Ch 12 review
Contrast chemically gated and voltage gated channels. How do their functions differ? In which segments of a neuron are they found?
Section 12.6 addresses this question. Chemically gated channels are generally receptors for a ligand, and they open when the ligand is present, while voltage gated channels open in response to a change in change. Chemically gated channels are found in receptive segments of neuron (dendrites, soma), While voltage gated channels are found in the initial conductive and transmissive segments (hillock, axon, knob).
The afferent division of the nervous system is also known as the ______ division.
Sensory
A mixed nerve refers to one that contains both?
Sensory and motor neurons
The monoamine that has functions related to sleep, appetite, cognition, and mood is?
Serotonin
Maintenance of appropriate ion concentrations (especially after nerve impulses that involved ion diffusion) is primarily the job of?
Sodium-potassium pumps
Which part of the neuron contains the nucleus?
Soma
The portion of the nervous system that has voluntary control over skeletal muscles is the ______ division.
Somatic motor
The portion of the nervous system that conducts impulses from the skin, joints, skeletal muscles, and special senses is the ______ division.
Somatic sensory
In a mixed nerve?
Some axons transmit sensory information and other transmit motor information
When multiple presynaptic neurons release neurotransmitter at various locations onto the postsynaptic neuron at the same time results in?
Spatial summation
As an axon approaches the cell onto which it will terminate, it generally branches repeatedly into several?
Telodendria
When a single presynaptic neuron repeatedly releases neurotransmitter in a very short period of time it results in ______ summation in the postsynaptic neuron.
Temporal
The electrochemical gradient refers to?
The combination of electrical and chemical gradients between two area.
The glossy-whit appearance of most axons is due to?
The higher lipid content of myelin sheath
When transmission occurs at a synapse, neurotransmitter is released by?
The presynaptic neuron's synaptic knob into the synaptic cleft
Wallerian degeneration involves the breakdown of?
The segments of axon and myelin sheath between the sire of damage and the peripheral effector.
A graded potential occurs when?
The voltage inside the neuron becomes more positive.
As a neuron's refractory period ends, its sodium channels are changing from?
Their inactivated state to their activated state
What do all glial cells have in common?
They assist neurons in their respective functions
Which statement accurately compares the transmission speed of the different types of synapses?
Transmission at chemical synapses involves a brief synaptic delay, but electrical synapses are faster
Which part of a neuron interacts through the synaptic knob with the next cell?
Transmissive segment
Which is not a function of the motor division of the nervous system?
Transmits impulses from the viscera
Which is not a general function of the nervous system?
Transporting materials throughout the body
Which is not a type of neuronal pool?
Triangular-pre-discharge
A neuron's membrane contains more potassium leak channels than sodium leak channels.
True
A postsynaptic potential is a graded potential
True
Although severing a peripheral axon leads to some degeneration, the neurilemma remains largely intact.
True
An action potential involves a temporary reversal of polarity across the plasma membrane ( that is, the inside of the axon becomes relatively positive compared to the interstitial fluid).
True
Chemical synapses are more common than electrical synapses.
True
Glial cells help maintain the structure of synapses and they can modify neural transmission.
True
Negatively charged protein molecules are more prevalent within a neuron's cytosol than in the interstitial fluid.
True
Nerve impulses are only transmitter along exposed portions of an axon.
True
Neurotransmitter is released from the synaptic knob by exocytosis, and it then diffuses across the synaptic cleft.
True
One main category of neurotransmitters is amino acids.
True
Saltatory conduction of a nerve impulse occurs only along myelinated axons.
True
Some inhibitory neurotransmitters exert their effect by causing the opening of chloride channels, which results in the postsynaptic membrane becoming more negative
True
Substance P is a neuropeptide that functions in the transmission of pain information to the brain.
True
The spinal cord is part of the central nervous system?
True
Typically, a multi polar neuron has many dendrites and one axon extending from the cell body.
True
Voltage-gated sodium channels at a neuron's initial segment are triggered to open when the membrane becomes more positive.
True
Continuous conduction of a nerve impulse occurs only along?
Unmyelinated axons
A graded potential is one that?
Varies in size depending on the magnitude of the stimulus (larger voltage change for stronger stimulus)
A neuron conducting an impulse from the stomach wall to the CNS would be classified as an _______ neuron.
Visceral sensory
What type of sensory structures detect changes in internal organs?
