cellular neurophysiology lecture 3

Questions and Answers

Why do cells need to communicate?

To integrate functions (correct)

To synchronise events (correct)

Adapt to their environment (correct)

Turn pathways on and off (correct)

What is the disease associated with the degeneration of the myelin sheath called?

Multiple Sclerosis (correct)

Alzheimer's Disease

Parkinson's Disease

Amyotrophic Lateral Sclerosis

What is Myasthenia Gravis?

An autoimmune disease that affects muscle communication (correct)

A type of bacterial infection

A genetic disorder that causes bone deformities

A mental health condition characterized by severe anxiety

What is slow communication within cells called?

Autocrine signaling Signup and view all the answers

What is slow communication between cells mediated by?

Hormonal signaling Signup and view all the answers

What mediates fast transmission between cells?

Neurotransmission Signup and view all the answers

What is fast communication within cells mediated by?

Electrical signals Signup and view all the answers

What are the features of hormonal signaling? (Select all that apply)

Slower response times compared to nerve signals Signup and view all the answers

What is electrical signaling?

The transmission of signals through electrical impulses in neurons via rapid changes in membrane potential Signup and view all the answers

What are features of electrical signaling in excitable cells? (Select all that apply)

Rapid transmission of signals Signup and view all the answers

Where does electrical signaling occur in the body?

In the synapses between neurons Signup and view all the answers

What is the resting membrane potential of a typical neuron?

-70 mV Signup and view all the answers

Why is there a resting membrane potential in cells?

It is due to the difference in ion concentrations inside and outside the cell- inside negative to outside Signup and view all the answers

Which ions contribute significantly to resting membrane potential?

Sodium (Na+) Signup and view all the answers

How do ions move across the resting membrane potential?

All of the above. Signup and view all the answers

Why is the cell relatively impermeable to Na+?

Far fewer channels for Na+ making it relatively impermeable to Na+ Signup and view all the answers

What pump transports Na+ and K+ in and out of the cell?

Sodium-Potassium Pump Signup and view all the answers

What does the sodium-potassium pump require to function?

ATP Signup and view all the answers

How many potassium ions are exchanged for sodium ions in the sodium-potassium pump?

3 sodium ions for 2 potassium ions Signup and view all the answers

What allows K+ to leak out of the cell?

Potassium leaky channels Signup and view all the answers

What is a chemical gradient?

The difference in concentration of a chemical inside and outside of a cell Signup and view all the answers

What is the electrical gradient?

The difference in ion concentration across a membrane. Signup and view all the answers

Why is there a higher concentration of Na+ ions outside the cell?

Na+ ions are actively transported out of the cell by the sodium-potassium pump. Signup and view all the answers

Why does K+ (potassium ion) want to move down its chemical gradient?

To achieve equilibrium within the cell Signup and view all the answers

What is the equilibrium potential?

The membrane potential at which there is no net movement of a particular ion across the membrane Signup and view all the answers

What equation determines the equilibrium potential of an ion?

Nernst Equation Signup and view all the answers

What is the equilibrium potential for potassium (K+) in millivolts (mV)?

-80 mV Signup and view all the answers

What is the equilibrium potential for sodium (Na+)?

+60 mV Signup and view all the answers

What is the equilibrium potential for chloride ions (Cl⁻)?

-65 mV Signup and view all the answers

What equation is used to calculate the resting membrane potential while taking into account the permeability of the membrane?

Goldman equation Signup and view all the answers

What is an action potential?

A rapid rise and fall in membrane potential Signup and view all the answers

What do ions cross the membrane through?

Voltage -gated Ion channels Signup and view all the answers

At what threshold do sodium channels typically open during depolarization?

-55 mV Signup and view all the answers

What occurs when sodium enters a cell?

Depolarization of the membrane potential Signup and view all the answers

What occurs during repolarization in a neuron?

Potassium ions exit the neuron Signup and view all the answers

What is hyperpolarization the result of?

Increased potassium ion permeability Signup and view all the answers

Why does hyperpolarization occur in relation to potassium channels?

Potassium channels close slowly, allowing K+ to exit the cell. Signup and view all the answers

What is the absolute refractory period?

The time period during which no new action potential can be initiated, regardless of the strength of the stimulus. Signup and view all the answers

What is a relative refractory period?

The time during which a second action potential can occur with a stronger stimulus Signup and view all the answers

What is neurotransmission?

The process of communication between neurons through chemical signals. Signup and view all the answers

What is an excitatory postsynaptic potential?

A type of electrical signal that increases the likelihood of an action potential. Signup and view all the answers

At what membrane potential do voltage-gated sodium channels (VGScs) typically open?

-55 mV Signup and view all the answers

Where do action potentials start in a neuron?

Axon hillock Signup and view all the answers

How does action potential move along the neuron?

