chapter 5 : membrane potentials and action potentials
true or false : diffusion of ions carries positive charges to the inside but leaves the nondiffusible negative anions on the outside , thus creating electronegativity on the inside.
false : charges to outside anions on inside
true or false: sodium channels can be over activated by a toxin called tetrodotoxin when it is applied to the outside of the cell membrane where the sodium activation gates are located
false : blocked
true or false :The membranes of almost all cells of the body have a chloride pump similar to the sodium pump, and chloride serves along with (or instead of) sodium in some cells to cause most of the action potential
false : calcium
true or false: the calcium ion concentration needs to fall only 50 percent below normal before spontaneous discharge occurs in some peripheral nerves. rarely this drop causes muscle "tetany"
false: often causing
true or false: not possible for the sodium channels to close again without first repolarizing the nerve fiber.
false: open again
true or false:a rapid inflow of sodium ions, causes a further rise in the membrane potential, thus closing voltage-gated sodium channels and allowing less streaming of sodium ions to the interior of the fiber. This process is a positive-feedback cycle that
false: opening more voltage gated channels and allows more streaming of sodium ions
true or false :any factor that causes sodium ions to begin to diffuse inward through the membrane in sufficient numbers can set off automatic regenerative closing of the sodium channels
false: opening of sodium channels
true or false :The large fibers are unmyelinated, and the small ones are myelinated
false: opposite
what can rhythmical discharges cause ( name all 3)
(1) the rhythmical beat of the heart, (2) rhythmical peristalsis of the intestines, and (3) such neuronal events as the rhythmical control of breathing.
true or false: sodium channels are often called slow channels
false: calcium slow sodium fast
true or false :The average nerve trunk contains about twice as many unmyelinated fibers as myelinated fibers
true
why is saltatory conduction function valuable ?
2 reason 1 : by causing the depolarization process to jump long intervals along the axis of the nerve fiber, this mechanism increases the velocity of nerve transmission in myelinated fibers as much as 5- to 50 2:conserves energy for the axon because only the nodes depolarize
what is saltatory conduction?
action potentials are conducted from node to node
where are calcium channels numerous in
cardiac and smooth muscle
true or false : An action potential will occur even if the initial rise in membrane potential is not great enough to create the positive feedback
false : An action potential will not occur until the initial rise in membrane potential is great enough to create the positive feedback
true or false : voltage-gated calcium channels-When the channels open in response to a stimulus that repolarizes the cell membrane, calcium ions flow to the interior of the cell.
false : depolarizes
true or false:depolarization process travels over the entire membrane even if conditions are not right. This principle is called the all-or-nothing principle
false : does not travel if all conditions are not right
true or false : During the resting state, the gate of the potassium channel is closed and potassium ions are prevented from passing through this channel to the interior
false : exterior
true or false: When the membrane potential rises from −90 millivolts toward zero, this voltage change causes a conformational opening of the potassium channel gate and allows decreased potassium diffusion outward through the channel
false : increased
true or false :The membrane of a Schwann cell first envelops the axon. The Schwann cell then rotates around the axon many times, laying down a single layer of Schwann cell membrane containing the lipid substance sphingomyelin
false : multiple layers
true or false : not really necessary, but still plays a role in causing both depolarization and repolarization of the nerve membrane during the action potential is the voltage-gated sodium channel.
false : necessary actor in causing both
true or false :Inside the axon are many positively charged ions that cannot go through the membrane channels
false : negatively
true or false: the closing (blocking) of the potassium channels, which close slowly and reach their full closed state only after the sodium channels have almost completely closed.
false : opening activation of potassium which open and reach full open state
true or false: sodium channels can be blocked by a toxin called tetrodotoxin when it is applied to the inside of the cell membrane where the sodium activation gates are located
false : outside of the cell membrane
true or false : calcium channels are often called fast channels
false : slow
true or false : potassium channels can be blocked by a toxin called tetrodotoxin when it is applied to the outside of the cell membrane where the potassium activation gates are located
false : sodium
true or false :For spontaneous rhythmicity to occur, the membrane—even in its natural state—must be permeable enough to potassium ions (or to calcium and potassium ons through the slow calcium-potassium channels) to allow automatic membrane depolarization
false : sodium not potassium
true or false : sodium channels can be blocked by a toxin called tetraethylammonium when it is applied to the outside of the cell membrane where the sodium activation gates are located
false : tetrodotoxin
true or false :a typical myelinated fiber., The central core of the fiber is the node of ranvier , and the membrane of the node is the membrane that actually conducts the action potential
false : the central core of the fiber is the axon and the membrane of the axon is the membrane that conducts action potential
true or false: Muscle tetany is never lethal
false :Muscle tetany is sometimes lethal because of tetanic contraction of the respiratory muscles.
true or false :Surrounding the axon is a myelin sheath that is often much thinner than the axon itself.
false thicker
true or false :plateau in some action potentials -This type of action potential occurs in heart muscle fibers, where the plateau lasts for as long as 0.4 to 0.5 second and causes contraction of heart muscle to last for this same long period.
false: 0.2 to 0.3 seconds
true or false :About once every 3 to 5 millimeters along the length of the myelin sheath is a node of Ranvier.
false: 1 to 3 millimeters
true or false: the calcium ion concentration needs to fall only 10 percent below normal before spontaneous discharge occurs in some peripheral nerves, often causing muscle "tetany"
false: 50 percent
true or false: The membrane of a Schwann cell first rotates around the axon many times then it envelops the axon. then it begins to lay down multiple layers of Schwann cell membrane containing the lipid substance sphingomyelin
false: The membrane of a Schwann cell first envelops the axon. The Schwann cell then rotates around the axon many times
true or false : a slow and steady inflow of sodium ions, causes a further rise in the membrane potential, thus opening still more voltage-gated sodium channels and allowing more streaming of sodium ions to the interior of the fiber. This process is a positive-feedback cycle that
false: a rapid inflow
true or false:toward the end of each resting membrane potential, and continuing for a short period thereafter, the membrane becomes more permeable to potassium ions.
