Biology Chapter: Nervous System Overview
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Questions and Answers

What is one key difference between the nervous system and the endocrine system?

  • The nervous system acts slowly and lasts longer.
  • The endocrine system responds swiftly but briefly.
  • The nervous system coordinates activities of other organ systems. (correct)
  • The endocrine system monitors the external environment.

    • Which function is NOT performed by the nervous system?

  • Integrating sensory information.
  • Directing long-term processes like growth. (correct)
  • Monitoring external environmental conditions.
  • Coordinating voluntary responses.

    • The central nervous system (CNS) is primarily responsible for which of the following?

  • Integrating sensory information and issuing commands. (correct)
  • Connecting the brain to the rest of the body.
  • Monitoring only the internal organs.
  • Directing muscle contractions.

    • How does the nervous system respond to stimuli?

    <p>By briefly adjusting body position.</p> Signup and view all the answers

    What are the two major divisions of the nervous system?

    <p>The central and peripheral systems.</p> Signup and view all the answers

    Which of the following activities does the nervous system NOT perform?

    <p>Adjusting energy use.</p> Signup and view all the answers

    Which statement is true about the nervous system?

    <p>It can take almost an instant to change patterns of activity.</p> Signup and view all the answers

    Which aspect of the nervous system's function enhances its ability to maintain homeostasis?

    <p>Immediate response to stimuli.</p> Signup and view all the answers

    What is the initial change in membrane potential that leads to the generation of an action potential?

    <p>Graded depolarization to threshold</p> Signup and view all the answers

    During what phase of an action potential can the membrane not respond to further stimulation?

    <p>Refractory period</p> Signup and view all the answers

    What occurs when voltage-gated sodium channels open during an action potential?

    <p>Sodium ions rush into the cell</p> Signup and view all the answers

    What happens to the membrane potential at the peak of an action potential?

    <p>It reaches +30 mV</p> Signup and view all the answers

    Which of the following correctly describes the role of potassium channels during an action potential?

    <p>They close at +30 mV, initiating repolarization</p> Signup and view all the answers

    What triggers the closing of sodium channels during the action potential?

    <p>Repolarization phase</p> Signup and view all the answers

    What is the primary function of microglia in the central nervous system?

    <p>To remove unwanted substances and pathogens</p> Signup and view all the answers

    What type of conduction occurs in unmyelinated axons during action potential propagation?

    <p>Continuous propagation</p> Signup and view all the answers

    Which cells are responsible for forming the myelin sheath around axons in the central nervous system?

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

    Which neurotoxin is known to prevent sodium ion movement in neurons?

    <p>A and C only</p> Signup and view all the answers

    What distinguishes white matter from gray matter in the central nervous system?

    <p>Existence of myelinated axons</p> Signup and view all the answers

    Which potential represents the membrane state just before reaching the threshold for action potential generation?

    <p>-60 mV</p> Signup and view all the answers

    How do Schwann cells function differently from oligodendrocytes in the peripheral nervous system?

    <p>Each Schwann cell myelinates a single segment of an axon</p> Signup and view all the answers

    What is the final step in the generation of an action potential?

    <p>Return to resting potential</p> Signup and view all the answers

    Which type of cell lines the cavities in the central nervous system and assists with the circulation of cerebrospinal fluid?

    <p>Ependymal cells</p> Signup and view all the answers

    What are the small gaps between adjacent cell processes of oligodendrocytes called?

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

    Which cells in the peripheral nervous system surround and support neuron cell bodies?

    <p>Satellite cells</p> Signup and view all the answers

    Which condition is characterized by the progressive destruction of myelin sheaths in the nervous system?

    <p>Multiple sclerosis</p> Signup and view all the answers

    What is the main function of oligodendrocytes in the nervous system?

    <p>Insulate axons with myelin</p> Signup and view all the answers

    Which structure contains the cell bodies of neurons in the peripheral nervous system?

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

    What type of matter is primarily composed of myelinated axons in the central nervous system?

    <p>White matter</p> Signup and view all the answers

    What is the primary function of astrocytes in the central nervous system?

    <p>Support and anchor neurons</p> Signup and view all the answers

    Which neuroglial cell is responsible for creating the blood-brain barrier?

