BIOL336 Neurophysiology I and II
Given an extracellular Na+ concentration of 150 mM and an intracellular Na+ concentration of 15 mM, what is the equilibrium potential of a plasma membrane permeable only to Na+?
+61 mV
Imagine an artificial cell with a plasma membrane permeable only to Na+ due to the presence of a Na+ leak channel in the plasma membrane. The artificial cell rests in a buffer with a [Na+] of 150mM. If the intracellular [Na+] of this cell is 15mM, what is the Na+ equilibrium potential of this artificial cell?
+61mV
Given an extracellular Cl- concentration of 100 mM and an intracellular Cl- concentration of 10 mM, what is the equilibrium potential of a plasma membrane permeable only to Cl-?
-61 mV
Most neurons have a resting membrane potential of:
-70mV
What is the value for the resting membrane potential for most neurons?
-70mV
If every ligand-gated Na+ channel on a neuronal soma depolarized the cell by 2mV, how many channels would you need to activate to reach a threshold value of exactly -50mV? (Assume a typical resting membrane potential.)
10
What is the difference in charge between two compartments where the charge of one compartment is -1 and the other compartment is +1?
2
Which is the correctly written Nernst equation? Eion =
61/z x log [ion]out / [ion]in
What is the relative release of catecholamines from the adrenal medulla?
80% epinephrine; 20% norepinephrine
In myelinated axons, sodium and potassium channels would be concentrated in what area?
Nodes of Ranvier
The regions of axon membrane that lie between regions of myelin are the:
Nodes of Ranvier
The __________ refractory period of an action potential is primarily due to __________ permeability of the plasma membrane to K+.
Relative; increased
The period during an action potential when voltage-gated Na+ channels are inactivated and voltage-gated K+ channels are open is best described as:
Repolarizing phase
Ions are unequally distributed across the plasma membrane of all cells. This ion distribution creates an electrical potential difference across the membrane. What is the name given to this potential difference?
Resting membrane potential (RMP)
Which area of the brain plays an important role in sleep-wake cycles, arousal of the cerebral cortex, and consciousness?
Reticular formation
Myelin in the peripheral nervous system (PNS) is formed by:
Schwann cells
What region of the diencephalon filters and refines sensory information, allowing us to direct our attention to specific external stimuli?
Thalamus
What limits the maximum number of action potentials on an axon?
The absolute refractory period
The term "saltatory conduction" refers to:
The conduction of an action potential along a myelinated axon.
When potassium exits a neuron during an action potential:
The inside of the cell loses positive ions and produces a negative charge inside.
The Nernst equation predicts:
The membrane potential resulting from permeability to a single ion.
As an action potential is propagated away from the axon hillock, why does propagation continue in one direction?
The region just behind the action potential is in the absolute refractory period.
Given an extracellular Cl- concentration of 100 mM and an intracellular Cl- concentration of 10 mM, what is the net direction of movement of Cl- across a membrane permeable only to Cl- when the membrane is at the equilibrium potential? At the equilibrium potential:
There is no net direction of movement of Cl- across the plasma membrane
T/F: The Na+/K+ pump distributes three sodium ions to the outside of the membrane and two potassium ions to the inside of the membrane.
True
T/F: The cerebral cortex carries out the highest level of neural processing.
True
T/F: The facilitated diffusion of molecules across the blood-brain barrier relies on protein carriers that are specific for the movement of particular molecules.
True
T/F: The sulci and gyri of the brain provide more surface area more volume for the cerebral cortex to reside
True
For an unmyelinated axon, conduction velocity is primarily determined by the
Diameter of the axon
Where are the cell bodies of afferent neurons located?
Dorsal root ganglia
Afferent and efferent axons travel together in spinal nerves, but they separate into different bundles when they leave and enter the spinal cord. The afferent axons enter the spinal cord via the __________ root and efferent axons leave the spinal cord via the _________ root.
Dorsal; ventral
A(n) _________ neuron carries information from the central nervous system (CNS) to skeletal muscle in the periphery.
Efferent
What portion of the peripheral nervous system communicates to effector organs?
Efferent nervous system
T/F: A myelinated axon is shielded from direct contact with the extracellular fluid all along its length.
False
T/F: Dorsal root ganglia contain the cell bodies of efferent neurons.
False
T/F: Graded potentials are of equal magnitude and travel over long distances along the axon.
False
T/F: Leak channels are most concentrated in the soma of neurons.
False
T/F: The membrane potential of a cell is determined exclusively by that cell's sodium and potassium permeability.
False
T/F: The primary hormone released from the adrenal medulla is norepinephrine.
