Chapter 9 Nervous System

Motor Neurons (efferent)

Are multipolar and conduct impulses out of the brain or spinal cord to effectors. Motor impulses control muscle contraction and the secretion glands.

Sensory Neurons (afferent)

Conduct impulses from peripheral body parts into the brain or spinal cord.

Which types of neurons are likely to increase muscular activities? A)accelerator neurons B)inhibitory neurons C)bipolar neurons D)sensory neurons

accelerator neurons

Myasthenia gravis reflects a deficiency in communication by _______________ because receptors for this neurotransmitter have been destroyed. A)acetylcholine B)norepinephrine C)GABA D)dopamine

acetylcholine

The most common neurotransmitter in the body is _____. A)serotonin B)dopamine C)acetylcholine D)norepinephrine

acetylcholine

Branched nerve fibers that convey impulses toward the cell body of a neuron are called _____________. A)axons B)dendrites C)axon collaterals D)axon terminals

dendrites

refractory period

ensures that the impulses progress in only one direction- down the axon. because the area upstream from where the action potential has just occurred is still in the refractory period from the previous action.

Which type of neuroglial cells help regulate the composition of cerebrospinal fluid?A)astrocytes B)oligodendrocytes C)microglia D)ependyma

ependyma

Cerebrospinal Fluid (CSF)

fluid in the ventricles of the brain, subarachnoid space of the meninges, and the central canal of the spinal cord.

The _______________ are the types of neuroglial cells that provide myelin in the central nervous system. A)astrocytes B)oligodendrocytes C)microglia D)ependyma

oligodendrocytes

PNS (peripheral nervous system)

parts of the nervous system outside the brain and the spinal cord; cranial nerves and spinal nerves

microglial cell

phagocytic glial cell that removes waste products from the central nervous system

Axon Collaterals

Side branches of axon, carry signal to other cells.

nerve impulse conduction

1. neuron membrane maintains resting potential. 2. threshold stimulus is received. 3. sodium channels in the trigger zone of the axon ope. 4. potassium channels in the axon membrane open. 5. potassium ions diffuse outward, repolarizing the axon membrane. 7. the resulting action potential causes a local electric current that stimulates the adjacent portions of the axon membrane. 8. a series of action potentials occurs along the axon wall.

dopamine

A neurotransmitter associated with movement, attention and learning and the brain's pleasure and reward system.

norepinephrine

A neurotransmitter involved in arousal, as well as in learning and mood regulation

serotonin

A neurotransmitter that affects hunger,sleep, arousal, and mood.

acetylcholine

A neurotransmitter that enables learning and memory and also triggers muscle contraction

False

All neurons have at least one dendrite but one or more axons.

GABA

An inhibitory neurotransmitter in the brain.

Axon Terminals

Fine processes at the end of axons.

Unipolar neurons (pseudounipolar)

Have a single process extending from the cell body. A short distance from the cell body, this process divides into two branches, which function as a single axon. One branches off near a peripheral body part and the other enters the brain or spinal cord.

Bipolar Neurons

Have only two processes, one arising from each end of the cell body. These processes are structurally similar, but one is an axon and the other a dendrite. Neurons in specialized parts of the eyes, nose, and ears are bipolar.

True

Impulses within a neuron always travel from the dendrite towards the axons.

Accelerator Neurons

Increase muscular activities

Interneurons (association or internuncial)

Lie entirely within the brain or spinal cord. They are multipolar and link other neurons.

Myelin Sheath

Lipid-rich layer formed from certain neuroglia that wraps around an axon, providing insulation.

Secretory Vesicles

Mediates the vesicular transport of hormones or neurotransmitters from an organelle to specific sites at the cell membrane.

False

Motor neurons receive impulses from the muscles in order to regulate glandular secretions.

True

Motor neurons usually have a more complex structure than sensory neurons.

Microglia

Neuroglia of the CNS that support neurons and phagocytize bacterial cells and cellular debris.

Ependyma Cells

Neuroglia that line the ventricles of the brain and the central canal of the spinal cord.

Repolarization

Period during which potassium ions diffuse out of the neuron

Dendrites

Process of a neuron that receives input from other neurons.

Astrocytes

Provide structural and metabolic support for neurons.

Cut neurons possess limited capabilities for regeneration. The type of neuroglial cell that aids regeneration by forming a regeneration tube to help reestablish the former connection is the _______________. A)Schwann cell B)astrocyte C)microglial cell D)ependymal cell

Schwann cell

The myelin sheath around a neuron is actually produced by the: A)neuron B)axon C)dendrite D)Schwann cell

Schwann cell

Myelin sheaths on the outsides of many axons are contributed by ______________. A)the axon itself B)secretory vesicles C)Schwann cells D)the cell bodies of the neuron

Schwann cells

True

The enzyme acetylcholinesterase acts to inhibit the stimulation between neurons.

