A&P checkpoint chp 12

Which of the following axons is myelinated: one that propagates action potentials at 50 meters per second, or one that carries them as 1 meter per second?

Action potentials travel along myelinated axons at much higher speeds; the axon with a propagation speed of 50 meters per second must be the myelinated axon.

Identify the neuroglia of the peripheral nervous system.

PNS neuroglia include satellite cells (amphicytes) and Schwann cells (neurilemmocytes)

Identify the three function groups into which neurotransmitters and neuromodulators fall.

(1) compounds that have a direct effect on membrane potential, (2) compounds that have an indirect effect on membrane potential, (3) lipid-soluable gases that exert their effects inside the cell.

List the steps involved in the generation and propagation of an action potential.

(1) depolarization to threshold; (2) activation of sodium channels and rapid depolarization; (3) inactivation of sodium channels and activation of potassium channels; and (4) return to normal permeability.

Are unipolar neurons in a tissue sample more likely to function as sensory neurons or motor neurons?

Because most sensory neurons of the PNS are unipolar, these neurons most likely function as sensory neurons.

One pathway in the central nervous system consists of three neurons, another of five neurons. If the neurons in the two pathways are identical, which pathway will transmit impulses more rapidly?

Because of synaptic delay, the pathway with fewer neurons will transmit impulses more rapidly.

Differentiate between a neurotransmitter and a neuromodulator.

Both neurotransmitter and neuromodulator are compounds that are released by one neuron and affect another neuron. A neurotransmitter alters the transmembrane potential of the other neuron, whereas a neuromodulator alters the other neuron's response to specific neurotransmitters.

Identify the neuroglia of the central nervous system.

CNS neuroglia include ependymal cells, astrocytes, oligodendrocytes, and microglia.

What effect would blocking voltage-gated calcium channels at a cholinergic synapse have on synaptic communication?

Calcium ions could not enter the presynaptic terminal and trigger the release of ACh into the synapse, so no communication would take place across the synapse.

Name structural components of a typical neuron.

Cell body or soma, an axon, dendrities, telodendria, Nissl bodies, neurofilaments, intermediate neurotubulues, neurofibrils, axoplasm, axolemma, initial segment, axon hillock, and collaterals.

What effect would a chemical that blocks the voltage have on a neuron's ability to depolarize?

If the voltage-gated sodium channels in a neuron's plasma membrane could not open, sodium ions could not flood into the cell, and it would not be able to depolarize.

What is the relationship between myelin and the propagation speed of action potentials?

It greatly increases the propagation speed of action potentials.

What effect would decreasing the concentration of extracellular potassium ions have on the transmembrane potential of a neuron?

More potassium would leave the cell, and the electrical gradient across the membrane (the transmembrane potential) would increase. This is called hyperpolarization.

Classify neurons according to their structure.

Neurons are classified as anaxonic, bipolar, unipolar, and multipolar

Classify neurons according to their function.

Neurons are classified as sensory neurons, motor neurons, and interneurons

25.) One EPSP depolarizes the initial segment from a resting potential of -70 mV to -65 mV, and threshold is at -60mV. Will an action potential be generated?

No action potential will be generated.

What would be the effect of damage to the afferent division of the PNS?

Since the PNS is composed of nerves that carry sensory information to brain and spinal cord, it would interfere with a person's ability to experience a variety of sensory stimuli.

Identify the two components of the efferent division of the PNS.

Somatic nervous system (SNS) and the autonomic nervous system (ANS)

If the two EPSPs in 26 occurred simultaneously, what form of summation would occur?

Spatial summation would occur if the two EPSPs happened simultaneously.

Identify the two functional divisions of the peripheral nervous system, and cite their primary functions.

The afferent division, which brings sensory information to the CNS from receptors in peripheral tissues and organs, and the efferent division, which carries motor commands from the CNS to muscles and glands.

Identify the two anatomical divisions of the nervous system.

The divisions are the central nervous system (CNS), with the brain and spinal cord, and the peripheral nervous system (PNS) with all neural tissue outside the CNS

Describe the general structure of a synapse.

The major structural components f a synapse, the site where a neuron communicates with another cell, are a presynaptic cell and a postsynaptic cell, whose plasma membranes are separated by a narrow synaptic cleft.

Define action potential.

The propagated change in the transmembrane potential of excitable cells, initiated by a change in the membrane permeability to sodium ions.

Define the resting potential.

The resting potential is the transmembrane potential of a normal cell under homeostatic conditions.

Which type of neuroglia would occur in larger-than-normal numbers in the brain tissue of a person with a CNS infection?

The small phagocytic cells called microglia occur in increased numbers in infected (and damaged) areas of the CNS

26.) Given the situation in 25, if a second, identical EPSP occurs immediately after the first, will an action potential be generated?

Yes, an action potential will be generated.

If a synapse involves direct physical contact between cells, it is termed _________; if the synapse involves a neurotransmitter, it is termed _______.

electrical; chemical