false: action potential
true or false: because of the slight delay in opening of the potassium channels, for the most part, they open just at the same time that the sodium channels are beginning to close because of activation
false: activation
true or false: an excitable membrane has no single direction of propagation, but the action potential travels in all directions toward from the stimulus—even along all branches of a nerve fiber—until the entire membrane has become depolarized
false: away from
true or false: an excitable membrane has no single direction of propagation, but the action potential travels in all directions away from the stimulus—even along all branches of a nerve fiber—until the entire membrane has become repolarized
false: become depolarized
true or false : the sodium ion concentration needs to fall only 50 percent below normal before spontaneous discharge occurs in some peripheral nerves, often causing muscle "tetany"
false: calcium
true or false: A major function of the voltage-gated potassium ion channels is to contribute to the depolarizing phase on the action potential in some cells.
false: calcium
true or false:The membranes of almost all cells of the body have a calcium pump similar in certain aspects to the sodium pump, a major difference is that calcium goes in contrast with sodium in some cells to cause the cell to return to its resting potential
false: calcium is similar to sodium pump and can cause action potential with or without sodium
true or false :for continued propagation of an impulse to occur, the ratio of action potential to threshold for excitation must at all times be greater than 1. This "greater than 1" requirement is called the action potential factor for propagation.
false: called the safety factor
true or false :Inside the axon are many negatively charged ions that can go through the membrane channels
false: cannot
true or false :new action potential can occur in an excitable fiber as long as the membrane is still depolarized from the preceding action potential
false: cannot occur
true or false: The increased outflow of potassium ions carries tremendous numbers of negative charges to the outside of the membrane, leaving considerably more positivity inside the fiber
false: carries out positive leaving negative inside the the fiber
true or false : Repetitive self-induced discharges occur normally in the heart, in most smooth muscle, and in many of the neurons of the peripheral nervous system
false: central nervous system
true or false: During the resting state, the gate of the potassium channel is open and potassium ions are allowed freely to pass through this channel to the exterior
false: close and prevented from passing
true or false :a typical myelinated fiber., The central core of the fiber is the axon, and the membrane of the axon is the membrane that actually allows the fiber to return to its resting membrane potential
false: conducts the action potential
true or false:The cause of the plateau is a combination of several factors. First, in heart muscle, two types of channels contribute to the repolarization process: (1) the usual voltage-activated sodium channels, called fast channels, and (2) voltage-activated calcium-sodium channels (L-type calcium channels), which are slow to open and therefore are called slow channels. Opening of fast channels causes the spike portion of the action potential, whereas the prolonged opening of the slow calcium-sodium channels mainly allows calcium ions to enter the fiber, which is largely responsible for the plateau portion of the action potential.
false: contribute to the depolarization process
true or false:membrane-stabilizing factors, can increase excitability
false: decrease
true or false:When there is an increase of calcium ions, the sodium channels become activated (opened) by a small increase of the membrane potential from its normal, very negative level
false: deficit
true or false: When there is a deficit of sodium ions, the sodium channels become activated (opened) by a small increase of the membrane potential from its normal, very negative level
false: deficit of calcium
true or false : calcium channels provides a more sustained repolarization, whereas the sodium channels play a key role in initiating action potentials.
false: depolarization
true or false: in relation to propagation of the action potential - This transmission of the repolarization process along a nerve or muscle fiber is called a nerve or muscle impulse.
false: depolarization
true or false: the plateau greatly prolongs the period of repolarization
false: depolarization
true or false :new action potential cannot occur in an excitable fiber as long as the membrane is still repolarized from the preceding action potential
false: depolarized
true or false :A major function of the voltage-gated calcium ion channels is to contribute to the repolarizing phase on the action potential in some cells.
false: depolarizing
true or false :any factor that causes sodium ions to begin to diffuse outward through the membrane in sufficient numbers can set off automatic regenerative opening of the sodium channels
false: diffuse inward
true or false: The probable way in which calcium ions affect the sodium channels is as follows: These ions appear to bind to the exterior surfaces of the sodium channel protein molecule. The positive charges of these calcium ions in turn alter the chemical state of the sodium channel protein, thus altering the voltage level required to open the sodium gate
false: electrical state
true or false :the calcium pump transports calcium ions from the interior to the exterior of the cell membrane (or into the mitocondria of the cell),
false: endoplasmic reticulum
true or false :The axon is filled in its center with axoplasm, which is a viscid intracellular fluid
true
true or false: The probable way in which calcium ions affect the sodium channels is as follows: These ions appear to bind to the interior surfaces of the sodium channel protein molecule. The positive charges of these calcium ions in turn alter the electrical state of the sodium channel protein, thus altering the voltage level required to open the sodium gate
false: exterior
true or false :high intracellular fluid calcium ion concentration decreases membrane permeability to sodium ions and simultaneously reduces excitability. Therefore, calcium ions are said to be a "stabilizer."
false: extracellular
true or false: the calcium ion concentration needs to rise only 50 percent above normal before spontaneous discharge occurs in some peripheral nerves, often causing muscle "tetany"
false: fall 50 below normal
true or false :for continued propagation of an impulse to occur, the ratio of action potential to threshold for excitation must at all times be greater than 5. This "greater than 5" requirement is called the safety factor for propagation.
false: greater than 1
true or false: plateau in some action potentials -This type of action potential occurs in skeletal muscle fibers, where the plateau lasts for as long as 0.2 to 0.3 second and causes contraction of skeletal muscle to last for this same long period.
