Nervous System Chapter 11 Quiz
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Questions and Answers

Match the levels of organization in the nervous system:

Central nervous system (CNS) = Main control center of the body. Peripheral nervous system (PNS) = Connects CNS to limbs and organs. Sensory (afferent) division = Transmits sensory information to the CNS. Motor (efferent) division = Transmits information from CNS to muscles and glands.

Which neuroglial cell type is the most abundant in the CNS?

astrocyte

Where in the neuron is an action potential initially generated?

axon hillock

The depolarization phase of an action potential results from the opening of which channels?

<p>voltage gated Na+ channels</p> Signup and view all the answers

The repolarization phase of an action potential results from

<p>the opening of voltage-gated K+ channels</p> Signup and view all the answers

Hyperpolarization results from

<p>slow closing of voltage-gated K+ channels</p> Signup and view all the answers

What is the magnitude (amplitude) of an action potential?

<p>100 mV</p> Signup and view all the answers

The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____.

<p>K+, Na+</p> Signup and view all the answers

During depolarization, which gradient(s) move(s) Na+ into the cell?

<p>both the electrical and chemical gradients</p> Signup and view all the answers

What is the value for the resting membrane potential for most neurons?

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

In which direction is each ion pumped by the Na+-K+ pump?

<p>Na+ is pumped out of the cell and K+ is pumped into the cell</p> Signup and view all the answers

The concentrations of which two ions are highest outside the cell?

<p>Na+ and Cl-</p> Signup and view all the answers

Why does injection of a local anesthetic into a finger still cause a loss of sensation of touch?

<p>Action potentials are still not initiated because propagation requires the opening of voltage-gated Na+ channels.</p> Signup and view all the answers

What are the steps in transferring across chemical synapses?

<ol> <li>An action potential arrives at the synaptic terminal. 2. Calcium channels open, and calcium ions enter the synaptic terminal. 3. Vesicles containing neurotransmitter fuse with the plasma membrane. 4. Neurotransmitter molecules diffuse across the synaptic cleft. 5. Neurotransmitter binds to receptors on the receiving neuron.</li> </ol> Signup and view all the answers

The small space between the sending neuron and the receiving neuron is the _______.

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

A molecule that carries information across a synaptic cleft is a ____________.

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

What happens when calcium ions enter the synaptic terminal?

<p>They cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane.</p> Signup and view all the answers

What happens when neurotransmitter molecules bind to receptors in the receiving neuron?

<p>Ion channels in the membrane of the receiving neuron open.</p> Signup and view all the answers

If a signal from a sending neuron makes the receiving neuron more negative inside, what occurs?

<p>The receiving neuron is less likely to generate an action potential.</p> Signup and view all the answers

Which membrane potential occurs because of the influx of Na+ through chemically gated channels in a neuron?

<p>excitatory postsynaptic potential</p> Signup and view all the answers

Which neurotransmitter(s) is/are the body's natural pain killer?

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

Which neuron circuit pattern is involved in the control of rhythmic activities such as breathing?

<p>reverberating circuit</p> Signup and view all the answers

What component of the reflex arc determines the response to a stimulus?

<p>integration center</p> Signup and view all the answers

Which of the following allows us to consciously control our skeletal muscles?

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

Name the 3 nervous system functions.

<ol> <li>Sensory input 2. Integration 3. Motor output</li> </ol> Signup and view all the answers

Which of the neuroglial cell types control the flow of cerebrospinal fluid within the CNS?

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

Which neuroglial cell types form myelin sheaths within the CNS?

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

Which neuroglial cell types are found in the PNS?

<p>satellite cell</p> Signup and view all the answers

Which glial cells monitor the health of neurons and can transform into macrophages?

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

Which PNS neuroglia form the myelin sheaths around larger nerve fibers in the PNS?

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

Which are bundles of neurofilaments that maintain the shape and integrity of neurons?

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

A neuron can have only one axon, but the axon may have occasional branches along its length.

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

Which is the conducting region of the neuron?

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

What criterion is used to functionally classify neurons?

<p>the direction in which the nerve impulse travels relative to the central nervous system</p> Signup and view all the answers

Multipolar is a functional classification of neurons.

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

Most association neurons are confined within the peripheral nervous system (PNS).

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

Neurons are also called nerve cells.

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

Unmyelinated fibers conduct impulses faster than myelinated fibers.

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

Which neuroglia are the most abundant and versatile of the glial cells?

