Neuroscience Chapter on Membrane Potential

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Questions and Answers

What does the Nernst Equation calculate?

Resting membrane potential of a neuron

Equilibrium potential for one ion (correct)

Membrane potential for multiple ions

Total ion concentration inside a cell

Which variable represents the concentration of an ion outside the cell in the Nernst Equation?

(I)i

(I)o (correct)

What is hyperpolarization defined as?

A change to a more negative value (correct)

A change to a less negative value

Returning to resting membrane potential

A change in sodium ion concentrations

What does repolarization indicate?

Potential returns to resting state after depolarization Signup and view all the answers

In the Goldman-Hodgkin-Katz (GHK) Equation, what ions are primarily considered for calculating membrane potential?

K+ and Na+ Signup and view all the answers

What initiates the changes in membrane potential?

Gated-ion channels opening or closing Signup and view all the answers

Which term describes a change in membrane potential to a less negative or positive value?

Depolarization Signup and view all the answers

What does the valence of the ion (Z) indicate in the Nernst Equation?

The type of ion and its charge Signup and view all the answers

What primarily determines the resting membrane potential of a neuron?

Concentration gradients created by the Na+/K+ pump Signup and view all the answers

Which channel type is responsible for maintaining the resting membrane potential?

Leak channels Signup and view all the answers

Which division of the nervous system is responsible for voluntary control of skeletal muscles?

Somatic motor nervous system Signup and view all the answers

What characterizes ligand-gated ion channels?

They open or close in response to the binding of a chemical messenger Signup and view all the answers

What is primarily responsible for the transmission of neural impulses?

Axon Signup and view all the answers

Which component of the central nervous system includes both the brain and spinal cord?

Central nervous system Signup and view all the answers

Where are voltage-gated Na+ channels mostly found in a neuron?

Axon and axon hillock Signup and view all the answers

What is the primary function of glial cells in the nervous system?

Support and protect neurons Signup and view all the answers

Which of the following ions contributes to the inside of the cell being negatively charged at rest?

Potassium (K+) Signup and view all the answers

What happens to the permeability of the plasma membrane when ion channels open?

It increases for specific ions Signup and view all the answers

Which of the following is NOT a part of the peripheral nervous system?

Brain Signup and view all the answers

The concentration gradient of K+ across the plasma membrane is primarily established by which mechanism?

The Na+/K+ pump Signup and view all the answers

Which subdivision of the peripheral nervous system carries sensory information to the central nervous system?

Afferent division Signup and view all the answers

What primarily triggers the release of neurotransmitters in neurons?

Changes in membrane potential Signup and view all the answers

What structures lack centrioles, indicating their maturity in neuron development?

Mature neurons Signup and view all the answers

Which part of a neuron is primarily involved in receiving information?

Dendrites Signup and view all the answers

What happens during the depolarization phase of an action potential?

There is a sudden increase in permeability to Na+, leading Na+ to enter the cell. Signup and view all the answers

What occurs during repolarization of an action potential?

Na+ permeability decreases while K+ permeability increases. Signup and view all the answers

What is the primary factor that influences the threshold for action potential initiation?

The graded potentials that meet the threshold. Signup and view all the answers

What characterizes the all-or-none principle of action potentials?

All action potentials have the same amplitude once the threshold is reached. Signup and view all the answers

Which ion's movement primarily contributes to after-hyperpolarization?

K+ ions exiting the cell. Signup and view all the answers

How does increased permeability to Na+ affect the membrane potential?

It causes the membrane potential to become more positive. Signup and view all the answers

What is the role of voltage-gated K+ channels during an action potential?

They contribute to the repolarization and after-hyperpolarization phases. Signup and view all the answers

What occurs at the peak of the action potential?

Na+ channels are completely inactive. Signup and view all the answers

Which factor primarily determines the conduction velocities of nerve fibers?

Diameter of the nerves Signup and view all the answers

What triggers the release of neurotransmitters in the presynaptic neuron?

Calcium ion entry through channels Signup and view all the answers

What is the relationship between myelination and conduction velocity?

Higher myelination increases conduction velocities Signup and view all the answers

Which neurotoxin blocks voltage-gated Na+ channels?

Tetrodotoxin (TTX) Signup and view all the answers

What occurs after the neurotransmitter binds to receptors on the postsynaptic membrane?

Cell responses are initiated Signup and view all the answers

What characteristic of nerve fibers most significantly influences their conduction speed?

Presence of myelin Signup and view all the answers

Which of the following describes a fate of the neurotransmitter after its release?

