HW 11: Overview of Nervous System
Which term applies to the small swellings at the distal end of the axon of a neuron that contain synaptic vesicles?
Axon terminals
Which term refers to the passage of proteins, organelles and other materials along an axon?
Axonal transport
Axon collateral
Branch that originates from an axon
What are the two major anatomical subdivisions of the nervous system?
Central and peripheral nervous systems
Which term refers to a synapse that releases acetylcholine from the presynaptic axon terminal?
Cholinergic
Axoplasm
Cytoplasm of the axon
The soma of a neuron gives rise to branch-like processes called what? They are the primary sites for receiving signals from other neurons.
Dendrites
List the fundamental physiological properties of neurons.
Excitability, conductivity, secretion
This picture illustrates neural transmission at which type of synapse?
Excitatory cholinergic synapse
Satellite cells
In the PNS; surround somas of neurons in ganglia, provide electrical insulation, and regulate the chemical environment of neurons
Choose all that are names for the cell body of a neuron.
Neurosoma, Soma
Stimulation of the postsynaptic neuron will end when nerve signals stop arriving at the presynaptic axon terminal or when which of the following occurs?
Neurotransmitter is removed from postsynaptic receptors.
Which glial cell insulates nerve fibers from extracellular fluids and speeds up signal conduction in the brain?
Oligodendrocyte
Which type of glial cell is indicated by the arrow labeled A?
Oligodendrocytes
Taken together, the sensory and motor subdivisions make up which of the following?
Peripheral nervous system
Axolemma
Plasma membrane of the axon
Neural integration is based on the combining together of which of the following?
Postsynaptic potentials
Which ion has the greatest influence on the resting membrane potential of most neurons?
Potassium
An electrical potential is a form of what type of energy?
Potential energy
Which type of glial cell produces the myelin sheath in the PNS?
Schwann cell
Which type of glial cell aids in regeneration of damaged peripheral nerve fibers by forming a regeneration tube to help reestablish the former connection?
Schwann cells
The release of a neurotransmitter is an example of which physiological property exhibited by a neuron?
Secretion
True or false: Action potentials occur only where there are voltage-gated ion channels.
True
True or false: Unmyelinated nerve fibers (axons) in the PNS are enveloped in Schwann cells.
True
Which lists the structural categories of neurons?
Unipolar, bipolar, anaxonic, and multipolar
An axon lacking a myelin sheath is said to be what?
Unmyelinated
Together, the sympathetic and parasympathetic nervous systems make up the entirety of which division of the nervous system?
Visceral motor
The refractory period in which no stimulus of any strength will trigger a new action potential is the ______ refractory period.
absolute
The brain and spinal cord are components of the ______ nervous system, while the nerves and ganglia are components of the ______ nervous system.
central, peripheral
Which process of a neuron is specialized for rapid conduction of nerve signals to structures relatively far away from the neuron cell body?
Axon
Schwann cells
In the PNS; form neurilemma around all PNS fibers and myelin around most of them; aid in regeneration of damaged nerve fibers.
Which best describes an electrical potential?
A form of potential energy that can produce current
Choose all of the following statements that are true about signal conduction along unmyelinated fibers.
- A zone of depolarization excites voltage-gated channels immediately distal to the action potential. - Unmyelinated fibers have voltage-gated channels along their entire length.
Choose all the ways neuromodulators alter synaptic transmission.
- Altering the breakdown and/or reuptake of neurotransmitter - Adjusting the sensitivity of postsynaptic neurons to neurotransmitters - Increasing the release of neurotransmitters by presynaptic neurons
Choose all that would cause postsynaptic stimulation to end.
- Cessation of signals in the presynaptic nerve fiber - Reuptake of neurotransmitter into the presynaptic knob - Enzymatic degradation of neurotransmitter in the synaptic cleft - Diffusion of neurotransmitter from the synaptic cleft into extracellular fluid
Choose all that are characteristics of local potentials.
- Decremental - Graded
Which types of glial cells are found in the central nervous system?
- Ependymal cells - Oligodendrocytes - Astrocytes - Microglia
Which correctly describe axonal transport?
- It is bidirectional (retrograde and anterograde transport). - It involves transport of proteins within the axon (i.e. synaptic knob enzymes or proteins that maintain the axolemma).