False
T/F: When voltage-dependent calcium channels open, calcium moves out of the cell.
False
Clusters of nerve cell bodies in the peripheral nervous system (PNS) are called:
Ganglia
For cells that communicate by electrical synapses, the message travels between cells via
Gap junctions
In the human brain, the most abundant cell type is the:
Glial cell
What type of potential can sum?
Graded potentials
What type of central nervous system (CNS) glial cell is "star-shaped" and involved in formation of the blood-brain barrier?
Astrocytes
What portion of the efferent branch of the nervous system communicates to glands and cardiac muscle?
Autonomic nervous system
Which of the following correctly completes the sentence? The period of time after an action potential when another action potential cannot be generated is the __________.
Absolute refractory period
Parasympathetic preganglionic neurons release the neurotransmitter ________; sympathetic preganglionic neurons release the neurotransmitter ________.
Acetylcholine; acetylcholine
What type of potential is affected by refractory periods?
Action potentials
A(n) _________ neuron transmits information from the periphery to the central nervous system (CNS).
Afferent
What portion of the peripheral nervous system transmits information from sensory receptors to the central nervous system?
Afferent nervous system
A subthreshold stimulus will not generate an action potential whereas a suprathreshold stimulus does generate an action potential. This is an example of
All-or-none principle
The middle layer of the three meninges is the:
Arachnoid
What type of potential results from the opening and closing of ion channels?
Both graded and action potentials
When the body is stressed, what is the relative contribution of the sympathetic and parasympathetic nervous systems to the regulation of homeostasis?
Both systems are active but the sympathetic predominates.
Dual innervation means that:
Both the parasympathetic and the sympathetic divisions of the autonomic nervous system supply an organ.
The central nervous system includes the:
Brain and spinal cord
The brain and spinal cord are part of which of the following branches of the nervous system?
Central nervous system
What two structures make up the forebrain?
Cerebrum and diencephalon
Cerebrospinal fluid is produced by the:
Choroid plexus
What cells of the adrenal medulla release epinephrine?
Chromaffin cells
The purpose of the folding that occurs in the mammalian cerebral cortex is to:
Increase the surface area without increasing the volume
The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____.
K+; Na+
Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?
Leak channels
To help pay for medical school, you get a part-time job in the anatomy lab. In an examination of the respiratory control center found in the brainstem, you must separate the brainstem from the overlying forebrain for your students. In order to separate the brainstem from the forebrain, a cut must be made between the:
Midbrain and diencephalon
A 12-year old boy has a severe asthmatic attack with wheezing. He experiences rapid breathing and becomes cyanotic (the appearance of a blue or purple coloration of the skin due to the tissues near the skin surface being low on oxygen). To treat this individual, you should administer: a) an adrenergic receptor agonist b) a muscarinic AChR agonist c) a nicotinic AChR antagonist d) an adrenergic receptor antagonist e) a nicotinic AChR agonist
a) An adrenergic receptor agonist
How is an action potential propagated along an axon? a) An influx of sodium ions from the current action potential depolarizes the adjacent area. b) An efflux of potassium from the current action potential depolarizes the adjacent area. c) Stimuli from the graded (local) potentials from the soma and dendrites depolarize the entire axon.
a) An influx of sodium ions from the current action potential depolarizes the adjacent area.
Which of the following about glial cells is false? Glial cells: a) are outnumbered by neurons 10 to 1 in the central nervous system. b) are important for the growth and development of the nervous system. c) form the myelin for axons. d) deliver fuel molecules to neurons and remove the waste products of metabolism. e) regulate the composition of the extracellular fluid in the CNS.
a) Are outnumbered by neurons 10 to 1 in the central nervous system.
Voltage-gated calcium channels in the axon terminal open in response to which of the following? a) arrival of an action potential at the axon terminal b) initiation of an action potential in the axon hillock c) summation of graded potentials at the axon hillock d) neurotransmitter binding to receptor e) paracrines released from the post-synaptic cell
a) Arrival of an action potential at the axon terminal
During depolarization, which gradient(s) move(s) Na+ into the cell? a) both the electrical and chemical gradients b) only the chemical gradient c) Na+ does not move into the cell. Na+ moves out of the cell. d) only the electrical gradient
a) Both the electrical and chemical gradients
What type of conduction takes place in unmyelinated axons? a) Continuous conduction b) Synaptic transmission c) Saltatory conduction d )Electrical conduction
a) Continuous conduction
Which of the following statements about myelin is false? Myelin: a) covers all parts of the neuron, including the axon, cell body, and dendrites. b) is formed by glial cells. c) influences the velocity of conduction of an electrical signal down an axon. d) is a fatty membranous sheath.
a) Covers all parts of the neuron, including the axon, cell body, and dendrites.