false: heart muscles
true or false: in relation to propagation of the action potential - This transmission of the depolarization process along a nerve or muscle fiber is called a nerve or muscle tetany
false: impulse
true or false: an excitable membrane has no single direction of propagation, but the action potential travels in one directions away from the stimulus until the entire membrane has become depolarized
false: in all directions
true or false: When there is a deficit of calcium ions, the sodium channels become activated (opened) by a small decrease of the membrane potential from its normal, very negative level
false: increase
true or false :outside the axon are many negatively charged ions that cannot go through the membrane channels
false: inside
true or false : tetraethylammonium ion blocks the potassium channels when it is applied to the exterior of the nerve fiber
false: interior
true or false :voltage-gated calcium channels-When the channels open in response to a stimulus that depolarizes the cell membrane, calcium ions flow to the exterior of the cell.
false: interior
true or false :a rapid inflow of sodium ions, causes a further rise in the membrane potential, thus opening still more voltage-gated sodium channels and allowing more streaming of sodium ions to the exterior of the fiber. This process is a positive-feedback cycle that
false: interior of the fiber
true or false :the calcium pump transports calcium ions from the exterior to the interior of the cell membrane (or into the endoplasmic reticulum of the cell),
false: interior to the exterior
true or false: The probable way in which calcium ions affect the sodium channels is as follows: These ions appear to bind to the exterior surfaces of the sodium channel protein molecule. The positive charges of these calcium ions in turn alter the electrical state of the sodium channel protein, but this does not alter the voltage level required to open the sodium gate
false: it does alter
true or false: during a plateau potassium channels are faster to open than usual, often opening fully before the end of the plateau
false: much slower , not opening much until the end of the plateau
true or false :Surrounding the axon is a unmyelinate sheath that is often much thicker than the axon itself.
false: myelin sheath
true or false :a typical unmyelinated fiber., The central core of the fiber is the axon, and the membrane of the axon is the membrane that actually conducts the action potential
false: myelinated
true or false:When there is a deficit of calcium ions, the sodium channels become activated (opened) by a small increase of the membrane potential from its normal, very positive level
false: negative level
true or false within a few 10,000ths of a second after the membrane becomes highly permeable to sodium ions , the sodium channel begins to close and potassium channels open to a greater degree than normal . then, rapid diffusion of potassium ions to the exterior establishes the abnormal positive resting membrane potential this is call repolarization
false: normal negative resting membrane potential
true or false :When the membrane potential rises from −90 millivolts toward zero, this voltage change causes a conformational opening of the potassium channel gate and allows increased potassium diffusion inward through the channel
false: outward
true or false :toward the end of each action potential, and continuing for a short period thereafter, the membrane becomes more impermeable to potassium ions.
false: permeable to potassium ions
true or false: An action potential will not occur until the initial rise in membrane potential is great enough to create the negative feedback
false: positive
true or false : The probable way in which calcium ions affect the sodium channels is as follows: These ions appear to bind to the exterior surfaces of the sodium channel protein molecule. The negative charges of these calcium ions in turn alter the electrical state of the sodium channel protein, thus altering the voltage level required to open the sodium gate
false: positive charges of calcium
true or false :a rapid inflow of sodium ions, causes a further rise in the membrane potential, thus opening still more voltage-gated sodium channels and allowing more streaming of sodium ions to the interior of the fiber. This process is a negative-feedback cycle that
false: positive-feedback
true or false :When the membrane potential rises from −90 millivolts toward zero, this voltage change causes a conformational opening of the sodium channel gate and allows increased sodium diffusion outward through the channel
false: potassium
true or false :once the sodium channels open, they remain open for the entire duration of the positive membrane potential and do not close again until after the membrane potential is decreased back to a negative value
false: potassium
true or false :tetraethylammonium ion blocks the sodium channels when it is applied to the interior of the nerve fiber
false: potassium
true or false: The increased outflow of sodium ions carries tremendous numbers of positive charges to the outside of the membrane, leaving considerably more negativity inside the fiber
false: potassium
true or false:during a plateau sodium channels are slower to open than usual, often not opening much until the end of the plateau
false: potassium
true or false :toward the end of each action potential, and continuing for a short period thereafter, the membrane becomes more permeable to sodium ions.
false: potassium ions
true or false within a few 10,000ths of a second after the membrane becomes highly permeable to sodium ions , the sodium channel begins to close and potassium channels open to a greater degree than normal . then, rapid diffusion of potassium ions to the interior reestablishes the normal negative resting membrane potential this is call repolarization
false: potassium to the exterior
true or false within a few 10,000ths of a second after the membrane becomes highly permeable to sodium ions , the sodium channel begins to close and potassium channels open to a greater degree than normal . then, slow diffusion of potassium ions to the exterior reestablishes the normal negative resting membrane potential this is call repolarization
false: rapid diffusion of potassium
true or false: once the potassium channels open, they remain open for the entire duration of the negative membrane potential and do not close again until after the membrane potential is increased back to a positive value
false: remain open during positive potential until it is decreased back to a negative value
true or false :not possible for the sodium channels to open again without first depolarizing the nerve fiber.
false: repolarizaing
true or false :For spontaneous rhythmicity to occur, the membrane—even in its natural state—must be permeable enough to sodium ions (or to calcium and sodium ions through the slow calcium-sodium channels) to allow automatic membrane repolarization
false: repolarization
true or false :sodium ions diffuse to the inside during depolarization and potassium ions diffuse to the outside during depolarization
false: repolarization
true or false : Muscle tetany is sometimes lethal because of tetanic contraction of the cardiac muscles.
false: respiratory muscle
true or false:During the action potential , the gate of the potassium channel is closed and potassium ions are prevented from passing through this channel to the exterior
false: resting state
true or false :the opening (activation) of the sodium channels, which open slowly and reach their full open state only after the potassium channels have almost completely closed.