It can diffuse out of the synaptic cleft Signup and view all the answers

What type of neurotoxin is primarily found in some marine dinoflagellates?

Saxitoxin (STX) Signup and view all the answers

What role do enzymes play in neurotransmitter activity?

They degrade some neurotransmitter molecules Signup and view all the answers

What initiates the opening of calcium channels in the presynaptic neuron?

Depolarization due to action potential Signup and view all the answers

What is a common feature of neurotoxins affecting the nervous system?

They interfere with normal nerve function Signup and view all the answers

Which of the following statements about conduction velocities is true?

Myelinated fibers generally conduct faster than unmyelinated fibers Signup and view all the answers

What concentration level makes Tetrodotoxin (TTX) toxic?

Nanomolar concentrations Signup and view all the answers

Study Notes

Nervous System Physiology - Neurophysiology

Nervous System Divisions: Central Nervous System (CNS) encompasses the brain and spinal cord. Peripheral Nervous System (PNS) includes sensory (afferent) and motor (efferent) components. Somatic nervous system controls skeletal muscles; autonomic nervous system regulates involuntary functions with sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) branches.
Neurons: The structural and functional units; glial cells support them. Neuron types are diverse based on function and structure.
Glial Cells: Outnumber neurons (70-90% in CNS), support neurons structurally and metabolically and play roles in the blood-brain barrier, and forming myelin sheaths.
Resting Membrane Potential: The electrical potential difference across a neuron's cell membrane at rest, typically -70mV, largely due to ion concentration gradients.
Action Potential: Rapid changes in membrane potential, initiated by stimulation, and propagated by ion movement creating an electrical signal. Ion channels are key.
Nerve Fiber Types: Myelinated and unmyelinated fibers differ in conduction speed. Myelinated fibers are faster allowing saltatory conduction.
Synapse: The junction between two neurons or a neuron and an effector (muscle or gland), mediating communication. Transmission is via chemical signals- neurotransmitters at chemical synapses.
Synaptic Transmission: Neurotransmitters are released from presynaptic neuron, bind to receptors on postsynaptic neuron, initiating changes in the postsynaptic cell.
Types of Synapses: Electrical synapses transmit signals quickly; chemical synapses use neurotransmitters for transmission. Specialized chemical synapses are lonotropic and metabotropic receptors.
Neurotransmitters: Various kinds (e.g., acetylcholine, glutamate, GABA) are involved, triggering specific responses in the receiving cells based on the receptors to which they bind.
Excitatory Postsynaptic Potentials (EPSPs) and Inhibitory Postsynaptic Potentials (IPSPs): Graded potentials; EPSPs depolarize membrane, IPSPs hyperpolarize, influencing whether an action potential is generated in the receiving neuron.
Neurotransmitters and Synaptic Transmission: Neurotransmitter binding elicits postsynaptic potential (PSP), excitatory (EPSP) or inhibitory (IPSP), changing membrane potential, potentially leading to action potentials.
Neural Integration: Processes by which multiple synaptic inputs are combined to produce a response in a neuron. Divergent and convergent pathways in nervous system circuits influence response and behavior, and summation of signals.
Action Potential Propagation: Depolarization in myelinated axons is faster via saltatory conduction happening at Nodes of Ranvier, while unmyelinated axons have continuous conduction.
Refractory Period: A period following an action potential when the neuron is less responsive or cannot generate another action potential. Periods are absolute and relative.
Neurotoxins: Chemicals can interfere with normal nervous system function by affecting ion channels.

Neuronal Structures and Functions, Classification

Neuron structure: Cell body (soma) with nucleus, dendrites (receiving signals), axons (transmitting signals), and axon terminals (sending signals to other cells).
Neuron classification (structural): Bipolar (one axon and dendrite);
Pseudo-unipolar (single extension that branches into two);
multipolar (multiple dendrites and one axon).
Neuron classification (functional): Sensory (afferent), motor (efferent), interneurons.
Glial Cells: Support, protect, and nourish neurons. Types include astrocytes, oligodendrocytes, microglia, and ependymal cells (with different functions).

Neural Integration

Divergent Pathways: A single neuron synapses on multiple downstream neurons, amplifying a signal.
Convergent Pathways: Multiple neurons synapse onto a single downstream neuron.

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Description

Test your knowledge on the concepts of membrane potential, ion channels, and the Nernst and GHK equations in this neuroscience quiz. Understand key terms like hyperpolarization and repolarization, and their importance in neural activities.