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

    What is the role of the nodes of Ranvier in myelinated axons?

    <p>To increase conduction speed of action potentials</p> Signup and view all the answers

    What are the two main components of the central nervous system (CNS)?

    <p>Brain and spinal cord</p> Signup and view all the answers

    Which division of the peripheral nervous system (PNS) is responsible for carrying sensory information to the CNS?

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

    What is a reflex?

    <p>An automatic, involuntary response to a stimulus</p> Signup and view all the answers

    Which systems are included in the autonomic nervous system (ANS)?

    <p>Sympathetic and parasympathetic systems</p> Signup and view all the answers

    What is the primary function of the somatic nervous system (SNS)?

    <p>Control muscular contractions</p> Signup and view all the answers

    How do neuroglia differ from neurons in the nervous system?

    <p>Neuroglia support neurons but do not participate directly in signaling</p> Signup and view all the answers

    What role do receptors play in the nervous system?

    <p>They detect changes in the environment and respond to stimuli</p> Signup and view all the answers

    What is the primary output of a neuron?

    <p>Action potentials</p> Signup and view all the answers

    What is the color of gray matter primarily attributed to?

    <p>Clusters of Nissl bodies</p> Signup and view all the answers

    What initiates the generation of an action potential in a neuron?

    <p>Chemical, mechanical, or electrical stimulation of the dendrites</p> Signup and view all the answers

    Which part of the neuron is responsible for carrying outgoing signals?

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

    What effect would damage to the afferent division of the PNS likely have?

    <p>Impaired sensory perception from receptors</p> Signup and view all the answers

    In which type of muscle does the autonomic nervous system primarily operate?

    <p>Cardiac and smooth muscle</p> Signup and view all the answers

    What is the role of effector organs in the nervous system?

    <p>Respond to motor commands from the CNS</p> Signup and view all the answers

    Which of the following are common signs and symptoms of multiple sclerosis (MS)?

    <p>Partial loss of vision and problems with speech</p> Signup and view all the answers

    What is the typical resting membrane potential of a neuron?

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

    Which type of ions is found in high concentrations in the extracellular fluid?

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

    What is the role of the sodium-potassium exchange pump in neurons?

    <p>To maintain resting membrane potential</p> Signup and view all the answers

    What occurs to the membrane potential during an action potential?

    <p>It becomes less polarized and reaches a threshold</p> Signup and view all the answers

    Which neuroglia would likely increase in number during a CNS infection?

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

    What is a characteristic feature of a polarized plasma membrane?

    <p>Separation of positive and negative charges</p> Signup and view all the answers

    What happens to the permeability of the cell membrane during depolarization?

    <p>Increases for sodium ions</p> Signup and view all the answers

    How does the selective permeability of the plasma membrane affect ion movement?

    <p>It allows specific ions to pass while restricting others</p> Signup and view all the answers

    What contributes to the potential difference across the plasma membrane?

    <p>Differences in electrical charge and ionic composition</p> Signup and view all the answers

    What primarily maintains the negative charge inside a resting neuron?

    <p>Negatively charged proteins within the cell</p> Signup and view all the answers

    In which part of the nervous system are unipolar neurons primarily found?

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

    What causes the resting potential to be stable over time?

    <p>The sodium-potassium exchange pump functioning effectively</p> Signup and view all the answers

    What is the primary consequence of a disturbed resting membrane potential?

    <p>It can trigger an action potential if sufficiently depolarized</p> Signup and view all the answers

    What happens to the membrane potential during depolarization?

    <p>It shifts toward 0 mV.</p> Signup and view all the answers

    What is the effect of opening gated potassium channels in a cell membrane?

    <p>Hyperpolarization of the membrane.</p> Signup and view all the answers

    What distinguishes graded potentials from action potentials?

    <p>Graded potentials do not propagate like action potentials.</p> Signup and view all the answers

    How does pressure relate to the generation of an action potential?

    <p>It is analogous to the firing of a gun.</p> Signup and view all the answers

    Which statement correctly describes the all-or-none principle?

    <p>It indicates a threshold must be reached for action potentials to occur.</p> Signup and view all the answers

    Where does an action potential typically begin in a neuron?

