Anatomically the nervous system can be divided into two divisions. What division consists of the brain and spinal cord?
central nervous system (CNS)
Anatomically the nervous system can be divided into two divisions. What division consists of the cranial nerves and spinal nerves?
the peripheral nervous system (PNS)
What type of nerves arise from the brain?
What type of nerves arise from the spinal cord?
What type of cells are the structural and functional units of the nervous system and function to generate and transmit impulses?
What type of cells support and maintain neurons?
What are the three principle regions of a neuron?
the cell body
What part of a neuron contains the nucleus?
the cell body
What are clusters of cell bodies of neurons within the CNS?
What are clusters of nerve cell bodies within the PNS?
What part of a neuron functions as the receptive area of the cell?
What part of a neuron carries impulses away from the cell body?
What is the origin of an axon near the cell body?
the axon hillock
What are side branches of an axon?
What type of neurons conduct impulses from sensory receptors into the CNS?
sensory (afferent) neurons
What type of neurons conduct impulses away from the CNS to effectors (muscles and glands)?
motor (efferent) neurons
What type of neurons are found entirely within the CNS and function in the associative or integrative
actions of the nervous system?
association neurons (interneurons)
What type of motor neuron innervates skeletal muscle?
somatic motor neurons
What type of neuron innervates smooth muscle, cardiac muscle, and glands?
What functional division of the nervous system controls conscious perceptions and activities?
the somatic nervous system
What functional division of the nervous system controls involuntary, vital functions of the body?
the autonomic nervous system (ANS)
What are the two division of the ANS?
the sympathetic and parasympathetic divisions
What division of the ANS functions in the fight-or-flight response?
the sympathetic division
What division of the ANS functions in the rest-and-digest response?
Based on structure, what type of neuron has a single short process that branches like a T to form a pair of longer processes? These function as sensory neurons.
a pseudounipolar neuron
Based on structure, what type of neuron has two processes, one on either side?
a bipolar neuron
Based on structure, what type of neuron has several dendrites and one axon extending from the cell body? These are the most common them. Many serve as motor neurons.
a multipolar neuron
What is a bundle of neurons outside of the CNS?
What type of supporting cells of the nervous system form myelin sheaths around axons?
What type of supporting cells form myelin sheaths within the CNS?
What is the insulating covering around some axons?
the myelin sheath
What are the unmyelinated segments between Schwann cells on an axon?
nodes of Ranvier
All axons have neurilemma of myelin formed by Schwann cells, but not all axons are myelinated.
What is the difference?
Myelinated axons have several layers of myelin formed by the Schwann cells wrapping around them many times.
Oligodendrocytes form myelin sheaths around axons in the CNS, but how they do it is different. How?
Oligodendrocytes each have extensions like the tentacles of an octopus and form a sheath around several axons
What is an area of the CNS that contains a high concentration of axons?
What is an area of the CNS that contains a concentration of cell bodies and dendrites and which thus lack myelin sheaths?
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?
They are phagocytized by the surrounding Schwann cells
What is formed by Schwann cell after they have phagocytized the unattached, distal portions of
axons severed from the cell bodies of the neurons?
a regeneration tube
What are substances that promote growth in the fetal brain and function in the maintenance and
regeneration in the adult nervous system?
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?
What cells induce the formation of the blood-brain barrier?
What is formed by the tight junctions found between endothelial cells within the capillaries of the brain?
the blood-brain barrier
What is the ability to produce and conduct changes in the membrane potential?
excitability or irritability
What event takes place if positively charged ions rush into a cell thus decreasing the polarity between the inside and outside of the cell?
Following depolarization, what is the return to the resting membrane potential?
What condition occurs if the inside of a cell becomes more negative than it usually is at its resting membrane potential?
What is the effect of depolarization on a dendrite or cell body?
What is the effect of hyperpolization on a dendrite or cell body?
What are proteins that act as passageways through the cell membrane and which may be opened and closed?
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 a cell?
the electrochemical gradient
What type of gated channels open in response to depolarization?
voltage-regulated (voltage-gated) channels
When a stimulus takes a neuron to threshold, what substance causes the depolarization of the cell membrane?
When gated Na+ channels open at the beginning of depolarization, what causes Na+ ions to rush into the cell?
diffusion brought about by the electrochemical gradient
What brings about the repolarization of an axon?
the time-delayed opening of K+ channels thus allowing K+ to diffusion out of the cell
The movement of what substance brings about repolarization?
What amplifying process takes place when depolarization occurs?
a positive feedback mechanism
What is the total event produced by the depolarization and repolarization of the cell membrane?
an action potential
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?
the all-or-none law
If all action potentials along an axon are the same (and they are), how are stimuli of greater intensities coded?
an increase in the frequency (frequency modulation) and an increase in the number of axons activated (recruitment)
What is the period when an axon is incapable of responding to another stimulus, no matter how intense?
the absolute refractory period
What is the period of time when an axon is theoretically capable of responding, but only to a very strong stimulus?
the relative refractory period
What term refers to the ability of a neuron to transmit charges through its cytoplasm?
What term refers to the conduction of an impulse along an unmyelinated axon?
A stimulus must cause an neuron to reach what point before the axon will depolarize and regenerate an action potential along its length?
Once an axon has been depolarized to threshold, what action causes the depolarization to be regenerated along the length of the axon?
diffusion of Na+
What prevents an action potential from being regenerated in the wrong direction?
the refractory period
What type of conduction takes place along a myelinated axon?
What two factors increase the speed of conduction along an axon?
an increase in the diameter
What is a functional connection between a neuron and a second cell?
