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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

    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</p> Signup and view all the answers

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

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

    Neurons transmit information primarily through chemical signals.

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

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

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

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

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

    Ion movement across the membrane occurs through active transport only.

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

    Repolarization of the axon membrane makes its charge positive.

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

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

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

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

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

    Myelination has little benefit for very small axon diameters.

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

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

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

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

    <p>False</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

    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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