Visercal sensory receptors
The separation of oppositely charged ionic particles across a resting neuron's membrane results in a potential that is measured as a?
Voltage
Action potentials are generated by the opening of _____ gated channels and they occur on the _____.
Voltage-, axon
The type of voltage-gated channels that possesses an inactivation gate that temporarily closes after the channel is active is the?
Voltage-gated sodium channel
A nerve?
is a cable like bundle of parallel axons
One of the ways that neurotransmitter is removed from the synaptic cleft is?
reuptake by the presynaptic cell
Somatic motor neuron axons fall into the category of?
A fibers
A graph of an EPSP would plot time against a voltage trace that would resemble?
A hill where the high point approaches the threshold value
Conductive activity in a neuron generally causes it to secrete:
A specific neurotransmitter that either excites or inhibits its target
Chose the answer that correctly list, in chronological order, the events involved in synaptic transmission. a: A nerve impulse reaches the synaptic knob b: Neurotransmitter molecules diffuse across the synaptic cleft c: A nerve impulse begins in the postsynaptic cell d: Neurotransmitter molecules bind to receptors in the postsynaptic cell e: A voltage change occurs in the postsynaptic cell
A,B,D,E,C
Which occurs first?
Absolute refractory period
What effect would an acetylcholinesterase inhibitor have on an acetylcholine synapse?
Ach E inhibitors cause more Ach to be in the synapse. One application for this is treating myasthenia gravis, where the drugs inhibit Ach breakdown and facilitate muscle stimulation by nerve. SSRIs also cause more neurotransmitter to remain in the synapse longer, and are known to elevate mood.
Fast axonal transport is?
Active (requires ATP) and can occur in either the anterograde or retrograde direction.
A nerve cell that has dendrites but no axons is catagorized as an ________ neuron.
Anaxonic
Glial cells differ from neurons in that they?
Are smaller and capable of mitosis
The endoneurium is composed of?
Areolar connective tissue
The glial cell that helps form the blood-brain barrier is the?
Astrocyte
The glial cell that provides structural support and organizations to the CNS is the?
Astrocyte
The glial cell with perivascular feet that wrap around capillaries in the CNS is the?
Astrocyte
The glial cell with the responsibility of occupying the space left by dead or dying neurons is the?
Astrocyte
What is the most abundant glial cell in the CNS?
Astrocyte
Where are synaptic knobs located?
At the tips of telodendria
A neuron conducting an impulse from the CNS to the detrusor muscle of the urinary bladder would be classified as an ________ neuron.
Autonomic motor
The conductive segment of a neuron is it's ______, a region that contains many ______ gated channels.
Axon, voltage-
In order to trigger the release of neurotransmitter from a neuron terminal, calcium ions?
Bind to proteins on the surface of synaptic vesicles
The slowest category of nerve fibers are the?
C fibers, and they conduct impulses at 1 meter per second.
When a nerve impulse reaches the transmissive segment of a neuron?
Calcium diffuses into the neuron and neurotrasmitter is released by exocytosis.
Neural stem cells in the CNS?
Can form new neurons in only certain portions of the CNS such as the hippocampus
The type of transport protein that moves a substance down it's concentration gradient is a:
Channel
There are two types of synapses, based on mode of communication. What are they?
Chemical and electrical
Receptors are parts of the nervous system that allow it to?
Collect information
The type of neuronal circuit in which several nerve impulses come together at a single postsynaptic neuron is a ________ circuit.
Converging
You walk into a restaurant and amidst the sights, sounds, and smells of food preparation, you notice that you have begun to salivate. This is evidence that a particular neuronal circuit has been activated. Which one?
Converging
Spinal nerves extend from the spinal cord, whereas ________ nerves extend from the brain.
Cranial
An excitatory postsynaptic potential occurs when? a: Na+ channels open b: the inside of the neuron becomes slightly more positive c: Na+ moves down its concentration gradient d: All of these are correct
D: All of these are correct
With damage to nerve fibers, larger distances between the sire of damage and the target structure innervated result in _______ chances of successful regeneration.
Decreased
The main way acetylcholine is cleared from a synapse is by?
Degradation by an enzyme
The receptive segment of a neuron contains/consists of?q
Dendrites and cell body
Electrical signals are conducted toward the cell body of a neuron by its?
Dendrites or dendrite
The epineurium is composed of?
Dense irregular connective tissue
Axon regeneration always requires?