Toward the end of the relative refractory period, the continued decrease in stimulus intensity required to initiate an action potential is caused by: a) decreased potassium permeability. b) increased potassium permeability. c) the number of sodium channels whose inactivation gate has not opened. d) decreased sodium permeability. e) closure of the sodium activation gate.
a) Decreased potassium permeability.
How can action potentials relay information about the intensity of a stimulus, such as distinguishing between a loud and soft sound? a) due to the frequency of action potentials b) due to electrotonic conduction c) due to the decremental properties of graded potentials d) due to the magnitude of action potentials e) due to summation of several action potentials
a) Due to the frequency of action potentials
Dr. Wilder Penfield (1891-1976) was the first to map functional areas of the human brain by electrically stimulating cortical regions (see https://www.youtube.com/watch?v=8uUvWmXUodE). In a similar cortical stimulation study, you expect to find a disproportionate amount of the motor cortex is devoted to the control of movements of the: a) fingers b) toes c) arms d) elbow e) eyebrows
a) Fingers
What equation is used to calculate the membrane potential based on ion concentration gradients and permeabilities? a) GHK equation b) Ficks equation c) NAD equation d) Nernst equation e) None of the answers is correct.
a) GHK equation
Which of the following potentials dissipate in size as the potential moves away from the site of initiation? a) graded potentials b) threshold potentials c) action potentials d) both graded potentials and action potentials e) neither graded potentials nor action potentials
a) Graded potentials
What prevents the Na+ and K+ gradients from dissipating? a) Na+-K+ ATPase b) H+-K+ ATPase c) Na+ cotransporter d) Na+ and K+ leaks
a) Na+-K+ ATPase
A young boy receives a sharp blow to the back of his head resulting in a loss of one of his senses. Which of the following pairings correctly matches this observation? a) occipital lobe and vision b) frontal lobe and taste c) temporal lobe and taste d) parietal lobe and vision e) occipital lobe and smell
a) Occipital lobe and vision
At a chemical synapse, which of the following occurs first? a) opening of voltage-gated calcium channels b) exocytosis of secretory vesicles c) receptor-ligand binding at the post-synaptic membrane d) re-uptake of the neurotransmitter or parts of the neurotransmitter
a) Opening of voltage-gated calcium channels
Which area of the brain relays sensory information to the cerebral cortex? a) thalamus b) hypothalamus c) basal nuclei d) corpus callosum e) cerebellum
a) Thalamus
Which of the following statements about the Na+/K+ ATPase pump is FALSE? The Na+/K+ ATPase pump: a) transports Na+ and K+ in a 1:1 ratio. b) transports Na+ out of the cell and K+ into the cell. c) requires the expenditure of metabolic (cellular) energy. d) is expressed in neurons.
a) Transports Na+ and K+ in a 1:1 ratio.
Which of the following events occurs FIRST after an action potential arrives at an axon terminal? a) Voltage-gated calcium channels open. b) Exocytosis of neurotransmitter. c) Vesicles containing neurotransmitters fuse with the plasma membrane of the axon terminal. d) Neurotransmitter binds to receptors on the postsynaptic cell. e) Calcium ions enter the axon terminal.
a) Voltage-gated calcium channels open.
In the peripheral nervous system, __________ neurons carry sensory and visceral information to the central nervous system, and __________ neurons leave the central nervous system and innervate organs, which are usually muscles or glands.
afferent; efferent
Which of the following receptor types is found on the dendrites and cell bodies of postganglionic parasympathetic neurons? a) muscarinic acetylcholine receptors (M-AChR) b) nicotinic acetylcholine receptors (N-AChR) c) adrenergic receptors d) epidermal growth factor receptors (EGFR) insulin receptors (InR)
b) Nicotinic acetylcholine receptors (N-AChR)
Which ion(s) is/are higher in concentration inside the cell compared to outside? a) Sodium b) Potassium c) More than one of these d) Chloride
b) Potassium
The region of the brainstem important in the sleep-wake cycle, the arousal of the cerebral cortex, and in consciousness is known as the a) midbrain. b) reticular formation. c) medulla oblongata. d) pons. e) corpus callosum.
b) Reticular formation.
