Neurophysiology
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Neurophysiology

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What is the main reason for the electrical difference (voltage) across the cell membrane?

  • The accumulation of excess positive charges just outside the cell membrane and excess negative charges immediately inside the cell membrane. (correct)
  • The higher concentration of sodium ions (Na⁺) inside the cell compared to outside.
  • The higher permeability of the cell membrane to potassium ions (K⁺) compared to sodium ions (Na⁺).
  • The higher concentration of potassium ions (K⁺) inside the cell compared to outside.

    • What is the main factor that contributes to the resting membrane potential?

  • The higher concentration of positively charged ions outside the cell compared to inside.
  • The higher permeability of the cell membrane to sodium ions (Na⁺) compared to potassium ions (K⁺).
  • The concentration gradient of ions across the cell membrane. (correct)
  • The higher concentration of negatively charged ions inside the cell compared to outside.

    • What is the main reason for the higher permeability of the cell membrane to potassium ions (K⁺) compared to sodium ions (Na⁺) at rest?

  • The cell membrane actively pumps more potassium ions out of the cell than sodium ions into the cell.
  • The electrical potential difference across the cell membrane is higher for potassium ions than for sodium ions.
  • The cell membrane has more potassium leak channels than sodium leak channels. (correct)
  • The concentration gradient of potassium ions is higher than the concentration gradient of sodium ions across the cell membrane.

    • What is the typical resting membrane potential in mammalian neurons?

    <p>$-70$ mV</p> Signup and view all the answers

    Which of the following statements about the equilibrium potential for an ion species is correct?

    <p>The equilibrium potential is the potential at which the net flow of the ion across the membrane is zero.</p> Signup and view all the answers

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

    <p>To provide structural and metabolic support for neurons</p> Signup and view all the answers

    Which type of neuron has a single stem axonal process that branches to form two processes?

    <p>Pseudounipolar neuron</p> Signup and view all the answers

    Which of the following is a major functional unit of the nervous system?

    <p>Neurons</p> Signup and view all the answers

    What is the primary role of the axon hillock or trigger zone in a neuron?

    <p>To generate and propagate the action potential</p> Signup and view all the answers

    Which type of neuron is responsible for transmitting information from the brain or spinal cord to muscles and glands?

    <p>Motor neuron</p> Signup and view all the answers

    What is the primary function of the myelin sheath surrounding the axons of some neurons?

    <p>To enhance the speed of information transfer</p> Signup and view all the answers

    What is the primary function of the Na+, K+ pump (ATPase) in cell membranes?

    <p>Pumps Na+ out of the cell and K+ into the cell against their concentration gradients</p> Signup and view all the answers

    How do synaptic signals from another cell change the membrane potential of a neuron or muscle cell?

    <p>Synaptic signals open or close ion-selective channels, changing the membrane potential</p> Signup and view all the answers

    What is the difference between an EPSP (excitatory postsynaptic potential) and an IPSP (inhibitory postsynaptic potential)?

    <p>An EPSP makes the inside of the cell more positive, increasing the chance of reaching the threshold and triggering an action potential, while an IPSP makes it more negative</p> Signup and view all the answers

    What is the primary reason that the change in membrane potential caused by an EPSP or IPSP only lasts for a short time (milliseconds)?

    <p>The neurotransmitter is quickly removed from the synapse, and the ion channels close again</p> Signup and view all the answers

    What is the relationship between the resting membrane potential and the ability of a cell to generate an action potential?

    <p>The resting membrane potential can be changed by synaptic signals, which can then influence the cell's ability to reach the threshold and generate an action potential</p> Signup and view all the answers

    What is the primary function of the Na+, K+ pump (ATPase) in maintaining the resting membrane potential of a cell?

    <p>The Na+, K+ pump actively pumps Na+ out of the cell and K+ into the cell, creating a concentration gradient that drives the resting membrane potential</p> Signup and view all the answers

    What is responsible for the propagation of action potentials down the axon?

