between adjacent glial cells along the axon’s length

Question 34

Primary difference in function between oligodendrocytes and Schwann cells

Answer 34

Oligodendrocytes myelinate multiple axons and Schwann cells myelinate (wrap around) single axons.

Question 34

What characterizes Nodes of Ranvier in terms of ion channels?

Answer 34

Nodes of Ranvier are characterized by a high density of voltage-gated sodium (Na+) channels on the axonal membrane, which open in response to changes in membrane potential and are crucial for the rapid initiation of action potentials.

Question 35

What distinguishes Nodes of Ranvier from myelinated axonal segments in terms of potassium (K+) channels?

Answer 35

Nodes of Ranvier lack voltage-gated potassium (K+) channels, unlike myelinated axonal segments where K+ channels are abundant. This absence prevents the early repolarization phase of the action potential in these regions.

Question 36

What is the term for the mode of rapid nerve signal propagation that occurs at Nodes of Ranvier?

Answer 36

“Saltatory” conduction refers to the rapid transmission of action potentials where the signal “jumps” or “skips” from one Node of Ranvier to the next along a myelinated axon, significantly increasing signal speed and efficiency.

Question 37

How does a lack of myelin impact the propagation of action potentials in neurons?

Answer 37

A lack of myelin slows down and disrupts the smooth transmission of nerve signals, making them less efficient, leading to symptoms and issues with motor control, sensation, and coordination as seen in MS

Question 38

What does lambda represents and affect?

Answer 38

Represents (how far a current can go) and what affects it (how thick myelin is…goes farther!…and how low axon resistance is