Unit 2 homework questions
where most graded potentials originate
dendrites
The photosensitive pigment derived from vitamin A is
retinal
What causes the myosin head to disconnect from actin?
binding of ATP
receive(s) most of the incoming synapses
dendrites
Which neural term is a synonym for action potential?
Nerve impulse
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?
arrival of an action potential
The division of the efferent nervous system that controls smooth and cardiac muscles and many glands is the __________ division.
autonomic
The diameter of bronchioles varies under the control of __________ neurons, which cause the diameter to __________.
autonomic; constrict under parasympathetic control and dilate under sympathetic control
may be covered with myelin
axon
"Dual innervation" refers to an organ receiving
both sympathetic and parasympathetic nerves
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
voltage-gated calcium channels
Put these structures of the visual system in the order that they transmit light to the retina. 1. lens 2. aqueous humor 3. cornea 4. vitreous chamber
3, 2, 1, 4 cornea, aqueous humor, lens, vitreous chamber
can involve ion channels regulated by chemicals
graded potential
Visceral pain is poorly localized and can be perceived to come from a region of the body that is different from its actual location; this is called
referred pain.
It dominates during resting-and-digesting activities.
true only for the parasympathetic division
The cell bodies of preganglionic neurons are found either in the brain stem or in the sacral region of the spinal cord.
true only for the parasympathetic division
In order for a synapse to be an effective means of cellular communication, removal of neurotransmitter molecules from the synapse is important.
False
A neuron that has responded to a stimulus causes decreased activity in neighboring neurons in which process?
Lateral inhibition
What is the subjective perception that occurs when nociceptors are stimulated?
Pain
The tip of an embryonic nerve cell's axon is called a
growth cone.
Which of the following structures is/are necessary to initiate the muscle action potential?
muscle fiber acetylcholine motor neuron ACh receptor-channels motor end plate
A damaged neuron has a better chance of survival and repair if the ________ is/are undamaged.
cell body
Which ion stimulates shape changes at the beginning of skeletal muscle contraction?
Ca2+
How does the process of smooth muscle contraction differ from contraction in skeletal muscle?
Ca2+ comes from the extracellular fluid and the SR.
Which is NOT a property of single-unit smooth muscles?
Each cell functions independent of its neighbor.
Inadequate calcium in the neuromuscular junction would directly affect which of the following processes?
Release of acetylcholine from the synaptic vesicles
The velocity of the action potential is fastest in which of the following axons?
a small myelinated axon
Choose the items that are correctly matched.
activation gate - opens during depolarization
During an action potential, when does sodium ion permeability begin to significantly decline?
at the peak of depolarization
The presence of two peripheral efferent neurons in a pathway is typical of the ________ division.
autonomic
Which has its cell body in a ganglion?
postganglionic neuron
The two-point discrimination test is used to measure
receptive field size for touch receptors.
The ciliary muscle helps to control the
the shape of the lens
The total amount of neurotransmitter released at the axon terminal is directly related to the
total number of action potentials.
What is name given to the regularly spaced infoldings of the sarcolemma?
transverse or T tubules
The binding of calcium to which molecule causes the myosin binding sites to be exposed?
troponin
Smooth muscle cells do not have which protein(s)?
troponin only
What structure most directly stimulates a skeletal muscle fiber to contract?
Motor neuron
Which is a characteristic of slow-twitch oxidative skeletal muscle fibers?
long contraction duration and high capillary density
Which statement is true when a neuron is at rest?
The activation gate is closed and the inactivation gate is open.
Identify the FALSE statement.
The amplitude of the action potential depends on the amplitude of the graded potential that precedes it.
Why does the action potential only move away from the cell body?
The areas that have had the action potential are refractory to a new action potential.
The sympathetic and parasympathetic nervous systems are divisions of which system?
The autonomic nervous system
What characterizes depolarization, the first phase of the action potential?
The membrane potential changes from a negative value to a positive value.
result(s) from influx of sodium
Both (graded and action potentials)
Which of the following processes produces 36 ATP?
Krebs cycle and oxidative phosphorylation
What structure is the functional unit of contraction in a skeletal muscle fiber?