    <p>Voltage-gated Na+ channels</p> Signup and view all the answers

    What factor influences the speed of action potential conduction in the nervous system?

    <p>Degree of myelination and axon diameter</p> Signup and view all the answers

    How do myelinated axons contribute to faster conduction velocity?

    <p>By allowing the current to jump between nodes (saltatory conduction)</p> Signup and view all the answers

    What ion enters the cell during the opening of Ca2+ voltage-gated channels at the axon terminal?

    <p>Calcium (Ca2+)</p> Signup and view all the answers

    Which class of neurotransmitters includes GABA and glutamate?

    <p>Amino acids and derivatives</p> Signup and view all the answers

    What is responsible for releasing neurotransmitters into the synaptic cleft by exocytosis?

    <p>Synaptic vesicles</p> Signup and view all the answers

    Which organelle is primarily responsible for producing ATP in neurons?

    <p>Mitochondria</p> Signup and view all the answers

    What is the function of the axon hillock and initial axon segment?

    <p>Integrate different signals and generate action potentials</p> Signup and view all the answers

    What is the function of the myelin sheath?

    <p>Facilitate electrical insulation and saltatory conduction</p> Signup and view all the answers

    What are the functions of dendritic spines?

    <p>Contain specialized receptors to recognize neurotransmitters</p> Signup and view all the answers

    What determines the conduction velocity of myelinated axons?

    <p>The diameter of the axon and the length of the internodes</p> Signup and view all the answers

    What is the function of the presynaptic terminal?

    <p>Release neurotransmitters to signal adjacent cells</p> Signup and view all the answers

    Which of the following is NOT one of the 6 major classes of neurotransmitters?

    <p>Alkaloids</p> Signup and view all the answers

    Which type of neuron is responsible for transmitting information from receptors in sensory organs towards the brain or spinal cord?

    <p>Sensory neuron</p> Signup and view all the answers

    Which of the following is NOT one of the three major factors contributing to the resting membrane potential?

    <p>The electrical attraction between oppositely charged ions</p> Signup and view all the answers

    What is the primary reason for the accumulation of excess positive charges outside the cell membrane and excess negative charges inside the cell membrane?

    <p>The differential permeability of the membrane to different ions</p> Signup and view all the answers

    Which of the following statements about the equilibrium potential for an ion species is correct?

    <p>The equilibrium potential is the potential at which the ion species is in dynamic equilibrium across the membrane</p> Signup and view all the answers

    What is the primary function of the sodium-potassium pump (Na⁺/K⁺ ATPase) in maintaining the resting membrane potential?

    <p>To actively transport sodium ions out of the cell and potassium ions into the cell</p> Signup and view all the answers

    How does myelination contribute to faster conduction velocity in axons?

    <p>It facilitates saltatory conduction where the action potential 'jumps' between nodes</p> Signup and view all the answers

    What is the primary determinant of conduction velocity in unmyelinated axons?

    <p>The square root of the axon diameter</p> Signup and view all the answers

    Which of the following statements about the resting membrane potential is correct?

    <p>It is typically around -70 mV in mammalian neurons</p> Signup and view all the answers

    What would happen if a drug inhibited the postsynaptic potential of a sensory neuron?

    <p>It would decrease the likelihood of triggering an action potential in that neuron</p> Signup and view all the answers

    What is the primary role of voltage-gated sodium (Na⁺) channels in generating an action potential?

    <p>They allow Na⁺ to flow into the cell, causing depolarization</p> Signup and view all the answers

    What is the role of voltage-gated potassium (K⁺) channels in the action potential?

    <p>They allow K⁺ to flow out of the cell, causing repolarization</p> Signup and view all the answers

    What is the role of hyperpolarization in the action potential?

    <p>It is the refractory period that prevents continuous firing</p> Signup and view all the answers

    What is the primary function of the myelin sheath surrounding some axons?

