Neuroscience: Nernst Equation and Ion Gradients
44 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What happens when the chemical and electrical gradients reach equilibrium?

  • The system can change direction.
  • The Nernst equation is applied. (correct)
  • The membrane becomes impermeable to ions.
  • The concentration of ions inside the membrane increases.

What is the primary role of the Nernst equation in this context?

  • To determine membrane potential at equilibrium. (correct)
  • To measure the volume of the cell.
  • To establish ion permeability of the membrane.
  • To calculate ion concentrations outside the cell.

What would likely occur if the chemical gradient of K+ was greater than the electrical gradient?

  • K+ would move into the cell, increasing the electrical potential.
  • K+ would lead to cell depolarization immediately.
  • K+ would move out of the cell until equilibrium is reached. (correct)
  • K+ would remain static, as gradients do not affect motion.

Which ion is primarily referenced for establishing the Nernst equation in the content?

<p>K+ (C)</p> Signup and view all the answers

What describes the relationship between the concentration gradient and electrical gradient at equilibrium?

<p>They are equal and opposite. (B)</p> Signup and view all the answers

What is the primary factor contributing to the negative charge inside the neuronal membrane at rest?

<p>Presence of impermeant negatively charged ions (A-) (C)</p> Signup and view all the answers

Which ion has the highest concentration outside the neuronal membrane at rest?

<p>Na+ (C)</p> Signup and view all the answers

At rest, which ion is the neuronal membrane most permeable to?

<p>K+ (A)</p> Signup and view all the answers

What happens to K+ ions as a result of their concentration gradient?

<p>They leak out of the cell (D)</p> Signup and view all the answers

What is the K+ concentration inside the neuronal cell at rest?

<p>140 mM (B)</p> Signup and view all the answers

What effect does the permeability of the neuronal membrane have on the distribution of Cl- ions?

<p>Cl- ions cannot diffuse across the membrane (A)</p> Signup and view all the answers

What is the Na+ concentration outside the neuronal membrane at rest?

<p>145 mM (B)</p> Signup and view all the answers

How do the impermeant negatively charged ions (A-) affect membrane potential?

<p>They contribute to the resting membrane potential being negative (A)</p> Signup and view all the answers

What initiates the activation of sodium channels in the membrane?

<p>Depolarization of the membrane to threshold (D)</p> Signup and view all the answers

What is the membrane potential at which 60% of sodium channels are reported to open?

<p>-70 mV (A)</p> Signup and view all the answers

Which of the following best describes the resultant effect when sodium channels open?

<p>Membrane undergoes further depolarization (B)</p> Signup and view all the answers

What pattern describes the opening of sodium channels upon reaching threshold?

<p>Positive feedback loop (B)</p> Signup and view all the answers

What is the typical value of the resting membrane potential?

<p>-70 mV (A)</p> Signup and view all the answers

What is the primary ion involved in the depolarization process described?

<p>Sodium ions (Na+) (B)</p> Signup and view all the answers

What primarily causes the resting membrane potential?

<p>A small excess of negatively charged ions inside the cell (D)</p> Signup and view all the answers

Which ion's gradient is most significant for establishing resting membrane potential?

<p>Potassium ions (D)</p> Signup and view all the answers

How does the excess of negatively charged ions affect resting membrane potential?

<p>It creates a negative voltage within the cell (A)</p> Signup and view all the answers

In terms of ion distribution, what occurs at resting membrane potential?

<p>Higher concentration of potassium ions inside the cell (D)</p> Signup and view all the answers

What is the role of ion concentration gradients at resting membrane potential?

<p>They stabilize the electrical charge across the membrane (B)</p> Signup and view all the answers

Which statement is true about the resting membrane potential?

<p>It reflects the balance of ionic charge inside and outside the cell (A)</p> Signup and view all the answers

What happens to the resting membrane potential when sodium permeability increases?

<p>The potential becomes more positive (A)</p> Signup and view all the answers

Which ion's concentration is usually lower inside the cell compared to outside at resting membrane potential?

<p>Sodium ions (B)</p> Signup and view all the answers

Which ions contribute to the establishment of the resting membrane potential?

<p>Potassium and sodium ions (A)</p> Signup and view all the answers

What characterizes the absolute refractory period in neuronal activity?

<p>Sodium channels are inactive and the membrane is completely unexcitable. (C)</p> Signup and view all the answers

Which of the following statements is correct regarding action potentials?