The sarcomere
Sympathetic pathways originate in which regions of the spinal cord?
Thoracic and lumbar
Which of the following is a modified sympathetic ganglion?
Adrenal medulla
What is the role of calcium in the cross bridge cycle?
Calcium binds to troponin, altering its shape.
How many molecules of ACh bind to a cholinergic nicotinic receptor on a skeletal muscle cell?
Two
The ion necessary to initiate the release of acetylcholine into the synaptic cleft is
calcium.
During heavy exercise, the ATP requirements of active muscle are likely to be met by metabolism of
carbohydrates.
Which of the following is/are targets of the efferent nervous system?
cardiac muscle smooth muscle skeletal muscle glands
Learning and memory are thought to be due to synaptic changes known as
long-term potentiation.
In most cells, the concentration of ions contributing to the membrane potential is __________ in the intracellular fluid compared with the extracellular fluid, with the exception of __________ ions.
lower; potassium
Which of the following is an effect of the parasympathetic nervous system?
Airway constriction
A patient has damage to one somatic motor neuron. What will this affect?
One motor unit
target receptor for preganglionic neurons
cholinergic nicotinic receptor
Spatial summation refers to
multiple graded potentials arriving at one location.
a single muscle cell
muscle fiber
Thick filaments are made up of __________.
myosin
primary sympathetic neurotransmitter
norepinephrine
An important difference between single-unit and multiunit smooth muscle is the
numerous gap junctions in single-unit smooth muscle, which allow many cells to work together as a sheet.
A motor unit consists of
one neuron and all the skeletal muscle fibers it controls
In response to binding a neurotransmitter, a postsynaptic cell can
open chemically gated ion channels, causing graded potentials known as fast synaptic potentials, close ion channels through G proteins and second messenger systems, producing slow responses, and regulate protein synthesis and affect the metabolic activities of the postsynaptic cell.
Skeletal muscle fibers with the greatest endurance rely on ________ for energy.
oxidative phosphorylation
Movement of the cupula in the ampullae of the semicircular canals allows detection of
rotational acceleration.
Sensations of the forces of gravity and linear acceleration are detected in the
saccule and utricle.
Match the structures with the accurate description. the muscle cell membrane
sarcolemma
How is acetylcholine (ACh) removed from the synaptic cleft?
simple diffusion away from the synaptic cleft and acetylcholinesterase (AChE; an enzyme)
A single neuron is stimulated at the central nervous system; this signal travels all the way to the target tissue, where the neurotransmitter acetylcholine is released onto the target tissue. The acetylcholine binds to a nicotinic receptor to induce skeletal muscle contraction. These steps describe the function of which branch of the efferent nervous system? Choose the best answer.
somatic
Match the response with the type of chemical. fat breakdown
sympathetic agonist
Match the response with the type of chemical. pupil dilation
sympathetic agonist
Match the response with the type of chemical. blocks secretion of adrenal catecholamines
sympathetic antagonist
Match the response with the type of chemical. blocks sweating
sympathetic antagonist
The small space between the sending neuron and the receiving neuron is the
synaptic cleft.
Acetylcholine binds to its receptor in the sarcolemma and triggers __________.
the opening of ligand-gated cation channels
The neural pathway from the spinal cord to the target tissue has two neurons, the preganglionic neuron and the postganglionic neuron.
true for both divisions
Which of the following neurons or groups of neurons is NOT considered to be a part of the efferent pathway?
Sensory
It releases norepinephrine at the neuroeffector synapse.
true only for the sympathetic division
What stimulates ACh release into the synaptic cleft of a neuromuscular junction?
An action potential opens voltage-gated Ca2+ channels in the axon terminal.
How is the energy released by ATP hydrolysis used during the contractile cycle in skeletal muscle?
It causes rotation of the myosin head, thus "cocking" it.
A receptor potential is a(n) __________ potential.
graded
After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?
ATP binds to the myosin head.
Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine?
Acetylcholine is degraded by acetylcholinesterase.
Which of the following best describes the contraction phase of the excitation-contraction coupling reaction? Choose the best answer
Actin and myosin filaments slide past each other to shorten the sarcomere, bringing Z disks closer together.
Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?
Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.
Identify the FALSE statement.
IPSPs depolarize the membrane
What would be the effect of ACh binding to its receptor on a skeletal muscle cell?
Na+ would flow into the cell, and K+ would flow out of the cell.
Which nervous system division has parasympathetic and sympathetic branches?
The autonomic division of the efferent nervous system
Which of the following processes produces molecules of ATP and has two pyruvic acid molecules as end products?
glycolysis
Relative to skeletal muscle, smooth muscle
uses less energy to generate a given amount of force, can sustain contractile force without fatigue and uses calcium from the sarcoplasmic reticulum and extracellular space.
Drag and drop each of the following phrases so that they occur in the correct sequential order.
1.) An action potential that travels down the T-tubule changes the structural confirmation of the DHP L-type Ca2+ channel 2.) Ryanodine receptor channels open 3.) Ca2+ leaves the sarcoplasmic reticulum 4.) Acting and myosin bind to one another 5.) Myosin heads utilize energy from ATP hydrolysis to produce the power stroke 6.) Actin filaments slide toward the M line, shortening the sarcomere
Which ratio between primary neuron and secondary neuron would allow for the greatest receptive field sensitivity?
1:1
Put these events in the correct chronological sequence:
3, 1, 2, 4 3. Acetylcholine binds to receptors on the motor end plate. 1. End-plate potentials trigger action potentials. 2. Transverse tubules bring potentials into the interior of the cell. 4. Ca2+ is released from the sarcoplasmic reticulum.
The following are steps involved in transmission at the cholinergic synapse:
3, 2, 4, 5, 1. 3. An action potential depolarizes the axon terminal at the presynaptic membrane. 2. Calcium ions enter the axon terminal. 4. Acetylcholine is released from storage vesicles by exocytosis. 5. Acetylcholine binds to receptors on the postsynaptic membrane. 1. Chemically gated ion channels on the postsynaptic membrane are opened.
muscle contraction steps 1). Motor Neuron - Action potential reaches terminus 2) Opening calcium channels, allowing calcium to flow in 3) Releasing ACh by exocytosis (ATP) in cleft 4) ACh bind receptors in sarcolemma motor end plate 5) Instigates Sodium gates to open, Sodium into cell starting Action potential 6)AP spreads across the Sarcolemma into the T-tubule 7) Calcium released from SR 8) Calcium binds with troponin, pulls tropomyosin away from active sites. Exposing acting binding site
9)Crossbridge formation occurs between actin and myosin (ATP needs to bind with myosin and cock head back beforehand) 10) Powerstroke- Myosin head pivots and ADP &P1 released . Pulls actin 11) Crossbridge detachment (rigor state) - ATP binds and cocks the myosin head back SARCOMERE shortening will power contraction
__________ occurs when myosin crossbridges attach to actin filaments and pull them toward the middle of the sarcomere.
A power stroke
What is the definition of an ionotropic receptor?
A receptor that alters ion flow when it binds with its ligand
A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?
A series of proteins that control calcium release.
What is a varicosity in the autonomic nervous system?
A series of swollen ends of neurons where neurotransmitter is released
Which is a similarity between taste and smell?
Both detect chemical signals dissolved in body fluids.
Which of the following is a similarity between slow synaptic potentials and fast synaptic potentials?
Both stimulate the opening or closing of ion channels.
Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber?
Calcium ions are stored in the sarcoplasmic reticulum.
What specific event triggers the uncovering of the myosin binding site on actin?
Calcium ions bind to troponin and change its shape.
Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?
Calcium ions.
Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?
Calcium release from the sarcoplasmic reticulum initiates the contraction.
Which is the main enzyme responsible for the breakdown of catecholamines?
Monoamine oxidase
Which of the following is the smallest structure?
Myosin
Which loss of function would occur if you introduced a chemical that functioned as an inhibitor of the ryanodine receptor channel? Choose the best answer.
Myosin would not be able to bind to actin in order to cause shortening of the sarcomere
How is a neuroeffector junction different from a neuromuscular junction (NMJ)?
