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Questions and Answers

What is the main purpose of dendrites in a neuron?

  • Conduct electrical impulses away from the cell body
  • Store neurotransmitters
  • Receive signals from other neurons (correct)
  • Generate action potentials

    • The resting potential of a neuron is positive due to the high concentration of sodium ions inside the cell.

    False (B)

    What are the two types of ion pumps involved in establishing the resting potential of a neuron?

    Sodium and potassium pumps

    Neurotransmitters are released from the ______ membrane.

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

    Match the type of nerve fiber with its characteristics:

    <p>Myelinated fibers = Faster transmission due to insulation Non-myelinated fibers = Slower transmission due to lack of insulation Giant axons of squid = Very fast transmission Small nerve fibers = Variable speed, generally slower</p> Signup and view all the answers

    How do nerve impulses (action potentials) propagate along a neuron?

    <p>Through the movement of positively charged ions across the membrane (A)</p> Signup and view all the answers

    A signal can pass in both directions at a typical synapse.

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

    What role does calcium play in neurotransmitter release?

    <p>Calcium influx leads to the release of neurotransmitters.</p> Signup and view all the answers

    What is the typical resting potential of a neuron?

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

    Neurons transmit information primarily through chemical signals.

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

    What are the primary ions involved in generating a nerve impulse?

    <p>Sodium (Na+) and Potassium (K+)</p> Signup and view all the answers

    The change in potential difference across a neuron during an impulse is known as __________.

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

    Match the following terms with their definitions:

    <p>Resting potential = The potential difference when the neuron is not stimulated Action potential = The reversal and restoration of electrical potential during a nerve impulse Nerve fibers = Long narrow outgrowths of neurons Neurons = Basic functional unit of the nervous system</p> Signup and view all the answers

    What happens during the depolarization phase of an action potential?

    <p>Sodium ions move into the neuron (C)</p> Signup and view all the answers

    The cytoplasm of a neuron is located in its cell body.

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

    What is the role of the membrane potential in neurons?

    <p>It establishes the electrical charge across the cell membrane, crucial for impulse transmission.</p> Signup and view all the answers

    What is the primary role of sodium-potassium pumps in neurons?

    <p>To maintain ion concentration gradients (C)</p> Signup and view all the answers

    Three potassium ions are pumped into the neuron for every two sodium ions pumped out.

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

    What charge is the membrane potential of a neuron at rest approximately?

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

    The leakage of _______ ions contributes to the imbalance of ions across the membrane.

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

    Match the ion with its movement direction in the sodium-potassium pump:

    <p>Na+ = Out of the neuron K+ = Into the neuron</p> Signup and view all the answers

    Which factor does NOT contribute to the resting potential?

    <p>Equal concentration of ions (C)</p> Signup and view all the answers

    Ion movement across the membrane occurs through active transport only.

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

    What type of transport is used by sodium-potassium pumps?

    <p>Active transport</p> Signup and view all the answers

    What causes the depolarization of the axon membrane?

    <p>Sodium ions flowing into the cytoplasm of the axon (B)</p> Signup and view all the answers

    Repolarization of the axon membrane makes its charge positive.

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

    What is the normal resting membrane potential of a neuron in millivolts?

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

    The lipid-rich substance that surrounds nerve fibres is known as _____.

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

    Which adaptation helps squid increase the speed of nerve impulses?

    <p>Giant axons with larger diameter (C)</p> Signup and view all the answers

    Nerve impulses travel at about 100 m/s in humans due to large diameter axons.

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

    What is the role of Schwann cells in relation to axons?

    <p>They provide myelin sheath around the axons.</p> Signup and view all the answers

    What is the effect of the myelin sheath on the speed of nerve impulse transmission?

    <p>It increases the speed of transmission (D)</p> Signup and view all the answers

    Saltatory conduction refers to the continuous transmission of an action potential along a myelinated fiber.

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

    What tiny gap exists between the pre-synaptic neuron and the post-synaptic neuron?

    <p>synaptic cleft</p> Signup and view all the answers

    In myelinated fibers, action potentials '_______' from node to node.

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

    Match the type of synapse with its description:

    <p>Neuron-to-neuron = Synapse between two neurons in the brain or spinal cord Neuron-to-muscle = Synapse between a neuron and a muscle fiber Neuron-to-gland = Synapse between a neuron and a gland Neuron-to-sensory receptor = Synapse between a neuron and sensory receptors of sense organs</p> Signup and view all the answers

    At which locations are the axon membranes exposed in myelinated fibers?