    <p>To increase the speed of action potential propagation</p> Signup and view all the answers

    Study Notes

    Cellular Electrical Difference and Membrane Potential

    • The electrical difference (voltage) across the cell membrane is mainly due to ion concentration gradients, primarily between K⁺ and Na⁺.
    • The resting membrane potential is primarily influenced by the permeability of the cell membrane to potassium ions (K⁺) compared to sodium ions (Na⁺).
    • At rest, the cell membrane exhibits higher permeability to K⁺ due to more open potassium channels.

    Typical Resting Membrane Potential

    • The typical resting membrane potential in mammalian neurons is approximately -70 mV.

    Equilibrium Potential

    • The equilibrium potential for an ion species is determined by the Nernst equation, which factors in ion concentration across the membrane.

    Functions of Glial Cells

    • Neuroglia or glial cells primarily support, protect, and maintain the function of neurons in the nervous system.

    Neuron Types

    • Unipolar neurons have a single stem axonal process that branches to form two processes, typically found in sensory pathways.
    • A major functional unit of the nervous system is the neuron.

    Axon Functions

    • The axon hillock or trigger zone in a neuron serves as the site of action potential initiation.
    • Efferent neurons transmit information from the brain or spinal cord to muscles and glands.

    Myelin Sheath

    • The myelin sheath surrounding some neurons increases the speed of action potential conduction along the axons by providing insulation.

    Sodium-Potassium Pump

    • The Na⁺/K⁺ pump (ATPase) maintains resting membrane potential by actively transporting Na⁺ out of the cell and K⁺ into the cell, countering diffusion forces.

    Synaptic Signals

    • Synaptic signals alter the membrane potential of a neuron or muscle cell through graded potentials.
    • EPSP (excitatory postsynaptic potential) depolarizes the membrane, while IPSP (inhibitory postsynaptic potential) hyperpolarizes it.
    • The transient nature of EPSP/IPSP is due to the quick inactivation of receptors and reuptake of neurotransmitters.

    Action Potential and Conduction

    • The generation of an action potential depends on the resting membrane potential; a sufficient depolarization must occur.
    • Action potential propagation depends on the opening of voltage-gated Na⁺ and K⁺ channels.

    Propagation Speed Factors

    • Factors influencing action potential conduction speed include axon diameter and myelination.
    • Myelinated axons conduct action potentials faster due to saltatory conduction, jumping between nodes of Ranvier.

    Calcium Ions and Neurotransmitter Release

    • During the opening of voltage-gated Ca2+ channels at the axon terminal, Ca²⁺ enters the cell, triggering neurotransmitter release via exocytosis.

    Neurotransmitter Classes and Functions

    • GABA and glutamate are classified as amino acid neurotransmitters.
    • Synaptic vesicles in the presynaptic terminal are responsible for storing and releasing neurotransmitters.

    Mitochondrial Function

    • Mitochondria are the primary organelle for ATP production in neurons, providing energy for cellular functions.

    Dendritic Spines and Axon Functions

    • Dendritic spines enhance synaptic strength and connectivity, facilitating communication between neurons.
    • The axon hillock and initial axon segment are crucial regions for action potential initiation and integration of synaptic signals.

    Conductivity of Myelinated Axons

    • Myelinated axons achieve faster conduction velocity due to reduced capacitance and increased resistance, facilitating rapid signal transmission.
    • In unmyelinated axons, conduction velocity is primarily determined by the properties of the axon membrane and internal resistance.

    Postsynaptic Potentials and Drugs

    • If a drug inhibits the postsynaptic potential of a sensory neuron, it would disrupt normal signal transmission to the brain.
    • Voltage-gated Na⁺ channels play a critical role in generating action potentials through rapid depolarization.

    Role of Ion Channels in Action Potential

    • Voltage-gated K⁺ channels help repolarize the membrane during action potentials, restoring resting conditions after depolarization.
    • Hyperpolarization helps stabilize the membrane potential, preventing excessive neuronal firing.

    Summary on Myelin Sheath Function

    • The myelin sheath primarily functions to insulate axons, enhance conduction speed of electrical impulses, and improve signal integrity.

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