Axon terminal
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Neurotransmitters are released at the ________.
Nissl bodies
The rough ER of the cell.
Dendrites
Receptive region of the neuron.
Axon
Conducting region of the neuron.
Absolute refractory period
Period during which the neuron cannot respond to a second stimulus, no matter how strong.
Depolarization
The interior of the cell becomes less negative due to an influx of sodium ions.
Repolarization
The specific period during which potassium ions diffuse out of the neuron due to a change in membrane permeability.
Action potential
Also called a nerve impulse transmitted by axons.
Relative refractory period
An exceptionally strong stimulus can trigger a response.
Temporal summation
Numerous nerve impulses arriving at a synapse at closely timed intervals exert a cumulative effect.
Spatial summation
Stimulation of a postsynaptic neuron by many terminals at the same time.
Subthreshold stimulus
An insufficient stimulus
Threshold stimulus
Any stimulus below this intensity will result in no response in a neuron.
open ion channels to provoke rapid responses
Direct-acting neurotransmitters ________.
Current is directly proportional to the voltage
Which of the following is correct relative to Ohm's law?
ependymal cells
Ciliated CNS neuroglia that play an active role in moving the cerebrospinal fluid are called ________.
neurilemma
The sheath of Schwann is also called the ________.
found in the retina of the eye
Bipolar neurons are commonly ________.
acetylcholine
An excitatory neurotransmitter secreted by motor neurons innervating skeletal muscle is ________.
reverberating circuit
A neural circuit in which a single impulse is transmitted over and over is a ________.
absolute refractory period
The period after an initial stimulus when a neuron is not sensitive to another stimulus is the ________.
converging circuit
A neuronal circuit that concentrates or directs a large number of incoming impulses to a rather small number of neurons is called a(n) ________.
synaptic cleft
Which of the following is not a structural feature of a neuron?
axon
The part of a neuron that conducts impulses away from its cell body is called a(n) ________.
Ca2+
The chemically gated channel, NMDA, allows ________ ions entry into the nerve cell.
synapse
The point at which an impulse from one nerve cell is communicated to another nerve cell is the ________.
destroy ACh a brief period after its release by the axonal endings
The role of acetylcholinesterase is to ________.
innervation of skeletal muscle
Which of the following is not a function of the autonomic nervous system?
ganglia
Collections of nerve cell bodies outside the central nervous system are called ________.
brain and spinal cord
The term central nervous system refers to the ________.
neurotransmitter
The substance released at axon terminals to propagate a nervous impulse is called a(n) ________.
association neuron
A neuron that has as its primary function the job of connecting other neurons is called a(n) ________.
the myelin sheath
Saltatory conduction is made possible by ________.
Na
Which of these ions is actively transported through the cell membrane to establish a resting potential?
a dendrite
The part of the neuron that normally receives stimuli is called ________.
Voltage would be measured by placing one electrode inside the membrane and another outside the membrane.
Choose the statement that is most correct about membrane potential
pumps three sodium ions outside the cell and two potassium ions inside
The sodium-potassium pump ________.
is essential for impulse propagation
An action potential ________.
The synaptic cleft prevents an impulse from being transmitted directly from one neuron to another.
Select the correct statement about synapses.
nitric oxide
Which of the following is a good example of a neuromodulator?
group C fibers
Which group of fibers spreads impulses at up to 1 meter per second?
autonomic nervous system
The sympathetic and parasympathetic are subdivisions of the ________.
help to circulate the cerebrospinal fluid
Ependymal cells ________.
astrocytes
Neuroglia that control the chemical environment around neurons by buffering potassium and recapturing neurotransmitters are ________.
oligodendrocytes
Schwann cells are functionally similar to ________.
potassium
Immediately after an action potential has peaked, which cellular gates open?
are crucial for the development of neural connections
Nerve cell adhesion molecules (N-CAMs) ________.
hyperpolarization
An inhibitory postsynaptic potential (IPSP) is associated with ________.
A single type of channel will open, permitting simultaneous flow of sodium and potassium.