    <p>At the nodes of Ranvier (C)</p> Signup and view all the answers

    Myelination has little benefit for very small axon diameters.

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

    What is the primary function of synapses?

    <p>To link neurons together</p> Signup and view all the answers

    What is the primary role of neurotransmitters?

    <p>To carry nerve impulses between neurons (B)</p> Signup and view all the answers

    The influx of calcium ions (Ca2+) into a neuron triggers the release of neurotransmitters.

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

    What happens to the postsynaptic membrane when neurotransmitters bind to neuroreceptors?

    <p>Protein channels open, allowing the influx of Na+ ions.</p> Signup and view all the answers

    Neurotransmitters are made in the _____ apparatus of the pre-synaptic neuron.

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

    Match the neurotransmitter with its common function:

    <p>Acetylcholine = Muscle activation Dopamine = Reward and pleasure Serotonin = Mood regulation GABA = Inhibition of neuronal excitability</p> Signup and view all the answers

    Which ion influx is responsible for initiating an excitatory action potential?

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

    An action potential can cross the synaptic cleft directly from one neuron to another.

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

    The pre-synaptic neuron releases neurotransmitters via _____ that fuse with the membrane.

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

    Flashcards

    Neuron function

    Neurons are nerve cells that transmit electrical signals, enabling internal communication in the nervous system.

    Nerve impulse

    An electrical signal that travels along a neuron's axon.

    Resting potential

    The electrical charge difference across a neuron's membrane when it's not transmitting a signal.

    Action potential

    A rapid change in membrane potential that travels along the axon.

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    Synapse

    The junction between two neurons or a neuron and an effector cell.

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    Neurotransmitter

    A chemical signal released at a synapse to transmit the signal to the next cell.

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    Axon

    The long, single fiber that transmits nerve impulses away from the cell body.

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    Dendrites

    Multiple shorter fibers that receive signals from other neurons.

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    Neuron structure

    Neurons have a cell body with cytoplasm, a nucleus, and nerve fibers.

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    Membrane potential

    Voltage difference across a cell membrane due to ion imbalance.

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    Sodium (Na+) and Potassium (K+)

    Ions whose concentration difference drives nerve impulse generation.

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    Basic functional unit of nervous system

    The neuron is the fundamental component of the nervous system responsible for information transfer.

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    Electrical impulse

    Momentary reversal in electrical potential difference in the membrane.

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    Sodium-Potassium Pumps

    Membrane proteins that actively transport sodium ions (Na+) out of and potassium ions (K+) into the neuron, maintaining concentration gradients.

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    Ion Leakage

    Passive movement of ions across the neuron membrane through channels, contributing to the resting potential.

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    Concentration Gradient

    Difference in ion concentration across the cell membrane, driving ion movement.

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    Active Transport

    Movement of ions against their concentration gradient, requiring energy (ATP).

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    Unequal Ion Distribution

    Imbalance in the concentration of different ions (e.g. Na+, K+) inside and outside the neuron.

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    Negatively Charged Proteins

    Proteins inside the neuron that contribute to the negative resting potential.

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    Myelinated Nerve Fiber

    A nerve fiber surrounded by a myelin sheath, a fatty substance that insulates the axon and speeds up nerve impulse transmission.

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    Nodes of Ranvier

    Gaps in the myelin sheath along an axon where the membrane is exposed.

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    Saltatory Conduction

    The process of nerve impulse transmission in myelinated fibers where the action potential 'jumps' from node to node.

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    Axon Diameter and Speed

    The diameter of an axon affects the speed of nerve impulse transmission: larger diameter axons conduct impulses faster.

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    Myelination and Speed

    Myelination significantly increases the speed of nerve impulse transmission.

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    Synaptic Knob

    The swollen tip of the axon of a presynaptic neuron where neurotransmitters are released.

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    Synaptic Cleft

    The tiny gap between the presynaptic and postsynaptic neurons where chemical signals are transmitted.

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    Depolarization

    The process where a neuron's membrane potential becomes more positive, allowing an action potential to occur. This is caused by sodium ions (Na+) flowing into the cell.

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    Repolarization

    The process where a neuron's membrane potential returns to its resting negative state after depolarization. This is caused by potassium ions (K+) flowing out of the cell.

