Chapter 12 Nervous Tissue
Which of the following is true of acetylcholine, a common neurotransmitter in the body?
It can have either excitatory or inhibitory effects depending on the tissue in which it binds.
Which statement best describes a neuromuscular junction?
It is the synapse of a motor neuron with a muscle fiber.
More ____ ions than Na+ will leak across the plasma membrane of neurons, which means the membrane is continually losing more positive charges than it gains.
K (potassium)
IPSPs are caused by all of the following EXCEPT A) Cl- channels B) K+ channels C) Na+ channels
NA+ channels
A resting nerve fiber is polarized because the concentration of
Na+ is higher on the outside and K+ is higher on the inside
What helps offset the ion diffusion through leak channels on neurons and helps return the membrane potential to its resting voltage?
Na+/K+ ATPase pumps
Neuron A has a diameter that is twice that of Neuron B. Based only on this information, which of the following is true?
Neuron A will transmit action potentials faster than Neuron B.
Neurotransmitters consisting of 3 to 40 amino acids linked by peptide bonds are called
Neuropeptides
If a postsynaptic cell receives EPSPs but not enough to reach the threshold, which of the following will happen?
No action potential will be propagated.
Chromatolysis is a process that happens during which of the following processes?
PNS regeneration
The Nissl bodies function in
Protein production
Nervous system & actions
Somatic nervous system - Controls voluntary actions Autonomic nervous system - Controls involuntary actions Enteric nervous system - Controls involuntary actions
Once neurotransmitters are released, they do not remain in the synapse. What happens to them?
Some are degraded by enzymes while some are transported back into the presynaptic cell.
The resting membrane potential in most neurons is about -70mV. What does this tell you?
The inside of the membrane is more negatively charged than the outside of the membrane.
In a given neuron, the current membrane potential is -60 mV. What does this tell you about the current potential compared to the resting membrane potential of -70 mV?
The membrane is depolarized compared to the resting membrane potential.
If the dendrites of a neuron are damaged, which of the following will be affected in the neuron?
ability to transmit messages t other neurons ability to release neurotransmitters ability to trigger an action potential
Some neurons in the body stretch for several feet. Which of the following is a type of electrical impulse that allows communication over such a distance?
action potential
When the threshold of voltage-gated channels is reached and voltage-gated channels open, the resulting change in membrane potential is known as a(n)
action potential.
Sensory impulses are carried to the central nervous system by
afferent neurons
Can new neurons be formed in adult human brains?
Yes they can, in certain areas of the brain.
Hyperpolarization requires
a decrease of K+ inside the cell
A change in membrane potential from −70 to −60 mV is
a depolarizing graded potential
A small deviation from the resting membrane potential that occurs because ligand-gated or mechanically-gated channels open or close is called
a graded potential
A change in membrane potential from −70 to −80 mV is
a hyperpolarizing graded potential
Simple series circuits allow
a single presynaptic cell to stimulate a single postsynaptic cell
A regeneration tube in the PNS helps direct further growth of ______ after an injury.
an axon
Which glial cells rapidly proliferate after a CNS injury, physically blocking regeneration of CNS neurons?
astrocytes
Which of the following controls the "fight-or-flight" response?"
autonomic nervous system
A person with a reduced number of Schwann cells would experience difficulty forming which of the following after a PNS injury?
axon
Strychnine works by
binding to and blocking glycine receptors
You need sutures to close a cut on your hand, and lidocaine is used to numb the area. Lidocaine works by
blocking the opening of sodium channels
The lungs are innervated by both the sympathetic and parasympathetic nervous systems. These two systems will have opposing effects on the lungs. This is an example of an effector that receives
both excitatory and inhibitory potentials from many presynaptic cells
During this, ions flow through their channels in each adjacent segment of the membrane.
continuous conduction
Which type of circuit does a neuron receive impulses from several different sources?
converging
The optic (II) nerve emerges from the brain; therefore, it is a type of
cranial nerve
Glutamate is considered an
excitatory small molecule neurotransmitter
As Ca++ ions enter the presynaptic membrane _____ of neurotransmitters occurs.
exocytosis
Graded potentials are named based on their end results.
false
A PNS neuron with Schwann cells wrapped around it will transmit action potentials
faster than a PNS neuron without Schwann cells
The autonomic nervous system mediates two types of responses in the body.
