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A/P Ch 11

Question	Answer
The conductive region of the neuron where the action potential occurs is called:	the axon
The specific region on the axon where an action potential is generated is called:	the axon hillock
What support cell forms the myelin sheaths in the peripheral nervous system?	Schwann cells
The gaps between Schwann cells that are essential for the conduction of the action potential are called:	nodes of Ranvier.
Neurons can communicate with, or stimulate, which of the following?	Neurons, muscles, and glands
Signals from other neurons are received on what parts of the neuron?	Both dendrites and the soma
If an axon branches, these branches of the neuron are called:	axon collaterals
What is the correct order of the path of information in a neuron from input to output?	Dendrites, soma, axon
In myelination, what part of the Schwann cell becomes the insulation?	The cell membrane
The number of processes extending from their cell body can classify neurons structurally. Which is the most common neuron type in humans?	Multipolar
The sensory, or afferent, division of the peripheral nervous system transmits information from the _________ to the CNS.	skin
The interior of a nerve cell has a slight excess of negative charge because:	potassium diffuses out of the cell.
The Nissl bodies seen in the neuron cell body represents which cellular organelle?	Rough endoplasmic reticulum
Which of the following statements best describes the membrane situation in the resting state in the neuron?	All the voltage-gated Na+ and K+ channels are closed.
Which of the following line the central cavities of the brain and spinal cord and provide a barrier between the CSF and nervous tissue?	Ependymal cells
Which of the following characteristics is NOT associated with a myelinated nerve fiber?	Slow conduction of nerve impulses
Which of the following electrical events occurs when a certain threshold is reached?	Action potential
Which of the following factors is associated with increased conduction velocity in an axon?	Large diameter The larger the diameter of the axon, the faster it conducts impulses.
A potential of -90 mV is considered:	hyperpolarized
During which phase of an action potential are voltage-gated K+ channels open, while voltage gated Na+ channels are closed?	Repolarizing phase
Which of the following neurotransmitters acts as a natural opiate?	Endorphins Endorphins act as naturally occurring opiates and reduce the perception of pain under certain stressful conditions.
Spatial summation occurs when:	multiple local potentials occur at different places on the same cell at the same time.
Which of the following statements concerning inhibitory synapses (IPSPs) is correct?	Postsynaptic membrane becomes more permeable to K and Cl.Most inhibitory neurotransmitters induce hyperpolarization of the postsynaptic membrane by making the membrane more permeable to K ions,Cl ions, or both.Na ion permeability is not affected.
Which of the following is NOT a biogenic amine neurotransmitter?	Acetylcholine ACh is in a chemical class by itself.
Which of the following neuroglia is most responsible for the blood-brain barrier?	Astrocytes Astrocytes cover capillaries in neural tissue.
Which of the following types of neurons is found in the retina of the eye?	Bipolar
Which of the following defines "integration"?	Processing and interpretation of sensory input and determining what should be done each moment in the body. Processing and interpretation of sensory input and determining what should be done each moment in the body is known as "integration."
Which of the following divisions of the nervous system is also known as the involuntary nervous system?	The autonomic nervous system
Organelles for degradation in the axon are moved by:	retrograde movement.
Where do axon collaterals emerge on a myelinated nerve?	From the nodes of Ranvier
Which of the following membrane ion channels in the neuron are always open?	Leakage channels
Which of the following substances plays the major role in generating the membrane potential of a neuron?	Potassium
The sodium-potassium ion pump will:	pump three sodium ions out of the cell for every two ions of potassium it brings into the cell.
A neuron will not respond to a second stimulus of equal strength to the first stimulus to which it has already responded because:	the neuron is in the absolute refractory period.
Which of the following conditions would cause synaptic potentiation?	Opening of NMDA (N-methyl-D-aspartate) receptors
Which of the following neurotransmitters is thought to be the most primitive?	ATP
Which of the following substances is NOT a neurotransmitter?	Fibrin
True or False? A reverberating circuit involves an incoming signal that travels along a chain of neurons and quickly dies out.	False Reverberating, or oscillating, circuits give continuous output signals until one neuron in the circuit fails to fire. These circuits may continue to fire for seconds, hours, or even a lifetime, such as those controlling the rhythm of breathing.
True or False? Acetylcholine is only found at the neuromuscular junction.	False Acetylcholine is a widely distributed neurotransmitter and is released by neurons that stimulate skeletal muscles and some neurons of the autonomic nervous system. It is also prevalent in the CNS.
