Chapter 11 human anatomy and physiology

opening and then closing of the Na+ channels

A. depolarization phase in the generation of an action potential

Which of the following is NOT a biogenic amine neurotransmitter? serotonin dopamine norepinephrine epinephrine acetylcholine

Acetylcholine

Which of the following electrical events occurs when a certain threshold is reached? action potential resting membrane potential EPSP IPSP

Action potential

Which of the following statements best describes the membrane situation in the resting state in the neuron? All the voltage-gated Na+ and K+ channels are closed. Only the voltage-gated K+ channels are open. Only the voltage-gated K+ are closed. Only the voltage-gated Na+ channels are open. Only the voltage-gated Na+ channels are closed.

All the voltage-gated Na+ and K+ channels are closed.

Which of the following neuroglia is most responsible for helping determine capillary permeability in nervous tissue? microglia Schwann cells astrocytes oligodendrocytes ependyma

Astrocytes

Which of the following is a rare type of sensory neuron that is found in special sensory structures like the retina of the eye? unipolar pseudounipolar multipolar bipolar

Bipolar

Which of the following events is NOT involved in the transfer of information across a chemical synapse? Ions flow directly from one neuron to the next. Ion channels open in the postsynaptic membrane. A neurotransmitter is released by exocytosis. Calcium channels open in the presynaptic region. Neurotransmitters bind to the postsynaptic receptors.

Direct flow of ions from one neuron to the next

Which of the following neurotransmitters acts as a natural opiate?

Endorphins

Which of the following line the central cavities of the brain and spinal cord and provide a fairly permeable barrier between the CSF and nervous tissue?

Ependymal cells

Acetylcholine is released only by neurons at neuromuscular junctions.

FALSE Acetylcholine is a widely distributed neurotransmitter and is released by neurons that stimulate skeletal muscles and some neurons of the autonomic nervous system. It is also prevalent in the CNS.

All neurons are amitotic

FALSE Although 90% of neurons are incapable of dividing, olfactory nerves and some neurons in the hippocampus retain the ability to divide and reproduce themselves throughout life.

The CNS is the control center for ALL human activities.

FALSE Although the CNS is a great control center, it does NOT control everything. The endocrine system monitors some things, and certain processes are managed at the cellular level.

Although a variety of molecules act as neurotransmitters, amino acid neurotransmitters have NOT yet been found.

FALSE Amino acids occur in all cells of the body. The amino acids that have been proven to be neurotransmitters are GABA, glycine, aspartate and glutamate.

A neuron becomes depolarized during an inhibitory postsynaptic potential (IPSP).

FALSE An IPSP causes hyperpolarization.

Due to the amount of space between cells, over 30% of the CNS is extracellular space.

FALSE Nervous tissue is very cellular, and less than 20% of the CNS is extracellular space.

In neural processing, input either travels along one single pathway to a specific destination (serial) or it travels along several different pathways to integrate in different CNS regions (parallel), but NOT both.

FALSE Processing of input in the various circuits is both serial and parallel.

A reverberating circuit involves an incoming signal that travels along a chain of neurons and quickly dies out.

FALSE Reverberating, or oscillating, circuits give continuous output signals until one neuron in the circuit fails to fire. These circuits may continue to fire for seconds, hours, or even a lifetime, such as those controlling the rhythm of breathing.

Schwann cells myelinate axons in the CNS.

FALSE Schwann cells myelnate axons in the PNS only.

The sodium-potassium pump provides energy for neurons, but does NOT affect resting membrane potential.

FALSE The pump actually uses energy and maintains the ion concentrations that are necessary to keep a negative resting potential.

From where can collaterals emerge on a myelinated nerve?

From the nodes of Ranvier

Neurons can be classified structurally by the number of processes extending from their cell bodies. Which of the following is the most common neuron type in humans?

Multipolar

Which of the following substances is NOT a neurotransmitter? epinephrine carbon dioxide acetylcholinesterase histamine

acetylcholinesterase

Caffeine's stimulatory effects result from blocking receptors for which neurotransmitter?

adenosine

Which of the following conditions would cause synaptic potentiation? opening of NMDA (N-methyl-D-aspartate) receptors and influx of Ca++ opening of voltage-gated K+ channels closure of NMDA (N-methyl-D-aspartate) receptors influx of Na+ channels

Opening of NMDA (N-methyl-D-aspartate) receptors

`Which of the following characteristics is NOT associated with a myelinated nerve fiber?

Slow conduction of nerve impulses

the all-or-none phenomenon

an action potential occurring only if enough Na+ enters the cell and threshold is achieved

At an excitatory synapse, only one type of channel is opened, allowing both sodium and potassium to diffuse simultaneously in opposite directions. This still allows depolarization to take place.

TRUE Although both ions can flow, influx of Na+ is predominant because of the negative potential inside the cell.