Neurotransmitter receptors are concentrated on the postsynaptic membrane in the NMJ but diffusely arranged across the tissue in a varicosity in a neuroeffector junction.
Which type of receptor is found in the neuromuscular junction?
Nicotinic
Which type of receptor would bind acetylcholine and be found in skeletal muscle?
Nicotinic cholinergic
Which happens when a myofibril contracts?
Thin and thick filaments slide past each other, but do not change in length.
What happens when calcium binds troponin?
Tropomyosin is pulled away from the myosin-binding site on actin.
How does troponin facilitate cross bridge formation?
Troponin controls the position of tropomyosin on the thin filament, enabling myosin heads to bind to the active sites on actin
What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?
Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.
A receptor potential is
a graded potential.
The mechanism by which the neurotransmitter is returned to a presynaptic neuron's axon terminal is specific for each neurotransmitter. Which of the following neurotransmitters is broken down by an enzyme before being returned?
acetylcholine
A myosin head binds to which molecule to form a cross bridge?
actin
sympathetic tissue receptor
adrenergic receptor
location of voltage-gated ion channels
axon
Match the stimulus to the type of receptor that typically responds to it. pH
chemoreceptor
parasympathetic tissue receptor
cholinergic muscarinic receptor
Where in the cross bridge cycle does ATP hydrolysis occur?
during the cocking of the myosin head
Neurotransmitters are usually released into synapses by __________.
exocytosis
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
exocytosis
Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________.
extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber
Convergence describes
how multiple presynaptic sensory neurons synapse on one postsynaptic neuron.
When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron,
ion channels in the plasma membrane of the receiving neuron open.
Match the stimulus to the type of receptor that typically responds to it. pressure
mechanoreceptor
The larger the receptive field, the
more primary sensory neurons synapse on one secondary sensory neuron.
What, specifically, is a cross bridge?
myosin binding to actin
The primary problem in hyperkalemia is that
neurons are easier to excite because their resting potential is closer to threshold and neurons respond too quickly to smaller graded potentials.
A molecule that carries information across a synaptic cleft is a
neurotransmitter.
The inhibitory neurotransmitters of the CNS act by opening ________ channels.
only Cl-
What causes the power stroke?
release of ADP and Pi
Sharp, localized (fast) pain is rapidly transmitted to the central nervous system along
small, myelinated A-delta fibers
The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?
terminal cisterns (cisternae) of the sarcoplasmic reticulum
Accommodation describes the focusing of light on the retina by changing
the shape of the lens.
These receptors slowly adapt, and would be activated when the skin is between 20−40∘∘C.
thermoreceptors
It is important during stress or emergencies (fight-or-flight).
true only for the sympathetic division
Which type of muscle fiber has a large quantity of glycogen and mainly uses glycolysis to synthesize ATP?
white fast twitch fibers
Muscarine, a chemical produced by certain mushrooms, binds to muscarinic receptors mimicking the effect of acetylcholine. How do you think administering this chemical would change body function? The drug would _____________.
*change the functionality of the smooth muscles within the digestive system *change the functionality of certain exocrine and endocrine glands *change the functionality of the heart
What is the magnitude (amplitude) of an action potential?
100 mV
The following are the main steps in the generation of an action potential:
4, 6, 7, 1, 2, 5, 3. 4. a graded depolarization brings depolarization to threshold 6. sodium channels open 7. sodium ions enter the cell and further depolarization occurs 1. sodium channels are closed 2. more voltage-regulated potassium channels open and potassium moves out of the cell, initiating repolarization 5. a temporary hyperpolarization occurs 3. sodium channels return to their resting properties
The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?
A myosin head bound to actin
Which event causes cross bridge detachment?
ATP binding to the myosin head
Neurons in the parasympathetic pathway use which of the following neurotransmitters?
Acetylcholine
The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction?
Acetylcholine is released by axon terminals of the motor neuron.
Which of the following is a similarity between the somatic motor and autonomic pathways?
Acetylcholine is secreted from the neuron that originates in the CNS.
How/when does the myosin head cock back to store energy for the next cycle?
