Anatomy Exam - second to last
Action potentials (nerve impulses) are changes in the membrane potential that, once started, will affect the entire excitable membrane. The first action potential is usually generated at the initial segment of the neuron's axon. This activity will test your understanding of the sequence of events that occur at the membrane of the initial segment of the axon during generation of an action potential.
1. Threshold stimulus; Na+ channels open 2. Na+ influx; depolarization 3. Na+ channels close; K+ channels open 4. K+ efflux; Repolarization 5. Hyperpolarization; K+ channels close
Which of the following is NOT correct concerning nerves?
Nerves are collection of axons of either sensory or motor neurons but not both
Imagine that the cell membrane from the previous problem becomes more permeable to Na+. Predict how this will affect the RMP.
The RMP will be more positive.
You are going to record RMP from a cell using an electrode. You place your electrode and record a resting membrane potential every millisecond. You record an initial value of -70mV; however, over time you notice that your recordings become more and more positive until the RMP reaches 0mV. Assuming that Na+ and K+ are the major determinants of RMP in this cell, which of the following could best explain your results?
The cell's Na+ -K+ ATPase pumps have stopped functioning.
Why does regeneration of the action potential occur in one direction, rather than in two directions?
The inactivation gates of voltage-gated Na+ channels close in the node, or segment, that has just fired an action potential.
What is the function of the myelin sheath?
The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.
When calcium ions enter the synaptic terminal _______
They cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron
Which choice best characterizes K+ leakage channels?
Transmembrane protein channels that are always open to allow K+ to cross the membrane without the additional input of energy.
Which of the following cranial nerves carries only motor information?
abducens
Cold sores on the skin of the mouth occur when herpes simplex viruses that are dormant in neural ganglia become active and travel to the skin of the mouth. Which of the following is the mechanism by which these viruses travel from the ganglia (located within the head) to the skin of the mouth?
anterograde transport
The meningeal layer resembling spider legs is the......
arachnoid mater
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
The part of a spinal nerve that innervates the meninges is the _______
meningeal branch
Complete the following sentence. The operation of the Na+−K+ ATPase pump __________.
moves 3 Na+ to the ECF and 2 K+ to the cytoplasm
A molecule that carries information across a synaptic cleft is a _________
neurotransmitter
In multiple sclerosis, the cells that are the target of an autoimmune attack are the _________.
oligodendrocytes
Let's consider a scenario in which the resting membrane potential changes from −70 mV to +70 mV, but the concentrations of all ions in the intracellular and extracellular fluids are unchanged. Predict how this change in membrane potential affects the movement of Na+. The electrical gradient for Na+ would tend to move Na+ __________ while the chemical gradient for Na+ would tend to move Na+ __________.
out; in
Receptors that respond to light are _________
photoreceptor
Which of the following lists the hierarchy of motor control from lowest to highest level of control?
segmental level projection level precommand level
division of the nervous system controls skeletal muscle.,,,,,
somatic motor
The small space between the sending neuron and the receiving neuron is the __________
synaptic cleft
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 cranial nerve innervates most of the visceral organs?
vagus
The generation of an action potential in a neuron requires the presence what type of membrane channels?
voltage-gated channels
The concentrations of which two ions are highest outside the cell?
Na+ and Cl−
Assume you have a membrane with only potassium leakage channels. The RMP is -90mV. Predict the RMP if we add Na+ leakage channels.The most likely RMP value of Na+ is __________
-70 mV
Cl− is a common, negatively charged extracellular ion. Predict the effect on the RMP if many Cl− gated channels are suddenly opened.
A more negative RMP would result.
What type of conduction takes place in unmyelinated axons?
Continuous conduction
You are removing a hot pan of cookies from the oven, using a pot holder. Suddenly, you feel a surge of heat through the pot holder. Why don't you react by dropping the baking pan and spilling cookies all over the floor?
Cortical integration centers override the spinal reflex.
The concentration of _______ is higher outside than inside the cell.
Na+
What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?
Inactivation gates of voltage-gated Na+ channels close, while activation gates of voltage-gated K+ channels open.
The concentration of ________ is higher inside than outside the cell.
K+
The membrane is more permeable to __________
K+
The resting membrane potential is maintained by Na+-K+ pumps that actively transport _______ into and _______ out of the cell
K+ Na+
In which type of axon will velocity of action potential conduction be the fastest?
Myelinated axons with the largest diameter
Evolutionary development of a head and brain containing neural and sensory organs is a process called.........
cephalization
Bleeding in the brain, known as a stroke, is more accurately called................
cerebrovascular accident
The phrenic nerve is a branch from the __________.
cervical plexus
The senses of taste and smell use ________ to detect and process taste and smell information.
chemoreceptors
Nerves that emerge from the base of the brain and pass through the skull are ______ nerves
cranial
Which reflex is triggered when a stranger suddenly grasps your arm?
crossed-extensor reflex
An action potential is self-regenerating because __________.
depolarizing currents established by the influx of Na+ flow down the axon and trigger an action potential at the next segment
What is the specific function of the structure labeled F?
determine amount of muscle stretching
Which connective tissue layer directly surrounds individual axons in a nerve?
endoneurium
