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The Nervous System
Matt Hobbs
143
Physiology
Undergraduate 3
09/28/2011

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Term
Anatomically the nervous system can be divided into two divisions. What division consists of the brain and spinal cord?
Definition
Central Nervous System (CNS)
Term
Anatomically the nervous system can be divided into two divisions. What division consists of the cranial nerves and spinal nerves?
Definition
The Peripheral Nervous System (PNS)
Term
What type of nerves arise from the brain?
Definition
Cranial Nerves
Term
What type of nerves arise from the spinal cord?
Definition
Spinal Nerves
Term
What type of cells are the structural and functional units of the nervous system and function to generate and transmit impulses?
Definition
Neurons
Term
What type of cells support and maintain neurons?
Definition
Glial Cells
Term
What are the three principle regions of a neuron?
Definition
Cell Body, Axon, Dendrites
Term
What part of a neuron contains the nucleus?
Definition
Cell Body
Term
What are clusters of cell bodies of neurons within the CNS?
Definition
Nuclei
Term
What are clusters of nerve cell bodies within the PNS?
Definition
Ganglia
Term
What part of a neuron functions as the receptive area of the cell?
Definition
Dendrites
Term
What part of a neuron carries impulses away from the cell body?
Definition
Axon
Term
What is the origin of an axon near the cell body?
Definition
The Axon Hillock
Term
What are side branches of an axon?
Definition
Axon Collaterals
Term
What type of neurons conduct impulses from sensory receptors into the CNS?
Definition
Sensory (Afferent)Neurons
Term
What type of neurons conduct impulses away from the CNS to effectors (Muscles and Glands)?
Definition
Motor (Efferent) Neurons
Term
What type of neurons are found entirely within the CNS and function in the associative or integrative actions of the nervous system?
Definition
association neurons (interneurons)
Term
What type of motor neurons innervates skeletal muscle?
Definition
Somatic Motor Neurons
Term
What type of neuron innervates smooth muscle, cardiac muscle, and glands?
Definition
Autonomic Neurons
Term
What functional division of the nervous system controls conscious perceptions and activities?
Definition
Somatic Nervous System (SNS)
Term
What functional division of the nervous system controls involuntary , vital functions of the body?
Definition
Autonomic Nervous System (ANS)
Term
What are the two divisions of the ANS?
Definition
Parasympathetic and Sympathetic
Term
What division of the ANS functions in the flight-or-flight response?
Definition
Sympathetic division
Term
What division of the ANS functions in the rest-and-digest response?
Definition
Parasympathetic division
Term
Bases on structure, what type of neuron has a single short process that branches like a T to from a pair of longer processes? These function as sensory neurons.
Definition
Pseudounipolar neurons
Term
Bases on structure, what type of neuron has two processes, one on either side?
Definition
Bipolar neuron
Term
Bases on structure, what type of neuron has several dendrites and one axon extending from the cell body? These are the most common of them. Many serve as motor neurons.
Definition
multipolar neuron
Term
What is a bundle of neurons outside of the CNS?
Definition
A nerve
Term
What type of supporting cells of the nervous system form myelin sheaths around axons?
Definition
Schwann Cells
Term
What type of supporting cells form myelin sheaths within the CNS?
Definition
Oligodendrocytes
Term
What is the insulating covering around some axons?
Definition
Myelin Sheath
Term
What are the unmyelinated segments between Schwann cells on an axon?
Definition
Nodes of Ranvier
Term
All axons have neurilemma of myelin formed by Schwann cells, bu not all axons are myelinated. What is the difference?
Definition
Myelinated axons have several layers of myelin formed by the Schwann cells wrapping around them many times
Term
Oligodendrocytes form myelin sheaths around axons in the CNS, but how they do it is different. How?
Definition
Oligodendrocytes each have extensions like the tentacles of an octopus and form a sheath around several axons
Term
What is an area of the CNS that contains a high concentration of axons?
Definition
White Matter
Term
What is an area of the CNS that contains a concentration of cell bodies and dendrites and which thus lack myelin sheaths?
Definition
Gray Matter
Term
If a nerve is severed, what happens to the portions of the axons that are no longer attached to the cell bodies of the neurons?