false: reverse sodium and potassium
true or false : a rapid inflow of sodium ions, causes a further decrease in the membrane potential, thus opening still more voltage-gated sodium channels and allowing more streaming of sodium ions to the interior of the fiber. This process is a positive-feedback cycle that
false: rise in the membrane potential
true or false: if any event causes enough initial decrease in the membrane potential from −90 millivolts toward a more negative level, the decreasing voltage will cause many voltage-gated sodium channels to begin opening
false: rise in the membrane toward zero cause a rise in voltage
true or false:any factor that causes sodium ions to begin to diffuse inward through the membrane in sufficient numbers can inhibit automatic regenerative opening of the sodium channels
false: set off automatic regenerative opening of the sodium channel
true or false : Repetitive self-induced discharges occur normally in the heart, in most skeletal muscle, and in many of the neurons of the central nervous system
false: smooth muscle
true or false :any factor that causes potassium ions to begin to diffuse inward through the membrane in sufficient numbers can set off automatic regenerative opening of the potassium channels
false: sodium
true or false :The cause of the plateau is a combination of several factors. First, in heart muscle, two types of channels contribute to the depolarization process: (1) the usual voltage-activated sodium channels, called slow channels, and (2) voltage-activated calcium-sodium channels (L-type calcium channels), which are fast to open and therefore are called fast channels. Opening of fast channels causes the spike portion of the action potential, whereas the prolonged opening of the fast calcium-sodium channels mainly allows calcium ions to enter the fiber, which is largely responsible for the plateau portion of the action potential.
false: sodium are called fast channels and calcium are the slow channels
true or false : potassium ions diffuse to the inside during depolarization and sodium ions diffuse to the outside during repolarization
false: sodium inside and potassium outside
true or false:high extracellular fluid calcium ion concentration decreases membrane permeability to potassium ions and simultaneously reduces excitability. Therefore, calcium ions are said to be a "stabilizer."
false: sodium not potassium
true or false :The membrane of a Schwann cell first envelops the axon. The Schwann cell then rotates around the axon many times, laying down multiple layers of Schwann cell membrane containing the lipid substance sphingoetanolmina
false: sphingomyelin
true or false:high extracellular fluid calcium ion concentration decreases membrane permeability to sodium ions and simultaneously reduces excitability. Therefore, calcium ions are said to be a "excitatory ion ."
false: stabilizer
true or false : because of the slight delay in closing of the potassium channels, for the most part, they close just at the same time that the sodium channels are beginning to open because of inactivation
false: switch close and open
true or false within a few 10,000ths of a second after the membrane becomes highly permeable to sodium ions , the sodium channel begins to open and potassium channels close to a greater degree than normal . then, rapid diffusion of potassium ions to the exterior reestablishes the normal negative resting membrane potential this is call repolarization
false: switch open and close
true or false : When there is a deficit of sodium ions, the calcium channels become activated (opened) by a small increase of the membrane potential from its normal, very negative level
false: switch sodium and calcium
true or false : sodium channels provides a more sustained depolarization, whereas the calcium channels play a key role in initiating action potentials.
false: switch sodium and calcium
true or false : tetrodotoxin blocks the potassium channels when it is applied to the interior of the nerve fiber
false: tetraethylammonium
true or false:The cause of the plateau is a combination of several factors. First, in heart muscle, two types of channels contribute to the depolarization process: (1) the usual voltage-activated sodium channels, called fast channels, and (2) voltage-activated calcium-sodium channels (L-type calcium channels), which are slow to open and therefore are called slow channels. Opening of slow channels causes the spike portion of the action potential, whereas the prolonged opening of the fast sodium channels mainly allows sodium ions to enter the fiber, which is largely responsible for the plateau portion of the action potential.
false: the calcium channels are largely responsible for the plateau portion and the sodium fast channels are cause the spike portion
true of false: a typical myelinated fiber., The distal ends of the fiber is the axon, and the membrane of the axon is the membrane that actually conducts the action potential
false: the central core of the fiber is the axon
true or false : The average nerve trunk contains about five times as many unmyelinated fibers as myelinated fibers
false: twice
true or false : The average nerve trunk contains about twice as many myelinated fibers as unmyelinated fibers
false: twice as many unmyelinated
true or false: Propagation of the Action Potential an action potential elicited at any one point on an excitable membrane can not excite adjacent portions of the membrane, resulting in propagation of the action potential along the membrane.
false: usually excites adjacent portions
true or false : chemical-gated calcium channels-When the channels open in response to a stimulus that depolarizes the cell membrane, calcium ions flow to the interior of the cell.
false: voltage
true or false :The necessary actor in causing both depolarization and repolarization of the nerve membrane during the action potential is the chemical-gated sodium channel.
false: voltage
true or false:A major function of the chemical-gated calcium ion channels is to contribute to the depolarizing phase on the action potential in some cells.
false: voltage
true or false :The cause of the plateau is a combination of several factors. First, in heart muscle, two types of channels contribute to the depolarization process: (1) the usual chemical-activated sodium channels, called fast channels, and (2) chemical-activated calcium-sodium channels (L-type calcium channels), which are slow to open and therefore are called slow channels. Opening of fast channels causes the spike portion of the action potential, whereas the prolonged opening of the slow calcium-sodium channels mainly allows calcium ions to enter the fiber, which is largely responsible for the plateau portion of the action potential.
false: voltage-activated sodium channels
true or false :hyperpolarization- As long as this state exists, self-re-excitation sometimes can occur
false: will not occur
true or false :Another important characteristic of the sodium channel inactivation process is that the inactivation gate will sometimes reopen before the membrane potential returns to or near the original resting membrane potential level
false: will not reopen
true or false: ions can only flow through the thick myelin sheaths of myelinated nerves, they cannot flow with ease through the nodes of Ranvier. Therefore, action potentials cannot occur at the nodes.