After the myosin head detaches, energy from ATP hydrolysis is used to re-cock the myosin head.
The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate (junctional folds of the sarcolemma) and sodium enters the cell.
Which is a similarity between spatial summation and temporal summation?
Both allow subthreshold graded potentials to trigger an action potential.
Which of the following is the most direct cause of muscle relaxation? Choose the best answer.
Ca2+ unbinds from troponin, which results in tropomyosin re-covering myosin binding sites.
Which of the following best describes the role of calcium (Ca2+ ) in the excitation-contraction coupling reaction? Choose the best answer
Ca2+ will bind to troponin, which leads to a conformational shift in tropomyosin, allowing for actin and myosin to attach.
Which of the following structure contains sensory receptors for hearing?
Cochlea
What type of conduction takes place in unmyelinated axons?
Continuous conduction
When does cross bridge cycling end?
Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.
Sympathetic neurons stimulate vasoconstriction in the GI tract, while sympathetic neurons stimulate vasodilation in arterioles supplying skeletal muscles. Which mechanism explains these opposite effects?
Different receptors for the same neurotransmitter
Most people are not actively aware of the sensation of clothes on their body throughout the day. This lack of awareness of the stimulus of clothing on the skin is due to which process?
Habituation
What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?
Inactivation gates of voltage-gated Na+ channels close, while activation gates of voltage-gated K+ channels open.
Which will best increase the conduction rate of action potentials?
Increase the diameter of the axon, increase the resistance of the axon membrane to ion leakage.
How would the absolute refractory period be affected if voltage-gated sodium channels remained inactivated?
It would be longer than normal.
Which of the following type of receptor is involved in hearing?
Mechanoreceptor
Which type of receptors are the hair cells of the ear?
Mechanoreceptors
Which of the following best summarizes the events of excitation-contraction coupling? Choose the best answer.
Muscle action potentials initiate calcium signals that activate a contraction-relaxation cycle
The neurotransmitter that controls skeletal muscle causes which of the following?
Muscle contraction
In which type of axon will velocity of action potential conduction be the fastest?
Myelinated axons with the largest diameter
BMD (2,3-butanedione 2-monoximime) inhibits myosin, such that ATP can bind to myosin but myosin is unable to hydrolyze the bound ATP. What effect would BMD have on the cross bridge cycle?
Myosin heads would remain detached, unable to cock.
Which of the following characteristics is similar between the sympathetic and parasympathetic branches for most neurons?
Neurotransmitter is secreted from the preganglionic neuron.
Which type of acetylcholine receptor is present on postganglionic neurons, and which type is present on the target tissues in autonomic pathways?
Nicotinic on the postganglionic neurons and muscarinic on the target tissues
The somatic nervous system and the parasympathetic nervous system both release acetylcholine (ACh) onto their target tissues. Do you predict that this would indicate that these two pathways carry out the same effects? Why or why not? Choose the best answer.
No, because the receptors found on the target tissue for each pathway are different.
If a hyperpolarizing graded potential and a depolarizing graded potential of similar magnitudes arrive at the trigger zone at the same time, what is most likely to occur?
Nothing. They will cancel each other out.
What characterizes repolarization, the second phase of the action potential?
Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.
Which is a difference between hearing and equilibrium?
One is stimulated by fluid movements in the cochlea, and the other is stimulated by movements in the vestibular apparatus.
Which of the following is an example of antagonistic control?
Parasympathetic stimulation causes bronchoconstriction, while sympathetic stimulation causes bronchodilation.
A patient is prescribed a muscarinic antagonist. This will inhibit signaling from which neurons?
Postganglionic parasympathetic
Which of the following would stop muscle contraction?
Pumping of calcium ions into the SR
The "rest and recovery" period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT __________.
Pyruvic acid is converted back to lactic acid.
Where do all tertiary somatic sensory neurons terminate?
Somato sensory cortex
Calcium entry into the axon terminal triggers which of the following events?
Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.
inward extensions of the muscle cell membrane
T tubules
What role does tropomyosin play in the cross bridge cycle?
The displacement of tropomyosin exposes the active sites of actin, allowing cross bridges to form.