True or False? All neurons are amitotic.	alse Although 90% of neurons are incapable of dividing, olfactory nerves and some neurons in the hippocampus retain the ability to divide and reproduce themselves throughout life.
True or False? Axons are the conducting component of the neuron, whereas dendrites are the collecting, or receiving, component.	True
True or False? The sodium/potassium pump provides energy for neurons, but does NOT affect resting membrane potential.	False The pump actually uses energy and maintains the ion concentrations that are necessary to keep a negative resting potential.
True or False? Although a variety of molecules act as neurotransmitters, amino acid neurotransmitters have NOT yet been found.	False Amino acids occur in all cells of the body. The amino acids that have been proven to be neurotransmitters are GABA, glycine, aspartate and glutamate.
True or False? Excitatory synapses can occur anywhere on a dendrite or soma, but it is at the axon hillock where an action potential is generated.	True An action potential is generated at the axon hillock.
True or False? A neuron becomes depolarized during an inhibitory postsynaptic potential (IPSP).	False An IPSP causes hyperpolarization.
True or False? Over 20% of the CNS is extracellular space.	False Nervous tissue is very cellular, and less than 20% of the CNS is extracellular space.
True or False? In neural processing, input either travels along one single pathway to a specific destination (serial) or it travels along several different pathways to integrate in different CNS regions (parallel), but NOT both.	False Processing of input in the various circuits is both serial and parallel.
True or False? The firing of one neuron can produce temporal summation. False	True, If the presynaptic neuron fires rapidly enough, neurotransmitter will be released several times in rapid succession. This produces successive EPSPs and a much greater depolarization of the postsynaptic membrane than would occur from a single EPSP.
True or False? The presence of the nodes of Ranvier speeds up the velocity of conduction along the axon.	True Nodes of Ranvier are the bare areas on myelinated axons. Myelinated axons propagate impulses by saltatory conduction, which is much faster than the propagation process that takes place in unmyelinated axons.
True or False? Unipolar neurons have a single short process that is an axon.	True. Unipolar neurons are more accurately known as pseudo unipolar neurons, because they originate as bipolar neurons. During embryonic development the two processes fuse, forming a central axon and a peripheral process that is an axon as well.
True or False? At an excitatory synapse only one type of channel is opened, allowing both sodium and potassium to diffuse simultaneously in opposite directions. This still allows depolarization to take place.	True Although both ions can flow, influx of Na+ is predominant because of the negative potential inside the cell.
True or False? The CNS is the control center for ALL human activities.	False Although the CNS is a great control center, it does NOT control everything. The endocrine system monitors some things, and certain processes are managed at the cellular level.
True or False? Schwann cells myelinate axons in the CNS.	False Schwann cells myelnate axons in the PNS only.
Nervous system	Fast-acting control system that triggers muscle contraction or gland secretion.
Central nervous system (CNS)	Brain and spinal cord.
Peripheral nervous system (PNS)	Portion of the nervous system consisting of nerves and ganglia that lie outside of the brain and spinal cord.
Afferent (sensory) nerve	Nerve that contains processes of sensory neurons and carries nerve impulses to the central nervous system.
Motor (efferent) nerves	Nerves that carry impulses leaving the brain and spinal cord, and destined for effectors.
Somatic nervous system (so-mä'tik)	Division of the peripheral nervous system that provides the motor innervation of skeletal muscles; also called the voluntary nervous system.
Autonomic nervous system (ANS)	Efferent division of the peripheral nervous system that innervates cardiac and smooth muscles and glands; also called the involuntary or visceral motor system.
Sympathetic division	The division of the autonomic nervous system that prepares the body for activity or to cope with some stressor (danger, excitement, etc.); the fight, fright, and flight subdivision.
Parasympathetic division	The division of the autonomic nervous system that oversees digestion, elimination, and glandular function; the resting and digesting subdivision.
Neuroglia (nu-rog'le-ah)	Nonexcitable cells of neural tissue that support, protect, and insulate the neurons; glial cells.
Astrocyte (as'tro-sīt)	A type of CNS supporting cell; assists in exchanges between blood capillaries and neurons.
Microglia (mi-kro'gle-ah)	A type of CNS supporting cell; can transform into phagocytes in areas of neural damage or inflammation.
Ependymal cell (ë-pen'dï-mul)	A type of CNS supporting cell; lines the central cavities of the brain and spinal cord.
