Chapter 11 Nervous system

Which of the following is FALSE regarding motor (efferent) neurons? Impulses from motor (efferent) neurons cause activity in skeletal muscles and glands. Motor (efferent) neurons carry impulses away from the CNS to the effector organs. Motor (efferent) neurons are bipolar. The cell bodies of most motor (efferent) neurons are located in the CNS

Motor (efferent) neurons are bipolar. Motor, or efferent, neurons carry impulses away from the CNS to the effector organs (muscles and glands) of the body periphery. Motor neurons are multipolar. Except for some neurons of the autonomic nervous system, their cell bodies are located in the CNS.

Which of the following is NOT a characteristic of neurons? Neurons can function optimally for over 100 years. In general, neurons cannot be replaced if destroyed. Neurons are relatively small, simple-structured cells. Neurons require continuous and abundant supplies of oxygen, and cannot survive for more than a few minutes without it.

Neurons are relatively small, simple-structured cells. Besides their ability to conduct nerve impulses, neurons are typically large, complex cells that have some other special characteristics: They have extreme longevity. Given good nutrition, neurons can function optimally for a lifetime (over 100 years). They are amitotic. As neurons assume their roles as communicating links of the nervous system, they lose their ability to divide. We pay a high price for this neuron feature because neurons cannot be replaced if destroyed. There are exceptions to this rule (olfactory epithelium and some hippocampal regions contain stem cells that can produce new neurons throughout life). They have an exceptionally high metabolic rate and require continuous and abundant supplies of oxygen and glucose. Neurons cannot survive for more than a few minutes without oxygen.

What is the difference between the clusters of cell bodies called nuclei and those known as ganglia? Nuclei exist in the PNS, ganglia in the CNS. Nuclei exist in all cells throughout the body, and ganglia exist only within the brain and spinal cord. Nuclei exist in the CNS, ganglia in the PNS. There is no difference between nuclei and ganglia.

Nuclei exist in the CNS, ganglia in the PNS.

__________ are muscles that oppose or reverse a particular movement. The nervous system processes and interprets sensory input and decides what should be done at each moment. The nervous system generates neurons in order to replace or repair damaged neurons; this permits optimal communication between the CNS and the body's effector organs. The nervous system uses its millions of sensory receptors to monitor changes occurring both inside and outside the body. The nervous system causes a response by activating effector organs, such as the muscles and glands.

The nervous system processes and interprets sensory input and decides what should be done at each moment. The nervous system processes and interprets sensory input and decides what should be done at each moment—a process called integration.

Which of the following is NOT a functional classification of neurotransmitters? excitatory indirect chemical direct

chemical Effects: Some neurotransmitters are excitatory, some are inhibitory, and others exert both effects, depending upon the specific receptor types with which they interact. Actions: Neurotransmitters that bind to and open ion channels are said to act directly. Neurotransmitters that act indirectly tend to promote broader, longer-lasting effects by acting through intracellular second-messenger molecules.

Which type of ion channel opens when a chemical binds to it? leakage channel voltage-gated channel mechanically gated channel chemically gated (ligand-gated) channel

chemically gated (ligand-gated) channel Leakage channels are always open. Chemically (ligand-gated) gated channels open when the appropriate chemical binds. Voltage-gated channels open and close in response to changes in the membrane potential. Mechanically gated channels open in response to physical deformation of the receptor.

Which of the following are the main receptive or input regions found in neurons? ganglia dendrites neurofibrils axons

dendrites Dendrites are the main receptive or input regions found in neurons.

Which of the following circuit types is exemplified by impulses that travel from a single neuron of the brain, activate one hundred or more motor neurons in the spinal cord, and excite thousands of skeletal muscle fibers? converging circuit reverberating circuit diverging circuit parallel after-discharge circuit

diverging circuit In diverging circuits, one incoming fiber triggers responses in ever-increasing numbers of neurons farther and farther along in the circuit. Therefore, diverging circuits are often amplifying circuits. Divergence can occur along a single pathway or along several pathways.

Which of the following types of glial cells line the central cavities of the brain and spinal cord, where they help to circulate the cerebrospinal fluid? astrocytes microglial cells oligodendrocytes ependymal cells

ependymal cells Ependymal cells line the central cavities of the brain and spinal cord, where they form a fairly permeable barrier between the cerebrospinal fluid that fills those cavities and the tissue fluid bathing the cells of the CNS. The beating of their cilia helps to circulate the cerebrospinal fluid that cushions the brain and spinal cord.

Which of the following diseases is directly related to demyelination? multiple sclerosis muscular dystrophy lupus cerebral palsy

multiple sclerosis The importance of myelin nerve transmission is painfully clear to people with demyelinating diseases such as multiple sclerosis (MS).