False

The nodes of Ranvier function in slowing the conduction of the impulse.

True

The nucleus of a neuron is always located within the cell body region.

False

The oligodendrocytes are capable of producing the myelin sheath that will wrap around a spinal nerve.

Axons

The process that conducts an impulse away from the neuron cell body. A nerve fiber.

Select the incorrect statement about nerve impulse conduction. A)Saltatory conduction involves Schwann cells and occurs at greater speed than on unmyelinated fibers. B)Nerve impulses occur in an all-or-none manner. C)The neuron cannot be stimulated during the absolute refractory period. D)The strength of impulses carried along a single nerve fiber can vary with the strength of their stimulus.

The strength of impulses carried along a single nerve fiber can vary with the strength of their stimulus.

Oligodendrocytes

Type of glial cell in the CNS that wrap axons in a myelin sheath.

Schwann Cell

Type of neuroglia that surrounds an axon of a peripheral neuron, forming the neurilemma and myelin sheath.

False

When a neuron is resting, the outside has more potassium ions than the inside.

Myasthenia gravis

a chronic autoimmune disease that affects the neuromuscular junction and produces serious weakness of voluntary muscles

convergence

a coming together. two or more presynaptic neurons forming synapses with the same postsynaptic neuron.

Nerves impulses always travel to the brain through _____ fibers. A)neuron B)dendrite C)nerve D)axon

axon

CNS (central nervous system)

consists of the brain and spinal cord

Fibers that originate from different parts of the nervous system and lead to the same neuron are exhibiting _____________. A)facilitation B)convergence C)divergence D)neuromodulation

convergence

ependymal cell

glial cell that lines membranes within the brain and spinal cord and helps form cerebrospinal fluid

Multipolar Neurons

have many processes arising from their cell bodies. Only one process of each neuron is an axon; the rest are dendrites. Most neurons whose cell bodies lie within the brain or spinal cord are multipolar.

In response to a stimulus, if the membrane potential becomes more negative than the resting potential, we say the membrane is _______________. A)hyperpolarized B)depolarized C)unpolarized D)polarized

hyperpolarized

Hyperpolarization

membrane potential becomes more negative which occurs in one-thousandth of a second (one milliseconds)

The _____ cells are capable of removing a blood clot from the brain. A)astrocyte B)oligodendrocyte C)microglia D)ependymal

microglia

When a neuron reaches action potential, it depolarizes and repolarizes in an amount of time on the order of ________________. A)seconds B)milliseconds C)microseconds D)nanoseconds

milliseconds

A neuron with many nerve fibers arising from its cell body and that carries impulses away from the brain would be classified as __________________. A)multipolar B)bipolar C)unipolar and sensory D)multipolar and motor

multipolar and motor

Which of these cells does not belong with the others? A)microglia B)neuron C)astrocyte D)oligodendroglia

neuron

The levels of which neurotransmitter are affected by the mood-elevator, cocaine? A)serotonin B)GABA C)norepinephrine D)acetylcholine

norepinephrine

facilitation

repeated impulses on an excitatory presynaptic neuron may cause that neuron to release more neurotransmitter in response to a single impulse, making it more likely to bring the postsynaptic cell to threshold

The cells that conduct messages towards the brain are the: A)motor neurons B)sensory neurons C)interneurons D)neuroglia

sensory neurons

polarized

separation of positive and negative charges across the membrane, such that the inside is negative compared to the outside.

Excessive sleeping is most likely due to the presence of too much of which neurotransmitter? A)GABA B)norepinephrine C)serotonin D)dopamine

serotonin

At resting potential, the ion distribution inside and outside of a neuron is such that __________ ions are most abundant on the outside of the cell, while __________ ions are most abundant on the inside of the cell. A)potassium; sodium B)sodium; potassium C)calcium; phosphate D)sulfate; potassium

sodium; potassium

Which items should not be grouped together? A)spinal nerve B)cranial nerve C)spinal cord D)PNS

spinal cord

Which term does not belong with the others? A)brain B)spinal cord C)CNS D)spinal nerve

spinal nerve, (correct answer)

divergence

spreading apart. a single presynaptic neuron forming synapses with two or more postsynaptic neurons.

Which of these is true when a neuron is at rest? A)the outside is positive B)the outside is negative C)there is no voltage D)the inside is positive

the outside is positive

neuromodulation

the physiological process by which a given neuron uses one or more chemicals to regulate diverse populations of neurons. typically bind to metabotropic, G-protein coupled receptors to initiate a second messenger signaling cascade that induces a broad, long-lasting signal

unpolarized

waves that are randomly polarized, vibrating in all directions

depolarized

when the membrane potential is less negative when compared to the outside

hyperpolarized

when the membrane potential is more negative