Oligodendrocyte (ol”ï-go-den'dro-sīt)	A type of CNS supporting cell that composes myelin sheaths.
Schwann cell	A type of supporting cell in the PNS; forms myelin sheaths and is vital to peripheral nerve fiber regeneration.
Neuron cell body	The biosynthetic center of a neuron; also called the perikaryon, or soma.
Process	(1) Prominence or projection; (2) series of actions for a specific purpose.
Tract	A collection of axons in the central nervous system having the same origin, termination, and function.
Nerve	A bundle of axons in the peripheral nervous system.
Dendrite (den'drīt)	Branching neuron process that serves as a receptive, or input, region; transmits an electrical signal toward the cell body.
Axon	Neuron process that carries impulses away from the nerve cell body; efferent process; the conducting portion of a nerve cell.
Nerve fiber	Axon of a neuron.
Terminal branches	Branching ends of an axon that allow it to form many axon terminals; telodendria.
Axon terminals (synaptic knobs, boutons)	The bulbous distal endings of the terminal branches of an axon.
Axolemma (ak”so-lem'ah)	The plasma membrane of an axon.
Myelin sheath (mi'ë-lin)	Fatty insulating sheath that surrounds all but the smallest nerve fibers.
Unmyelinated fibers (un-mi'ë-lï-na-t”ed)	Axons lacking a myelin sheath and therefore conducting impulses quite slowly.
White matter	White substance of the central nervous system; myelinated nerve fibers.
Gray matter	Gray area of the central nervous system; contains neuronal cell bodies and their dendrites.
Multipolar neurons	Neurons with three or more processes; most common neuron type in the CNS.
Bipolar neuron	Neuron with axon and dendrite that extend from opposite sides of the cell body.
Unipolar neuron	Neuron in which embryological fusion of the two processes leaves only one process extending from the cell body.
Pseudounipolar neuron (soo”do-u”nï-po'lar)	Another term for unipolar neuron.
Interneuron (association neuron)	Nerve cell located between motor and sensory neurons that shuttles signals through CNS pathways where integration occurs.
Electrochemical gradient	The combined difference in concentration and charge; influences the distribution and direction of diffusion of ions.
Sodium-potassium (Na+-K+) pump	A primary active transport system that simultaneously drives Na^+ out of the cell against a steep gradient and pumps K^+ back in.
Depolarization (de-po”ler-ah-za'shun)	Loss of a state of polarity; loss or reduction of negative membrane potential.
Hyperpolarization	An increase in membrane potential in which the membrane becomes more negative than resting membrane potential.
Graded potential	A local change in membrane potential that varies directly with the strength of the stimulus, declines with distance.
Action potential	A large transient depolarization event, including polarity reversal, that is conducted along the membrane of a muscle cell or a nerve fiber.
Nerve impulse	A self-propagating wave of depolarization; also called an action potential.
Absolute refractory period	Period following stimulation during which no additional action potential can be evoked.
Relative refractory period	Follows the absolute refractory period; interval when a threshold for action potential stimulation is markedly elevated.
Saltatory conduction	Transmission of an action potential along a myelinated fiber in which the nerve impulse appears to leap from node to node.
Multiple sclerosis (MS)	Demyelinating disorder of the CNS; causes hardened patches (sclerosis) in the brain and spinal cord.
Synapse (sin'aps)	Functional junction or point of close contact between two neurons or between a neuron and an effector cell.
Synaptic vesicles	Small membranous sacs containing neurotransmitter.
Synaptic cleft (si-nap'tik)	Fluid-filled space at a synapse.
Synaptic delay	Time required for an impulse to cross a synapse between two neurons.
Excitatory postsynaptic potential (EPSP)	Depolarizing graded potential in a postsynaptic neuron.
Inhibitory postsynaptic potential (IPSP)	A graded potential in a postsynaptic neuron that inhibits action potential generation; usually hyperpolarizing.
Summation	Accumulation of effects, especially those of muscular, sensory, or mental stimuli.
Neuropeptides (nu”ro-pep'tīds)	A class of neurotransmitters including beta endorphins and enkephalins (which act as euphorics and reduce perception of pain) and gut-brain peptides
Cyclic AMP	Intracellular second messenger that mediates the effects of the first (extracellular) messenger (hormone or neurotransmitter); formed from ATP by a plasma membrane enzyme (adenylate cyclase)
Neuronal pools	Functional groups of neurons that process and integrate information.