Which two organ systems are primarily responsible for coordinating the other bodily systems so as to maintain homeostasis?
- Nervous system - Endocrine system
Choose all that are properties of action potentials.
- Nondecremental (signal maintains amplitude) - Self-propagating - All or none
Choose all the factors that influence the speed of nerve signal conduction.
- Presence of myelin - Diameter of axon
Choose the three functional classes of neurons.
- Sensory neurons - Motor neurons - Interneurons
Choose all statements that are true about Schwann cells?
- They assist in the regeneration of damaged nerve fibers. - They form the neurilemma. - They form the myelin sheath in the PNS.
Choose all statements that are true regarding postsynaptic potentials?
- They include EPSPs and IPSPs. - They are changes in the membrane potential of the postsynaptic terminal of a chemical synapse. - They are caused by neurotransmitters.
Starting with a signal reaching the distal end of the presynaptic axon, indicate the correct order of events that occur during transmission at a cholinergic excitatory synapse.
1. Opening of calcium gates in synaptic knob as nerve signal arrives 2. Exocytosis of ACh; diffusion across synaptic cleft 3. Binding of ACh to receptors on postsynaptic neuron 4. Opening of sodium gates on post-synaptic membrane allowing influx of sodium 5. Depolarization of postsynaptic plasma membrane
What is the approximate ratio of glial cells to neurons?
10:1
Axon hillock
A mound located on one side of the soma from which the axon originates
Which best describes signal conduction in unmyelinated axons?
A wave of depolarization opens more voltage-gated channels immediately distal to the action potential.
A cholinergic synapse uses which of the following as its neurotransmitter?
Acetylcholine
True or false: Damaged nerve fibers in the CNS regenerate very fast whereas damaged nerve fibers in the PNS never regenerate.
False
True or false: The more synapses a neuron has, the lesser its information-processing capability.
False
______ cells protect the neurons and help them function.
Glial
Ependymal cells
In the CNS; line cavities of the brain and spinal cord; secrete and circulate CSF
Microglia
In the CNS; phagocytize microorganisms, foreign matter, and dead nervous tissue
Which of the following contributes to the development of the resting membrane potential in neurons?
K+ is more concentrated in the ICF than in the ECF.
The myelin sheath is composed mostly of which of the following?
Lipids
Which term refers to decremental changes in electrical potential along a dendrite or the soma?
Local potentials
Neurons with numerous dendrites and a single axon are structurally classified as which of the following?
Multipolar
The picture shows the most common structural type of neuron. It contains one axon and multiple dendrites, and it is classified as what type of neuron.
Multipolar
Which term describes the ability of neurons to process information, store and recall it, and make decisions?
Neural integration
Which alter synaptic transmission by adjusting the sensitivity of postsynaptic neurons to neurotransmitters or by affecting the breakdown and/or removal of a neurotransmitter?
Neuromodulators
Sensory, association and motor are the three classes of what?
Neurons
Which is true about a neuron with a large diameter, myelinated axon as compared to a neuron with a small diameter, unmyelinated axon?
Signal conduction will be faster
The sensory and motor divisions of the peripheral nervous system are further split into which two subdivisions?
Somatic and visceral
Which division inhibits digestion?
Sympathetic
At its distal end, an axon has an extensive complex of fine branches called what?
Terminal arborization
The processes of a neuron that usually receive signals from other neurons are called _____.
dendrites
The processes that branch from the somas of most neurons are called ______.
dendrites
Two organ systems are dedicated to internal coordination, communication between the other systems, and maintaining the overall homeostasis of the body. They are the _____ system, which communicates by means of hormones, and the _____ system which sends quick electrical and chemical messages from cell to cell.
endocrine, nervous
The myelin sheath is a spiral layer of ______ around a nerve fiber.
insulation
The refractory period in which it is possible to trigger a new action potential, but only with an unusually strong stimulus is the ______ refractory period.
relative
The neurons indicated by a letter "A" are structurally classified as ______ neurons. The neurons indicated by a letter "B" are structurally classified as ______ neurons.
multipolar, bipolar
In the CNS, myelin is produced by glial cells called _____.
oligodendrocytes
At a synapse, the neuron that responds to the neurotransmitter is the ______ neuron.
postsynaptic
At a synapse, the neuron that releases neurotransmitter is the ______ neuron.
presynaptic