How does the myosin head obtain the energy required for activation?
The energy comes from the hydrolysis of ATP.
Why does regeneration of the action potential occur in one direction, rather than in two directions?
The inactivation gates of voltage-gated Na+ channels close in the node, or segment, that has just fired an action potential.
Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?
The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.
During contraction, what prevents actin myofilaments from sliding backward when a myosin head releases?
There are always some myosin heads attached to the actin myofilament when other myosin heads are detaching.
Which of the following is NOT a similarity between somatic motor and autonomic pathways?
They all stimulate muscarinic receptors.
Which of the following is NOT a similarity between hearing and equilibrium?
They both respond to sound waves.
Which mechanism causes hair cell depolarization as stereocilia bend in response to sound waves?
Tip links open ion channels, which causes membrane depolarization.
A patient has a vitamin A deficiency. Which special sense would be most affected?
Vision
What opens first in response to a threshold stimulus?
Voltage-gated Na+ channels
The motor end plate is
a folded area of muscle cell membrane with ACh receptors clustered at the top of each fold.
released by all autonomic preganglionic neurons
acetylcholine
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
acetylcholine (ACh)
Which of the following statements best describes the resting membrane potential? Choose the best answer.
an electrical gradient that exists between the intracellular and extracellular fluids
Which of the following best describes the direction and function of efferent signals?
away from the central nervous system, cause motor effects in glands or muscles
Which type of synapse is most common in the nervous system?
chemical
Which is NOT a known drug effect on synaptic function?
change the type of neurotransmitter found in the synaptic vesicle
Binding of a neurotransmitter to its receptors opens __________ channels on the __________ membrane.
chemically gated; postsynaptic
Match the stimulus to the type of receptor that typically responds to it. oxygen
chemoreceptor
A molecule that prevents substance P from binding to its receptor would
decrease the perception of pain.
What is the type of chemical reaction used to rebuild ADP into ATP?
dehydration synthesis
A home satellite dish receives signals from a satellite in outer space, allowing your television to display TV shows. Which part of a neuron is similar to the satellite dish?
dendrites
Where do most action potentials originate?
initial segment
The neurons of the central nervous system are also known as __________.
interneurons
Within a single fiber, the tension developed during a twitch depends upon the
length of the sarcomeres prior to contraction.
The gate control theory of pain modulation states that pain transmission can be blocked by
mechanical stimulation of A-beta fibers.
Match the stimulus to the type of receptor that typically responds to it. Stretch
mechanoreceptor
Match the response with the type of chemical. salivation
parasympathetic agonist
Match the response with the type of chemical. blocks urination
parasympathetic antagonist
Inhibition of neural activity can result from
presynaptic events and postsynaptic events.
In a synapse, neurotransmitters are stored in vesicles located in the __________.
presynaptic neuron
highly organized bundles of contractile proteins within a skeletal muscle cell
sarcomere myofibril
A patient is born with a mutation in her calmodulin gene. This could affect the contraction of ________ muscles.
smooth
The two subdivisions of the efferent division of the peripheral nervous system are
somatic motor neurons and autonomic neurons.
Match the response with the type of chemical. decreased activity in digestive tract
sympathetic agonist
Which of the following are components of the efferent nervous system?
sympathetic neurons parasympathetic neurons somatic motor neurons
With the exception of olfaction, all sensory pathways first travel to the ________, which acts as a relay and processing station.
thalamus
The Nernst equation can be used to predict
the membrane potential resulting from permeability to a single ion
The repolarization phase of an action potential results from __________.
the opening of voltage-gated K+ channels
Which of the following statements best describes the neuromuscular junction? Choose the best answe
the point of synapse between a motor neuron and the muscle fiber that it innervates
Compared to fast-twitch glycolytic fibers (type IIX), slow-oxidative muscle fibers (type I) are characterized by a smaller diameter and __________.
the presence of myoglobin
When calcium ions enter the synaptic terminal,
they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.