Reflex	Automatic reaction to stimuli.
Cell Body	Bio synthetic Center and receptive region
Nissl Bodies	Location where neurotransmitter is made
Axon Hillock	Very beginning of axon where the first voltage regulated channels are found.
Axon	Impulse generating and conducting region (aka fiber)
Axon Collateral	branches along length of Axon
Telodendria	Any of the terminal or smaller branches of an axon; terminates with specialized ending that releases neurotransmitter.
Neuron Characteristics	1) Extreme life longevity 2) Amytotic 3) Huge ATP/Glucose requirement
CNS Nuclei	group of neuron cell bodies in the CNS
PNS Ganglia	Group of neuron cell bodies in PNS
Nerve Fiber	A long axon
Receptive Region (aka input regions)	Provide an enormous surface area for receiving signals from other neurons.
Biosynthetic center
Conducting Component	Axon; generates nerve impulses and transmits them along plasma membrane.
Secretory Component	Axon terminal
Myelination process	1)Schwann Cell envelopes an axon 2)Schwann cell then rotates around axon, wrapping plasma membrane loosely around it in layers. 3)Schwann Cell cytoplasm is forced from btwn the membranes.The tight wrappings surrounding the axon form the myelin sheath.
Significance of Myelination	Myelinated fibers conduct nerve impulses rapidly
Contrast CNS and PNS Myelination
Why is it not always easy to determine if a neuron process is an axon or a dendrite?
3 types of functional neurons	Sensory, Motor, Interneurons
Voltage	Measure of potential energy by separated charge
Polarized	State of a plasma membrane of an unstimulated neuron or muscle cell in which the inside of the cell is relatively negative in comparison to the outside; resting state.
Hyperpolarization	Occurs when the membrane potential increases, becoming more negative than the resting potential.
What is meant by integration, and does it primarily occur in the CNS or PNS?	Integration involves processing interpreting sensory information, and making a decision about motor output. Integration occurs primarily in the CNS.
Which subdivision of the PNS is involved in relaying the feeling of a "full stomach" after a meal, contracting the muscles to life your arm, increasing your heart rate?	a)full=sensory division of the PNS b)Somatic nervous system controls movement of skeletal muscle c)Autonomic Nervous System, controls heart rate.
Which type of neuroglia controls the extracellular fluid environment around neuron cell bodies in the CNS? PNS?	Astrocytes control the extracellular environment around neuron cell bodies in the CNS, where as satellite cells perform this function in the PNS.
which two types of neuroglia form insulating coverings called myelin sheaths?	Oligodendrocytes and Schwann cells form myelin sheaths in the CNS and PNS.
Which part of the neuron is its fiber? How do nerve fibers differ from the fibers of CT and the fibers in muscle?	Nerve fiber is a long axon, an extension of the cell. In CT fibers are extracellular proteins that provide support. In muscle tissue, a muscle fiber is a muscle cell.
How is nucleus within the brain different from a nucleus within a neuron?	Nucleus within the brain is a cluster of cell bodies, whereas the nucleus within each neuron is a large organelle that acts as the control center of the cell.
How is a myelin sheath formed in the CNS, and what is its function?	In the CNS, a myelin sheath is formed by oligodendrocytes that wrap their plasma membranes around the axon. The myelin sheath protects and electrically insulates fibers and increased the speed of transmission of nerve impulses.
Which structural and functional type of neuron is activated first when you burn your finger? Which type is activated last to move your finger away from the source of heat?	Burning a finger will first activate unipolar neurons that are sensory neurons. The impulse to move your finger away from the heat will be carried by multipolar neurons that are motor neurons.
For an open channel, what factors determine in which direction ions will move through that channel?	The concentration gradient and the elctrical gradient-together called the electrochemical gradient-determine the direction in which ions flow through an open membrane channel.
for which cation is there the greatest amount of leakage (through leakage channels) across the plasma membrane?	There is more leakage of K+ than of any other cations
Comparing graded potentials and action potentials, which is bigger? Which travels farthest? Which initiates the other?	APs are larger than GPs and travel futher. GPs generally initiate APs.
An action potential does not get smaller as it propagates along an axon. Why not?	An AP is regenerate anew at each membrane patch.
Why is conduction of action potentials faster in myelinated than in unmyelinated axons?	Conduction of action potentials is faster in myelinated axons because myelin allows the axon membrane between nodes to change its voltage rapidly and allows current to glow only at the widely spaces nodes.