Within the CNS with what other cells would a neuron form a synapse?
In the PNS, with what other cells would a neuron form a synapse?
effector cells (muscle cells or glandular cells)
Neuron-neuron synapses may occur between the axon of one neuron and what parts of another neuron?
What term refers to a neuron which transmits information to a second?
What term refers to a neuron receiving information from another?
What are chemicals released by presynaptic neurons to bring about an action potential in a postsynaptic neuron?
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?
What are the presynaptic endings of axons?
What is the narrow space between the presynaptic and the postsynaptic membranes?
the synaptic cleft
What protein molecules maintain the association of the pre- and postsynaptic membranes?
cell adhesion molecules (CAMs)
What structures within the terminal button of an axon store neurotransmitters?
What process releases neurotransmitter into the synaptic cleft?
A few synaptic vesicles are always docked to the presynaptic membrane. What ion causes exocytosis to occur?
How does Ca+ enter the terminal button of an axon to bring about exocytosis?
voltage-regulated calcium channels
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?
Calmodulin activates what enzyme?
What is the action of protein kinase?
to phosphorylate other regulatory proteins
How does a neurotransmitter move across the synaptic cleft?
What molecules does a neurotransmitter interact with on the postsynaptic membrane?
What is a smaller molecule that binds to and forms a complex with a larger protein molecule (a receptor)?
What type of gates occur on the postsynaptic membrane?
chemically-regulated (ligand-regulated) gates
What is a depolarization of the postsynaptic membrane?
an excitatory postsynaptic potential (EPSP)
What is a hyperpolarization of the postsynaptic membrane?
an inhibitory postsynaptic potential
What neurotransmitter is used by somatic motor neurons at the neuromuscular junction and by some
neurons in the CNS as an excitatory transmitter?
Is ACh excitatory or inhibitory?
It may be either, depending on the organ involved
ACh receptors may be named for the type of toxin they respond to. What type responds to muscarine?
muscarinic ACh receptors
ACh receptors may be named for the type of toxin they respond to. What type responds to nicotine?
nicotinic ACh receptors
Ligand-gated channels have what two functions?
They function as receptors and gated channels
Does the all-or-none law which applies to an action potential also apply to an EPSP at a synapse?
What ions pass through ligand-gated channels?
Na+ & K+
Does a refractory period occur in association with an EPSP at a synapse?
What term describes the addition or cumulative effect of EPSPs?
What type of ACh receptor opens channels that are separate from it?
What are the possible actions of G-protein-coupled channels?
the opening or closing of K+ channels thus creating IPSPs or EPSPs
What substance inactivates ACh?
Why is the action of AChE important?
Without it spastic paralysis would occur
What is the synapse between a somatic motor neuron and a skeletal muscle fiber?
the neuromuscular junction
What neurotransmitter occurs at a neuromuscular junction?
What adjective describes a neuron that uses ACh as its neurotransmitter?
How do depolarization spread from dendrites or cell bodies to the axon hillock?
Where does an action potential along an axon begin?
at the axon hillock
Where do chemically regulated gates occur on a neuron?
dendrites and the cell body
Where do voltage-regulated gates occur on a neuron?
on the axon
What chemical family contains the molecules epinephrine, norepinephrine, dopamine, and serotonin?
The monoamines include what molecules?
What neurotransmitters are derived from tyrosine?
Epinephrine, norepinephrine, and dopamine form what subfamily of monoamines?
Like ACh, monoamines must be quickly inhibited in the synapse for neural control. What processes bring about this inhibition?
reuptake and enzymatic degradation
How do monoamines work?
through a second messenger
What product of ATP acts as a second messenger?
cyclic adenosine monophosphate (cAMP)
What type of receptor do monoamines interact with?
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?
What effect do antidepressant drugs (Prozac, Paxil. Zoloft, and Luvox) have on serotonin?
They inhibit its uptake thus increasing its effectiveness
How does serotonin have so many different influences in the brain?
It has many types of receptors
What adjective describes neurons that use dopamine as a neurotransmitter?
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?
the nigrostriatal dopamine system and the mesolimbic dopamine system
What dopamine system has cell bodies of neurons located in substantia nigra of the midbrain and is involved in Parkinsonís disease?
the nigrostriatal dopamine system
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.
mesolimbic dopamine system
What amino acid most commonly functions as an excitatory neurotransmitter in the CNS?
What amino acid functions as an inhibitory neurotransmitter in the CNS by opening channels
which allow Cl into the postsynaptic neuron? This transmitter is important in the spinal cord.
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 Huntingtonís disease.
gamma-aminobutyric acid (GABA)
What are polypeptides that function as neurotransmitters?
What are neuropeptides which are made within the brain and function to relieve pain?
What are substances that function as retrograde neurotransmitters and interact with the same receptors that accept the active ingredient in marijauna?
What two gases may function as neurotransmitters?
nitric oxide (NO)
carbon monoxide (CO)
Unlike action potentials, synaptic potentials made differ in their strength. What term describes this?
What is the adding together of synaptic potentials?
What is the addition effect of numerous presynaptic nerve fibers which converge on a single neuron and release neurotransmitter at the same time?
What the successive activity of a presynaptic terminal releasing successive waves of neurotransmitter?
What is the ability of a synapse to change at a cellular or molecular level?
What is the improved efficacy of synaptic transmission due to frequent stimulation?
long-term potentiation (LTP)
What process occurs when the stimulation of a synapse inhibits synaptic transmission afterwards?
long-term depression (LTD)
What is the inhibition produced when a neurotransmitter causes the postsynaptic membrane to hyperpolerize?
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)?