Excitatory synapses can occur anywhere on a dendrite or soma, but it is at the axon hillock where an action potential can be generated.

TRUE An action potential is generated at the axon hillock.

Axons are the conducting component of the neuron, whereas dendrites are the collecting, or receptive, component.

TRUE Axons generate nerve impulses and transmit them. Dendrites are the receptive input regions of the neuron, and they provide enormous surface area for receiving information from other neurons.

The firing of one neuron can produce temporal summation.

TRUE If the presynaptic neuron fires rapidly enough, neurotransmitter will be released several times in rapid succession. This produces successive EPSPs and a much greater depolarization of the postsynaptic membrane than would occur from a single EPSP.

The presence of the nodes of Ranvier speeds up the velocity of conduction along the axon.

TRUE Nodes of Ranvier are the bare areas on myelinated axons. Myelinated axons propagate impulses by saltatory conduction, which is much faster than the propagation process that takes place in unmyelinated axons.

Unipolar neurons are more accurately called pseudounipolar neurons.

TRUE Unipolar neurons are more accurately known as pseudo unipolar neurons, because they originate as bipolar neurons. During embryonic development the two processes fuse, forming a central axon and a peripheral process that is an axon as well.

saltatory conduction

conduction process in myelinated axons where the electrical signal appears to jump from gap to gap along the axon

Which of the following membrane ion channels in the neuron are always open? mechanically gated channels leakage channels ligand-gated channels voltage-gated channels

leakage channels

Spatial summation occurs when __________.

multiple local potentials occur at different places on the same cell at the same time

Which of the following substances plays the major role in generating the membrane potential of a neuron through its passive movement? urea sodium chloride potassium

potassium

The interior of a nerve cell has a slight excess of negative charge because __________.

potassium diffuses out of the cell.

The sodium-potassium ion pump will __________

pump three sodium ions out of the cell for every two ions of potassium it brings into the cell.

reflexes

rapid automatic responses to a stimulus in which the particular stimulus always produces the same motor response

Organelles for degradation or recycling are moved through the axon by __________.

retrograde movement

The sensory, or afferent, division of the peripheral nervous system transmits information from the __________ to the CNS.

skin

from the opening of the Na+ channels until the Na+ channels begin to reset to their original resting state

the absolute refractory period

multiple sclerosis

the autoimmune disease that leads to destruction of the myelin sheaths in the CNS

Which of the following divisions of the nervous system is also known as the involuntary nervous system? the peripheral nervous system the autonomic nervous system the somatic nervous system the spinal division of the nervous system

the autonomic nervous system

A neuron will not respond to a second stimulus of equal strength to the first stimulus to which it has already responded because __________.

the neuron is in the absolute refractory period.

excessive potassium efflux as a result of relatively slower closure of the potassium gates

the phase in an action potential known as the "after hyperpolarization"

opening of potassium gates and the rushing out of K+

the repolarization phase in an action potential

all voltage-gated Na+ and K+ channels are closed

the resting state of a neuron

Which of the following factors is associated with increased conduction velocity in an axon? the absence of the myelin sheath small diameter large diameter presence of collaterals increased number of dendrites

Large diameter

Which of the following statements concerning inhibitory synapses (IPSPs) is correct? The postsynaptic membrane becomes less permeable to sodium. Channels allow both sodium and potassium ions to diffuse simultaneously through the membrane. The permeability of the postsynaptic membrane to sodium, potassium, and chloride is not changed. The postsynaptic membrane becomes more permeable to potassium and chloride. The postsynaptic membrane becomes less permeable to potassium.

Postsynaptic membrane becomes more permeable to potassium and chloride.

Which of the following defines integration? monitoring changes both inside and outside the body processing and interpretation of sensory input and determining what should be done at each moment in the body increasing the level of one substance in response to a decrease in the level of another activating effector organs

Processing and interpretation of sensory input and determining what should be done each moment in the body

During which phase of an action potential are voltage-gated K+ channels open, while voltage-gated Na+ channels are closed?

Repolarizing phase

The Nissle bodies seen in the neuron cell body represents which cellular organelle?

Rough endoplasmic reticulum

Which of the following statements about the developmental aspects of neurons is INCORRECT? Axons are attached to grow toward their "target" by multiple signals such as the nerve growth factor, the nerve cell adhesion factor, and older pathfinder neurons. The number of adult neurons is the same as the number formed during the embryonic period. Neuroepithelial cells become the CNS and then go through three phases of differentiation during maturation. They develop from neuroepithelial cells. Neurons that fail to make the appropriate synaptic contact will not receive appropriate nutrients and will die.

The number of adult neurons is the same as the number formed during the embryonic period.

A potential of -90 mV is considered __________.

hyperpolarized.

G-protein-linked receptors

indirect synaptic responses that are complex, prolonged, and often diffuse as a result of the production of intracellular second-messenger molecules