Definition
They are phagocytized by the surrounding Schwann Cells
Term
What is formed by Schwann cells after they have phagocytized the unattached, distal portions of axons severed from the cell bodies of the neurons?
Definition
Regeneration Tube
Term
What are substances that promote growth in the fetal brain and function in the maintenance and regeneration in the adult nervous system?
Definition
Neurotrophins
Term
What supporting cells of the CNS are large and star-shaped and make up as much as 90% of the nervous tissue in some areas of the brain?
Definition
Astrocytes
Term
What cells induce the formation of the blood-brain barrier?
Definition
Astrocytes
Term
What is formed by the tight junctions found between endothelial cells within the capillaries of the brain?
Definition
Blood-Brain Barrier
Term
What is the ability to produce and conduct changes in the membrane potential?
Definition
excitability or irritability
Term
What event takes place if positively charged ions rush into a cell thus decreasing the polarity between the inside and outside of the cell?
Definition
Depolarization
Term
Following depolarization, what is the return to the resting membrane potential?
Definition
Repolarization
Term
What condition occurs if the inside of a cell becomes more negative than it usually is at its resting membrane potential?
Definition
Hyperpolarization
Term
What is the effect of depolarization on a dendrite or cell body?
Definition
Excitatory
Term
What is the effect of hyperpolization on a dendrite or cell body?
Definition
Inhibitory
Term
What are closed proteins that act as passageways through the cell membrane and which may be opened and closed?
Definition
Gated Channels
Term
What is the difference in concentration of electrical charges and the amount of a substance, as measured for example in milliequivalents, between one area and another, for example the inside and outside of the cell?
Definition
The electrochemical gradient
Term
What type of gated channels open up in response to depolarization?
Definition
voltage-regulated (voltage-gated) Channels
Term
When a stimulus takes a neuron to threshold, what substance causes the depolarization of the cell membrane?
Definition
Na+
Term
When gated Na+ channels open at the beginning of depolarization, what causes Na+ ions to rush into the cell?
Definition
diffusion brought about the electrochemical gradient
Term
What brings about the repolarization of an axon?
Definition
the time-delayed opening of K+ channels thus allowing K+ to diffuse out of the cell
Term
What brings about the repolarization of an axon?
Definition
K+
Term
What amplifying process takes place when depolarization occurs?
Definition
A positive feedback mechanism
Term
What is the total event produced by the depolarization and repolarization of the cell membrane?
Definition
An action potential
Term
Along an axon action potentials are always of the same magnitude. There is never a partial action potential nor one of an extreme amplitude. What term explains this?
Definition
The all-or-none law
Term
If all action potentials along an axon are the same (and they are) how are stimuli of greater intensities coded?
Definition
an increase in the frequency (frequency modulation) and an increase in the number of axons activated (recruitment)
Term
What is the period when an axon is incapable of responding to another stimulus, no matter how intense?
Definition
The Absolute Refractory period
Term
What is the period of time when an axon is theoretically capable of responding, but only to a very strong stimulus?
Definition
The Relative Refractory Period
Term
What term refers to the ability of a neuron to transmit charges through its cytoplasm?
Definition
Cable Properties
Term
What term refers to the conduction of an impulse along an unmyelinated axon?
Definition
Cable Conduction
Term
A stimulus must cause an neuron to reach what point before the axon will depolarize and regenerate an action potential along its length?
Definition
The Threshold
Term
Once an axon has been depolarized to threshold, what action causes the depolarization to be regenerated along the length of the axon?
Definition
Diffusion of Na+
Term
What prevents an action potential from being regenerated in the wrong direction?
Definition
The Refractory Period
Term
What type of conduction takes place along a myelinated axon?
Definition
Saltatory Conduction
Term
What two factors increase the speed of conduction along an axon?
Definition
Myelination, and an increase in diameter
Term
What is the functional connection between a neuron and a second cell?
Definition
a synapse
Term
Within the CNS with what other cells would a neuron form a synapse?
Definition
other neurons
Term
In the PNS, with what other cells would a neuron form a synapse?
Definition
Effector cells (Muscle cells or glandular cells)
Term
Neuron-neuron synapses may occur between the axon of one neuron and what other parts of a neuron?