If an axon receives two stimuli close together in time, only one AP occurs. WHY?	If a 2nd stimulus occurs before the end of the absolute refractory period, no AP can occur because sodium channel are still in activated.
What is the structure that joins two neurons at an electrical synapse?	At an electrical synapses, neurons are joined by gap junctions.
Events at a chemical synapse usually involve opening of both voltage-gated ion channels and chemically gated ion channels. Where are these ion channels located and what causes each to open?	Voltage gated ion channels are found in the presynaptic axon terminal and open when an AP reaches the axon terminal. Chemically gated ion channels are found in the post synaptic membrane and open when neurotransmitter binds to the recepton protein.
What ions flow through chemically gated channels to produce IPSPs? EPSPs?	IPSPs result from the flow of either K+ or Cl- through chemically gated channels. EPSPs result from the flow of both Na+ and K+ though chemically gated channels.
What is the difference between temporal summation and spatial summation?	Temporal:summation in time of GPs occurring in quick succession at the postsynaptic membrane. Spatial: Summation is space-a postsynaptic neuron is stimulated b y a large # of terminals at the same time.
Ach excites skeletal muscle and yet it inhibits heart muscle. How can this be?	Ach interacts with more than one specific receptor type and this explains how it can excite at the some synapses and inhibit at others.
Why is cyclic AMP called a second messenger?	cAMP is called a second messenger because it relays the message between the first messenger outside of the cell and effector molecules that will ultimately bring about the desired response within the cell.
What types of neural circuits would give a prolonged output after a single input?	Reverberating circuits and parallel after-discharge circuits both result in prolonged output.
What pattern of neural processing occurs when we blink as an object comes toward the eye? What is the response called?	The pattern of neural processing is serial processing. The response is a reflex arc.
What pattern of neural processing occurs when we smell freshly baked apple pie and remember Thanksgiving at our grandparents' house, the odor of freshly cooked turkey and other such memories?	The pattern of neural processing is parallel processing.
What is the name of the growing tip of an axon that "sniffs out" where to go during development? Waht is the general name for the chemicals that tell it where to go.	The growing tip of an axon is called a growth cone. Neurotropins are chemicals that signal the growth cone.
3 Functions of the nervous system	1. monitors information about changes occurring in/outside of the body 2.Processes/interprets the info received + integrates it to make decisions 3.Commands responses:activates muscles, glands, + other parts of nervous system.
________ cells found in the CNS are called neuroglia.	Supporting
______ are mitotic and therefore are responsible for most brain neoplasms.	Neuroglia
Schwann cells and satellite cells are found only in the ______.	PNS
_______ cells show irritability and conductivity.	Neurons
Almost 50% of the volume of neural tissue in the CNS is made up of ______.	Neuroglia
In the CNS, ____________ engulf invading microorganisms and dead neural tissue	Microglia
________ cells line the central cavities of the brain.	Ependymal
________ wrap their cytoplasmic extensions around thick neuron fibers in the CNS.	Oligodendrocytes
The bulbous ends of the ______________ cling to capillaries.	Astocytes
Axon	* Conducts impulses away from the cell body * The process called a nerve fiber
Axon terminal	* releases neurotransmitter
Cell Body	* Location of the nucleus * Most are located and protected within the CNS * Site of biosynthetic activities
Dendrite	* Conducts local currents toward the soma * Short, tapering, diffusely branched extension from the cell body.
Myelin Sheath	* Increases the speed of impulse transmission * Formed by schwann cells in the PNS * Patchy disappearance in MS
Nissl bodies	Clustered ribosomes and rough ER
Axon function	Conducting component
Axon hillock function	Trigger Zone
Axon Terminal Function	Secretory Components
Dendrite	Receptive region
3 special characteristics of neurons	* extreme life longevity * amytotic * high metabolic rate
Ganglion	Collection of cell bodies frond outside the CNS
Neurotransmitter	Chemicals released by neurons that stimulate other neurons, muscles, or glands
Nerve	bundle of axons in the PNS
Nodes of Ranvier	Gaps in a myelin sheath
Nucleus	collection of cell bodies found within the CNS
synapse	junction or point of close contact between neurons
Stimuli	Changes, occurring inside or outside the body, that activate the nervous system
tract	bundle of axons in the CNS
Absolute Refractory Period	Period when a neuron cannot be restimulated because its sodium gates are open and an AP is being generated.

Created by: ejkaboom

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