Chapter 8 section 1-3
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Questions and Answers

What is the primary function of saltatory propagation in neurons?

  • To enhance the electrical signal throughout the neuron.
  • To slow down the speed of nerve impulses.
  • To prevent depolarization of the axon membrane.
  • To carry nerve impulses along the axon at higher speeds. (correct)

How does saltatory propagation compare to conventional propagation in terms of speed?

  • It propagates signals only in small, local regions.
  • It can reach speeds vastly exceeding those of unmyelinated axons. (correct)
  • It propagates signals at slower speeds than conventional methods.
  • It operates at a fixed speed regardless of axon type.

What effect would a chemical that blocks voltage-gated sodium channels have on a neuron's depolarization ability?

  • It would improve the ability to generate action potentials.
  • It would prevent depolarization by blocking sodium influx. (correct)
  • It would have no effect on the neuron's membrane potential.
  • It would enhance depolarization by increasing sodium entry.

What happens to the membrane potential of a neuron if extracellular potassium concentration decreases?

<p>The membrane potential becomes less negative and may depolarize. (D)</p> Signup and view all the answers

Which of the following axons is likely myelinated if one carries action potentials at 50 meters per second and the other at 1 meter per second?

<p>The axon carrying action potentials at 50 meters per second. (D)</p> Signup and view all the answers

What is the main difference between the responses of the nervous system and the endocrine system?

<p>The nervous system responds quickly but lasts briefly, while the endocrine system responds slowly but lasts longer. (C)</p> Signup and view all the answers

Which of the following is NOT a function of the nervous system?

<p>Regulating hormonal balance. (D)</p> Signup and view all the answers

What are the two major anatomical divisions of the nervous system?

<p>Central nervous system and peripheral nervous system. (B)</p> Signup and view all the answers

Which type of information does the afferent division of the PNS carry to the CNS?

<p>Sensory information from receptors. (C)</p> Signup and view all the answers

What is the role of receptors in the nervous system?

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

Which part of the nervous system integrates and coordinates sensory data and motor commands?

<p>Central nervous system. (A)</p> Signup and view all the answers

What is the main function of the efferent division of the PNS?

<p>To transmit motor commands from the CNS to effector organs. (A)</p> Signup and view all the answers

Which of the following statements about the nervous system is true?

<p>It plays a role in emotion and memory. (A)</p> Signup and view all the answers

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

<p>Controlling skeletal muscle contractions (B)</p> Signup and view all the answers

What type of response is an involuntary muscle contraction when placing your hand on a hot stove?

<p>Reflex response (D)</p> Signup and view all the answers

Which division of the nervous system is responsible for monitoring internal conditions?

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

What is the primary role of the autonomic nervous system?

<p>Controlling subconscious bodily functions (C)</p> Signup and view all the answers

Which of the following structures are classified as effectors?

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

What is the function of neuroglia in the nervous system?

<p>Supporting and protecting neurons (D)</p> Signup and view all the answers

What is a unique characteristic of neurons compared to neuroglia?

<p>Neurons cannot divide and replicate (B)</p> Signup and view all the answers

What is the primary role of dendrites in a neuron?

<p>Receiving incoming signals (A)</p> Signup and view all the answers

What happens at the axon hillock of a neuron?

<p>Action potentials are generated (C)</p> Signup and view all the answers

Which division of the autonomic nervous system is known for speeding up heart rate?

<p>Sympathetic division (C)</p> Signup and view all the answers

What does the term 'afferent division' refer to?

<p>Sensory input brought to CNS (B)</p> Signup and view all the answers

Which of the following best describes the central nervous system?

<p>Comprises the brain and spinal cord (D)</p> Signup and view all the answers

What is the result of the parasympathetic division's activity?

<p>Relaxation and maintenance processes (A)</p> Signup and view all the answers

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

<p>Create a protective blood-brain barrier (C)</p> Signup and view all the answers

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

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

What distinguishes multipolar neurons from unipolar neurons?

<p>Multipolar neurons have multiple dendrites and a single axon. (D)</p> Signup and view all the answers

What is the role of interneurons in the nervous system?

<p>Connect other neurons and coordinate motor activity (C)</p> Signup and view all the answers

Which of the following statements about neuroglia is true?