    <p>Near the axon hillock.</p> Signup and view all the answers

    What is primarily responsible for the propagation of an action potential?

    <p>Voltage-gated sodium and potassium channels.</p> Signup and view all the answers

    What role do leak channels play in relation to graded potentials?

    <p>They reduce the magnitude of depolarization over distance.</p> Signup and view all the answers

    What initiates muscle contraction in skeletal muscle fibers?

    <p>Action potentials traveling along the sarcolemma.</p> Signup and view all the answers

    What type of ion channels open in response to a depolarization reaching threshold?

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

    How do graded potentials affect large excitable cells like neurons?

    <p>They can induce action potentials if they reach threshold.</p> Signup and view all the answers

    What is the primary function of the initial segment of the axon membrane?

    <p>To serve as the site for action potential initiation.</p> Signup and view all the answers

    Which characteristic is unique to excitable membranes?

    <p>Ability to generate action potentials.</p> Signup and view all the answers

    What is the effect of a chemical stimulus that opens gated sodium channels?

    <p>It depolarizes the membrane at the site of stimulation.</p> Signup and view all the answers

    What is the primary function of axon terminals?

    <p>To transmit signals between neurons</p> Signup and view all the answers

    Which type of neuron has a continuous dendrite and axon with its cell body positioned to one side?

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

    Which neurons make up the efferent division of the PNS that carries instructions from the CNS to effectors?

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

    What role do astrocytes play in the nervous system?

    <p>Regulate blood-brain barrier</p> Signup and view all the answers

    Where are interneurons primarily found?

    <p>Brain and spinal cord</p> Signup and view all the answers

    What type of receptor monitors the activities of internal organs?

    <p>Visceral receptor</p> Signup and view all the answers

    Which of the following is a characteristic of multipolar neurons?

    <p>Multiple dendrites and one axon</p> Signup and view all the answers

    What is a major limitation of typical CNS neurons?

    <p>They lack organelles needed for division</p> Signup and view all the answers

    What is the role of sensory neurons in the nervous system?

    <p>To relay information from receptors to the CNS</p> Signup and view all the answers

    Which of the following best describes bipolar neurons?

    <p>Rare and connected to sensory organs</p> Signup and view all the answers

    What type of neurons interconnect different neurons and are involved in complex responses?

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

    Which type of receptor provides information about external environmental sensations?

    <p>External receptors</p> Signup and view all the answers

    What is not a characteristic of neuroglia?

    <p>They can conduct electrical impulses</p> Signup and view all the answers

    Neural stem cells are primarily ___ in the adult nervous system.

    <p>Inactive under normal conditions</p> Signup and view all the answers

    Study Notes

    Nervous System Introduction

    • Two systems maintain homeostasis: nervous and endocrine
    • Nervous system responds quickly, but briefly
    • Endocrine system responds slowly, but lasts longer
    • Nervous system coordinates body position, eye movements, and internal processes
    • Nervous system monitors internal/external environment, and issues commands for homeostasis
    • Nervous system activity patterns can shift quickly

    Anatomical and Functional Divisions

    • Nervous system has three main functions: monitors internal/external environments, integrates sensory information, coordinates organ system responses
    • Two major anatomical divisions:
      • Central Nervous System (CNS): brain and spinal cord, processes sensory data and motor commands, seat of higher functions (e.g., intelligence, memory, emotion)
      • Peripheral Nervous System (PNS): all neural tissue outside the CNS, communicates between CNS and body
    • Two functional divisions of PNS:
      • Afferent division: brings sensory information to CNS from receptors (sensory structures); detects internal and external changes
      • Efferent division: carries motor commands from CNS to muscles and glands (effectors); causes action in the target tissues or organs
    • Efferent division has two parts:
      • Somatic nervous system (SNS): controls skeletal muscle contractions (voluntary and involuntary); e.g., lifting a glass, or pulling hand back from a hot stove (reflex)
      • Autonomic nervous system (ANS): regulates smooth muscle, cardiac muscle, and glandular secretions at subconscious level; has sympathetic (speeds up heart rate) and parasympathetic (slows heart rate) divisions, which often have opposing effects