<p>They exhibit a frequency that conveys information. (A)</p> Signup and view all the answers

How do neurotoxins like tetrodotoxin and batrachotoxin affect sodium channels?

<p>They inhibit the activity of sodium channels. (D)</p> Signup and view all the answers

What is the primary mechanism by which action potentials propagate along an axon?

<p>By spreading electrotonic currents from the action potential site. (C)</p> Signup and view all the answers

During which period is the membrane potential overshooting its resting level due to open voltage-gated potassium channels?

<p>Relative refractory period. (C)</p> Signup and view all the answers

What is the equilibrium potential for K+ ions typically characterized as?

<p>Approximately $-90 mV$. (B)</p> Signup and view all the answers

How do sodium channels affect neuronal excitability after an action potential?

<p>They become inactive temporarily, promoting unexcitable states. (C)</p> Signup and view all the answers

What role does the frequency of action potentials play in neuronal signaling?

<p>It dictates the response level of the neuron to stimuli. (C)</p> Signup and view all the answers

What is the primary function of metabotropic glutamate receptors (mGluRs)?

<p>To relay a chemical signal inside the postsynaptic neuron (A)</p> Signup and view all the answers

Which of the following neurotransmitters primarily interacts with metabotropic receptors?

<p>Glutamate (C)</p> Signup and view all the answers

What type of signaling molecule is generated inside the postsynaptic spine upon activation of mGluRs?

<p>Second messenger (D)</p> Signup and view all the answers

What role do second messengers play in neuronal signaling?

<p>They activate cellular proteins such as kinases and transcription factors (A)</p> Signup and view all the answers

Which of the following is NOT a feature of ionotropic receptors?

<p>They relay signals via G-proteins (D)</p> Signup and view all the answers

Which protein type is specifically activated by second messengers?

<p>Protein kinases (D)</p> Signup and view all the answers

What distinguishes metabotropic receptors from ionotropic receptors?

<p>Metabotropic receptors initiate signaling cascades involving second messengers (C)</p> Signup and view all the answers

What is the effect of activating GABAB receptors in the synaptic environment?

<p>Generates a second messenger cascade within the postsynaptic neuron (C)</p> Signup and view all the answers

Flashcards

Resting Membrane Potential

The electrical potential difference across the cell membrane when the cell is at rest, typically around -70 mV.

Electrical Potential Difference

The difference in electrical charge between two points.

Membrane Potential

The voltage across a cell's membrane.

-70 mV

A common value for the resting membrane potential of a neuron.

Signup and view all the flashcards

Concentration Gradients

Differences in the concentration of ions inside and outside the cell.

Signup and view all the flashcards

Negative Ions Inside Cell

An excess of negatively charged ions (anions) inside the cell contributes to the resting potential

Signup and view all the flashcards

Physiological Ions

Ions crucial for cellular function, involved in generating & maintaining the membrane potential.

Signup and view all the flashcards

Neuron

A specialized cell transmitting nerve impulses.

Signup and view all the flashcards

Cell Membrane

The outer boundary of a cell, thin layer separating the inside from outside.

Signup and view all the flashcards

Resting State

The state of the cell when it is not actively sending signals.

Signup and view all the flashcards

Membrane Potential Equilibrium

When chemical and electrical forces balance across a membrane, creating no net movement of ions.

Signup and view all the flashcards

Nernst Equation

A mathematical equation that describes the membrane potential at which the chemical and electrical gradients of an ion are balanced.

Signup and view all the flashcards

Chemical Gradient

The difference in ion concentration across a membrane.

Signup and view all the flashcards

Electrical Gradient

The difference in electrical charge across a membrane.

Signup and view all the flashcards

Equilibrium

A state in which opposing forces or influences are balanced.

Signup and view all the flashcards

Ion concentrations (outside/inside)

Different ions have different concentrations inside and outside a neuron. For example, sodium (Na+) is higher outside the cell, while potassium (K+) is higher inside.

Signup and view all the flashcards

Selective Permeability (membrane)

A cell membrane lets some ions pass through more easily than others. At rest, the membrane is very permeable to potassium (K+).

Signup and view all the flashcards

K+ leakage

Potassium ions naturally move out of the cell down their concentration gradient.

Signup and view all the flashcards

Impermeant ions

Certain charged particles (ions) cannot easily cross the cell membrane.

Signup and view all the flashcards

Sodium (Na+) outside

The concentration of sodium ions is significantly higher outside the cell than inside.