Destruction of the axon attached to the nerve cell body
According to Ohm's law, current is?
Directly related to voltage and inversely related to resistance.
The type of neuronal circuit that spreads information from one presynaptic neuron to several postsynaptic neurons is a _______ circuit.
Diverging
What type of circuit is used to maintain body pressure posture while walking?
Diverging
When a neurotransmitter opens a chemically gated ion channel that allows sodium to enter the postsynaptic ccell, the results is an?
EPSP
Which is true regarding the action of a neuroloemmocyte?
Each meurolemmocyte can wrap only 1 mm portion of a single axon.
Which statement is true regarding the action of an oligodendrocyte?
Each oligodendrocyte can form a myelin sheath around many axons simultaneously.
The nervous system controls the activity of muscles and glands. Muscles and glands can generate changes and are therefore called?
Effectors
The motor nervous system is also known as the ______ nervous system.
Efferent
Hyperpolarization of a neuron results from?
Either the entry of an anion or the exit of a cation
Of the two types of synapses, based on mode of communication, which is less common but allows faster signal transmission?
Electrical synapse.
The perikaryon of a neuron is the?
Entire cell body
The glial cell that helps to circulate cerebrospinal fluid is the?
Ependymal cell
Which choice correctly orders the connective tissue wrappings of a nerve, beginning at the outermost layer?
Epineurium - perineurium - endoneurium
Which characteristic of a neuron facilitates its responsiveness to stimulation?
Excitability
The role of K+ in membrane potential is to?
Exit the neuron to maintain membrane potential
The conductive segment of a neuron?
Extends the full length of the axon
When a neuromodulator slows the reuptake of a neurotransmitter or causes expression of an increased number of receptors on postsynaptic neurons, the effect is called?
Facilitation
A neuropeptided is a molecule that is synthesized from an amino acid by the removal of a carboxyl group and the addition of another small functional group such as an amine group.
False
A tumor can occur in any tissue with in the CNS.
False
Anterograde transport is the movement of materials from synaptic knobs to the cell body.
False
As it moves from the tip of a dendrite to the axon hillock, a postsynaptic potential will maintain a constant amplitude.
False
As the distance between a damaged axon and its receptor organ increases, the possibility of repair increases.
False
Channels require energy in order to function as transport proteins.
False
Graded potentials generally occur only on the axon of a neuron.
False
In the CNS all axons are myelinated, but in the PNS, some are myelinated and some are unmyelinated.
False
The nervous system contains more neurons than glial cells.
False
The size of an EPSP is independent of the amount of excitatory neurotransmitter that is released by the presynaptic cell
False
Transmission of nerve impulses along myleniated axons requires more energy than transmission along unmyelinated axons.
False
Voltage-gated potassium channels in a neuron's axon are triggered to open when membrane potential becomes more negative.
False
Vesicles and glycoproteins required at the synapse are moved down a nerve fiber by _______ axonal transport.
Fast
The primary inhibitory neurotransmitter in the brain is?
GABA (Gamma-Amino Butyric acid)
Electrical synapses involve coupling of neurons by?
Gap Junctions
Which is not characteristic of neurons?
High mitotic rate
When a neurotransmitter causes the opening of chemically gated potassium channels on the postsynaptic cell, the postsynaptic potential that results in an?
IPSP, which is a hyperpolarization
The axon hillock makes up the _____ segment of a neuron.
Initial
The nervous system regulates body function by?
Initiating input information
Potassium has a higher concentration?
Inside the cell versus outside the cell, whereas sodium has a higher concentration outside versus inside the cell.
Based on function, 99 percent of neurons are?
Interneurons
The neurons that are responsible for integrating information by retrieving, processing, storing, and "deciding" how the body responds to stimuli are?
Interneurons
Which functional class of neurons lies entirely within the central nervous system?
Interneurons
Hyperpolarization occurs in an excitable neuron when?
K+ channels remain close
A depolarization is when the inside of a neuron becomes _______ the resting membrane potential
Less negative than
Which type of cell is small with slender branches, and represents the least prevalence in the nervous system?
Microglia
The glial cell that defends the body against pathogens is the?
Microglial cell
Catecholamines are a subtype of ______ neurotransmitter.
Monoamine
If there were no sodium leak channels, resting membrane potential of a neuron would be?
More negative
Which statement is consistent with the current understanding of neural tissue?
