Nervous System Overview
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Questions and Answers

What is the primary function of the presynaptic neuron in a synapse?

  • To bridge the gap between adjacent neurons
  • To release neurotransmitters into the synaptic cleft (correct)
  • To generate action potentials within the postsynaptic neuron
  • To receive neurotransmitters from the postsynaptic neuron

    • Which neurotransmitter is known to predominantly have excitatory effects at neuromuscular junctions?

  • Norepinephrine
  • Dopamine
  • GABA
  • Acetylcholine (correct)

    • What effect do excitatory neurotransmitters typically have on the postsynaptic membrane?

  • They cause an influx of potassium ions.
  • They depolarize the membrane and move it away from threshold.
  • They induce hyperpolarization of the membrane.
  • They cause an influx of sodium ions, moving the membrane toward threshold. (correct)

    • Which neurotransmitter is characterized as inhibitory in the brain and is increased by certain medications like Valium?

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

    Which substance is considered an antagonist of glycine?

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

    What role does dopamine play in the nervous system?

    <p>It primarily regulates mood and muscle control.</p> Signup and view all the answers

    How do inhibitory neurotransmitters affect the postsynaptic neuron?

    <p>They decrease the flow of sodium ions into the neuron.</p> Signup and view all the answers

    What physiological response is primarily associated with norepinephrine in the sympathetic nervous system?

    <p>Fight or flight reactions</p> Signup and view all the answers

    What is one of the effects of caffeine on neurotransmitter activity?

    <p>It inhibits the release of GABA.</p> Signup and view all the answers

    What happens to neurotransmitters after they have performed their function in the synaptic cleft?

    <p>They are degraded by enzymes or taken back up by transporters.</p> Signup and view all the answers

    What maintains the resting membrane potential in a neuron?

    <p>Differences in the distribution of ions across the neuronal membrane</p> Signup and view all the answers

    What occurs during depolarization of the neuronal membrane?

    <p>Sodium channels open and sodium rushes into the neuron.</p> Signup and view all the answers

    What is the all-or-nothing principle in the context of neuron firing?

    <p>Once the threshold is reached, the neuron depolarizes to the same extent regardless of stimulus intensity.</p> Signup and view all the answers

    How does the action potential propagate along a neuron?

    <p>By initiating depolarization in one section that opens Na+ channels in adjacent sections.</p> Signup and view all the answers

    What is the primary function of the sodium-potassium pump?

    <p>To maintain resting potential by moving more sodium out than potassium in.</p> Signup and view all the answers

    What is saltatory conduction?

    <p>The jumping of action potentials from node to node along myelinated axons.</p> Signup and view all the answers

    During repolarization, which ions are involved?

    <p>Potassium ions flow out of the neuron.</p> Signup and view all the answers

    What happens if the threshold is not reached during neuronal stimulation?

    <p>The neuron does not fire an action potential.</p> Signup and view all the answers

    What occurs during the absolute refractory period?

    <p>The neuron cannot fire, regardless of stimulus strength.</p> Signup and view all the answers

    Which of the following best describes the role of neurotransmitters in neuron function?

    <p>They transmit signals between neurons across synapses.</p> Signup and view all the answers

    What is the primary role of dendrites in a neuron?

    <p>Receive stimuli from the environment</p> Signup and view all the answers

    Which cells form the myelin sheath in the central nervous system?

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

    What distinguishes myelinated axons from unmyelinated axons?

    <p>Myelinated axons conduct impulses faster</p> Signup and view all the answers

    Which of the following best describes the function of efferent nerves?

    <p>Conduct impulses away from the central nervous system</p> Signup and view all the answers

    The gaps in the myelin sheath on an axon are known as:

    <p>Nodes of Ranvier</p> Signup and view all the answers

    Which type of neurons are responsible for transmitting signals from sensory receptors to the central nervous system?

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

    What is the main structural difference between the cell body and the axon of a neuron?

    <p>The cell body contains nucleoli while the axon does not</p> Signup and view all the answers

    Which of the following best describes the role of glial cells?

    <p>Provide support and protection for neurons</p> Signup and view all the answers

    Which of the following accurately describes white matter in the nervous system?

    <p>It consists of myelinated axons that conduct impulses rapidly</p> Signup and view all the answers

    The central nervous system is connected to which of the following?

    <p>Cranial and spinal nerves</p> Signup and view all the answers

    What is the primary distinction between white matter and gray matter?

    <p>Gray matter is primarily found in the brain's outer layer, while white matter is found deeper within the brain.</p> Signup and view all the answers

    Which type of nerve is responsible for carrying information from sensory receptors to the central nervous system?

    <p>Afferent nerves</p> Signup and view all the answers

    What are the two main components of the nervous system?

    <p>Central nervous system and peripheral nervous system</p> Signup and view all the answers

    What is the main difference between the autonomic and somatic nervous systems?

    <p>The autonomic nervous system manages involuntary actions, while the somatic nervous system controls voluntary actions.</p> Signup and view all the answers

    What process occurs when a neuron becomes more positive inside than outside?

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

    Which neurotransmitter is known for its role in inhibiting nerve impulses?

    <p>Gamma-aminobutyric acid (GABA)</p> Signup and view all the answers

    Which part of the nervous system is primarily involved in coordinating voluntary movement?

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

    What is the primary function of cerebrospinal fluid?

    <p>To act as a shock absorber and nourish the brain</p> Signup and view all the answers

    Which reflex involves the contraction of a muscle in response to its own stretch?

    <p>Stretch reflex</p> Signup and view all the answers

    What differentiates the sympathetic nervous system from the parasympathetic nervous system?

