What type of ion channels do pacemaker cells have?
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Leaky ion channels.
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What type of ion channels do pacemaker cells have?
Leaky ion channels.
What is the effect of distance on graded potentials?
Graded potentials decrease in amplitude as they spread away from the point of origin.
What happens to voltage-gated channels if a cell membrane is maintained above threshold voltage?
They become inactivated and cannot generate action potentials.
What is a generator potential?
A change in membrane potential that occurs in response to a stimulus at a sensory receptor.
What happens to membrane potential as the amount of separated charges increases?
The membrane potential increases.
What occurs when opposite charges are separated across a membrane?
Membrane potential exists.
What types of receptors respond to stimuli that generate receptor potentials?
Mechanoreceptors, thermoreceptors, nociceptors, chemoreceptors, and electromagnetic receptors.
What does the lipid bilayer separate?
Two very conductive (salty) solutions.
What happens to charge in graded potentials due to 'leaky' channels?
Charge is lost across the membrane, causing the magnitude of the potential to decrease with distance from the site of origin.
What is the role of the chemical gradient in membrane potentials?
It drives the movement of ions based on their concentration differences.
What role do graded potentials play in neurons?
They are important for the initiation and integration of long-distance signals.
What is the average duration of an action potential?
1 to 5 milliseconds.
What initiates an action potential?
A sufficient depolarization of the neuron's membrane.
What is constant along a nerve fiber during action potentials?
The size and shape of the action potential.
Is the duration of an action potential the same for specific tissues?
Yes, it is always the same for a specific tissue.
What influences the time frame of action potentials?
Specific transport protein cycle times.
What is a subthreshold response in graded potentials?
A local response that does not reach the threshold for action potential generation.
What happens during the depolarization phase of an action potential?
Sodium channels open, allowing Na+ ions to flow into the cell.
What does the equilibrium potential represent?
The charge that the membrane would have if only that ion could cross the membrane.
What is the electrical resistance of the lipid bilayer?
It has a high electrical resistance, meaning charged particles do not move easily across it.
What type of potential is established across a membrane when it is permeable to potassium ions?
Diffusion potential.
What are graded potentials?
Changes in membrane potential that vary in size and are not all-or-nothing.
What is potential in the context of voltage?
The voltage difference between two points.
What happens with small differences in the electrical balance of charges inside the cell?
They easily attract opposite charges to the outside of the cell.
What are graded potentials?
Changes in membrane potential that vary in size and are not all-or-nothing.
What is the role of ion channels in action potentials?
Ion channels open and close to allow the flow of ions, which changes the membrane potential and propagates the action potential.
What is the role of graded potentials in neurons?
They can lead to action potentials if the threshold is reached.
What is the answer to question 4?
E
What is the answer to question 5?
C
What is an action potential?
A rapid change in membrane potential that propagates along the axon of a neuron.
What role do sodium (Na+) ions play in action potentials?
They rush into the neuron during depolarization, causing the membrane potential to become more positive.
What mechanisms do action potentials depend on?
Action potentials depend on voltage-gated channels.
What is the significance of the all-or-nothing principle in action potentials?
Once the threshold is reached, an action potential will occur fully or not at all.
What occurs during the hyperpolarization phase?
The membrane potential becomes more negative than the resting potential.
What does 'all or none' mean in the context of action potentials?
When the membrane reaches threshold, an action potential is generated; it is not graded.
What is responsible for the potential across a membrane?
Unbalanced charges that accumulate in a thin layer along opposite surfaces of the membrane.
What are refractory periods in relation to action potentials?
Times when it is either impossible or more difficult than normal to generate a second action potential.
What are graded potentials that develop on the postsynaptic membrane called?
Postsynaptic potentials.
What effect does hyperkalemia have on nerve excitability?
Nerve is more excitable.
What is the difference between EPSP and IPSP?
EPSP is a depolarizing synaptic potential, while IPSP is a hyperpolarizing synaptic potential.
What happens to membrane polarity during an action potential?
It reverses, resulting in complete depolarization.
What is equilibrium potential?
The voltage difference across a membrane that produces a flux of a given ion species equal but opposite to the flux due to the concentration gradient of that same ion species.
How do graded potentials differ from action potentials?
Graded potentials can vary in magnitude, while action potentials are uniform and all-or-nothing.