fight/flight and rest/digest
An electrical signal that is sent over a short distance is known as a(n)
graded potential
The input of sensory information that is received as soon as you touch the screen of a phone to text your friend forms as a(n)
graded potential
Region #1 would have a slower rate of action potential transmission than Region #2.
gray matter (region 1) white matter (region 2)
Conversion of energy from potential to kinetic will generally release this.
heat
When the graded potential results in the membrane becoming more negative, it is said to be a
hyperpolarizing graded potential
Adult neurogenesis can occur
in certain areas of the CNS
In a neuron, where do graded potentials mainly occur?
in the cell body and the dendrites
Inhibiting the uptake of norepinephrine into a presynaptic cell would
increase the duration of action for norepinephrine in the synapse
The process of summation ___ the strength and duration of graded potentials that occur in the dendrites of a neuron.
increases
A neurotransmitter known as GABA stimulates a postsynaptic neuron to open channels that allow Cl- influx. In this event, GABA is considered
inhibitory
Endorphins are considered
inhibitory opioid peptide neurotransmitters
Resting membrane potential is maintained by
leak channels and sodium-Potassium pumps.
A channel that opens in response to the binding of a molecule like a neurotransmitter is known as a
ligand
Identify the type of ion channel that opens and closes in response to the binding of a chemical stimulus.
ligand- gated
Binding of acetylcholine to a receptor causes a _________________________ to open, resulting in a depolarizing graded potential.
ligand-gated channel on the dendrite of an interneuron
Identify the type of ion channel that opens and closes in response to mechanical stimulation such as tissue stretching or pressure.
mechanically gated
Lanthanides are rare earth elements that may block the function of stretch-activated ion channels. Based on this information, the action of lanthanides is to block the opening of
mechanically gated channels
When a person jerks his hand away from a hot stove, the movement is directly stimulated by
motor neurons
A medication that prevents anterograde transport would prevent which of the following actions?
movement of synaptic vesicles to the axon
Which of the following is a nervous system disorder characterized by hardening myelin sheaths on neurons in various places in the body?
multiple sclerosis
White matter is composed of
myelinated axons
If collagen fibers invade the regeneration tube of a PNS neuron, then
new axons will not be able to form
What gives gray matter its grayish color?
nissl bodies
A single presynaptic neuron stimulates a group of neurons each of which synapses with a common postsynaptic cell describes which of the following circuits?
parallel after discharge
John Franklin was previously against stem cell research, but after watching a friend suffer from paralysis after a spinal cord injury, he is now pro-stem cell research. In this example, Mr. Franklin's brain is showing characteristics of
plasticity
Most anions are not free to leave because they cannot follow this out of the cell.
potassium
The main cation in cytosol is
potassium
These channels are responsible for the repolarizing phase.
potassium channels
An example of a mechanically-gated channel is when a channel opens as a result of
pressure of a fingertip pushing on a doorbell
The synapse consists of
presynaptic and post synaptic cell membranes separated by a synaptic cleft.
An action potential maintains its strength as it spreads along the membrane. This mode of conduction is called
propagation
Which of the following characterizes bipolar disorder?
recurrent episodes of depression and extreme elation
Phenytoin is a medication that prevents seizures in patients with epilepsy. Phenytoin blocks the opening of voltage-gated Na+ channels; this causes
reduced depolarization of axons
The ______ membrane potential of the cell is maintained by leak channels and the Na+/K+ pump.
resting
An electrical potential difference across the plasma membrane of a neuron is known as a(n)
resting membrane potential
Short-term memory is believed to be a function of which type of neural circuit?
reverbating
The type of circuit in which branches of postsynaptic neurons synapse with earlier neurons in the path is a(n)
reverberating circuit
A photoreceptor in the eye could be classified into which of the following categories?
sensory receptor
Guillain-Barre syndrome (GBS) is an autoimmune disorder in which Schwann cells are attacked and destroyed. Which of the following would be a result of this disorder?
slowed action potential transmission in PNS neurons
Injury to an oligodendrocyte would cause
slower rate of action potential transmission in a neuron
_____________ ions diffuse into a muscle cell once the ligand gates are open.
sodium
These channels are responsible for the depolarizing phase.
sodium channels
In which part of the neuron would the Nissl bodies be found?
soma
The brachial plexus is a spinal nerve network that serves the muscles of the upper limbs. The brachial plexus is therefore considered part of the
somatic nervous system
An IPSP on one area of the membrane at the same time as an EPSP on another area of the membrane would both be considered for the purposes of
spatial summation
At essentially the same time, GABA, an inhibitory neurotransmitter, and glutamate, an excitatory neurotransmitter, bind to receptors at different locations on a postsynaptic membrane. Which of the following would be affected by this scenario?