<p>Neuroglia make up about half of the volume of the nervous system. (C)</p> Signup and view all the answers

What type of sensory neurons monitor the position and movement of skeletal muscles?

<p>Proprioceptors (D)</p> Signup and view all the answers

Which type of neuron is least common in the nervous system?

<p>Bipolar neurons (D)</p> Signup and view all the answers

How do astrocytes support the structure of the CNS?

<p>By providing nutrients to neurons (C)</p> Signup and view all the answers

Which neurons are involved in carrying instructions from the CNS to effectors like muscles and glands?

<p>Efferent neurons (D)</p> Signup and view all the answers

Which of the following is NOT a function of astrocytes?

<p>Transmitting sensory signals (D)</p> Signup and view all the answers

Which division of the peripheral nervous system includes motor neurons?

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

What type of sensory receptor provides data about external environmental stimuli?

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

What characterizes unipolar neurons?

<p>Their cell body is positioned off to one side. (A)</p> Signup and view all the answers

Which functional classification includes neurons that interpret and integrate sensory information?

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

Neurons in the peripheral nervous system are classified based on their axon structure and function. Which classification includes neurons with one axon and multiple dendrites?

<p>Multipolar neurons (C)</p> Signup and view all the answers

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

<p>To enhance the speed of action potential propagation (C)</p> Signup and view all the answers

Which cells are primarily responsible for myelinating axons in the CNS?

<p>Oligodendrocytes (D)</p> Signup and view all the answers

What term describes the small gaps between myelinated segments of an axon?

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

Which neuroglial cell type helps in the circulation of cerebrospinal fluid (CSF)?

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

What is the composition of myelin primarily made up of?

<p>Lipids (C)</p> Signup and view all the answers

How does action potential propagation differ in myelinated versus unmyelinated axons?

<p>Myelinated axons allow action potentials to jump from node to node (D)</p> Signup and view all the answers

What is the primary role of microglia in the CNS?

<p>Engulfing cellular waste and pathogens (A)</p> Signup and view all the answers

What distinguishes white matter from gray matter in the CNS?

<p>Concentration of myelinated axons (C)</p> Signup and view all the answers

What is the main structural difference between Schwann cells and oligodendrocytes?

<p>Schwann cells can enclose several unmyelinated axons (A)</p> Signup and view all the answers

What happens at the axon hillock during action potential generation?

<p>A local current develops and action potential begins (A)</p> Signup and view all the answers

Which term best describes the regions of an axon covered in myelin?

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

In which part of the nervous system are oligodendrocytes primarily located?

<p>Central nervous system (D)</p> Signup and view all the answers

Why are previous segments of axons unable to respond during action potential propagation?

<p>They are in a refractory period (D)</p> Signup and view all the answers

How does the structure of ependymal cells contribute to their function?

<p>Cilia aid in the circulation of CSF (C)</p> Signup and view all the answers

What distinguishes action potentials from graded potentials in terms of propagation?

<p>Graded potentials do not propagate along the entire axon (A)</p> Signup and view all the answers

Flashcards

What is the role of the nervous system?

The nervous system is the body's control center, responsible for coordinating all actions and responses to changes in the environment.

What are the two main parts of the nervous system?

The nervous system has two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS).

What is the Central Nervous System (CNS)?

The central nervous system (CNS) consists of the brain and spinal cord. It integrates and processes sensory information, and sends out motor commands.

What is the Peripheral Nervous System (PNS)?

The peripheral nervous system (PNS) includes all the nerves outside the central nervous system. It connects the CNS to the rest of the body.

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What does the afferent division of the PNS do?

The afferent division of the PNS receives sensory information from the body and sends it to the CNS.

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What does the efferent division of the PNS do?

The efferent division of the PNS carries motor commands from the CNS to muscles and glands.

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What are receptors?

Sensory structures that detect changes in the environment or respond to specific stimuli are called receptors.

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How do the nervous and endocrine systems compare in terms of response?

The nervous system responds quickly and temporarily to stimuli, while the endocrine system responds slowly but persistently.

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Effectors

Organs and tissues that respond to neural commands by performing an action.