    Neurons and Neuroglia

    • Neurons: basic functional units of nervous system; communicate with other neurons and cells
    • Neuroglia: regulate environment around neurons, provide support, and act as phagocytes (far more numerous than neurons); most can divide
    • Neuron structure (representative neuron): cell body, dendrites, axon, axon terminals

    Neuron Structure

    • Neuron cell body contains large, round nucleus with a nucleolus; organelles that provide energy and synthesize compounds
    • Cytoplasm also contains numerous mitochondria, ribosomes, and rough endoplasmic reticulum (RER)
    • Clusters of RER and free ribosomes are called Nissl bodies
    • Dendrites and a single axon project from the cell body
    • Dendrites and cell body plasma membrane are sensitive to stimulation
    • Electric signals are generated (action potentials) at the axon hillock and travel along the axon
    • Axon may branch into collaterals, which end in axon terminals (synaptic terminals or knobs)
    • Synapse: site of communication between neurons
    • Most CNS neurons cannot divide due to lack of centrioles

    Neuron Classification

    • Multipolar neurons: two or more dendrites, and one axon

    • Unipolar neurons: dendrites and axon are continuous; cell body lies off to one side; most sensory neurons in PNS, with long axons

    • Bipolar neurons: one dendrite, one axon, cell body between them; small and rare; found in special sense organs (vision, smell, hearing)

    Functional Neuron Classification

    • Sensory neurons: afferent; receive information from sensory receptors, relayed to other neurons in CNS
      • Somatic sensory receptors: detect external environment or position
      • External receptors: detect touch, pressure, pain, temperature, taste, smell, sight, equilibrium, hearing
      • Proprioceptors: monitor position and movement of skeletal muscles and joints
      • Visceral receptors: monitor digestive, respiratory, cardiovascular, urinary, and reproductive systems; detect distension, deep pressure, and pain
    • Motor neurons: efferent; carry instructions from CNS to effectors (other tissues, organs, or organ systems); SNS - skeletal muscles; ANS – smooth muscle, cardiac muscles, glands
    • Interneurons: association neurons; entirely within CNS; interconnect other neurons; responsible for distributing sensory info and coordinating motor activity

    Neuroglia of CNS

    • Astrocytes: largest and most numerous neuroglia; maintain blood-brain barrier, regulate chemical environment, wrap around capillaries
    • Oligodendrocytes: smaller cell bodies than astrocytes; have sheet-like processes that wrap around axons; myelination of several axons
    • Microglia: smallest and least numerous; phagocytic cells; derived from white blood cells; protect against pathogens
    • Ependymal cells: simple cuboidal epithelial cells; line cavities in CNS filled with CSF; some produce CSF, others circulate it with cilia

    Organization of neurons in nervous system

    • PNS: neuron cell bodies in ganglia, surrounded by satellite cells; axons bundled in nerves (spinal, cranial)
    • CNS: collection of neuron cell bodies (gray matter) with a common function is called a center; center with a discrete boundary (nucleus); white matter contains bundles of axons (tracts)

    Demyelination disorders

    • Demyelination: progressive destruction of myelin sheaths; loss of sensation, and motor control (e.g., multiple sclerosis (MS))

    Action Potentials

    • Action potential: propagated change in membrane potential of excitable cells; involves opening and closing of voltage-gated channels in response to a graded potential
    • All-or-none principle: given stimulus triggers a typical action potential or none at all
    • Resting membrane potential: -70 mV ; cell interior negatively charged relative to extracellular fluid; maintained by ion pumps and ion channels
    • Depolarization: shift in membrane potential toward 0 mV; opening of sodium channels speeds up sodium ion movement into the cell
    • Repolarization: return to resting potential; opening of potassium channels increases potassium ion movement out of cell; opening of sodium channels is blocked (refractory period)
    • Generation of action potentials involves graded depolarization, opening of voltage-gated sodium channels, inactivation of sodium channels, activation of potassium channels, return to resting potential

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    Test your knowledge on the nervous system and its functions in this quiz. Explore key concepts including the structure, divisions, and physiological processes involved in nervous system responses. Perfect for students studying biology and looking to reinforce their understanding of this essential topic.

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