false:no ions can flow through the thick myelin sheaths of myelinated nerves, they can flow with ease through the nodes of Ranvier. Therefore, action potentials occur only at the nodes.
what factors can lead to the automatic regenerative opening of sodium channels in the Process of Eliciting the Action Potential
mechanical disturbance of the membrane, chemical effects on the membrane, or passage of electricity through the membrane
what do you call the action potential that are conducted from node to node
saltatory conduction
true or false : voltage gated sodium channel -This channel has two gates—one near the inside of the channel called the activation gate, and another near the outside called the inactivation gate
switch inside and outside
true or false :because of the slight delay in opening of the sodium channels, for the most part, they open just at the same time that the potassium channels are beginning to close because of inactivation
switch sodium and potassium
what is the node of ranvier ?
the juncture between each two successive Schwann cells along the axon, a small uninsulated area only 2 to 3 micrometers in length remains where ions still can flow with ease through the axon membrane between the extracellular fluid and the intracellular fluid inside the axon
true or false : The membranes of almost all cells of the body have a calcium pump similar to the sodium pump, and calcium serves along with (or instead of) sodium in some cells to cause most of the action potential
true
true or false : When there is a deficit of calcium ions, the sodium channels become activated (opened) by a small increase of the membrane potential from its normal, very negative level
true
true or false : during a plateau potassium channels are slower to open than usual, often not opening much until the end of the plateau
true
true or false : for continued propagation of an impulse to occur, the ratio of action potential to threshold for excitation must at all times be greater than 1. This "greater than 1" requirement is called the safety factor for propagation.
true
true or false : in relation to propagation of the action potential - This transmission of the depolarization process along a nerve or muscle fiber is called a nerve or muscle impulse.
true
true or false : not possible for the sodium channels to open again without first repolarizing the nerve fiber.
true
true or false : once the potassium channels open, they remain open for the entire duration of the positive membrane potential and do not close again until after the membrane potential is decreased back to a negative value
true
true or false : plateau in some action potentials -This type of action potential occurs in heart muscle fibers, where the plateau lasts for as long as 0.2 to 0.3 second and causes contraction of heart muscle to last for this same long period.
true
true or false : sodium channels can be blocked by a toxin called tetrodotoxin when it is applied to the outside of the cell membrane where the sodium activation gates are located
true
true or false : the calcium ion concentration needs to fall only 50 percent below normal before spontaneous discharge occurs in some peripheral nerves, often causing muscle "tetany"
true
true or false : the plateau greatly prolongs the period of depolarization
true
true or false : voltage gated sodium channel -This channel has two gates—one near the outside of the channel called the activation gate, and another near the inside called the inactivation gate
true
true or false :About once every 1 to 3 millimeters along the length of the myelin sheath is a node of Ranvier.
true
true or false :Another important characteristic of the sodium channel inactivation process is that the inactivation gate will not reopen until the membrane potential returns to or near the original resting membrane potential level
true
true or false :For spontaneous rhythmicity to occur, the membrane—even in its natural state—must be permeable enough to sodium ions (or to calcium and sodium ions through the slow calcium-sodium channels) to allow automatic membrane depolarization
true
true or false :Surrounding the axon is a myelin sheath that is often much thicker than the axon itself.
true
true or false :The cause of the plateau is a combination of several factors. First, in heart muscle, two types of channels contribute to the depolarization process: (1) the usual voltage-activated sodium channels, called fast channels, and (2) voltage-activated calcium-sodium channels (L-type calcium channels), which are slow to open and therefore are called slow channels. Opening of fast channels causes the spike portion of the action potential, whereas the prolonged opening of the slow calcium-sodium channels mainly allows calcium ions to enter the fiber, which is largely responsible for the plateau portion of the action potential.
true
true or false :The increased outflow of potassium ions carries tremendous numbers of positive charges to the outside of the membrane, leaving considerably more negativity inside the fiber
true
true or false :The large fibers are myelinated, and the small ones are unmyelinated
true
true or false :When the membrane potential rises from −90 millivolts toward zero, this voltage change causes a conformational opening of the potassium channel gate and allows increased potassium diffusion outward through the channel
true
true or false :a rapid inflow of sodium ions, causes a further rise in the membrane potential, thus opening still more voltage-gated sodium channels and allowing more streaming of sodium ions to the interior of the fiber. This process is a positive-feedback cycle .
true
true or false :a typical myelinated fiber., The central core of the fiber is the axon, and the membrane of the axon is the membrane that actually conducts the action potential
true
true or false :any factor that causes sodium ions to begin to diffuse inward through the membrane in sufficient numbers can set off automatic regenerative opening of the sodium channels
true
true or false :because of the slight delay in opening of the potassium channels, for the most part, they open just at the same time that the sodium channels are beginning to close because of inactivation
true
true or false :if any event causes enough initial rise in the membrane potential from −90 millivolts toward the zero level, the rising voltage will cause many voltage-gated sodium channels to begin opening
true
true or false :membrane-stabilizing factors, can decrease excitability
true
true or false :new action potential cannot occur in an excitable fiber as long as the membrane is still depolarized from the preceding action potential
true
true or false :no ions can flow through the thick myelin sheaths of myelinated nerves, they can flow with ease through the nodes of Ranvier. Therefore, action potentials occur only at the nodes.
true
true or false :the calcium pump transports calcium ions from the interior to the exterior of the cell membrane (or into the endoplasmic reticulum of the cell),
true
true or false :toward the end of each action potential, and continuing for a short period thereafter, the membrane becomes more permeable to potassium ions.