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Efferent division

The part of the peripheral nervous system that carries motor commands from the CNS to the body.

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Somatic nervous system

The part of the peripheral nervous system that controls skeletal muscle contractions.

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Involuntary contractions

Simple or complex movements controlled at the subconscious level.

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Reflex

An instantaneous, automatic response to a stimulus.

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Autonomic nervous system

The part of the peripheral nervous system that automatically regulates smooth muscle, cardiac muscle, and glandular secretions.

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Sympathetic division

The division of the autonomic nervous system that generally prepares the body for 'fight-or-flight' responses.

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Parasympathetic division

The division of the autonomic nervous system that generally calms the body and promotes 'rest-and-digest' functions.

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Receptors

Sensory structures that detect changes in the internal or external environment.

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Neurons

Specialized cells that transmit information throughout the nervous system.

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Neuroglia

Cells that support and protect neurons.

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Dendrites

The part of a neuron that receives incoming signals.

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Axon

The long, slender projection of a neuron that carries outgoing signals.

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Axon hillock

The thickened region of the cell body where action potentials begin.

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Axon terminals

The branching endings of an axon that transmit signals to other cells.

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Synapse

A site where a neuron communicates with another cell.

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Centrioles

Organelles responsible for moving chromosomes during cell division.

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Limited CNS neuron regeneration

Neurons in the central nervous system (CNS) typically cannot divide, meaning they can't be replaced if damaged.

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Neural stem cells

Specialized cells in the adult nervous system that have the potential to develop into neurons.

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Multipolar neuron

Type of neuron with multiple dendrites and a single axon.

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Unipolar neuron

Type of neuron with a single process extending from the cell body that branches into dendrites and an axon.

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Bipolar neuron

Type of neuron with one dendrite and one axon.

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Motor neurons

Neurons that transmit impulses from the CNS to effector organs, such as muscles and glands.

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Sensory neurons

Neurons that carry sensory information from receptors to the CNS.

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Interneurons

Neurons located within the CNS that connect other neurons.

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Astrocytes

Star-shaped neuroglia that maintain the blood-brain barrier, provide structural support, and help repair damaged tissues.

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Ependymal cells

Simple cuboidal epithelial cells lining fluid-filled spaces in the CNS.

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Microglia

Phagocytic neuroglia that remove debris and pathogens in the CNS.

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Saltatory propagation

The movement of a nerve impulse along an axon, jumping from one node of Ranvier to the next, resulting in faster signal transmission.

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Blocking Sodium Channels

The action of a chemical that blocks the movement of sodium ions across the neuron's membrane, preventing the depolarization phase of an action potential.

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Decreasing Potassium Concentration

Decreasing the concentration of potassium ions outside the neuron would cause the membrane potential to become more positive, making the neuron more likely to fire an action potential.

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Steps in Action Potential Generation & Propagation

  1. Resting potential - The neuron is at rest, maintaining a negative charge.
  2. Depolarization - Sodium ions rush into the neuron, making it more positive.
  3. Repolarization - Potassium ions flow out of the neuron, returning it to a negative charge.
  4. Hyperpolarization - The neuron becomes slightly more negative than its resting potential.
  5. Refractory period - The neuron is unable to fire another action potential for a brief period.
  6. Propagation - The action potential travels down the axon.
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Which axon is myelinated?

The axon with a propagation velocity of 50 meters per second is myelinated. Myelin acts as an insulator, allowing the action potential to jump from one node to the next, increasing its speed.

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Oligodendrocyte

A type of glial cell in the CNS that wraps around axons, forming a myelin sheath that speeds up nerve impulse transmission.

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Central canal of spinal cord

The fluid-filled central cavity of the spinal cord, lined by ependymal cells.

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Gray matter

Areas of the CNS dominated by neuron cell bodies, dendrites, and unmyelinated axons. It appears gray due to the lack of myelin.

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White matter

Areas of the CNS dominated by myelinated axons, which appears white due to the presence of myelin.

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Myelinated axons

Axons that are covered by a myelin sheath, which increases the speed of nerve impulse transmission.

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Myelin

A fatty, lipid-rich substance that forms a sheath around axons, insulating them and increasing the speed of nerve impulse transmission.