Signup and view all the flashcards

Potassium (K+) inside

The concentration of potassium ions is significantly higher inside the cell than outside.

Signup and view all the flashcards

Depolarization

The process of the membrane potential becoming more positive, moving towards zero.

Signup and view all the flashcards

Threshold

The critical membrane potential that must be reached to trigger an action potential.

Signup and view all the flashcards

Sodium Channels

Specialized protein channels in the cell membrane that allow sodium ions (Na+) to pass through.

Signup and view all the flashcards

Positive Feedback Loop

A process where a change in a variable triggers a response that further increases the change.

Signup and view all the flashcards

Action Potential

A rapid, short-lasting change in the membrane potential of a neuron, propagated along the axon.

Signup and view all the flashcards

Metabotropic Receptors

Receptors that trigger a chain of intracellular events through signaling molecules (G-proteins) when activated by neurotransmitters.

Signup and view all the flashcards

Ionotropic Receptors

Receptors that directly open ion channels when activated by neurotransmitters, allowing ions to flow across the cell membrane.

Signup and view all the flashcards

Glutamate Synapse

A specialized junction between neurons where the neurotransmitter glutamate is released and binds to receptors.

Signup and view all the flashcards

Second Messenger

A molecule inside a cell that carries a signal from a neurotransmitter receptor to other cellular components, triggering various cellular responses.

Signup and view all the flashcards

Neuromodulators

Neurotransmitters that act primarily, or entirely, through metabotropic receptors, influencing the overall activity and responsiveness of neurons.

Signup and view all the flashcards

mGluRs

Metabotropic glutamate receptors, responsible for activating intracellular pathways that can lead to various cellular responses.

Signup and view all the flashcards

GABAB Receptors

Metabotropic GABA receptors, responsible for activating intracellular pathways that can lead to various cellular responses, including reducing neuronal activity.

Signup and view all the flashcards

Presynaptic Terminal

The end of a neuron where neurotransmitters are released into the synapse.

Signup and view all the flashcards

Sodium-Potassium Pump

A protein pump that actively transports sodium ions out of the cell and potassium ions into the cell, maintaining the concentration gradients essential for action potential generation.

Signup and view all the flashcards

Action Potential Propagation

The movement of an action potential along an axon, caused by the spread of electrical current from one region to the next.

Signup and view all the flashcards

Absolute Refractory Period

A brief time immediately following an action potential during which the neuron cannot generate another action potential, regardless of the stimulus strength.

Signup and view all the flashcards

Relative Refractory Period

The period following the absolute refractory period during which the neuron is less excitable than usual, requiring a stronger stimulus to trigger an action potential.

Signup and view all the flashcards

Neuron's Communication

Neurons transmit information by varying the frequency and pattern of action potentials.

Signup and view all the flashcards

Tetrodotoxin

A potent neurotoxin produced by pufferfish, which blocks sodium channels, preventing action potential generation.

Signup and view all the flashcards

Batrachotoxin

A neurotoxin found in Phyllobates frogs, which acts as a potent sodium channel activator, leading to excessive action potential firing.

Signup and view all the flashcards

Sodium Channel Modulators

Various substances, including pyrethroid insecticides, scorpion toxins, and anemones toxins, can modulate the activity of sodium channels.

Signup and view all the flashcards

Study Notes

Course Information

  • Course name: PHGY 209
  • Course topic: Introduction to the Nervous System
  • Instructor: David Ragsdale
  • Affiliation: Montreal Neurological Institute
  • Email: [email protected]

Remembering Past Events

  • Students are asked to recall past events
  • A picture of a group of people at a skating rink is displayed

Quote on the Mind

  • "Our mind is the pattern of information processing running on a special kind of machine: our brain. ... Its information processing all the way down and all the way up."
  • Author: Read Montague

Organization of the Nervous System

  • The nervous system is divided into central and peripheral systems
  • The central nervous system consists of the brain and spinal cord
  • The peripheral nervous system includes afferent (sensory) fibers, efferent (motor) fibers, and the autonomic and enteric nervous systems
  • Afferent fibers carry sensory information to the central nervous system to the CNS
  • Efferent fibers carry motor information from the central nervous system to muscles and glands
  • The autonomic nervous system controls involuntary functions
  • The enteric nervous system controls the gastrointestinal tract

Neurons

  • The nervous system includes approximately 100 billion neurons
  • Neurons communicate with each other at specialized sites called synapses
  • The human nervous system comprises hundreds of trillions of synapses
  • Neurons show a wide range of shapes and sizes