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

Which part of the neuron is responsible for generating a nerve impulse?

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

Which types of neurons carry impulses away from the central nervous system (CNS)?

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

Where do most action potentials originate?

<p>initial segment</p> Signup and view all the answers

What opens first in response to a threshold stimulus?

<p>voltage gated Na+ channels</p> Signup and view all the answers

What characterizes depolarization, the first phase of the action potential?

<p>The membrane potential changes from a negative value to a positive value.</p> Signup and view all the answers

What characterizes repolarization, the second phase of the action potential?

<p>Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.</p> Signup and view all the answers

What event triggers the generation of an action potential?

<p>The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.</p> Signup and view all the answers

What is the first change to occur in response to a threshold stimulus?

<p>Voltage-gated Na+ channels change shape, and their activation gates open.</p> Signup and view all the answers

What potential difference is created by the unequal distribution of ions across the plasma membrane?

<p>Resting membrane potential (RMP)</p> Signup and view all the answers

Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?

<p>Leak channels</p> Signup and view all the answers

On average, what does the resting membrane potential of -70 mV indicate?

<p>The inside surface of the plasma membrane is much more negatively charged than the outside surface.</p> Signup and view all the answers

Why is the plasma membrane more permeable to K+ than to Na+?

<p>There are many more K+ leak channels than Na+ leak channels in the plasma membrane.</p> Signup and view all the answers

What two factors influence the resting membrane potential?

<p>The presence of concentration gradients and leak channels</p> Signup and view all the answers

What prevents the Na+ and K+ gradients from dissipating?

<p>Na+-K+ ATPase</p> Signup and view all the answers

Arrange these parts in order, from left to right, of a successful direct depolarization path within one neuron: axon, axon hillock, cell body, dendrite, presynaptic terminal.

<p>dendrite, cell body, axon hillock, axon, presynaptic terminal</p> Signup and view all the answers

Which best characterizes depolarization?

<p>Small consecutive steps of Na+ penetration into the axon along its length.</p> Signup and view all the answers

What is the primary stimulus for vesicles to move towards the cell membrane and release neurotransmitter?

<p>Voltage-gated membrane channels open, and Ca+2 enters the cytoplasm, increasing intracellular calcium.</p> Signup and view all the answers

Which statement best describes exocytosis?

<p>Membrane organelles fuse with the membrane and release contents out of the cell.</p> Signup and view all the answers

What conditions will increase the diffusion of molecules, such as neurotransmitters?

<p>An increase in the amount of neurotransmitter exocytized by the presynaptic axon.</p> Signup and view all the answers

What must happen for a postsynaptic dendrite to set up a graded potential after neurotransmitter release?

<p>The neurotransmitter bound at postsynaptic receptors to open postsynaptic ion channels.</p> Signup and view all the answers

Sequence at the chemical synapse in correct order:

<ol> <li>Action potential sweeps down presynaptic axon. 2. Calcium channels open in axon terminal. 3. Synaptic vesicles fuse and exocytize neurotransmitter. 4. Diffusion of neurotransmitter into extracellular fluid separating two neuron's membranes. 5. Graded potential at postsynaptic membrane.</li> </ol> Signup and view all the answers

Which best represents synaptic transmission?

<p>presynaptic axon to synapse to dendrite or postsynaptic cell body</p> Signup and view all the answers

What effect does blocking neurotransmitter receptors on the postsynaptic membrane have?

<p>Local graded potentials and action potential transmission are blocked with no response by the postsynaptic cell.</p> Signup and view all the answers

What is an example of a presynaptic cell?

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

Which component has a role in the postsynaptic cell during synaptic activity?

<p>chemically gated channels</p> Signup and view all the answers

What is the role of calcium in synaptic activity?

<p>Calcium influx into the synaptic terminal causes vesicle fusion.</p> Signup and view all the answers

What is the role of neurotransmitter at a chemical synapse?

<p>Neurotransmitter binds to receptors on the postsynaptic cell membrane and allows ions to diffuse across the membrane.</p> Signup and view all the answers

Neurotransmitter is released from presynaptic neurons through what mechanism?

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

What type of channel on the postsynaptic membrane binds neurotransmitter?

<p>a chemically gated channel</p> Signup and view all the answers

In addition to diffusion, what are two mechanisms that terminate neurotransmitter activity?

<p>reuptake and degradation</p> Signup and view all the answers

Arrange the events during synaptic activity in the correct order:

<p>(c) Action potential arrives at axon terminal; (a) Voltage-gated calcium channels open; (e) Neurotransmitter released into synaptic cleft; (b) Neurotransmitter binds to receptors; (f) Graded potential generated in postsynaptic cell; (d) Neurotransmitter is removed from the synaptic cleft.</p> Signup and view all the answers

In a synapse, neurotransmitters are stored in vesicles located in the __________.

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

An action potential releases neurotransmitter from a neuron by opening which of the following channels?

<p>voltage-gated Ca2+ channels</p> Signup and view all the answers

Binding of a neurotransmitter to its receptors opens __________ channels on the __________ membrane.

<p>chemically gated; postsynaptic</p> Signup and view all the answers

Binding of the neurotransmitter to its receptor causes the membrane to __________.

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

Which neurotransmitter is broken down by an enzyme before being returned?

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

Study Notes

Levels of Organization in the Nervous System

  • Central nervous system (CNS) includes the brain and spinal cord.
  • Peripheral nervous system (PNS) divided into sensory (afferent) and motor (efferent) divisions.
  • Motor division further splits into somatic and autonomic nervous systems (ANS) with sympathetic and parasympathetic divisions.

Neuroglial Cells

  • Astrocytes are the most abundant neuroglial cells in the CNS, providing support and nutrition.
  • Ependymal cells regulate cerebrospinal fluid flow within the CNS.
  • Oligodendrocytes form myelin sheaths in the CNS, while Schwann cells do so in the PNS.
  • Microglia act as immune cells, transforming into macrophages to protect neurons.

Action Potentials

  • Action potentials are initially generated at the axon hillock.
  • The depolarization phase occurs due to the opening of voltage-gated Na+ channels.
  • Repolarization follows through the opening of voltage-gated K+ channels.
  • Hyperpolarization takes place from the slow closing of voltage-gated K+ channels.
  • The maximum amplitude of an action potential is approximately 100 mV.
  • The resting membrane potential for most neurons is -70 mV, with higher permeability to K+ compared to Na+.

Ion Flow and Membrane Potential

  • During depolarization, both electrical and chemical gradients drive Na+ into the cell.
  • Sodium and chloride ions have higher concentrations outside the cell.
  • The Na+-K+ pump actively maintains ion gradients by transporting Na+ out and K+ into the cell.

Synaptic Transmission

  • Local anesthetics block voltage-gated Na+ channels, preventing action potential generation despite mechanical stimulation.
  • Chemical synapse transmission involves the release of neurotransmitters from presynaptic terminals into the synaptic cleft.
  • Action potential arrival opens calcium channels, allowing Ca2+ influx and leading to neurotransmitter release via exocytosis.
  • Graded potentials in the postsynaptic neuron occur when neurotransmitters bind to receptors, opening ion channels.

Reflex Arcs and Neural Circuits

  • Reflex arcs consist of sensory input, integration centers, and motor output.
  • The integration center determines responses to stimuli.
  • Reverberating circuits support rhythmic activities, such as breathing.

Neurotransmitters and Receptors

  • Endorphins serve as natural painkillers.
  • Neurotransmitter activity is terminated through diffusion, reuptake, or degradation.
  • The binding of neurotransmitters to receptors opens chemically gated channels on the postsynaptic membrane.

Neuron Structure and Function

  • Neurons contain structures like axons (the conducting region), cell bodies, and dendrites.
  • Neurons can have multiple branches from a single axon but only one axon overall.
  • Neurons are classified functionally based on impulse direction relative to the CNS, categorized as sensory, motor, and association neurons.

Mechanisms of Action Potential Generation

  • An action potential is triggered when the membrane potential reaches a threshold of -55 mV from -70 mV.
  • Depolarization involves a rapid shift from a negative to a positive membrane potential, peaking at +30 mV, followed by repolarization.
  • Leak channels are responsible for the diffusion of Na+ and K+ across membranes, helping establish resting membrane potential.

Importance of Calcium and Vesicle Function

  • Calcium's influx into the axon terminal is crucial for vesicle fusion and neurotransmitter release.
  • Calcium channels open in response to action potentials, initiating synaptic transmission processes.

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Test your knowledge on the nervous system and its organization with this Chapter 11 quiz. Covering topics from the central and peripheral nervous systems to neuroglial cells, this quiz will help reinforce your understanding of nervous tissue. Challenge yourself to master the key concepts!

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