spatial summation
Which is NOT part of the central nervous system?
spinal nerve
Caffeine is an inhibitor of acetylcholinesterase. Therefore, an indirect effect of caffeine would be to
stimulate skeletal muscle contractions
When compared to pushing a long row of dominos down, the ____________ is when the first domino is pushed hard enough to cause the entire row to topple.
stimulus causes depolarization to threshold
What is the process by which graded potentials add together?
summation
Hirschsprung's disease is a disorder in which the large intestine has no nerves and cannot function as it should. This is a problem with which of the following parts of the nervous system?
the enteric nervous system
The amplitude of a graded potential depends on
the stimulus strength
why does sodium have trouble moving through structure?
there are only a few sodium leak channels
If a neurolemma is absent from a damaged PNS neuron,
there will be no regeneration of the neuron
Why can't trapped anions follow potassium out of the cell?
they are attached to ATP
Electrical synapse
they occur when there is direct contact between electrically excitable cells. they allow rapid communication between cells. they allow synchronization of cellular activities. they are found in heart muscle
Which is NOT a function of a neuroglial cell?
to generate graded potentials
A neuron might be at -80 mV instead of the resting membrane potential of -70 mV for which of the following reasons?
too much K+ outflow and inflow of Cl-
With what are "A" fibers are associated?
touch and pressure
As potassium ions exit, the inside of the membrane becomes more and more negative.
true
The depolarization of one area of the cell membrane provides enough positive charge to cause neighboring voltage-gated channels to reach threshold allowing the action potential to spread across the membrane.
true
To establish and maintain resting membrane potential, more potassium ions move out of the cell than sodium ions move into the cell.
true
When the cell membrane has an accumulation of positive charges on the outside and negative charges on the inside it is considered to be polarized.
true
A channel that opens in response to a change in the membrane potential is known as a
voltage
When the neuron's membrane potential reaches approximately +30 mV, which of the following events is likely to happen next?
voltage-gated K+ channels open
If the accumulation of graded potentials in the trigger zone reaches threshold, the result is
voltage-gated channels open.
In the spinal cord, this surrounds the gray matter.
white matter
Which cells are ciliated and function to move CSF?
ependymal cells
The resting membrane potential range in neurons is between ______ mV and ______mV.
-40; -90
In neurons, the normal resting membrane potential is
-70
In the depolarizing phase, the negative membrane reaches this before it becomes positive.
0mV
A person who experiences episodes of depression alternating with periods of feeling well would likely be diagnosed with
Dysthymia
Which of the following neurotransmitters is only excitatory?
Glutamate
Morphine works by stimulating the same receptors as the opioid peptides. Morphine must have effects similar to
endorphins
Gray matter includes unmyelinated axons, dendrites, cell bodies and neuroglia. In the brain, a thin layer of gray matter covers the cerebrum and cerebellum. True or False
True
The regeneration tube guides the growth of a new axon from the proximal area across the injured area to the distal area where it replaces the original axon.
True
A certain neuron has too many Na+ leak channels. Which of the following could be the result of this abnormal structure?
depolarization due to Na+ influx
Myelinated axons are capable of saltatory conduction. This allows for more rapid action potential conduction because
depolarization occurs only at the Nodes of Ranvier.
When the inside of the membrane becomes less negative, the membrane potential is said to be
depolarized.
A pressure stimulus opens a mechanically-gated channel. As sodium ions (Na+) flow into the cell through the channel, which of the following is created?
depolarizing becomes less negative
When a neurotransmitter attaches to a chemically-gated sodium channel, the sodium channel briefly opens to allow sodium ions to diffuse in. This action produces what type of graded potential?
depolarizing graded potential
What is the function(s) of the nervous system?
detecting stimuli processing information sending a response to muscles or glands
If a depolarizing and hyperpolarizing are equal in graded potentials and summate, the overall graded potential does this.
disappears
If tyrosine levels in a CNS neuron were reduced, the synthesis of which of the following molecules might also be reduced?
dopamine
Which of the following is biogenic amine?
dopamine norepinephrine serotonin
Motor neurons from the hypoglossal (XII) nerve innervate the tongue. Destruction of these motor neurons due to traumatic injury would result in the loss of a(n)
effector for the hypoglossal (XII) nerve