Definition
dendrites, cell body, axon
Term
What term refers to a neuron that transmits information to a second?
Definition
presynaptic
Term
What term refers to a neuron that receives information from another?
Definition
postsynaptic
Term
What are chemicals released by presynaptic neurons to bring about an action potential in a postsynaptic neuron?
Definition
Neurotransmitters
Term
Electrical synapses are uncommon but do exist between some neurons in the brain, some glial cells, and smooth and cardiac muscle cells. What is a synonym for them?
Definition
Gap Junctions
Term
What are the presynaptic endings of axons?
Definition
terminal buttons
Term
What is the narrow space between the presynaptic and the postsynaptic membranes?
Definition
the synaptic cleft
Term
What protein molecules maintain the association of the pre- and postsynaptic membranes?
Definition
Cell adhesion molecules (CAMs)
Term
What structures within the terminal button of an axon store neurotransmitters?
Definition
synaptic vesicles
Term
What process releases neurotransmitter into the synaptic cleft?
Definition
Exocytosis
Term
A few synaptic vesicles are always docked to the presynaptic membrane. What ion causes exocytosis to occur?
Definition
Ca+
Term
How does Ca+ enter the terminal button of an axon to bring about exocytosis?
Definition
voltage-regulated calcium channels
Term
The diffusion of Ca+ into the axon terminal activates many regulatory proteins. Which of these is a protein that is involved in many other regulatory processes?
Definition
Calmodulin
Term
Calmodulin activates what enzyme?
Definition
Protein kinase
Term
What is the action of protein kinase?
Definition
to phosphorylate other regulatory molecules
Term
How does a nrurotransmitter move across the synaptic cleft?
Definition
Diffusion
Term
What molecules does a neurotransmitter interact with on the postsynaptic membrane?
Definition
receptor proteins
Term
What is a smaller molecule that binds to and forms a complex with a larger protein molecule (a receptor)?
Definition
a ligand
Term
What type of gates occur on the postsynaptic membrane?
Definition
chemically regulated (ligand-regulated) gates
Term
What is a depolarization of the postynaptic membrane?
Definition
an excitatory postsynaptic potential (EPSP)
Term
What is the hyperpolarization of the postsynaptic membrane?
Definition
Inhibitory Postsynaptic Potential (IPSP)
Term
What neurotransmitter is used by somatic motor neurons at the neuromuscular junction and by some neurons in the CNS as an excitatory transmitter?
Definition
Acetylcholine (ACh)
Term
Is ACh excitatory or inhibitory?
Definition
It may be either depending on the organ involved
Term
ACh receptors may be named for the type of toxin they respond to. What type responds to muscarine?
Definition
muscarinic ACh receptors
Term
ACh receptors may be named for the type of toxin they respond to.What type responds to nicotine?
Definition
Nicotinic ACh receptors
Term
Ligand-gated channels have what two functions?
Definition
They function as receptors and gated channels
Term
Does the all-or-none law which applies to an action potential also apply to an EPSP at a synapse?
Definition
No
Term
What ions pass through ligand-gated channels?
Definition
Na+ & K+
Term
Does a refractory period occur in association with an EPSP at a synapse?
Definition
No
Term
What term describes the addition or cumulative effect of EPSPs?
Definition
Summation
Term
What type of ACh receptor opens channels that are separate from it?
Definition
G-Protein-Coupled channels
Term
What are the possible actions of G-Protein-Coupled channels?
Definition
The opening or closing off k+ channels thus creating IPSPs or EPSPs
Term
What substance inactivates ACh?
Definition
Acetylcholinesterase (AChE)
Term
Why is the action of AChE important?
Definition
Without it spastic paralysis would occur
Term
What is the synapse between a somatic motor neuron and a skeletal muscle fiber?
Definition
The neuromuscular junction
Term
What neurotransmitter occurs at a neuromuscular junction?
Definition
ACh
Term
What adjective describes a neuron that uses ACh as its neurotransmitter?
Definition
cholinergic
Term
How do depolarization spread from dendrites or cell bodies to the axon hillock?
Definition
Cable conduction
Term
Where does an action potential along an axon begin?
Definition
at the axon hillock
Term
Where do chemically regulated gates occur on a neuron?
