Exam 4: Principles of Neural and Hormonal Communication

Use these figures to answer the corresponding questions. Which number identifies the structure that is primarily responsible for the absolute refractory period during an action potential? a. 1 b. 2 c. 3-5 d. 4 e. No number identifies this structure.

Complete each of the following statments. When EPSPs occurring simultaneously from two different presynaptic inputs add together or sum to bring the postsynaptic cell to threshold, it is called ____________________.

Divergence refers to the neuronal arrangement wherein the dendrites diverge to synapse with as many presynaptic inputs as possible.

The nodes of Ranvier are Schwann cells or oligodendrocytes that wrap themselves "jelly roll fashion" around the axon.

At an excitatory synapse, an action potential in the presynaptic neuron increases the

Neuron A is excitatory to neuron B. Describe three ways that the nervous system might prevent neuron B from experiencing an action potential.

The absolute refractory period

The refractory period limits the frequency of action potentials.

Complete each of the following statments. When EPSPs originating from a single presynaptic input occur so close together in time that they add together or sum, thereby bringing the postsynaptic cell to threshold, it is called ____________________.

Complete each of the following statments. Axon terminals possess ____________________ voltage-gated channels that when operational induce neurotransmitter release.

An unmyelinated fiber with a large diameter can conduct action potentials more rapidly than an unmyelinated fiber with a smaller diameter.

When an excitatory neurotransmitter binds to a postsynaptic neuron

The tyrosine-kinase pathway is activated in response to certain lipophilic hormones, whereas the second messenger pathway is activated in response to certain hydrophilic hormones.

The falling phase of the action potential is due to

Which statement about a graded potential is false?

Permeability of which ion is affected by a positive feedback mechanism once threshold is reached?

Use these figures to answer the corresponding questions. The structure labeled "4" is a. part of a channel that allows Na+ ions to diffuse into the ECF b. the activation gate for a gated K+ channel c. the inactivation gate for a gated Na+ channel d. part of a second messenger system e. the activation gate for a gated K+ channel and part of a second messenger system

When the membrane potential is +15 mV, that portion of the membrane

Neuropeptides are mainly neuromodulators that function as second messengers in cells that respond to hydrophilic hormones.

The myelin on a myelinated fiber in the peripheral nervous system is part of Schwann cells wrapped around the axon.