Through the opening and closing of voltage-gated ion channels Signup and view all the answers

What does the speed of movement of action potentials depend on?

The diameter of the axon Signup and view all the answers

What is the velocity of action potentials in neurons?

1-100 m/s Signup and view all the answers

Why is myelination important for nerve function?

It increases the speed of electrical impulses. Signup and view all the answers

What are the nodes of Ranvier?

Gaps in the myelin sheath of a neuron Signup and view all the answers

What is the function of the Nodes of Ranvier in a neuron?

They facilitate the rapid conduction (jumping) of nerve impulses. Signup and view all the answers

Which of the following options are types of neurotransmitters? (Select all that apply)

Amines- Dopamine Signup and view all the answers

Where are neurotransmitters synthesized?

In the cell body of neurons Signup and view all the answers

Where are neurotransmitters stored?

In synaptic vesicles Signup and view all the answers

Why are neurotransmitters stored in synaptic vesicles?

To protect them from degradation before release Signup and view all the answers

How are neurotransmitters released?

Through exocytosis upon the arrival of an action potential, opening of CA2+ which promotes fusing of vesicles Signup and view all the answers

What are SNARE proteins?

Proteins involved in vesicle fusion Signup and view all the answers

How are neurotransmitters removed from the synaptic cleft?

All of the above Signup and view all the answers

What are the two classes of neurotransmitter receptors?

Ionotropic and Metabotropic Signup and view all the answers

What is an ionotropic receptor?

A type of receptor that directly opens ion channels in response to ligand binding Signup and view all the answers

What is a metabotropic receptor?

A receptor that activates a signaling cascade through a G-protein Signup and view all the answers

Which signaling type is slower, ionotropic or metabotropic?

Metabotropic signaling Signup and view all the answers

How does the binding of a neurotransmitter to a metabotropic receptor lead to an action potential?

G protein hydrolyses (GDP-GTP)- intracellular messengers are increased/reduced- kinases are inactivated/activated and Ca2+ is mobilised or sequestered- membrane is therefore more or less excitable Signup and view all the answers

What type of receptor is GABAa?

Ionotropic receptor Signup and view all the answers

What type of receptor is GABAB?

Metabotropic receptor Signup and view all the answers

What type of receptor does noradrenaline bind to?

Alpha-adrenergic receptor Signup and view all the answers

What is the primary function of selective serotonin reuptake inhibitors (SSRIs)?

They increase the levels of serotonin in the brain by blocking its reabsorption Signup and view all the answers

What do monoamine oxidase inhibitors do?

They increase the levels of neurotransmitters in the brain. Signup and view all the answers

What effects do amphetamines and ecstasy have on neurotransmission?

They increase the release of neurotransmitters such as dopamine and serotonin. Signup and view all the answers

Which of the following drugs cause non-impulse dependent release of dopamine?

Amphetamine Signup and view all the answers

What causes the after hyperpolarization (AHP) during an action potential?

Slow closure of voltage-gated K+ channels Signup and view all the answers

What is a primary characteristic of the absolute refractory period?

Na+ channels remain inactivated for a short period post-action potential Signup and view all the answers

What primarily initiates an action potential in a neuron?

Influx of Na+ ions Signup and view all the answers

During which phase of the action potential does the membrane potential rise towards +30 mV?

Depolarization Signup and view all the answers

What is the effect of K+ moving out of the cell during the action potential?

Repolarization of the membrane Signup and view all the answers

What results from the slow closing of voltage-gated K+ channels after an action potential?

After hyperpolarization Signup and view all the answers

How does the influx of Na+ ions affect the membrane potential during an action potential?

It causes a rapid depolarization above 0 mV Signup and view all the answers

Which of the following is NOT a key feature of the action potential?

Closure of Na+ channels results in hyperpolarization Signup and view all the answers

What is the primary role of the voltage-gated Na+ channel during an action potential?

Causing depolarization of the membrane Signup and view all the answers

At what membrane potential does the voltage-gated Na+ channels typically open?

-55 mV Signup and view all the answers

What happens immediately after the rapid influx of Na+ during depolarization?

The Na+ channel enters a state of inactivation Signup and view all the answers

Which ions are primarily responsible for the repolarization phase of an action potential?

K+ and Cl- Signup and view all the answers

What is the resting membrane potential (RMP) of a typical neuron?

-70 mV Signup and view all the answers

What causes the after hyperpolarization stage following an action potential?

Prolonged K+ permeability Signup and view all the answers

Which statement about voltage-gated ion channels is true?

They open at specific membrane potentials Signup and view all the answers

What occurs during the repolarization phase of an action potential?

K+ ions begin to exit the cell Signup and view all the answers

What factor most significantly influences the resting membrane potential according to the Goldmann Equation?

