Name:
A&P
Date:
Evaluating Understanding & Applying Knowledge:
Fundamentals of the Nervous System & Nervous Tissue (Chp 11)
1. Describe the events that must occur to generate an action potential. Indicate how the ionic gates are
controlled, and explain why the action potential is an all-or-none phenomenon.
2. Since all action potentials generated by a given nerve fiber have the same magnitude, how does the CNS
“know” whether a signal is strong or weak?
3. During a neurobiology lecture, a professor repeatedly refers to type A and type B fibers, absolute refractory
period and nodes of Ranvier. Define these terms.
Go on to the next page 
4. Explain an IPSP. What determines whether an EPSP or an IPSP will be the difference between as EPSP and
generated at the post-synaptic membrane?
Critical Thinking:
1. How do drugs, such as Novocaine, effectively block the transmission of pain impulses? Why don’t they
transmission of motor impulses, or do they?
2. How can some people eat hot peppers without experiencing the same pain that others normally have?
Name:
A&P
Date:
Evaluating Understanding & Applying Knowledge:
Fundamentals of the Nervous System & Nervous Tissue (Chp 11)
1. Describe the events that must occur to generate an action potential. Indicate how the ionic gates
are controlled, and explain why the action potential is an all-or-none phenomenon.
a. The generation of an action potential involves 3 main events. (1) an increase in sodium permeability and
the reverse of the membrane potential, as the sodium gates are opened briefly an sodium rushed in. (2) A
decrease in sodium permeability, as the gates close back up. (3) an increase of potassium permeability and
repolarization.
b. The ionic gates are controlled by changes in the membrane potential and activated by local currents.
c. The all-or-none phenomenon means that the local depolarizing current must reach critical “firing” or
threshold point before it will respond, and when it responds, it will respond completely by conducting the
action potential along the entire length of its axon.
2. Since all action potentials generated by a given nerve fiber have the same magnitude, how does the
CNS “know” whether a signal is strong or weak?
The CNS “knows” a stimulus is strong when the frequency or rate of action potential generation is high.
3. During a neurobiology lecture, a professor repeatedly refers to type A and type B fibers, absolute
refractory period and nodes of Ranvier. Define these terms.
Type A fibers – large diameter and thick myelin sheaths, conduct nerve impulses quickly
Type B fibers – lightly myelin with smaller diameters, conduct impulses more slowly
Absolute refractory period is when the neuron is incapable of responding to another stimulus because sodium
gates are still open or inactive.
A node of Ranvier is an interruption of the myelin sheath between the wrapping of individual Schwann cells or
of the oligodendrocyte processes.
Go on to the next page 
4. What determines whether an EPSP or an IPSP will be the difference between as EPSP and generated
at the post-synaptic membrane?
An EPSP is an excitatory (depolarizing) postsynaptic potential that increases the chance of a depolarization
event. Depolarizing occurs because allows both sodium and potassium ions to diffuse. Since the gradient for
sodium is higher, it rushes in compared to potassium and a net depolarization occurs. An IPSP is an inhibitory
(hyperpolarizing) post synaptic potential that decreases the chance of a depolarizing event.
Hyperpolarization occurs because the membrane is more permeable to potassium ions, chloride ions or both.
The type and amount of neurotransmitter that binds at the post-synaptic neuron and the specific receptor
subtype it binds to determines which type of event will occur.
Critical Thinking:
5. How do drugs, such as Novocaine, effectively block the transmission of pain impulses? Why don’t they
transmission of motor impulses, or do they?
Reduce membrane permeability to sodium ions. Motor neurons direct a response and blocking their impulses
will not affect perception of pain.
6. How can some people eat hot peppers without experiencing the same pain that others normally have?
May have less receptor sites or altered receptor sites for the capsaicin.
Chronic exposure weakens the response and enhances endorphin release.