Most preganglionic neurons originate in the thoracic and lumbar regions of the spinal cord.
true only for the sympathetic division
The adrenal medulla is closely allied with this system.
true only for the sympathetic division
The ganglia are found in a chain that runs close to the spinal cord or along the descending aorta.
true only for the sympathetic division
An action potential releases neurotransmitter from a neuron by opening which of the following channels?
voltage-gated Ca2+ channels
The depolarization phase of an action potential results from the opening of which channels?
voltage-gated Na+ channels
Hyperpolarization results from __________.
slow closing of voltage-gated K+ channels
A chemical synapse ALWAYS includes which of the following?
1, 2, 3, 4 1. axon terminal 2. presynaptic cell 3. synaptic cleft 4. postsynaptic cell
Which of the following would have the fastest action potentials?
A myelinated axon with a large diameter
Which is a difference between the synaptic cleft and the synapse?
A synaptic cleft is the space between a presynaptic axon terminal and a postsynaptic dendrite, and a synapse includes all three of these structures.
When two or more graded potentials arrive at the trigger zone, which of the following could happen?
An excitatory and inhibitory signal can cancel each other out; two excitatory stimuli may be additive, and summation could occur; and two inhibitory stimuli may be additive, resulting in lower excitability.
How is an action potential propagated along an axon?
An influx of sodium ions from the current action potential depolarizes the adjacent area.
The two cells below are hypothetical cells with a concentration of 100 mOsm of K+ inside the cells and containing only leak channels for K+ within the membrane. Each cell is placed into a different solution containing different concentrations of K+ in the extracellular fluid. Which of the two cells below has a higher permeability to K+ and why? Choose the best answer.
B, because it has more ion leak channels for K+ than A.
In the membrane of a resting nerve cell, when chemically gated Cl- channels open,
Cl- ions enter the cell.
When more action potentials arrive at the axon terminal, how is a postsynaptic neuron affected?
Neurotransmitter release increases, increasing the frequency or magnitude of graded potentials in the postsynaptic neuron.
Repair of damaged neurons can be assisted by certain neurotrophic factors secreted by the
Schwann cells only.
What event triggers the generation of an action potential?
The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.
What is the function of the myelin sheath?
The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.
What is the first change to occur in response to a threshold stimulus?
Voltage-gated Na+ channels change shape, and their activation gates open.
Whether a neuron fires an action potential depends on __________.
a graded potential above threshold voltage reaching the trigger zone
Graded potentials can
act as signals over short distances and make an action potential more or less likely.
originate(s) at the trigger zone
action potential
The basis of integration of neural information is
addition of postsynaptic potentials overlapping in time and space.
Part complete A ligand binds to a receptor-channel that stimulates a channel to open. This is a chloride channel. This will stimulate __________.
an inhibitory postsynaptic potential (IPSP)
Where in the neuron is an action potential initially generated?
axon hillock
Some neurotoxins work essentially the same way as some local anesthetics, which is to
bind to Na+ channels and prevent depolarization by blocking Na+ entry into the cell.
The pattern of synaptic connectivity where a large number of presynaptic neurons provide input to a single postsynaptic neuron, is known as
convergence.
An action potential is self-regenerating because __________.
depolarizing currents established by the influx of Na+ flow down the axon and trigger an action potential at the next segment
Binding of the neurotransmitter to its receptor causes the membrane to __________.
either depolarize or hyperpolarize
The neurotransmitter thought to be involved in learning and memory is
glutamate.
originate(s) on dendrites and cell bodies
graded potential
size increases if stimulus strength increases
graded potential
When comparing action potentials to graded potentials, an/two important distinguishing characteristic/s is/are
graded potentials can undergo summation and the rate of action potentials is limited by the refractory period.
Presynaptic facilitation makes a pathway
more likely to be in use, just through depolarization of selected neurons and capable of alteration, just through training and conditioning.
Which of the following statements best describes the concept of permeability? Choose the best answer.
the ability of a molecule to cross the cell membrane
If a signal from a sending neuron makes the receiving neuron more negative inside,
the receiving neuron is less likely to generate an action potential.
During an action potential, the rapid decrease in sodium ion permeability and the simultaneous and rapid increase in potassium ion permeability is responsible for __________.
the repolarization phase