The movement of which ion out of the cell through leakage channels establishes the negative membrane potential? chloride calcium potassium sodium

potassium K+ loss through abundant leakage channels establishes a negative membrane potential.

Which part of the action potential occurs when the voltage-gated Na+ channels are inactivating and voltage-gated K+ channels open? depolarization repolarization hyperpolarization resting state

repolarization Na+ channels are inactivating and K+ channels open during repolarization. The lack of positive charges (sodium) entering the cell and the movement of positive charges (potassium) out of the cell reestablish the negativity on the inside of the membrane.

Which of the following is NOT a structural classification of neurons? multipolar unipolar bipolar sensory

sensory Neurons are grouped structurally according to the number of processes extending from their cell body. Three major neuron groups make up this classification: multipolar, bipolar, and unipolar.

Which criterion is used to structurally classify neurons? the direction the nerve impulse travels relative to the central nervous system the number of processes extending from their cell body whether the nerve fibers are myelinated or not whether the neurons are found within the CNS or the PNS

the number of processes extending from their cell body Neurons are grouped structurally according to the number of processes extending from their cell body.

Which of the following is NOT a function of the myelin sheath? to recapture and recycle released neurotransmitters to increase the speed of transmission of nerve impulses to protect nerve fibers to electrically insulate nerve fibers

to recapture and recycle released neurotransmitters

True or False Dendrites and axons are both armlike processes that extend from neuron cell bodies.

true

Which of the following membrane ion channels open and close in response to changes in the membrane potential? chemically gated channels mechanically gated channels nongated channels voltage-gated channels

voltage-gated channels Voltage-gated channels open and close in response to changes in the membrane potential.

True or False An action potential is a phenomenon that either happens completely or doesn't happen at all.

True

Which of the following types of glial cells are the most abundant and versatile, and aid in making exchanges between capillaries and neurons? oligodendrocytes ependymal cells astrocytes microglial cells

astrocytes Astrocytes are the most abundant and most versatile glial cells. Their numerous radiating processes cling to neurons and their synaptic endings and cover nearby capillaries, supporting and bracing the neurons and anchoring them to their nutrient supply lines, the blood capillaries. Astrocytes have a role in making exchanges between capillaries and neurons, in helping to determine capillary permeability, in guiding the migration of young neurons, and in forming synapses.

What is the difference between nerves and tracts? Bundles of neuron processes are called tracts in the CNS and nerves in the PNS. Bundles of neuron processes are called nerves in the CNS and tracts in the PNS. Tracts are composed of many nerves wrapped into long, ropelike extensions. Tracts are bundles of neuron processes, and nerves are the conducting regions of neurons.

Bundles of neuron processes are called tracts in the CNS and nerves in the PNS.

What is the primary difference between the somatic nervous system and the autonomic nervous system? The somatic nervous system allows us to consciously control our skeletal muscles, and the autonomic nervous system controls activity that humans cannot consciously control, such as the pumping of the heart and the movement of food through the digestive tract. The autonomic nervous system allows us to consciously control our skeletal muscles, and the somatic nervous system controls activity that humans cannot consciously control, such as the pumping of the heart and the movement of food through the digestive tract. The somatic nervous system enables us to control our involuntary muscles, while the autonomic nervous system controls our glands. The autonomic nervous system enables us to control our involuntary muscles, while the somatic nervous system controls our glands.

The somatic nervous system allows us to consciously control our skeletal muscles, and the autonomic nervous system controls activity that humans cannot consciously control, such as the pumping of the heart and the movement of food through the digestive tract. The motor division has two main parts. The somatic nervous system allows us to consciously control our skeletal muscles. The autonomic nervous system regulates the activity of smooth muscles, cardiac muscles, and glands—those activities that we generally cannot consciously control.

Which of the following is FALSE regarding chemical synapses? They communicate unidirectionally. They transmit nerve impulses directly from one neuron to another. They possess pre- and postsynaptic membranes separated by a synaptic cleft. Each is composed of an axon terminal and a receptor region.

They transmit nerve impulses directly from one neuron to another. In contrast to electrical synapses, which are specialized to allow the flow of ions between neurons, chemical synapses are specialized for release and reception of chemical neurotransmitters. A typical chemical synapse is made up of two parts: A knoblike axon terminal of the presynaptic neuron, which contains many tiny, membrane-bounded sacs called synaptic vesicles, each containing thousands of neurotransmitter molecules A neurotransmitter receptor region on the membrane of a dendrite or the cell body of the postsynaptic neuron Presynaptic and postsynaptic membranes are always separated by the synaptic cleft, a fluid-filled space approximately 30-50 nm wide. As a result, nerve impulses are not directly transmitted from one neuron to another.