Definition
dendrites and the cell body
Term
Where do voltage-regulated gates occur on a neuron?
Definition
on the axon
Term
What chemical family contains the molecules epinephrine, norepinephrine, dopamine, and serotonin?
Definition
monoamines
Term
The monoamines include what molecules?
Definition
epinephrine, norepinephrine, dopamine, and serotonin
Term
What neurotransmitters are derived from tyrosine?
Definition
epinephrine, norepinephrine, dopamine
Term
Epinephrine, norepinephrine, and dopamine form what subfamily of monoamines?
Definition
Catecholoamines
Term
Like ACh, monoamines must be quickly inhibited in the synapse for neural control. What processes bring about this inhibition?
Definition
reuptake and enzymatic degradation
Term
How do monoamines work?
Definition
through a second messenger
Term
What product of ATP acts as a second messenger?
Definition
cyclic adenosine monophosphate (cAMP)
Term
What type of receptor do monoamines interact with?
Definition
G-Protein
Term
What neurotransmitter is used by neurons with their cell bodies in the raphe nuclei along the midline of the brain stem and is derived from L-tryptophan?
Definition
serotonin
Term
What effect do antidepressant drugs (Prozac, Paxil, Zoloft, and Luvox) have on serotonin?
Definition
They inhibit its uptake thus increasing its effectiveness
Term
How does serotonin have so many different influences in the brain?
Definition
it has many types of receptors
Term
What adjective describes neurons that use dopamine as a neurotransmitter?
Definition
dopaminergic
Term
The cell bodies of dopaminergic neurons are highly concentrated in the midbrain. Their axons project to different parts of the brain and can be divided into what two systems?
Definition
the nigrostriatal dopamine system and the mesolimbic dopamine system
Term
What dopamine system has cell bodies of neurons located in substantia nigra of the midbrain and is involved in Parkinsons disease?
Definition
the nigrostriatal dopamine system
Term
What dopamine system involves neurons that originate in the midbrain and send axons to parts of the limbic system in the forebrain? This system is involved in behavior and reward and addiction
Definition
mesolimbic dopamine system
Term
What amino acid most commonly functions as an excitatory neurotransmitter in the CNS?
Definition
glutamic acid
Term
What amino acid functions as an inhibitory neurotransmitter in the CNS by openin chennels which allow CL into the postsynaptic neuron? This transmitter is important in the spinal cord.
Definition
glycine
Term
What inhibitory neurotransmitter is the most prevalent one found in the brain and is derived from glutamic acid? A deficiency of this transmitter is responsible for the uncontrolled movements seen in individuals suffering from Huntingtons disease.
Definition
gamma-aminobutyric acid (GABA)
Term
What are polypeptides that function as neurotransmitters?
Definition
neuropeptides
Term
What are neuropeptides which are made within the brain and function to relieve pain
Definition
endogenous opioids
Term
What are substances that function as retrograde neurotransmitters and interact with the same receptors that accept the active ingredient in marijuana?
Definition
endocannabinoids
Term
What two gases may function as neurotransmitters?
Definition
nitric oxide (NO) and carbone monoxide (CO)
Term
Unlike action potentials, synaptic potentials may differ in strength,. What term describes this?
Definition
graded
Term
What is the adding together of synaptic potentials?
Definition
summation
Term
What is the addition effect of numerous presynaptic nerve fibers which converge on a single neuron and release neurotransmitter at the same time?
Definition
spatial summation
Term
What successive activity of a presynaptic terminal releasing successive waves of neurotransmitter?
Definition
temporal summation
Term
What is the ability of a synapse to change at a cellular or molecular level?
Definition
synaptic plasticity
Term
What is the improved efficacy of synaptic transmission due to frequent stimulation?
Definition
long-term potentiation (LTP)
Term
What process occurs when the stimulation of a synapse inhibits synaptic transmission afterwards?
Definition
long-term depression (LTD)
Term
What is the inhibition produced when a neurotransmitter causes the postsynaptic membrane to hyperpolerize?
Definition
postsynaptic inhibition
Term
What is the inhibition produced by a decrease in the amount of neurotransmitter released due to the effect of another neuron which synapses with the axon of the first neuron(axoaxonic synapse)?
Definition
presynaptic inhibition
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