true
true or false :voltage-gated calcium channels-When the channels open in response to a stimulus that depolarizes the cell membrane, calcium ions flow to the interior of the cell.
true
true or false: Propagation of the Action Potential an action potential elicited at any one point on an excitable membrane usually excites adjacent portions of the membrane, resulting in propagation of the action potential along the membrane.
true
true or false: A major function of the voltage-gated calcium ion channels is to contribute to the depolarizing phase on the action potential in some cells.
true
true or false: An action potential will not occur until the initial rise in membrane potential is great enough to create the positive feedback
true
true or false: During the resting state, the gate of the potassium channel is closed and potassium ions are prevented from passing through this channel to the exterior
true
true or false: Inside the axon are many negatively charged ions that cannot go through the membrane channels
true
true or false: Repetitive self-induced discharges occur normally in the heart, in most smooth muscle, and in many of the neurons of the central nervous system
true
true or false: The membrane of a Schwann cell first envelops the axon. The Schwann cell then rotates around the axon many times, laying down multiple layers of Schwann cell membrane containing the lipid substance sphingomyelin
true
true or false: The necessary actor in causing both depolarization and repolarization of the nerve membrane during the action potential is the voltage-gated sodium channel.
true
true or false: The probable way in which calcium ions affect the sodium channels is as follows: These ions appear to bind to the exterior surfaces of the sodium channel protein molecule. The positive charges of these calcium ions in turn alter the electrical state of the sodium channel protein, thus altering the voltage level required to open the sodium gate
true
true or false: an excitable membrane has no single direction of propagation, but the action potential travels in all directions away from the stimulus—even along all branches of a nerve fiber—until the entire membrane has become depolarized
true
true or false: calcium channels are often called slow channels
true
true or false: depolarization process travels over the entire membrane if conditions are right, but it does not travel at all if conditions are not right. This principle is called the all-or-nothing principle
true
true or false: high extracellular fluid calcium ion concentration decreases membrane permeability to sodium ions and simultaneously reduces excitability. Therefore, calcium ions are said to be a "stabilizer."
true
true or false: hyperpolarization- As long as this state exists, self-re-excitation will not occur.
true
true or false: sodium ions diffuse to the inside during depolarization and potassium ions diffuse to the outside during repolarization
true
true or false: sodium, potassium, and chloride ions are the most important ions involved in the development of membrane potentials in nerve and muscle fibers
true
true or false: tetraethylammonium ion blocks the potassium channels when it is applied to the interior of the nerve fiber
true
true or false: the opening (activation) of the potassium channels, which open slowly and reach their full open state only after the sodium channels have almost completely closed.
true
true or false:Muscle tetany is sometimes lethal because of tetanic contraction of the respiratory muscles.
true
true or false:The myelin sheath is deposited around the axon by Schwann cells
true
origin of normal resting membrane potential , what contributes to it ?
Contribution of the Potassium Diffusion Potential Contribution of Sodium Diffusion through the Nerve Membrane. Contribution of the Na+-K+ Pump.
true or false : The resting membrane potential of large nerve fibers when they are not transmitting nerve signals is about −61 millivolts
false : -90mv
true or false :a negative ion concentration gradient from inside the membrane to the outside causes electronegativity inside the membrane
false : a positive ion concentration
true or false :Because of the large potassium concentration gradient from inside toward outside, there is a weak tendency for extra numbers of potassium ions to diffuse outward through the membrane
false : a strong tendency
true or false : sodium, potassium, and chloride ions are the most important ions involved in the development of membrane potentials in only nerve fibers
false : and muscle fibers
true or false : diffusion of ions carries positive charges to the outside but leaves the nondiffusible negative cationes on the inside, thus creating electronegativity on the inside.
false : aniones
true or false : The resting membrane potential of large nerve fibers when they are transmitting nerve signals is about −90 millivolts
false : are not transmitting
true or false : diffusion of ions carries negative charges to the outside but leaves the nondiffusible negative anions on the inside, thus creating electronegativity on the inside.
false : carries positive
true or false: the permeability of the sodium and potassium channels undergoes rapid changes during transmission of a nerve impulse, whereas the permeability of the chloride channels also will change greatly during this process
false : chloride channels do not change
true or false : chemical potentials exist across the membranes of virtually all cells of the body
false : electrical
true or false : diffusion of ions carries positive charges to the outside but leaves the nondiffusible negative anions on the inside, thus creating electropositivity on the inside.
false : electronegativity
true or false : a decrease in positive ions diffuse to the outside when their concentration is higher inside than outside
false : excess
true or false : a positive ion concentration gradient from outside the membrane to the inside causes electronegativity inside the membrane
false : from the inside to the outside
true or false : potassium concentration is very low inside a nerve fiber membrane but great outside the membrane
false : great - inside , very low - outside
true or false : Electrical potentials exist across the membranes of very few cells of the body
false : in almost all cells
true or false : excess positive ions diffuse to the outside when their concentration is higher outside than inside
false : inside than outside
true or false :resting potential outside the nerve fiber is 90 millivolts more negative than the potential in the intracellular fluid on the inside of the
false : inside the fluid , extracellular fluid
true or false :a positive ion concentration gradient from inside the membrane to the outside causes electronegativity outside the membrane
false : inside the membrane
true or false : excess positive ions diffuse to the outside when their concentration is lower inside than outside
false : is higher
the Na+-K+ pump is an electrogenic pump because more negative charges are pumped to the outside than to the inside (three Na+ ions to the outside for each two K+ ions to the inside)
false : more positive
true or false: sodium, potassium, and chloride ions are the least important ions involved in the development of membrane potentials in nerve and muscle fibers
false : most important
true or false : diffusion of ions carries positive charges to the outside but leaves the nondiffusible positive anions on the inside, thus creating electronegativity on the inside.