Neuron Structure

  • Neurons have a cell body (soma), branching dendrites, and an axon
  • Axons can range in length from a few millimeters to more than a meter
  • Dendrites receive information
  • Axons transmit information
  • Presynaptic terminals transmit information to the next neuron

Electrical Properties of Neurons

Resting Membrane Potential

  • The inside of a typical neuron is -60 to -70 mV compared to the outside
  • This resting membrane potential is caused by a slight excess of negatively charged ions inside the cell
  • The resting membrane potential is created by concentration gradients for ions like Na+, K+, Cl- and A-

Concentration/Permeability gradients

  • Na+ : outside = 145mM, inside = 10mM
  • K+ : outside = 5mM, inside = 150mM
  • Cl- : outside = 100mM, inside = 5mM
  • A- : outside = 50mM, inside = 155mM
  • The neuronal membrane is highly permeable to K+ but much less permeable to other ions.
  • K+ ions leak out of the cell down the concentration gradient, leaving negatively charged ions inside, creating an electrical gradient that pulls K+ ions back in
  • The equilibrium state of the concentration and electrical gradients is described by the Nernst Equation.

Nernst Equation

  • Eion = 2.3RT/ZF * log [ion]out/[ion]in
  • The equilibrium potential for potassium (EK) plays a significant role in the resting membrane potential (approximate -90 mV)
  • The actual resting membrane potential is slightly closer to –70 mV due to some sodium leakage through the membrane.
  • Resting permeability to K+ is caused by leak channels
  • Leak channels are proteins that form K+ selective pores through the membrane.
  • The channels are open at rest.

Action Potential

  • Action potential is a short, rapid change in the electrical potential across a neuron’s membrane. An all-or-none event
  • Action potentials usually start at the initial segment of the axon and propagate along the axon to the presynaptic terminals
  • The rising phase (depolarization) of the action potential is caused by sodium ions flowing into the cell. Voltage-gated sodium channels
  • The falling phase (repolarization) is caused by potassium ions flowing out of the cell . Voltage-gated potassium channels.
  • The action potential is initiated when the membrane potential depolarizes to a threshold level.
  • The threshold is determined by the properties of voltage-gated sodium channels.
  • Sodium channels have three critical properties: Closed at resting potential, open when the membrane depolarizes, selective for Na+, open channel rapidly inactivates, stopping the flow of Na+ ions.
  • The density of voltage-gated sodium channels in the axon membrane is much higher than the density of leak potassium channels.
  • Action Potential Propagation
  • Action potential propagation is caused by spread of electrotonic currents from the site of the action potential.

Refractory Periods

  • Absolute refractory period: A brief period after an action potential where the membrane cannot be re-excited. Sodium channels are inactivated
  • Relative refractory period: A somewhat longer period after the absolute refractory period where the membrane is less excitable. Voltage-gated potassium channels are open

Synaptic Transmission

  • Synapses are specialized junctions between neurons or between neurons and other cells
  • Different types of synapses
  • Axodendritic
  • Axosomatic
  • Axoaxonic
  • Spine synapses
  • Shaft synapses
  • Presynaptic terminal
  • Postsynaptic terminal

Summary of LTP (Long-Term Potentiation)

  • High-frequency activity in active synapses increases the strength of synapses.
  • Involved opening of NMDA receptors enabling Calcium influx.
  • This strengthens the synapse.
  • This can impact neuron survival and play a significant role in neurodegenerative and stroke related diseases.

Other important factors

  • Excitotoxicity: High glutamate concentrations are toxic. Calcium influx through NMDA receptors causes this toxicity
  • Neuromodulators: Dopamine, serotonin, norepinephrine and neuropeptides do not directly transmit neural information, but influence global neural conditions such as alertnes, attention and mood.
  • Multiple sclerosis: A disease resulting from loss of myelin
  • Types of synapses: Excitatory and Inhibitory
  • Main neurotransmitter for excitatory synapses: Glutamate
  • Main neurotransmitter for inhibitory synapses: GABA

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

PHGY 209: Introduction to the Nervous System PDF

Description

Explore the dynamics of neuronal ion gradients and the role of the Nernst equation in this quiz. Discover how electrical and chemical gradients interact at equilibrium and the significance of various ions in maintaining resting membrane potential. Perfect for students studying neurobiology and biophysics.

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser