Chapter 11 Nervous

Which of the following is NOT true of association neurons? A. Most association neurons are confined within the peripheral nervous system (PNS). B. Association neurons account for over 99% of the neurons in the body. C. Association neurons are also known as interneurons. D. Most association neurons are multipolar.

A. Most association neurons are confined within the peripheral nervous system (PNS). Most association neurons are confined within the CNS (not PNS).

Which of the following is a factor that determines the rate of impulse propagation, or conduction velocity, along an axon? A. degree of myelination of the axon B. the number of axon collaterals extending from a truncated axon C. whether the axon is located in the central nervous system or in the peripheral nervous system D. length of the axon

A. degree of myelination of the axon

Which of the choices below describes the ANS? A. motor fibers that conduct nerve impulses from the CNS to smooth muscle, cardiac muscle, and glands B. sensory and motor neurons that supply the digestive tract C. sensory neurons that convey information from somatic receptors in the head, body wall, and limbs and from receptors from the special senses of vision, hearing, taste, and smell to the CNS D. motor fibers that conduct nerve impulses from the CNS to skeletal muscles

A. motor fibers that conduct nerve impulses from the CNS to smooth muscle, cardiac muscle, and glands

Which of the following allows us to consciously control our skeletal muscles? A. the somatic nervous system B. the parasympathetic division of the autonomic nervous system C. the sympathetic division of the autonomic nervous system D. the afferent division of the nervous system

A. the somatic nervous system The somatic nervous system is composed of somatic motor nerve fibers that conduct impulses from the central nervous system to skeletal muscles. It is often referred to as the voluntary nervous system because it allows us to consciously control our skeletal muscles.

Which membrane potential occurs because of the influx of Na+ through chemically gated channels in the receptive region of a neuron? inhibitory action potential excitatory postsynaptic potential action potential inhibitory postsynaptic potential

An excitatory postsynaptic potential, a type of graded potential, occurs because of the influx of Na+ through chemically gated channels in the receptive region, or postsynaptic membrane, of a neuron. Graded potentials are generated by chemically gated channels, whereas action potentials are produced by voltage-gated channels.

Which neuroglia are the most abundant and versatile of the glial cells? astrocytes Schwann cells oligodendrocytes ependymal cells

Astrocytes are the most abundant and versatile glial cells. Examples of their many functions include: anchoring neurons to capillaries, aiding in the exchanges between neurons and blood, guiding the migration of young neurons, and helping control the chemical environment around neurons.

The __________ is due to the difference in K+ and Na+ concentrations on either side of the plasma membrane, and the difference in permeability of the membrane to these ions.

At rest, the cell membrane is about 25 times more permeable to potassium than to sodium, and so more potassium ions diffuse out of the neuron down their concentration gradient than sodium ions diffuse into the neuron down theirs. The consequence is a cell membrane that has more positive charges (ions) along its external surface and relatively more negative charges along its internal surface. This separation of charges, or membrane voltage, is called the resting membrane potential.

Cold sores on the skin of the mouth occur when herpes simplex viruses that are dormant in neural ganglia become active and travel to the skin of the mouth. Which of the following is the mechanism by which these viruses travel from the ganglia (located within the head) to the skin of the mouth? A. transport along nerve impulses that travel down the axons B. anterograde transport C. retrograde transport D. travel of the viruses along neurofibrils

B. anterograde transport

Which of the following is true of axons? A. Neurons can have multiple axons but only one dendrite. B. Axons use chemically gated ion channels to generate graded potentials. C. A neuron can have only one axon, but the axon may have occasional branches along its length. D. Smaller (thinner) axons are more likely to bear myelin sheaths than larger (thicker) axons.

C. A neuron can have only one axon, but the axon may have occasional branches along its length. This is true; a neuron can have only one axon, but the axon may have occasional branches along its length.

Which of the following is NOT a difference between graded potentials and action potentials? A. Graded potentials occur along dendrites, whereas action potentials occur along axons. B. Greater stimulus intensity results in larger graded potentials, but not larger action potentials. C. Spatial summation is used to increase the amplitude of a graded potential; temporal summation is used to increase the amplitude of an action potential. D. Graded potentials can result from the opening of chemically gated channels; action potentials require the opening of voltage-gated channels.

C. Spatial summation is used to increase the amplitude of a graded potential; temporal summation is used to increase the amplitude of an action potential.

Which criterion is used to functionally classify neurons? A. the number of processes extending from the cell body neuron B. whether the nerve fibers are myelinated or unmyelinated C. the direction in which the nerve impulse travels relative to the central nervous system D. whether the neurons are found within the CNS or the PNS

C. the direction in which the nerve impulse travels relative to the central nervous system Functional classification groups neurons according to the direction in which the nerve impulse travels relative to the central nervous system. Based on this criterion, there are sensory neurons, motor neurons, and interneurons.

Local anesthetics block voltage-gated Na+ channels, but they do not block mechanically gated ion channels. Sensory receptors for touch (and pressure) respond to physical deformation of the receptors, resulting in the opening of specific mechanically gated ion channels. Why does injection of a local anesthetic into a finger still cause a loss of the sensation of touch from the finger? A. The local anesthetic prevents Na+ from causing the initial depolarization of this sensory receptor. B. The local anesthetic prevents any type of repolarization of this sensory receptor. C. Touch stimulation of this sensory receptor requires that there be a simultaneous opening of voltage-gated Na+ channels and mechanically gated ion channels. D. Touch stimulation of this sensory receptor will open the mechanically gated ion channels, but action potentials are still not initiated because propagation of an action potential requires the opening of voltage-gated Na+ channels

D. Touch stimulation of this sensory receptor will open the mechanically gated ion channels, but action potentials are still not initiated because propagation of an action potential requires the opening of voltage-gated Na+ channels

Which of the following is NOT one of the basic functions of the nervous system? A. control the activity of muscles and glands B. monitor changes occurring both inside and outside the body C. integration of sensory input D. regulation of neurogenesis

D. regulation of neurogenesis Most active during pre-natal development, neurogenesis (formation of neurons) is the process by which neurons are generated from neural stem cells. It is not one of the basic functions of the nervous system.

At which of the points along the illustrated action potential can a second action potential be produced, but only with a stimulus significantly greater than that which produced the first?

Despite the hyperpolarized state of the membrane at point D, a significantly strong stimulus may create enough depolarization to return the membrane to threshold. Point D would be considered within the relative refractory period. An important consequence of this design is that greater stimulus intensity will result in an increase in nerve impulse frequency. Once the membrane potential returns to its normal resting value (E), the same magnitude stimulus that initiated the first action potential should be sufficient to produce a second.

Which neurotransmitter(s) is/are the body's natural pain killer? norepinephrine substance P acetylcholine endorphins

Endorphins are natural opiates that inhibit substance P, the neurotransmitter that mediates pain transmission in the peripheral nervous system.

The all-or-none phenomenon as applied to nerve conduction states that the whole nerve cell must be stimulated for conduction to take place. True False

False

The autonomic nervous system is under voluntary control; whereas, the somatic nervous system is involuntary. True False

False

The nodes of Ranvier are found only on myelinated, peripheral neuron processes. True False

False

The sodium-potassium pump ejects two Na+ from the cell and then transports three K+ back into the cell in order to maintain the concentration gradients for sodium and potassium. True False

False; Actually, the sodium-potassium pump ejects three Na+ from the cell and then transports two K+ back into the cell. This action is essential to maintaining the concentration gradients for sodium and potassium, which are needed to generate and maintain the resting membrane potential.

Unmyelinated fibers conduct impulses faster than myelinated fibers. True False

False; Myelinated fibers (axons bearing a myelin sheath) conduct nerve impulses rapidly, whereas unmyelinated fibers conduct impulses more slowly. Note that myelin sheaths are associated only with axons; dendrites are always nonmyelinated.

Which of the following are bundles of neurofilaments that are important in maintaining the shape and integrity of neurons? chromatophilic substance neurofibrils perikaryon axolemma

Microtubules and neurofibrils, which are bundles of intermediate filaments (neurofilaments), are important in maintaining cell shape and integrity. They form a network throughout the cell body. The neuron cell body, or perikaryon, consists of a spherical nucleus with a conspicuous nucleolus surrounded by cytoplasm. It is the major biosynthetic center of a neuron and so it contains the usual organelles needed to synthesize proteins and other chemicals.

Which of the following types of neurons carry impulses away from the central nervous system (CNS)? motor sensory association afferent

Motor, or efferent, neurons carry impulses away from the CNS to the effector organs (muscles and glands) of the body periphery.

In multiple sclerosis, the cells that are the target of an autoimmune attack are the _________.

Oligodendrocytes are a type of neuroglial cell that function to form the myelin sheath around the axons of neurons within the central nervous system.

Which of the following types of glial cells produces the myelin sheaths that insulate axons, or nerve fibers, in the central nervous system (CNS)? oligodendrocytes microglia ependymal cells astrocytes

Oligodendrocytes wrap their processes around the thicker axons in the CNS, producing an insulating covering called a myelin sheath that increases the transmission speed of nerve impulses.

Which neuron circuit pattern is involved in the control of rhythmic activities such as breathing? reverberating circuit parallel after-discharge circuit converging circuit diverging circuit

Reverberating circuits are involved in the control of rhythmic activities such as breathing, the sleep-wake cycle, and repetitive motor activities like walking. A signal travels through a chain of neurons, each feeding back to previous neurons in the pathway.

Which of the following peripheral nervous system (PNS) neuroglia form the myelin sheaths around larger nerve fibers in the PNS? oligodendrocytes astrocytes Schwann cells satellite cells

Schwann cells (also called neurolemmocytes) surround all nerve fibers in the PNS and form myelin sheaths around the larger fibers. Myelin protects and electrically insulates nerve fibers, and it increases the transmission speed of nerve impulses.

What type of stimulus is required for an action potential to be generated? multiple stimuli a suprathreshold stimulus hyperpolarization a threshold level depolarization

The axolemma must be depolarized to threshold in order to generate an action potential.

Which part of the neuron is responsible for generating a nerve impulse? axon dendrite chromatophilic substance soma

The axon is the conducting region of the neuron. It generates nerve impulses (action potentials) and transmits them, typically away from the cell body, along the axolemma (cell membrane of the axon).

What part of the nervous system performs information processing and integration? somatic nervous system parasympathetic nervous system central nervous system sympathetic nervous system

The central nervous system, which consists of the brain and spinal cord, is the integrating and control center of the nervous system. It interprets sensory input and dictates motor output based on reflexes, current conditions, and past experience.

What component of the reflex arc determines the response to a stimulus? receptor integration center effector sensory neuron

The integration center receives sensory information (input), determines the proper response, and then signals the appropriate effector(s) to produce the response.

Which of the following is NOT true of an electrical synapse? A. They are less common than chemical synapses. B. Transmission across these synapses is very rapid. C. They are specialized for release and reception of chemical neurotransmitters. D. Communication through these synapses may be unidirectional or bidirectional.

They are specialized for release and reception of chemical neurotransmitters. This is incorrect; electrical synapses do not involve the release and reception of neurotransmitters. Instead, the neurons are electrically coupled by gap junctions, which allow ions to flow directly from one neuron to the next.

Axon diameter and degree of myelination determine nerve impulse conduction velocity. True False

True

Efferent nerve fibers may be described as motor nerve fibers. True False

True

Large-diameter nerve fibers conduct impulses much faster than small-diameter fibers. True False

True

Myelination of the nerve fibers in the central nervous system is the job of the oligodendrocyte. True False

True

Neurons in the CNS are organized into functional groups. True False

True

Reflexes are rapid, automatic responses to stimuli. Reflexes are rapid, automatic responses to stimuli. True False

True

The action potential is caused by permeability changes in the plasma membrane. True False

True

The oligodendrocytes can myelinate several axons. True False

True

The overlapping functions of the nervous system are sensory input, integration, and motor output. True False

True

Neurons are also called nerve cells. True False

True; The billions of neurons, also called nerve cells, are the structural units of the nervous system. They are typically large, highly specialized cells that conduct messages in the form of nerve impulses from one part of the body to another.

What structural classification describes the neuron associated with the neuroglia shown by E and F?

Unipolar

Which of the following is an excitatory neurotransmitter secreted by motor neurons innervating skeletal muscle? cholinesterase gamma aminobutyric acid norepinephrine acetylcholine

acetylcholine

Neuroglia that control the chemical environment around neurons by buffering ions such as potassium and recapturing and recycling neurotransmitters are ________. microglia Schwann cells oligodendrocytes astrocytes

astrocytes

The part of a neuron that conducts impulses away from its cell body is called a(n) ________. dendrite axon Schwann cell neurolemma

axon

The term central nervous system refers to the ________. spinal cord and spinal nerves brain, spinal cord, and peripheral nerves peripheral and spinal nerves brain and spinal cord

brain and spinal cord

Which of the following is NOT one of the chemical classes into which neurotransmitters fall? chlorides amino acids gases and lipids peptides

chlorides Neurotransmitters fall into several chemical classes based on molecular structure, but "chlorides" is not one of these classes.

Schwann cells are functionally similar to ________. oligodendrocytes microglia ependymal cells astrocytes

oligodendrocytes

Which of the following neurotransmitters inhibits pain and is mimicked by morphine, heroin, and methadone? endorphin serotonin acetylcholine nitric oxide

endorphin

Collections of nerve cell bodies in the peripheral nervous system are called ________. nuclei ganglia nerves tracts

ganglia

Which of the following is not a function of the autonomic nervous system? innervation of skeletal muscle innervation of glands innervation of cardiac muscle innervation of smooth muscle of the digestive tract

innervation of skeletal muscle

Which of the following types of glial cells monitors the health of neurons, and can transform into a special type of macrophage to protect endangered neurons? oligodendrocytes microglia ependymal cells astrocytes

microglia Microglial cells are small andovoid with relatively long "thorny" processes. Their processes touch nearby neurons, monitoring their health, and when they sense that certain neurons are injured or are in other trouble, the microglial cells migrate toward them. Where invading microorganisms or dead neurons are present, the microglial cells transform into a special type of macrophage that phagocytizes the microorganisms or neuronal debris.

Which of the following is NOT a functional classification of neurons? sensory interneurons efferent multipolar

multipolar Multipolar is a structural classification that groups neurons according to the number of processes extending from their cell body. Multipolar neurons have three or more processes - one axon and multiple dendrites

In what way does the interior surface of a cell membrane of a resting (nonconducting) neuron differ from the external environment? The interior is ________. positively charged and contains less sodium negatively charged and contains less sodium positively charged and contains more sodium negatively charged and contains more sodium

negatively charged and contains less sodium

The substance released at axon terminals to propagate a nervous impulse is called a(n) ________. biogenic amine neurotransmitter ion cholinesterase

neurotransmitter

Which of the following are gaps found along a myelin sheath? terminal boutons axolemma nodes of Ranvier outer collar of perinuclear cytoplasm

nodes of Ranvier Adjacent Schwann cells along an axon do not touch one another, so there are gaps in the sheath. These myelin sheath gaps, or nodes of Ranvier, occur at regular intervals (about 1 mm apart) along a myelinated axon. Axon collaterals can emerge from the axon at these gaps.

Which of the following is NOT a type of circuit? pre-discharge circuits converging circuits reverberating circuits diverging circuits

pre-discharge circuits; The patterns of synaptic connections in neuronal pools, called circuits, determine the pool's functional capabilities. Pre-discharge circuits are not one of the four basic types of circuits.

Which pattern of neural processing works in a predictable, all-or-nothing manner, where reflexes are rapid and automatic responses to stimuli in which a particular stimulus always causes the same response? oscillative processing serial processing reflexive processing parallel processing

serial processing; In serial processing, the whole system works in a predictable, all-or-nothing manner. One neuron stimulates the next, which stimulates the next, and so on, eventually causing a specific, anticipated response. The most clear-cut examples of serial processing are spinal reflexes - rapid, automatic responses to stimuli in which a particular stimulus always causes the same response.

An impulse from one nerve cell is communicated to another nerve cell via the ________. cell body receptor synapse effector

synapse