What types of changes can graded potentials cause?
Graded potentials can be either a depolarization or a hyperpolarization.
What is the threshold potential typically around?
Approximately -55 mV.
What ions are primarily involved in the conductance during an action potential?
Potassium (K) and Sodium (Na).
What is bioelectricity in the context of neurons?
Bioelectricity refers to the electrical properties and activities of neurons that enable communication within the nervous system.
What are the three factors that affect diffusion potential when the membrane is permeable to several different ions?
What occurs during the depolarization phase of an action potential?
Sodium channels open, allowing Na+ to flow into the neuron, making the inside more positive.
What happens when positive and negative charges are distributed equally across the membrane?
No membrane potential exists.
What characterizes an action potential?
A brief all-or-none depolarization of the membrane, reversing polarity in neurons; it has a threshold and refractory period and is conducted without decrement.
What is an action potential?
A rapid change in membrane potential that propagates along the membrane of a neuron.
What cannot pass through the membrane in this scenario?
Anions.
What causes graded potentials?
They are caused by the opening of ion channels in response to stimuli.
What specialized cells are involved in the pacemaker potential?
Specialized cells in the cardiac pacemaker region (SA node).
Why does the resting membrane potential of most cells approximate the Nernst potential for potassium (K)?
Because potassium ions (K+) are the most permeable ions at rest, influencing the membrane potential significantly.
What is an action potential?
A rapid, temporary change in the membrane potential of a neuron.
What triggers the generation of an action potential?
A depolarization that reaches a threshold level.
What are the phases of an action potential?
Depolarization, repolarization, and hyperpolarization.
What mechanisms do graded potentials depend on?
Graded potentials depend on ligand-sensitive channels or other chemical or physical changes.
How do graded potentials differ?
They have different names depending on the type of stimulus and location where they occur.
Where do action potentials occur?
Only on regions of cell membranes that are electrically excitable.
What is the resting membrane potential for skeletal muscle cells?
-83 mV.
What is the typical resting membrane potential of a neuron?
Approximately -70 mV.
Are graded potentials always hyperpolarizing?
A. Graded potentials are always hyperpolarizing, whereas action potentials are always depolarizing.
What are the two types of physiochemical disturbances produced by stimuli?
What does the Nernst Equation calculate?
The equilibrium potential for a specific ion.
What are graded potentials?
Changes in membrane potential that vary in size and are conducted with decrement.
What is the graded potential called when it occurs in response to stimuli?
Receptor potential.
How thick is the lipid bilayer?
About 5 nm.
What is a receptor potential?
A graded potential produced at the peripheral endings of afferent neurons in response to a stimulus.
Which option describes the effect of hyperkalemia on nerve threshold potential?
Nerve becomes more excitable.
What is the electrogenic nature of the Na+/K+ ATPase pump?
It contributes to inside-negativity by moving 3 Na+ out for every 2 K+ in.
Why is it more difficult to generate a second action potential during the relative refractory period?
Due to the hyperpolarization of the cell.
What happens during hypopolarizing graded potentials?
There is a decrease in potential difference.
What is resting membrane potential?
The steady transmembrane potential of a cell that is not producing an electric signal.
What initiates the action potential in a neuron?
A depolarization that reaches the threshold potential.
What is the first stage of the action potential?
Resting stage.
What does it mean that graded potentials are local?
Changes in membrane potential are confined to relatively small regions of the plasma membrane.
What is the role of potassium channels during the action potential?
They open during repolarization, allowing K+ ions to exit the cell.
What is the resting membrane potential for heart pacemaker cells?
-60 mV.
What is the value calculated by the Goldman equation in this context?
86 mV.
What is an action potential?
A transient change in the membrane potential that conveys information within the nervous system.
What are the two gradients responsible for the movement of ions across the membrane?
Electrical gradients and chemical (concentration) gradients.
What happens to the EPP if generated by an action potential (AP) in the innervating α motor neuron?
It reaches threshold.
What happens if graded potentials reach the threshold?
An action potential develops.
How can the Na+/K+ ATPase pump be neutral regarding membrane charge?
By moving equal numbers of K+ in and Na+ out.
What does the relative refractory period correspond to in action potentials?
The positive after potential period.
How are action potentials propagated?
Without decrement.