The velocity of the action potential is fastest in which of the following axons? a) a large unmyelinated axon b) a small unmyelinated axon c) a small myelinated axon
c) A small myelinated axon
Which of the following potentials are affected by refractory periods? a) graded potentials b) threshold potentials c) action potentials d) both graded potentials and action potentials e) neither graded potentials nor action potentials
c) Action potentials
A cell has a membrane potential of -100mV (more negative inside than outside) and has 1000 times more calcium ions outside the cell than inside. Which of the following describes the electrical and chemical gradients that influence the movement of calcium across the plasma membrane of this cell that is permeable to calcium? a) The chemical gradient favors and the electrical gradient opposes the entry of calcium into the cell. b) The electrical gradient favors and the chemical gradient opposes the entry of calcium into the cell. c) Both the chemical and the electrical gradients favor calcium entry into the cell. d) Both the chemical and the electrical gradients oppose calcium entry into the cell.
c) Both the chemical and the electrical gradients favor calcium entry into the cell.
Which of the following is NOT a component of the brainstem? a) medulla oblongata b) pons c) cerebellum d) midbrain e) reticular formation
c) Cerebellum
Which of the following axons would have the fastest conduction velocity? a) diameter = 5 microns, unmyelinated b) diameter = 5 microns, myelinated c) diameter = 20 microns, myelinated d) diameter = 20 microns, unmyelinated e) diameter = 1 micron, myelinated
c) Diameter = 20 microns, myelinated
How does myelin "insulate" an axon? a) It forms a single, very thick layer around the axon, which slows the diffusion of ions. b) The multiple layers of myelin slow down the diffusion of ions into the axon because it takes the ions a long time to cross each layer before they can diffuse into the axon. c) It is made of multiple layers of mostly lipids, which are impermeable to ions. d) It generates an electrical charge, which repels ions from crossing the plasma membrane.
c) It is made of multiple layers of mostly lipids, which are impermeable to ions.
What are the purposes of cerebrospinal fluid (CSF)? The CSF: a) reduces pressure at the base of the brain. b) cushions the brain to prevent damage caused by a blow to the head. c) provides a carefully regulated environment to support the electrical activity of neuronal cells. d) all of the above
d) All of the above
Which of the following degrades certain neurotransmitters? a) microglia b) oligodendrocyte c) ependymal cell d) astrocyte e) Schwann cell
d) Astrocyte
An action potential is self-regenerating because __________. a) repolarizing currents established by the efflux of Na+ flow down the axon and trigger an action potential at the next segment b) depolarizing currents established by the influx of K+ flow down the axon and trigger an action potential at the next segment c) repolarizing currents established by the efflux of K+ flow down the axon and trigger an action potential at the next segment d) depolarizing currents established by the influx of Na+ flow down the axon and trigger an action potential at the next segment
d) Depolarizing currents established by the influx of Na+ flow down the axon and trigger an action potential at the next segment
Through physical examination, neurologists can easily determine which spinal nerve has been damaged and at what level in the spinal cord an injury has occurred due to mapping out the various sensory regions called a) commissural fibers. b) association fibers. c) ganglia. d) dermatomes. e) projection fibers.
d) Dermatomes
Once a membrane potential has been developed, the force that drives a particular ion across the membrane is its a) concentration gradient. b) electrical gradient. c) chemical gradient. d) electrochemical gradient. e) electrogenic pump.
d) Electrochemical gradient.
Which statement about graded membrane potentials is FALSE? a) The strength of a graded potential is proportional to the concentration of neurotransmitter near the dendrite of a neuron. b) Graded potentials can add up to produce greater depolarizations. c) Graded potentials diminish in strength over distance. d) Graded potentials are mainly produced by voltage-gated sodium and potassium channels. e) Graded potentials can hyperpolarize a membrane.
d) Graded potentials are mainly produced by voltage-gated sodium and potassium channels
Which is a FALSE statement about the cerebrospinal fluid (CSF)? The CSF: a) acts as a protective cushion for the brain and spinal cord. b) is secreted by cells lining the ventricles of the brain. c) circulates within brain ventricles and surrounds the brain and spinal cord. d) has the same composition as blood plasma.
d) Has the same composition as blood plasma.
What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization? a) Inactivation gates of voltage-gated Na+ channels close, while inactivation gates of voltage-gated K+ channels open. b) Activation gates of voltage-gated Na+ channels close, while inactivation gates of voltage-gated K+ channels open. c) Activation gates of voltage-gated Na+ channels close, while activation gates of voltage-gated K+ channels open. d) Inactivation gates of voltage-gated Na+ channels close, while activation gates of voltage-gated K+ channels open.
d) Inactivation gates of voltage-gated Na+ channels close, while activation gates of voltage-gated K+ channels open.