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Nodes of Ranvier

Gaps between adjacent myelin sheaths on a myelinated axon, where the axon membrane is exposed. These nodes are important for saltatory conduction of nerve impulses.

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Capillary

Small, thin-walled blood vessels that permeate tissues, bringing oxygen and nutrients and removing waste products.

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Satellite cells

The glial cells that support neuron cell bodies in the PNS, similar to astrocytes in the CNS.

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Schwann cells

Glial cells in the PNS that myelinate axons, forming a neurilemma around each.

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Neurilemma

The outermost layer of a Schwann cell, covering an axon in the PNS.

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Saltatory conduction

The process by which an action potential jumps from one node of Ranvier to the next along a myelinated axon, significantly increasing the speed of nerve impulse transmission.

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Study Notes

Nervous System Organization

  • Two organ systems (nervous and endocrine) maintain homeostasis by responding to environmental changes.
  • Nervous system responses are fast but short-lived, while endocrine system responses are slow but lasting.
  • Nervous system examples include body positioning and eye movement.
  • Endocrine system examples include adjusting energy use and growth.

Nervous System Anatomy and Function

  • Nervous system has three main functions: monitoring internal/external environment, integration of sensory information, and coordinating voluntary/involuntary responses.
  • Two major anatomical divisions: central nervous system (CNS) and peripheral nervous system (PNS).
    • CNS includes the brain and spinal cord, integrating sensory input and outputting motor commands.
    • PNS contains all neural tissue outside the CNS, connecting CNS to the rest of the body.
      • Afferent division brings sensory information to the CNS from receptors.
      • Efferent division carries motor commands from CNS to muscles and glands.
        • Somatic nervous system controls skeletal muscle contractions (voluntary and involuntary).
        • Autonomic nervous system (ANS) regulates smooth muscle, cardiac muscle, and glandular secretions automatically.
          • ANS has sympathetic (accelerates heart rate) and parasympathetic (slows heart rate) divisions.

Neuron Structure and Function

  • Nervous system consists of neurons and neuroglia.
  • Neurons are the functional units communicating with one another and other cells.
  • Neuroglia support neurons by regulating their environment, providing framework, and acting as phagocytes. Neuroglia outnumber neurons.
    • Neuroglia can divide; neurons, generally, cannot.
  • Neuron types:
    • Multipolar: multiple dendrites, one axon (most common in CNS; motor neurons controlling skeletal muscles).
    • Unipolar: dendrites and axon continuous, single cell body (common in PNS; sensory neurons).
    • Bipolar: one dendrite, one axon, cell body between (rare, special sense organs).
  • Functional neuron classifications:
    • Sensory neurons (afferent): receive info from sensory receptors and relay to other neurons.
    • Motor neurons (efferent): carry instructions from CNS to effectors.
      • Somatic motor neurons innervate skeletal muscles.
      • Visceral motor neurons innervate other effectors (ANS).
    • Interneurons (association neurons): entirely within the brain/spinal cord, connect other neurons.

Neuroglia in the CNS

  • Astrocytes: largest and most numerous, maintain blood-brain barrier, create framework, repair tissue.
  • Oligodendrocytes: have processes forming myelin sheaths around axons.
  • Microglia: smallest and least numerous, phagocytic cells (engulf waste).
  • Ependymal cells: simple cuboidal epithelial cells lining cavities in CNS, produce/circulate cerebrospinal fluid.

Neuroglia in the PNS

  • Satellite cells: surround and support neuron cell bodies.
  • Schwann cells: ensheath axons outside CNS (with myelin).

Organization of Neurons

  • Neuron cell bodies and axons organized into masses/bundles (with anatomical boundaries and specific terms).

Action Potential Propagation

  • Action potentials affect entire membrane surface.
  • Continuous propagation occurs along unmyelinated axons slowly (up to about 1 m/s).
  • Saltatory propagation jumps between nodes of Ranvier on myelinated axons much faster (from 18 to 140 m/s).

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Description

Explore the intricate workings of the nervous system and its role in homeostasis. This quiz covers the anatomy of the nervous system, its divisions, and the functions of both the nervous and endocrine systems. Test your understanding of how these systems respond to environmental changes and coordinate bodily functions.

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