What is voltage inactivation?
It is the state where voltage-gated channels are not reset and remain inactivated, preventing action potential generation.
Where do graded potentials typically occur?
In the dendrites and cell body of neurons.
What initiates graded potentials?
Graded potentials are initiated by environmental stimuli (receptors), neurotransmitters (synapses), or spontaneously.
What are receptor potentials?
Graded potentials that occur in sensory receptors.
What could be a consequence of increased action potential amplitude?
It could lead to stronger signals but does not explain the lack of response after ion concentration equilibration.
What equipment is typically used to record membrane potentials?
Microelectrodes and an oscilloscope or a voltmeter.
Which ion has a higher concentration inside the cell at rest?
Potassium (K+).
What is true about graded potentials?
D. Graded potentials are always decremental, whereas action potentials are always non-decremental.
What type of stimuli causes the generation of an action potential?
Threshold stimuli (Graded Potential).
How is the conduction of graded potentials characterized?
By decrement, meaning the conduction magnitude falls off the further you get from the point of origin.
What is the diffusion potential level across a membrane that opposes the net diffusion of a particular ion called?
Nernst potential.
What does the Nernst potential relate to?
The concentration difference of a particular ion.
What generates action potentials?
Graded potentials that reach threshold.
What property of the lipid bilayer allows it to store a large amount of charge?
Its thinness allows for high capacitance.
What is the role of graded potentials in the heart?
Graded potentials can potentially induce a true cardiac action potential.
What is the potential difference required for a normal mammalian nerve fiber?
About 94 millivolts.
Do action potentials have a specific size and shape?
Yes, they have a specific size and shape.
What is the answer to question 2?
C
What is the answer to question 3?
B
How does transduction occur in sensory receptors?
Transduction converts a stimulus into an electrical signal, typically a generator potential.
What is responsible for cardiac automaticity?
Graded potential.
What happens to sodium conductance during the depolarization phase of an action potential?
Sodium conductance increases rapidly.
What ions are primarily involved in generating an action potential?
Sodium (Na+) and potassium (K+).
What happens during repolarization?
Potassium (K+) ions exit the neuron, restoring the negative membrane potential.
What is the first step in setting up for recording membrane potentials?
Insert a microelectrode into the cell.
How do action potentials vary among different cell types?
They generally have a standard size and shape for a specific cell type.
What is the role of myelin in nerve impulse propagation?
Myelin insulates the axon, allowing for faster transmission of action potentials via saltatory conduction.
What are some functions that action potentials are important for?
Nerve traffic, muscle contraction, hormone release, G.I. secretions, and cognitive thought.
What are receptor (generator) potentials?
Graded potentials in response to stimuli from sensory receptors.
What is the End Plate Potential (EPP)?
A post synaptic potential at the neuromuscular junction that is always stimulatory.
What is a synaptic potential?
A graded potential change produced in the postsynaptic neuron in response to the release of a neurotransmitter by a presynaptic terminal; it may be depolarizing (EPSP) or hyperpolarizing (IPSP).
What is established when a nerve fiber membrane is permeable only to sodium ions?
A diffusion potential.
What does it mean for a cell to have a resting membrane potential difference?
It refers to the voltage difference across the cell membrane when the cell is not actively transmitting signals.
What ions are involved in the establishment of a diffusion potential in this context?
Sodium ions.
What is threshold potential?
The membrane potential at which an action potential is initiated.
What is the charge inside the nerve fiber in this scenario?
Negativity inside.
What happens when the ionic composition of the medium is equilibrated with the intracellular concentration in the giant squid axon?
No more action potentials are seen upon stimulation.
What occurs during accommodation to slow depolarization?
Voltage-gated channels do not respond, and no action potential occurs.
What happens when a generator potential reaches a certain threshold?
It can trigger an action potential in the sensory neuron.
What is the relationship between stimulus intensity and generator potential?
Higher stimulus intensity results in a larger generator potential.
What is the primary purpose of recording membrane potentials?
To measure the electrical activity across a cell membrane.
What causes action potentials?
Rapid changes in ion conductance.
What is a receptor in the context of sensory modalities?
A specialized cell or distal portion of a neuron that responds to specific sensory modalities like touch, pressure, cold, light, or sound, and converts it to an electrical signal.