The drug ephedrine is an adrenergic receptor agonist used as a nasal decongestant. Which of the following is an adverse effect caused by taking ephedrine? a) contraction of the pupils b) stimulation of liver, kidney, and bladder activity c) increased sexual arousal d) increased heart rate e) constriction inside the lungs
d) Increased heart rate
Which of these would you not find in the cerebral cortex? a) cell bodies b) dendrites c) unmyelinated axons d) myelinated axons
d) Myelinated axons
Which of the following statements is true of myelinated axons? a) Action potentials can be produced only where myelin is present on the axon. b) Myelinated axons are not affected by toxins like TTX (tetrodotoxin), which act on voltage-gated Na+ channels. This is because the myelin covers all the voltage-gated channels along the axon. c) Myelinated axons display electronic conduction of action potentials. d) Myelinated axons are present in the CNS and PNS.
d) Myelinated axons are present in the CNS and PNS.
The concentrations of which two ions are highest outside the cell. a) Na+ and A- (negatively charged proteins) b) K+ and A- (negatively charged proteins) c) K+ and Cl- d) Na+ and Cl-
d) Na+ and Cl-
Damage to the cerebellum will lead to which of the following symptoms? a) a complete inability to move (lack of execution) b) an inability to accurately plan a movement c) the generation of slow, fine movements only d) the generation of clumsy, poorly directed movements e) the generation of movement of large muscle groups only
d) The generation of clumsy, poorly directed movements
What is the function of the myelin sheath? a) The myelin sheath increases the insulation along the entire length of the axon. b) The myelin sheath decreases the resistance of the axonal membrane to the flow of charge. c) The myelin sheath decreases the speed of action potential conduction from the initial segment to the axon terminals. d) The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.
d) The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.
Which of the following statements about the resting membrane potential is TRUE? a) The resting membrane potential is normally equal to zero millivolts (mV). b) The inside of the plasma membrane is positively charged compared to the outside. c) The resting membrane potential is due, in part, to the presence of extracellular proteins. d) The resting membrane potential results, in part, from the concentration gradients for Na+ and K+.
d) The resting membrane potential results, in part, from the concentration gradients for Na+ and K+.
Which of the following statements is FALSE regarding the blood-brain barrier? a) Hydrophobic drugs pass through the blood-brain barrier more easily than hydrophilic drugs. b) Endothelial cells of the capillaries supplying the brain form tight junctions that restrict the passage of hydrophilic molecules into the extracellular fluid of the brain. c) Hydrophilic substances can be moved from the blood into the brain extracellular fluid via carrier proteins expressed by capillary endothelial cells. d) The walls of the capillaries supplying the brain are made up of several layers of cells, that act as a barrier to the release of drugs into the brain.
d) The walls of the capillaries supplying the brain are made up of several layers of cells, that act as a barrier to the release of drugs into the brain.
The plasma membrane is much more permeable to K+ than to Na+. Why? a) Ligand-gated cation channels favor a greater influx of Na+ than K+. b) The Na+-K+ pumps transport more K+ into cells than Na+ out of cells. c) There are many more voltage-gated K+ channels than voltage-gated Na+ channels. d) There are many more K+ leak channels than Na+ leak channels in the plasma membrane.
d) There are many more K+ leak channels than Na+ leak channels in the plasma membrane
In a cell that is permeable to only one ion, the equilibrium potential (Eion): a) is the membrane potential at which the ion has no net movement across the membrane. b) is the membrane potential at which the ion's chemical and electrical gradients are equal in magnitude and opposite in direction. c) can be calculated using the Nernst equation. d) refers to the membrane potential that exactly opposes the concentration gradient of the ion. e) all of these choices are correct.
e) All of these choices are correct.
Tight junctions between capillary endothelial cells in the central nervous system create the blood-brain barrier, thereby restricting what type of movement of molecules into the brain? a) active transport of b) transcytosis of c) facilitated diffusion of hydrophobic d) diffusion of lipophilic e) diffusion of hydrophilic
e) Diffusion of hydrophilic
Which of the following physiological responses are associated with an elevation in parasympathetic nervous system activity? a) shifting blood flow away from the gastrointestinal tract b) increased heart rate c) enhanced mobilization of energy stores d) increased contractile force of the heart e) enhanced absorption of nutrients
e) Enhanced absorption of nutrients
The influx of calcium into the axon terminal of a chemical synapse is responsible for which of the following? a) diffusion of the neurotransmitter across the membrane and into the cleft b) movement of calcium through gap junctions c) initiation of an action potential d) termination of an action potential e) fusion of vesicles to the membrane and of exocytosis neurotransmitter
e) Fusion of vesicles to the membrane and of exocytosis neurotransmitter
Which of the following substances requires mediated transport to cross the blood-brain barrier? a) hydrogen ions b) ethanol c) oxygen d) carbon dioxide e) glucose
e) Glucose
Administration of the drug Atropine causes a dry mouth by acting as a(n) _________. a) muscarinic AChR agonist b) nicotinic AChR antagonist c) adrenergic receptor antagonist d) nicotinic AChR receptor agonist e) muscarinic AChR antagonist
e) Muscarinic AChR antagonist
Which of the following potentials can reach or exceed the sodium equilibrium potential? a) graded potentials b) threshold potentials c) action potentials d) both graded potentials and action potentials e) neither graded potentials nor action potentials
e) Neither graded potentials nor action potentials
Compared to transmission across chemical synapses, transmission across an electrical synapse:
is mediated by gap junctions
Where are the cell bodies of efferent neurons located?