false : negative anions
true or false : the permeability of the sodium and potassium channels undergoes rapid changes during transmission of a muscle impulse, whereas the permeability of the chloride channels does not change greatly during this process
false : nerve impulses
true or false : sodium concentration is great inside a nerve fiber membrane but very low outside the membrane
false : potassium
true or false: the quality importance of each of the ions in determining the voltage is proportional to the membrane permeability for that particular ion
false : quantitative
true or false : slow changes in sodium and potassium permeability are primarily responsible for signal transmission in neurons
false : rapid
true or false : the permeability of the sodium and potassium channels undergoes slow changes during transmission of a nerve impulse, whereas the permeability of the chloride channels does not change greatly during this process
false : rapid changes
true of false : sodium, potassium, and calcium ions are the most important ions involved in the development of membrane potentials in nerve and muscle fibers
false : sodium , potassium , and chloride
true or false : rapid changes in calcium and potassium permeability are primarily responsible for signal transmission in neurons
false : sodium and potassium
true or false : sodium, phosphate, and chloride ions are the most important ions involved in the development of membrane potentials in nerve and muscle fibers
false : sodium, potassium , and chloride
true or false: the concentration gradient of each of ions across the membrane helps determine the chemicals in the membrane potential
false : the voltage
true or false : the Na+-K+ pump is an electrogenic pump because more positive charges are pumped to the outside than to the inside (two Na+ ions to the outside for each three K+ ions to the inside)
false : three Na+ and two K+
true or false : excess positive ions diffuse to the inside when their concentration is higher inside than outside
false : to the outside
the Na+-K+ pump is an electrogenic pump because more positive charges are pumped to the inside than to the outside (three Na+ ions to the outside for each two K+ ions to the inside)
false : to the outside than to the inside
true or false : the concentration gradient of each of ions across the membrane does not helps determine the voltage of the membrane potential
false does help
true or false: The resting stage is the resting membrane potential before the action potential begins. The membrane is said to be "polarized" during this stage because of the −61 millivolts negative membrane potential that is present.
false: -90mv
true or false:the Na+-K+ pump leaves positive ions on the inside and causes a negative potential outside the cell membrane.
false: a negative potential inside
true or false : that not all, but most cell membranes of the body have a powerful Na+-K+ pump that continually transports sodium ions to the outside of the cell and potassium ions to the inside,
false: all
true or false : sodium, potassium, and chloride ions are the most important ions involved in the development of membrane potentials in only muscle fibers
false: and nerve fibers
true or false : during the repolarization phase the membrane suddenly becomes permeable to sodium ions, allowing tremendous numbers of positively charged sodium ions to diffuse to the interior of the axon.
false: depolarization
true or false : the potential rising rapidly in the positive direction—it is called repolarization
false: depolarization
true or false : similarity in permeability is a key factor in determining the level of the normal resting membrane potential.
false: differential
true or false : potential difference between the inside and outside is called the action potential
false: diffusion potential
true or false: some but not all action potentials begin with a sudden change from the normal resting negative membrane potential to a positive potential and ends with an almost equally rapid change back to the negative potential
false: each potential
true or false:the Na+-K+ pump is an chemical pump because more positive charges are pumped to the outside than to the inside (three Na+ ions to the outside for each two K+ ions to the inside)
false: electrogenic
true or false : a positive ion concentration gradient from inside the membrane to the outside causes electropositivity inside the membrane
false: electronegativity
true or false : diffusion of ions carries positive charges to the outside but leaves the nondiffusible negative anions on the inside, thus creating electronegativity on the outside
false: electronegativity on the inside
true or false: Each action potential begins with a sudden change from the normal resting negative membrane potential to a positive potential and ends with an almost a slower change back to the negative potential
false: equally rapid change back
true or false within a few 10,000ths of a second after the membrane becomes highly permeable to sodium ions , the sodium channel begins to close and potassium channels open to a lesser degree than normal . then, rapid diffusion of potassium ions to the exterior reestablishes the normal negative resting membrane potential this is call repolarization
false: greater degree than normal
true or false : Because of the large potassium concentration gradient from outside toward inside , there is a strong tendency for extra numbers of potassium ions to diffuse outward through the membrane
false: inside toward outside
true or false : during the depolarization phase the membrane suddenly becomes permeable to sodium ions, allowing tremendous numbers of positively charged sodium ions to diffuse to the exterior of the axon.
false: interior
true or false : diffusion of ions carries positive charges to the outside but leaves the diffusible negative anions on the inside, thus creating electronegativity on the inside.
false: nondiffusible
true or false :differential in permeability is a key factor in determining the level of the abnormal resting membrane potential.
false: normal
true or false:the Na+-K+ pump leaves positive ions on the outside and causes a negative potential inside the cell membrane.
false: on the inside leave positive ions
true or false: during the depolarization phase the membrane suddenly becomes impermeable to sodium ions, allowing tremendous numbers of positively charged sodium ions unable diffuse to the interior of the axon.
false: permeable and able to diffuse
true or false: The resting stage is the resting membrane potential before the action potential begins. The membrane is said to be "depolarized" during this stage because of the −90 millivolts negative membrane potential that is present.
false: polarized
true or false : the potential rising rapidly in the negative direction—it is called depolarization
false: positive
true or false:The resting stage is the resting membrane potential before the action potential begins. The membrane is said to be "polarized" during this stage because of the 90 millivolts positive membrane potential that is present.
false: positive
true or false:the Na+-K+ pump leaves negative ions on the inside and causes a negative potential inside the cell membrane.
false: positive ions
true or false: the Na+-K+ pump leaves positive ions on the inside and causes a negative potential inside the cell membrane.