    <p>The sympathetic system stimulates the body in times of stress, whereas the parasympathetic system encourages relaxation.</p> Signup and view all the answers

    Study Notes

    Nervous System Overview

    • The nervous system is a highly advanced communication system.
    • It communicates using molecules.
    • Speed and distance of communication vary.
    • It is composed of the central nervous system (CNS) and peripheral nervous system (PNS).

    Nervous System Organization

    • The CNS includes the brain and spinal cord.
    • The spinal cord connects the brain to the peripheral nervous system (PNS).
    • The PNS carries messages to and from the CNS.
    • The PNS is composed of somatic nervous system and autonomic nervous system.
      • The somatic nervous system controls voluntary muscles.
      • The autonomic nervous system controls involuntary body functions.
        • It is further divided into sympathetic and parasympathetic nervous systems.
          • The sympathetic nervous system arouses the body for energy expenditure.
          • The parasympathetic nervous system calms the body to conserve and maintain energy.

    Nerves

    • Afferent nerves conduct impulses toward the central nervous system (CNS).
    • Afferent nerves are also called sensory nerves.
    • Efferent nerves conduct impulses away from the CNS.
    • Efferent nerves are also called motor nerves.
    • Cranial and spinal nerves in the PNS may carry nerve fibers that are sensory, motor, or both (mixed).

    Neurons and Neuroglial/Glial Cells

    • Neurons are the functional units of the nervous system.
    • Neuroglia/glial cells support neurons.
    • Different types of neuroglia include Astrocytes, Oligodendrocytes, Microglia, and Ependymal cells.

    Neuron Structure

    • Neuron structure includes a cell body (soma), dendrites, and an axon.
    • Dendrites receive stimuli.
    • Axons transmit impulses away from the cell body.
    • The axon hillock connects the axon to the cell body.
    • Synaptic terminals contain synaptic vesicles.

    Types of Neurons

    • Unipolar
    • Bipolar
    • Pseudounipolar
    • Multipolar

    Axons

    • Axons conduct nerve impulses away from the neuron.
    • Axons can be myelinated or unmyelinated.
    • Myelin sheath is made mostly of lipids.
    • Myelinated axons conduct impulses faster than unmyelinated axons.
    • White matter in the central nervous system contains tissue with myelinated axons.
    • The myelin sheath allows for faster signal conduction.
    • Nodes of Ranvier are gaps in the myelin sheath.

    Myelin Sheath

    • Myelinated axons have a myelin sheath.
    • Myelin sheath is formed by oligodendrocytes in the CNS and Schwann cells in the PNS.
    • Myelin sheath helps speed signal transmission (saltatory conduction).

    Nervous System Organization

    • Nervous system is divided in central and peripheral systems.
    • Includes the brain, spinal cord and nerves that connect these to the body.
    • Spinal cord connects brain to peripheral system.

    Resting Potential

    • Resting potential is the electrical difference across the neuronal membrane.
    • The inside of the neuron is more negatively charged than the outside.
    • This difference is maintained by the Sodium-Potassium Pump.

    Action Potential

    • Action potential is a rapid change in membrane potential.

    Depolarization

    • Involves a change in membrane potential toward a less negative value.
    • The influx of Na+ causes the inside to become more positive than the outside.
    • Initiated by stimulus exceeding threshold.

    Repolarization

    • A return to the resting membrane potential.
    • The efflux of K+ causes the inside to become more negative than the outside.
    • Caused by Na+ channels becoming inactivated and K+ channels opening.

    All-or-None Principle

    • All action potentials are the same strength in a neuron.
    • The neuron either fires completely or it does not fire at all.
    • The strength of the stimulus does not affect the size of the action potential, only the frequency.

    Propagation of Signal

    • Propagation of the signal along the axon.
    • Saltatory conduction (myelinated axons) occur in myelinated axons.
    • Saltatory propagation skips between Nodes of Ranvier.

    Refractory Periods

    • Period of time after an action potential where the neuron is unable to fire again.

    Synapse

    • Synapse is the junction between two neurons or a neuron and a target cell.
    • Presynaptic neuron is the neuron carrying the depolarizing wave to the synapse.
    • Neurotransmitters are released into the synaptic cleft.
    • These bind to receptors on the postsynaptic neuron.

    Neurotransmitters

    • Chemical messengers that transmit signals across the synapse.
    • Common neurotransmitter types include excitatory and inhibitory types.
      • Excitatory neurotransmitters usually cause an influx of sodium, thus more positive inside.
      • Inhibitory neurotransmitters usually move the charge further away from threshold.

    Specific Neurotransmitters

    • Acetylcholine (Ach) - excitatory at neuromuscular junctions, inhibitory in the parasympathetic nervous system.
    • Norepinephrine (noradrenaline) - arousal and "fight or flight" reactions, part of sympathetic nervous system.
    • Epinephrine (adrenaline) - acts as a hormone.
    • Dopamine - functions in the brain, autonomic functions, muscle control, behavior/learning, and mood.
    • GABA - major inhibitory neurotransmitter.
    • Glycine - inhibitory neurotransmitter (spinal cord).

    Action of Drugs

    • Drugs may function by mimicking neurotransmitters or by inhibiting their breakdown.

    Organophosphates

    • Organophosphate pesticides inhibit acetylcholinesterase.
    • This causes continuous signal transmission at the synapse.

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    Lecture 1 The Nervous System F24 PDF

    Description

    Explore the complex organization and functions of the nervous system in this quiz. Learn about the central nervous system (CNS), peripheral nervous system (PNS), and the roles of afferent and efferent nerves. Test your knowledge on how these systems interact and control both voluntary and involuntary actions.

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