Which criterion is used to functionally classify neurons?
the direction in which the nerve impulse travels relative to the central nervous system
During depolarization, which gradient(s) move(s) Na+ into the cell?
both the electrical and chemical gradients
The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____.
K+; Na+
The Na+-K+ pump actively transports both sodium and potassium ions across the membrane to compensate for their constant leakage. In which direction is each ion pumped?
Na+ is pumped out of the cell and K+ is pumped into the cell.
The concentrations of which two ions are highest outside the cell.
Na+ and Cl-
A patient is admitted to the hospital with exacerbation of multiple sclerosis (MS). She asks the nurse "Why did this have to happen to me again? I was doing so well." Why are some forms of MS characterized by periods of remission and exacerbation?
The axons are not damaged; growing numbers of sodium channels appear spontaneously in the demyelinated fibers, allowing conduction to resume.
Which of the following are bundles of neurofilaments that are important in maintaining the shape and integrity of neurons?
neurofibrils
Which of the following is NOT a functional classification of neurons?
multipolar
Which of the following types of glial cells monitors the health of neurons, and can transform into a special type of macrophage to protect endangered neurons?
microglia
Local anesthetics block voltage-gated Na+ channels, but they do not block mechanically gated ion channels. Sensory receptors for touch (and pressure) respond to physical deformation of the receptors, resulting in the opening of specific mechanically gated
Touch stimulation of this sensory receptor will open the mechanically gated ion channels, but action potentials are still not initiated because propagation of an action potential requires the opening of voltage-gated Na+ channels.
The period after an initial stimulus when a neuron is not sensitive to another stimulus is the
absolute refractory period
Which of the following best characterizes depolarization?
small consecutive steps of Na+ penetration into the axon along its length
Which statement best describes exocytosis?
Membrane organelles fuse with the membrane and release contents out of the cell.
What conditions will increase the diffusion of molecules, such as neurotransmitters?
An increase in the amount of neurotransmitter exocytized by the presynaptic axon.
Which best represents synaptic transmission?
presynaptic axon to synapse to dendrite or postsynaptic cell body
The small space between the sending neuron and the receiving neuron is the
synaptic cleft.
A molecule that carries information across a synaptic cleft is a
neurotransmitter.
When calcium ions enter the synaptic terminal,
they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron
When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron,
ion channels in the plasma membrane of the receiving neuron open
If a signal from a sending neuron makes the receiving neuron more negative inside
the receiving neuron is less likely to generate an action potential.
Which of the following is an excitatory neurotransmitter secreted by motor neurons innervating skeletal muscle?
acetylcholine
Which of the following is not a chemical class of neurotransmitters?
nucleic acid
Which of the following neurotransmitters inhibits pain and is mimicked by morphine, heroin, and methadone?
endorphin
Which neuron circuit pattern is involved in the control of rhythmic activities such as breathing?
reverberating circuit
Nerve cell adhesion molecules (N-CAMs) ________.
are crucial for the development of neural connections