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    How does axon diameter affect nerve impulse speed?

    A larger axon diameter reduces resistance, increasing the speed of nerve impulse conduction. This is because there's more space for ions to flow.

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    Myelination

    The process where a layer of fatty substance called myelin wraps around the axon, increasing the speed of nerve impulse conduction.

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    Giant axons

    Larger-diameter axons found in some animals, such as squid, that allow for faster nerve impulse transmission.

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    Squid's adaptation

    Having giant axons allows squid to react quickly to predators and prey, helping them survive in their environment.

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    Presynaptic Neuron

    The neuron that sends the nerve impulse and releases neurotransmitters into the synaptic cleft.

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    Postsynaptic Neuron

    The neuron that receives the nerve impulse after the neurotransmitter binds to its receptors.

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    Synaptic Vesicles

    Tiny sacs within the presynaptic neuron that store and release neurotransmitters.

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    Calcium Ions (Ca2+)

    Ions that trigger the release of neurotransmitters from synaptic vesicles.

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    Neuroreceptor

    Proteins embedded in the postsynaptic membrane that receive and bind to neurotransmitters.

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    Excitatory Postsynaptic Potential (EPSP)

    A temporary depolarization of the postsynaptic membrane, making it more likely to generate an action potential.

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    Study Notes

    Neural Signaling

    • Neurons are nerve cells within the nervous system that carry electrical impulses.
    • The nervous system uses neurons to communicate internally.
    • Neurons have a cell body containing cytoplasm and a nucleus.
    • Neurons have a long, single axon and multiple shorter dendrites extending from the cell body.
    • Electrical impulses travel along these fibres.
    • ATP provides energy for pumping sodium and potassium ions in opposite directions across the neuron's plasma membrane.
    • The concept of a membrane potential or polarization is crucial for neuronal signaling.
    • Neurons have a resting potential that is negative.
    • Electrochemical gradients are maintained through the pumping of ions.

    Nerve Impulses as Action Potentials

    • Nerve impulses are action potentials that are propagated along nerve fibers.
    • Positively charged ions move during nerve impulses.
    • The speed of nerve impulses varies dependent on the presence or absence of myelination.
    • Myelination increases the speed of nerve impulse transmission.
    • The transmission speed varies depending on fiber diameter.
    • Larger fibers conduct impulses faster.
    • Chemical synapses (also called synapses) are connections where signaling occurs.
    • Signals pass in one direction across synapses.
    • Calcium uptake depolarizes a presynaptic membrane and activates neurotransmitters.
    • Neurotransmitters diffuse across the synaptic gap.

    Synapses as Junctions Between Neurons

    • A synapse connects the end of one neuron to another neuron or effector cell.
    • Axons (part of pre-synaptic neuron) and dendrites (part of post-synaptic neuron) create synaptic contacts.
    • These junctions have a gap called a synaptic cleft.
    • Neurotransmitters are chemical messengers that carry the nerve impulse across the synapse.
    • Neurotransmitters are released from the pre-synaptic neuron, which is the sending neuron.
    • Neurotransmitters bind to receptors on the post-synaptic neuron, which is the receiving neuron, causing a response.
    • Some other types of synapses include synapses between neurons and muscle fibers (neuromuscular synapses), and synapses between neurons and glands (neuroglandular synapses).
    • Sensory receptors act in some synapses, like those in the skin.

    Generation of the Resting Potential

    • A nerve impulse, driven by changes in sodium and potassium ion concentration, creates a resting potential in neurons (approximately -70 mV).
    • The unequal distribution of ions across the membrane creates a negative charge inside the neuron.
    • Membrane potential develops due to the sodium-potassium pump, ion leakage, and negatively charged proteins within the cytoplasm.
    • The sodium-potassium pump moves three sodium ions out of the cell and two potassium ions into the cell.
    • The membrane is more permeable to potassium, leading to potassium leakage out of the cell.

    Variation in the Speed of Nerve Impulses

    • Larger axon diameters lead to faster conduction of nerve impulses.
    • Myelination increases the speed of impulse transmission (saltatory conduction).
    • The myelin sheath is an insulating layer around the axon that prevents ion leakage.
    • Impulses "jump" between gaps (nodes of Ranvier) in the myelin sheath.
    • Factors like axon diameter increase and myelination increase the conduction speeds.

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