Ventral horn
What type of ion channels is necessary for the function of the axon and the axon terminal?
Voltage-gated
Which brain tissue contains mostly axons?
White matter
Synaptic vesicles store
neurotransmitter
T/F: In the somatosensory cortex, the hands have a greater area of representation than the feet.
True
T/F: Spinal nerves are composed of the axons of both afferent and efferent neurons.
True
The neurotransmitter that is released from the presynaptic neuron must diffuse across the ________ to reach the postsynaptic neuron.
Synaptic cleft
Which cerebral lobe contains the visual cortex?
Occipital lobe
What type of cell enhances the velocity of electrical transmission of an action potential along an axon in the central nervous system?
Oligodendrocytes
Which of the following cell types is responsible for the formation of myelin in the central nervous system?
Oligodendrocytes
The all-or-none principle, associated with the action potential, states that
Once membrane potential reaches threshold, an action potential will be generated and that action potential will always be the same magnitude.
What two divisions of the autonomic nervous system have opposite effects on the organs they innervate?
Parasympathetic and sympathetic
The fact that a cell has an electrical potential difference across its membrane makes that cell
Polarized
The repolarization phase of action potentials in neurons is due primarily to:
Potassium flow out of the cell
The chemical synapse is bounded by the ________ neuron, from which neurotransmitters are released across the synaptic cleft, to the ________ neuron, where the receptors for that neurotransmitter are located.
Presynaptic; postsynaptic
The perception of vision begins in which area of the brain?
Primary visual cortex
The mammalian cerebral cortex has _____ layers of cells.
Six
What portion of the efferent nervous system communicates with skeletal muscle?
Somatic nervous system
Where do the preganglionic neurons of the sympathetic nervous system emerge from the spinal cord?
Thoracic and upper lumbar regions
Which part of a neuron is a region with a high density of voltage-gated sodium and potassium channels, at which action potentials initiate?
Trigger zone
T/F: Connexons are a necessary component of electrical synapses.
True
T/F: During the relative refractory period, the stimulus intensity required to initiate an action potential is elevated
True
T/F: Hydrogen ions cannot permeate the blood-brain barrier.
True
Which of the following statements regarding graded potentials compared to action potentials is FALSE? Graded potentials: a) occur in dendrites and the cell body, whereas action potentials occur in the axons. b) are suitable as long-distance signals, whereas action potentials decay quickly. c) vary in magnitude, whereas action potentials are always the same magnitude in a given cell type. d) are generated by the opening and closing of ligand-gated channels, whereas action potentials are generated by the opening and closing of voltage-gated ion channels.
b) Are suitable as long-distance signals, whereas action potentials decay quickly.
In order for ions to move across the capillary endothelial cells of the blood-brain barrier, they must a) be lipophobic. b) be transported across endothelial cells. c) move through pores between endothelial cells. d) move through the endothelial cell layer by transcytosis. e) be hydrophilic.
b) Be transported across endothelial cells.
At rest, what is the relative contribution of the sympathetic and parasympathetic nervous systems to the regulation of homeostasis? a) Only the sympathetic system is active. b) Both systems are active but the parasympathetic predominates. c) Only the parasympathetic system is active. d) Both systems are active but the sympathetic predominates. e) Neither system is active.
b) Both systems are active but the parasympathetic predominates.