The permeability of K+ Signup and view all the answers

Which ion's active transport is crucial for maintaining the resting membrane potential?

Na+ Signup and view all the answers

What is the approximate value of the resting membrane potential (RMP) in most neurons?

-70 mV Signup and view all the answers

What type of channels opens typically at depolarization during an action potential?

Sodium channels Signup and view all the answers

During which phase of the action potential does repolarization occur?

After the peak of the action potential Signup and view all the answers

In the context of a neuron, what is the role of fixed anions (A-) in maintaining resting membrane potential?

They remain inside the cell contributing to negative charge Signup and view all the answers

What is the all-or-nothing response characteristic of in excitable cells?

Action potential Signup and view all the answers

What primarily causes the rapid change in membrane potential during the action potential?

Increased permeability to Na+ ions Signup and view all the answers

What happens to voltage-gated sodium channels (VGScs) during the action potential when the membrane potential reaches +30 mV?

They become inactivated. Signup and view all the answers

At what membrane potential do voltage-gated potassium channels (VGKCs) begin to open?

-55 mV Signup and view all the answers

Which phase of the action potential is primarily responsible for repolarization?

Repolarization phase Signup and view all the answers

What is the role of the sodium-potassium pump in maintaining resting membrane potential?

It helps establish the electrochemical gradient by moving Na+ out and K+ in. Signup and view all the answers

Which statement best describes the inactivation state of voltage-gated sodium channels?

They cannot be activated until the membrane potential returns to a certain level. Signup and view all the answers

What primarily drives repolarization during an action potential?

Potassium efflux Signup and view all the answers

What happens to the Na+ channel after it returns to its closed state?

It is then ready to reopen at the next action potential threshold. Signup and view all the answers

Which of the following best describes the function of voltage-gated ion channels?

They open and close in response to changes in membrane potential. Signup and view all the answers

What primarily determines the resting membrane potential of a neuron?

The permeability of the neuronal membrane to different ions Signup and view all the answers

What does the Goldmann equation calculate?

The resting membrane potential considering the permeability of multiple ions Signup and view all the answers

Which voltage-gated ion channel opens during the depolarization phase of an action potential?

Sodium (Na+) channels Signup and view all the answers

What occurs during the repolarization phase of an action potential?

Potassium ions exit the cell, restoring the negative membrane potential Signup and view all the answers

What is the primary function of myelination in neurons?

To insulate axons and speed up action potential conduction Signup and view all the answers

What describes the absolute refractory period in a neuron?

A time when no action potentials can be generated regardless of stimulus strength Signup and view all the answers

Which structure in a neuron primarily receives incoming signals from other neurons?

Dendrites Signup and view all the answers

What characterizes the phases of an action potential?

Rapid depolarization followed by repolarization and hyperpolarization Signup and view all the answers

Study Notes

Voltage-Gated Ion Channels

Voltage-gated K+ channels close slowly, affecting membrane potential.
Na+ influx raises membrane potential towards +30 mV, while K+ efflux decreases it.
Action potentials are generated through the summation of Na+ and K+ currents.

After Hyperpolarization (AHP)

K+ moves out of the cell due to concentration gradient, leading to AHP.
Slow closure of K+ channels allows excess positive charge to leave, causing hyperpolarization.

Refractory Periods

Absolute refractory period restricts the generation of subsequent action potentials immediately after one occurs.
Na+ channels must return to a closed state before reopening.

Action Potential Dynamics

Initiated by Na+ channel openings when membrane potential reaches -55 mV.
Rapid Na+ influx results in depolarization; inactivation of Na+ channels follows.
K+ channels open slowly for repolarization, allowing K+ to exit the cell.

Ion Channel Function

Voltage-gated channels selectively permit ion passage based on size and charge.
K+ permeability dominates resting membrane potential (RMP) of approximately -70 mV.

Goldmann Equation

RMP represents the weighted sum of the equilibrium potentials for all ions.
K+ has the most significant contribution to the RMP due to high permeability.

Cellular Communication

Cells communicate to synchronize events, integrate functions, and adapt to environments.
Faulty communication can lead to neurological disorders, such as motor neuron disease or multiple sclerosis.

Types of Signaling

Hormonal signaling is slower and more sustained, while electrical signaling provides rapid and precise communication in excitable cells.
Fast, transient changes in membrane potential are key for neuronal and muscle communication.

Membrane Potential Overview

Membrane potential changes are fundamental for action potentials; these are all-or-nothing events in excitable cells.
Understanding action potentials is critical in neurophysiology, particularly in neurons and muscle cells.

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Description

Explore the essential reasons why cells need to communicate with each other. This quiz will cover various communication mechanisms and their importance in maintaining biological functions and homeostasis. Test your knowledge on cellular interactions and signaling pathways.