The extensions of postsynaptic neurons that provide the main receptive surface for presynaptic neurons are the
The long extension from the cell body of a neuron that provides the pathway for action potentials to the synapse is the
The substance that wraps around the axon of many neurons and provides for increased conduction speed is
generate neural impulses.
Glial cells are specialized to do all of the following except
sodium ions is higher on the outside of its membrane and of potassium ions is higher on the inside.
For the vast majority of animal cells, the concentration of
entry of Na+ ions into the cell through gated sodium channels.
The rapid depolarization of a neuron during the first half of an action potential is due to the
membrane voltage at which the membrane potential develops into an action potential.
The threshold of a neuron is the
It stimulates digestion.
Which of the following statements about the sympathetic division of the autonomic nervous system is false?
Controlled by glial cells
Synapses between a neuron and another cell can be all of the following except
bundle of axons carrying information to and from the central nervous system.
A nerve is a
Voltage-gated Na+ channels close and voltage-gated K+ channels open.
During the course of an action potential, the membrane potential rapidly spikes and then falls. What causes the fall?
concentrates potassium ions on the inside of the neuron and sodium ions on the outside of the neuron.
The sodium-potassium pump
What types of molecules in the cell serve as ion transporters and ion channels?
Only across cell membranes.
In living systems, voltage differences can exist only in locations where positive and negative charges can be separated. These differences are found
Evolutionarily, as animals increased in complexity, their nervous tissue began to cluster together. In active animals, the tissue clustered toward the head. This cluster became the _______, and the tendency to cluster toward the head is referred to as _______.
When gated channels open or close, the membrane potential of the cell changes. When the inside of a neuron becomes less negative due to the influx of Na+ ions, the membrane has
They occur along the entire axon simultaneously.
Which statement describing action potentials is false?
Action potentials normally travel in only one direction down an axon. This occurs because voltage-gated Na+ channels close rapidly but are delayed in reopening their inactivation gates. This delay contributes to the axon’s
An action potential
While recording the membrane potential of a neuron, you notice that the reading rapidly changes from -60 mV to +50 mV before returning to -60 mV. What has most likely caused this?
making transmission slower and less efficient.
Diseases such as multiple sclerosis and Guillain-Barre syndrome damage the myelin sheath that insulates and protects axons. This will likely affect the transmission of nerve impulses by
collect information from a wider range of sources.
A neuron having a large array of dendrites would be able to
If you were a postsynaptic cell waiting for an action potential to conduct information from another neuron, which part(s) of the presynaptic cell would be closest to you?
No neurotransmitter would be released into the synaptic cleft.
Toxins, such as those from the bacterium Clostridium, cause diseases such as botulism and tetanus by destroying proteins that anchor vesicles to the presynaptic membrane. How might this affect activity in the neuromuscular junction?
withdrawal reflex involving spinal nerves.
You step on a tack. Sensory receptors in your foot send action potentials via sensory neurons into the spinal cord. The sensory neurons synapse with interneurons, resulting in a(n)
convey impulses to a specific location in the CNS.
A neuron is said to be “addressed” because it is able to
The sea anemone is sessile; the deer moves forward into its environment.
A sea anemone has radial symmetry; its touch receptors and eye spots are located all around its circular body. A deer has large eyes and ears and a sensitive nose, all of which are clustered at the head end of its body. Which difference in these two organisms most likely accounts for this difference in the location of sensory organs?
After a test, Amanda relaxes, and her heart rate and breathing rate return to normal. This suggests that her _______ nervous system is activated and is releasing _______.
Before a test, Amanda is jittery, and her heart rate and breathing rate increase. This suggests that her _______ nervous system is activated and is releasing _______.