Which of the following changes in membrane potential is considered excitatory? a) hyperpolarization only b) depolarization only c) repolarization only d) both hyperpolarization and depolarization e) both hyperpolarization and repolarization
b) Depolarization only
A suprathreshold stimulus is more likely to generate multiple action potentials because __________. a) it generates larger action potentials b) it can generate another action potential during the relative refractory period c) it can generate another action potential during the absolute refractory period d) it generates another action potential before the refractory period takes place
b) It can generate another action potential during the relative refractory period
Which of the following ion channels located in the plasma membrane of the neuron are always open and are largely responsible for the resting membrane potential? a) aquaporins b) leak channels c) voltage-gated channels d) ligand-gated channels
b) Leak channels
Neuron F releases neurotransmitter onto the dendrite of Neuron G. A single impulse from Neuron F results in a 1mV depolarization at the site of synapse. Based on this, which of the following statements is FALSE? a) An individual excitatory graded potential generated by an impulse from Neuron F will cause less than 1mV depolarization at the axon hillock of Neuron G. b) Temporal summation of impulses from Neuron F would hyperpolarize Neuron G. c) Each time Neuron F "fires," it releases approximately the same amount of neurotransmitter onto Neuron G. d) Neuron F is the presynaptic cell, and Neuron G is the post-synaptic cell.
b) Temporal summation of impulses from Neuron F would hyperpolarize Neuron G.
Why does the action potential only move away from the cell body? a) The flow of the sodium ions only goes in one direction—away from the cell body b) The areas that have had the action potential are refractory to a new action potential.
b) The areas that have had the action potential are refractory to a new action potential.
The resting membrane potential depends on two factors that influence the magnitude and direction of Na+ and K+ diffusion across the plasma membrane. Identify these two factors. a) The presence of concentration gradients and voltage-gated channels b) The presence of concentration gradients and leak channels c) The presence of concentration gradients and Na+-K+ pumps d) The presence of a resting membrane potential and leak channels
b) The presence of concentration gradients and leak channels
Imagine an artificial cell with a plasma membrane permeable only to Na+ due to the presence of a Na+ leak channel in the plasma membrane. The artificial cell rests in a buffer with a [Na+] of 150mM. If the intracellular [Na+] of this cell is 15mM, what is the net direction of Na+ cation movement when the electrical potential of the plasma membrane is at the equilibrium potential (ENa+)? a) The net direction of Na+ movement will flow from the outside to the inside of the cell. b) There will be no net direction of movement of Na+ cations. c) The net direction of Na+ movement will flow from the inside to the outside of the cell. d) Na+ net movement will alternate between a large amount of flow from the outside to the inside of the cell, to a a large amount of flow from the inside to the outside of the cell. e) Na+ net movement will alternate between a large amount of flow from the inside to the outside of the cell, to a a large amount of flow from the outside to the inside of the cell.
b) There will be no net direction of movement of Na+ cations.
Solutions A and B are separated by membrane permeable to K+ but not to Cl-. Solution A is 100mM KCl and solution B is 1mM KCl. Which of the following statements about solutions A and B is TRUE? a) K+ ions will diffuse from solution A to solution B until the [K+] of both solutions is 50.5 mM. b) K+ ions will diffuse from solution B to solution A until the [K+] of both solutions is 50.5 mM. c) K+ will diffuse from solution A to solution B until a negative charge develops that opposes the movement of K+. d) KCl will diffuse from solution A to solution B until the [KCl] of both solutions is 50.5 mM
c) K+ will diffuse from solution A to solution B until a negative charge develops that opposes the movement of K+.
In which type of axon will velocity of action potential conduction be the fastest? a) Myelinated axons with the smallest diameters b) Unmyelinated axons with the largest diameter c) Myelinated axons with the largest diameter d) Unmyelinated axons of the shortest length
c) Myelinated axons with the largest diameter
The Na+-K+ pump actively transports both sodium and potassium ions across the membrane to compensate for their constant leakage. In which direction is each ion pumped? a) K+ is pumped out of the cell and Na+ is pumped into the cell. b) Both Na+ and K+ are pumped out of the cell. c) Na+ is pumped out of the cell and K+ is pumped into the cell. d) Both Na+ and K+ are pumped into the cell.
c) Na+ is pumped out of the cell and K+ is pumped into the cell.
The ________ maintains the resting membrane potential. a) equilibrium potential b) action potential c) Na+/K+ pump d) Na+/Ca2+ exchanger e) Na+/H+ antiporter
c) Na+/K+ pump
Where in the cerebral cortex does visual perception occur? a) corpus callosum b) parietal lobe c) occipital lobe d) frontal lobe e) temporal lobe
c) Occipital lobe
Which of the following is a feature of the sympathetic, but not the parasympathetic nervous system? a) Ganglia located in the effector organs. b) Long preganglionic neurons. c) Preganglionic neurons that originate in the thoracic and lumbar spinal cord regions. d) Postganglionic neurons synapse on effector organs. e) Most active when the body is at rest.
c) Preganglionic neurons that originate in the thoracic and lumbar spinal cord regions.