false: positive potential
true or false : Because of the large sodium concentration gradient from inside toward outside, there is a strong tendency for extra numbers of sodium ions to diffuse outward through the membrane
false: potassium
true or false : the quantitative importance of each of the ions in determining the voltage is disproportional to the membrane permeability for that particular ion
false: proportional
true or false : Nerve signals are transmitted by action potentials, which are slow but strong changes in the membrane potential that spread along the nerve fiber membrane
false: rapid changes
true or false : the potential rising slowly in the positive direction—it is called depolarization
false: rapidly
true or false within a few 10,000ths of a second after the membrane becomes highly permeable to sodium ions , the sodium channel begins to close and potassium channels open to a greater degree than normal . then, rapid diffusion of potassium ions to the exterior reestablishes the normal negative resting membrane potential this is call depolarization
false: repolarization
true or false:The depolarization stage is the resting membrane potential before the action potential begins. The membrane is said to be "polarized" during this stage because of the −90 millivolts negative membrane potential that is present.
false: resting stage
true or false: bicarbonate, potassium, and chloride ions are the most important ions involved in the development of membrane potentials in nerve and muscle fibers
false: sodium , potassium , and chloride
true or false : that all cell membranes of the body have a powerful Na+-K+ pump that continually transports sodium ions to the inside of the cell and potassium ions to the outside,
false: sodium - outside and potassium - inside
true or false : during the depolarization phase the membrane suddenly becomes permeable to potassium ions, allowing tremendous numbers of positively charged potassium ions to diffuse to the interior of the axon.
false: sodium ions not potassium ions
true or false : the Na+-K+ pump is an electrogenic pump because more positive charges are pumped to the outside than to the inside (three Na+ ions to the inside for each two K+ ions to the outside)
false: sodium outside and potassium inside
true of false :Each action potential begins with a progressively growing change from the normal resting negative membrane potential to a positive potential and ends with an almost equally rapid change back to the negative potential
false: sudden change
true or false: Each action potential begins with a sudden change from the normal resting positive membrane potential to a negative potential and ends with an almost equally rapid change back to the positive potential
false: switch all the negatives and positives
true or false Within a few 10,000ths of a second after the membrane becomes highly permeable to potassium ions, the potassium channels begin to close and the sodium channels open to a greater degree than normal. Then, rapid diffusion of sodium ions to the exterior re-establishes the normal negative resting membrane potential, this is called repolarization
false: switch potassium and sodium
true or false : the membrane is highly permeable to sodium but only slightly permeable to potassium, it is logical that the diffusion of sodium contributes far more to the membrane potential than does the diffusion of potassium
false: switch potassium and sodium
true or false within a few 10,000ths of a second after the membrane becomes highly permeable to sodium ions , the sodium channel begins to close and potassium channels open to a greater degree than normal . then, rapid diffusion of potassium ions to the exterior reestablishes the normal negative resting membrane potential this is call repolarization
true
true or false : Because of the large potassium concentration gradient from inside toward outside, there is a strong tendency for extra numbers of potassium ions to diffuse outward through the membrane
true
true or false : a positive ion concentration gradient from inside the membrane to the outside causes electronegativity inside the membrane
true
true or false : diffusion of ions carries positive charges to the outside but leaves the nondiffusible negative anions on the inside, thus creating electronegativity on the inside.
true
true or false : excess positive ions diffuse to the outside when their concentration is higher inside than outside
true
true or false : potassium concentration is great inside a nerve fiber membrane but very low outside the membrane
true
true or false : potential difference between the inside and outside is called the diffusion potential
true
true or false : rapid changes in sodium and potassium permeability are primarily responsible for signal transmission in neurons
true
true or false : resting potential inside the nerve fiber is 90 millivolts more negative than the potential in the extracellular fluid on the outside of the
true
true or false : the Na+-K+ pump is an electrogenic pump because more positive charges are pumped to the outside than to the inside (three Na+ ions to the outside for each two K+ ions to the inside)
true
true or false : the concentration gradient of each of ions across the membrane helps determine the voltage of the membrane potential
true
true or false : the permeability of the sodium and potassium channels undergoes rapid changes during transmission of a nerve impulse, whereas the permeability of the chloride channels does not change greatly during this process
true
true or false : the potential rising rapidly in the positive direction—it is called depolarization
true
true or false : the resting membrane potential of large nerve fibers when they are not transmitting nerve signals is about −90 millivolts
true
true or false :Nerve signals are transmitted by action potentials, which are rapid changes in the membrane potential that spread rapidly along the nerve fiber membrane
true
true or false :differential in permeability is a key factor in determining the level of the normal resting membrane potential.
true
true or false :the membrane is highly permeable to potassium but only slightly permeable to sodium, it is logical that the diffusion of potassium contributes far more to the membrane potential than does the diffusion of sodium
true
true or false :the quantitative importance of each of the ions in determining the voltage is proportional to the membrane permeability for that particular ion.
true
true or false: Electrical potentials exist across the membranes of virtually all cells of the body
true
true or false: The resting stage is the resting membrane potential before the action potential begins. The membrane is said to be "polarized" during this stage because of the −90 millivolts negative membrane potential that is present.
true
true or false: during the depolarization phase the membrane suddenly becomes permeable to sodium ions, allowing tremendous numbers of positively charged sodium ions to diffuse to the interior of the axon.
true
true or false: that all cell membranes of the body have a powerful Na+-K+ pump that continually transports sodium ions to the outside of the cell and potassium ions to the inside
true
true or false:the Na+-K+ pump leaves positive ions on the inside and causes a negative potential inside the cell membrane.
true
true or false : Because of the large potassium concentration gradient from inside toward outside, there is a strong tendency for extra numbers of potassium ions to diffuse inward through the membrane
true or false : outward toward the membrane