Which of the following will occur when an excitatory postsynaptic potential (EPSP) is being generated on the dendritic membrane?
generator potential
When a sensory neuron is excited by some form of energy, the resulting graded potential is called a(n) ________.
increase amplitude as they move away from the stimulus point
All of the following are true of graded potentials except that they ________.
Some ions are prevented from moving down their concentration gradients by ATP-driven pumps.
Which of the following is true about the movement of ions across excitable living membranes?
Serotonin
________ is an indolamine.
the membrane potential has been reestablished
A second nerve impulse cannot be generated until ________.
negatively charged and contains less sodium
In what way does the interior surface of a cell membrane of a resting (nonconducting) neuron differ from the external environment? The interior is ________.
the impulse would spread bidirectionally
If a motor neuron in the body were stimulated by an electrode placed about midpoint along the length of the axon ________.
Group C fibers are not capable of saltatory conduction.
Neurons may be classified according to several characteristics. Which of the following is correct?
Spinal reflexes are an example of serial processing.
Select the correct statement about serial processing.
somatic
That part of the nervous system that is voluntary and conducts impulses from the CNS to the skeletal muscles is the ________ nervous system.
Astrocytes
________ are found in the CNS and bind axons and blood vessels to each other.
node of Ranvier
A gap between Schwann cells in the peripheral system is called a(n) ________.
Ohm's
________ law is the relationship between voltage, current, and resistance.
electrical synapse
The synapse more common in embryonic nervous tissue than in adults is the ________.
parallel
When information is delivered within the CNS simultaneously by different parts of the neural pathway, the process is called ________ processing.
Graded
________ potentials are short-lived, local changes in membrane potential that can be either depolarized or hyperpolarized.
Multiple sclerosis (MS)
________ is a disease that gradually destroys the myelin sheaths of neurons in the CNS, particularly in young adults.
temporal
When one or more presynaptic neurons fire in rapid order it produces a much greater depolarization of the postsynaptic membrane than would result from a single EPSP; this event is called ________ summation.
GABA (gamma aminobutyric acid)
________ is a neurotransmitter of the CNS that is used by Purkinje cells of the CNS.
Neurotransmitters are chemical signals used as a means of communication. GABA and glycine are amino acid neurotransmitters; dopamine and norepinephrine are catecholamines; and endorphin and enkephalin are peptide transmitters.
Define neurotransmitter. Name two amino acid neurotransmitters, two catecholamines, and two peptides.
Increased diameter results in increased surface area on the membrane for sodium channels. This results in increased speed of impulse propagation.
What function is served by the increased axon diameter at the nodes of Ranvier?
Both excitatory and inhibitory potentials impinge on neurons. Inhibitory postsynaptic potentials (IPSPs) are "firing," but due to the neurotransmitter released and its action, the postsynaptic neuron is inhibited from "firing" (hyperpolarized).
Imagine a neuron that has several hundred axonal knobs impinging on it. The majority of these axonal knobs are shown to be "firing." However, the neuron in question does not transmit an impulse. Give a valid explanation of why this could occur.
Immediately after an action potential the potassium gates, being slow gates which do not respond to change in the electrical charge, allow additional K+ ions to flood into the cell. These K+ ions decrease the positive ion concentration momentarily below t
Why does a hyperpolarization phase generally follow a repolarization phase in an action potential?
Sensory and motor divisions. Motor has two divisions: the somatic and autonomic. The autonomic has two divisions: the sympathetic and parasympathetic.
What are the basic divisions of the peripheral nervous system?
The importance of a stimulus is derived from the number of stimuli received from the same source. The frequency of impulse transmission indicates the stimulus intensity and the brain responds appropriately.
Since all action potentials are alike, how does the brain separate situations that require immediate attention from ordinary "positional" reports?
Some axon terminals contain more than one kind of neurotransmitter. Therefore, the axon can release one or more neurotransmitters simultaneously, creating singular or multiple events.
How can a single axon respond to several different kinds of events?
They provoke a sensation of pain.
ATP neurotransmitters have what basic effect on the body?
These gasses are neurotransmitters that act indirectly. Similar to hormones, NO and CO promote longer-lasting effects by acting through intracellular second-messenger molecules.
How can potentially poisonous gasses like NO and CO be used by the body?