Why are the responses in the fight-or-flight system so widespread and lasting in the body, but activation of the parasympathetic nervous system is discrete in comparison? a) Acetylcholine is degraded three times faster than norepinephrine or epinephrine, so the responses appear disproportionate. b) The body does not produce as much acetylcholine as norepinephrine, so it releases it much more sparingly. c) The adrenal medulla releases epinephrine (adrenalin) and norepinephrine into the bloodstream, while parasympathetic nerves release only at synaptic junctions. d) Significantly more of the body is innervated by the sympathetic nervous system than the parasympathetic nervous system.
c) The adrenal medulla releases epinephrine (adrenalin) and norepinephrine into the bloodstream, while parasympathetic nerves release only at synaptic junctions.
Why does regeneration of the action potential occur in one direction, rather than in two directions? a) The activation gates of voltage-gated K+ channels open in the node, or segment, that has just depolarized. b) The inactivation gates of voltage-gated K+ channels close in the node, or segment, that has just fired an action potential. c) The inactivation gates of voltage-gated Na+ channels close in the node, or segment, that has just fired an action potential. d) The activation gates of voltage-gated Na+ channels close in the node, or segment, that has just depolarized.
c) The inactivation gates of voltage-gated Na+ channels close in the node, or segment, that has just fired an action potential.
On average, the resting membrane potential is -70 mV. What does the sign and magnitude of this value tell you? a) The inside surface of the plasma membrane is much more positively charged than the outside surface. b) There is no electrical potential difference between the inside and the outside surfaces of the plasma membrane. c) The inside surface of the plasma membrane is much more negatively charged than the outside surface. d) The outside surface of the plasma membrane is much more negatively charged than the inside surface.
c) The inside surface of the plasma membrane is much more negatively charged than the outside surface.
What does the Goldman-Hodgkin-Katz (GHK) equation take into account that the Nernst equation does NOT? a) the electrical charges of the ions b) the solubilities of the ions c) the permeabilities of the ions d) the temperature e) the sizes of the ions
c) The permeabilities of the ions
If the soma of a neuron became more permeable to potassium, which statement below best describes the graded potential that would be generated in the soma? a) Potassium would enter the cell, causing the membrane to depolarize and reach threshold. b) Potassium is a cation; therefore, it would cause an excitatory depolarization. c) Potassium is an inhibitory second messenger; therefore, it would cause amplification of the graded potential. d) Potassium would reach its equilibrium potential and the voltage inside the cell would not change. e) Potassium would leave the cell, causing the membrane to hyperpolarize.
e) Potassium would leave the cell, causing the membrane to hyperpolarize.
Which of the following is/are type(s) of neurons? a) motor neurons only b) sensory and interneurons only c) sensory neurons only d) interneurons only e) sensory, motor, and interneurons
e) Sensory, motor, and interneurons
Which of the following best describes the electrochemical forces acting on sodium and potassium ions at the resting membrane potential? a) Forces on both sodium and potassium ions are to move out of the cell. b) There is no force on either ion to move. c) The force on sodium ions is to move out of the cell, and the force on potassium ions is to move into the cell. d) Forces on both sodium and potassium ions are to move into the cell. e) The force on sodium ions is to move into the cell, and the force on potassium ions is to move out of the cell.
e) The force on sodium ions is to move into the cell, and the force on potassium ions is to move out of the cell.
As an action potential is propagated away from the axon hillock, why does propagation continue in one direction? a) The region just in front of the action potential is in the relative refractory period. b) They will travel the path of least resistance. c) The region just behind the action potential is in the relative refractory period. d) The region just in front of the action potential is in the absolute refractory period. e) The region just behind the action potential is in the absolute refractory period.
e) The region just behind the action potential is in the absolute refractory period.
In the motor and sensory homunculi, each body part is shown next to the area of cerebral cortex devoted to it. Which statement best describes what these homunculi represent? a) The homunculi are open to interpretation by neurologists, based upon his or her area of specialty. b) The relative size of the body parts corresponds to the ascending and descending tracts that control that body part. c) The homunculi map out the dermatomes of the body. d) The relative size of the body part distinguishes which part is primarily on the right side of the brain versus the left. e) The relative size of the body part represents the relative size of the cortical area devoted to that body part.
e) The relative size of the body part represents the relative size of the cortical area devoted to that body part.
Which of the following accurately describes afferent neurons? a) They are typically multipolar neurons. b) The cell body is located in the ventral horn of the spinal cord. c) They transmit information from the CNS to the periphery. d) They are the most abundant class of neurons. e) They transmit information from the periphery to the CNS.
e) They transmit information from the periphery to the CNS.