Most neurons formed in fetal development last a lifetime, but some brain regions in adults can generate new neurons
The membrane potential of a neuron is due to?
Movement of ions between the outside and inside of the membrane.
Based on structure, the most common type of neuron is the _____ neuron.
Multi polar
In the structural classification of neurons which neuron has numerous nerve processes?
Multi polar
A peripheral nervous system axon is wrapped in ______ by a neurolemmocyte.
Myelin
Saltatory conduction occurs in?
Myelinated axons, where action potentials occur only at neurofibril nodes.
A nerve impulse travels fastest along _____ axons of _____ diameter.
Myelinated, large
The periphery of a myelinating Schwann cell that contains its cytoplasm and nucleus is called the?
Neurilemma
In a myelinated axon, the greatest concentration of voltage-gated ion channels is in the?
Neurofibril nodes
What structures extend into the axon and dendrite of a neuron to provide tensile strength?
Neurofibrils
The glial cell the myelinates and insulates axons in the peripheral nervous system is the?
Neurolemmocyte
Channels require energy in order to function as transport proteins?
Neurolemmocytes, 100 mm/day
_______ is the release of chemicals that locally regulate the response of neurons to neurotransmitters
Neuromodulation
Imagine a genetic mutation that resulted in a malfunctioning inactivation gate in a voltage-gated sodium channel. The defective gate wouldn't always open and close when it should. What functional problems would this cause for the neurons?
Neurons' axons would not fire action potential appropriately. Sometimes, when the gate is improperly closed, they would not fire when they should (despite a strong stimulus). Other times, when the gate remained inappropriately open, the axon would lack a refractory period-- it might fire bursts of impulses when only one is called for and it might propagate impulses backwards and forwards.
Along an axon, the gaps between neurolemmocytes are called neurofibril?
Nodes
The glial cell that myelinates and insulates axons within the CNS is the?
Oligodendrocyte
A bipolar neurons has?
One axon and one dendrite extending from the cell body
To measure the resting potential of a neuron, a physiologist would place?
One micro electrode inside the neuron and another in the interstitial fluid
Chemically gated channels?
Only open if they bind a neurotransmitter
Leak channels are?
Open all the time
The hyperpolarization that occurs at the end of an action potential is due to the prolonged?
Open state of voltage-gated potassium channels.
Arrival of an action potential at the synaptic knob results in?
Opening of voltage-gated calcium channels and diffusion of calcium into the synaptic knob.
Which division of the nervous system shows a greater capacity for regeneration?
PNS
The type of neuronal circuit in which several neurons process the same information at one times is a _______ circuit.
Parallel-after-discharging
What type of circuit would you use to solve a higher-order mathematical problem?
Parallel-after-discharging
The cytoplasm within a cell body of a neuron is called the?
Perikaryon
The connective tissue wrapping that surrounds bundles (fascicles) of axons is the?
Perineurium
Which connective tissue wrapping surrounds bundles of axons?
Perineurium
Nerves and ganglia are structures found in the?
Peripheral nervous system
Billions of CNS interneurons are grouped in complex patterns called neuronal?
Pools
In neurophysiology, the term summation refers to the addition of?
Postsynaptic potentials at the node of Ranvier
When voltage-gated K+ channels open on the conductive segment of a neuron?
Potassium exits, repolarizing the cell to a negative value.
The most crucial factor determining the resting potential of a neuron is the diffusion of?
Potassium out of the cell through leak channels
Most commonly, a synapse is made between a?
Presynaptic neuron's axon and a postsynaptic neuron's dendrite
The function of myelin is to?
Produce faster nerve impulse propagation
Chemically gated ion channels are mainly found in the ______ segment of a neuron.
Receptive
After an impulse, the ________ refractory period is the time when it is possible to initiate another impulse, but it requires a stronger than usual stimulus.
Relative.
The type of neuronal circuit that ensures that we continue to breathe while asleep is a _______ circuit.
Reverberating
The type of neuronal circuit that uses feedback to produce a repeated, cyclical stimulation of the circuit is a _____ circuit.
Reverberating
The glial cell that protects and regulates nutrient and waste exchange for cell bodies in ganglia is the?
Satellite cell
The glial cell that protects neuron cell bodies located within ganglia is the?
Satellite cell
Following damage to axons nearby, oligondendrocytes?
Secrete growth -inhibitory molecules
Typically, the resting membrane potential of a neuron is?
-70 mV