In which phase of the action potential is the conductance velocity of potassium least?
Phase 4.
What is the Goldman equation also known as?
The Goldman - Hodgkin - Katz equation.
Which senses depend on action potentials for information transmission to the brain?
Sight, hearing, and touch.
What causes repolarization of the neuronal cell membrane when a nerve is stimulated?
Increase in outward permeability of K+ ion.
Which types of cells generate action potentials?
Electrically excitable cells, such as nerve and muscle cells.
What stimulates the generation of an action potential?
A change in membrane potential due to the flow of current in and out of the cell.
What happens if a graded potential reaches the threshold?
An action potential is generated, sending sensory information to the spinal cord and brain.
What is a graded potential?
A potential change of variable amplitude and duration that is conducted decrementally; it has no threshold or refractory period.
What is hyperkalemia?
An electrolyte disorder characterized by elevated potassium levels in the blood.
What does the electrical gradient influence in membrane potentials?
The movement of charged ions across the membrane.
What types of stimuli can graded potentials be during synaptic transmission?
They can be stimulatory (EPSP) or inhibitory (IPSP).
What ions can pass through the membrane in this scenario?
Potassium ions.
What is one characteristic of graded potentials?
They are the only type of communication by some neurons.
Is the End Plate Potential (EPP) excitatory or inhibitory?
It is always stimulatory.
How do graded potentials function in terms of distance?
They can function as signals over very short distances.
What does it mean that graded potentials are 'graded'?
Their magnitude can vary with the magnitude of the stimulus.
How do graded potentials differ from action potentials?
Graded potentials can vary in magnitude, while action potentials are uniform and all-or-nothing.
What are the types of action potentials?
There are different types based on the stimulus and the resulting response, such as graded potentials leading to action potentials.
What is a pacemaker potential?
A spontaneously occurring graded potential change that occurs in certain specialized cells.
What does membrane potential refer to?
The voltage difference between the inside and outside of a cell.
What are the two types of graded events?
Hypopolarizing (depolarizing) and hyperpolarizing.
How far do graded potentials typically die out from their origin?
In 1 - 2 mm of the origin.
How do changes in ion permeability affect membrane potential?
Changes in ion permeability can lead to depolarization or hyperpolarization of the membrane potential, depending on which ions are more permeable.
What is the answer to question 1?
D
What does the Na+/K+ ATPase pump maintain?
The concentration gradients for the two most important ions that determine the membrane potential.
What happens to the membrane potential when it becomes permeable to sodium ions?
It generates a diffusion potential due to sodium ion movement.
How does the duration of graded potentials compare to action potentials?
Graded potential duration varies with initiating conditions, while action potential duration is constant for a given cell type under constant conditions.
What are the properties of generator potentials?
They are graded, meaning their amplitude varies with the strength of the stimulus.
What does the term 'absolute refractory period' refer to?
A phase during which no new action potentials can be generated, regardless of stimulus strength.
What does RMP stand for in neurophysiology?
Resting Membrane Potential.
What is the typical value of resting membrane potential in neurons?
Approximately -70 mV.
What role does potassium conductance play during the repolarization phase of an action potential?
Potassium conductance increases, allowing K+ to exit the cell.
How does the polarity of the electrical charge of each ion affect diffusion potential?
It influences the movement of ions across the membrane based on their charge.
What happens during the repolarization phase of an action potential?
Potassium channels open, allowing K+ to flow out of the neuron, restoring the negative membrane potential.
What is the significance of the threshold potential?
It is the critical level that must be reached for an action potential to occur.
What happens during the repolarization phase?
Potassium channels open, allowing K+ ions to exit the neuron.
What occurs during hyperpolarization?
The membrane potential becomes more negative than the resting potential.
What are receptor or generator potentials?
Local, graded, non-propagated potentials produced by stimuli.
What energy source does the Na+/K+ pump use to function?
ATP (adenosine triphosphate).
Is there a threshold for graded potentials?
No, there is no threshold.
What factors influence the size of a graded potential?
The strength of the stimulus and the type of ion channels activated.
What type of change does an action potential cause?
An action potential is only a depolarization.
What is the effect of slow depolarization on action potential generation?
It prevents the generation of action potentials due to unresponsive voltage-gated channels.
What initiates action potentials?
Action potentials are initiated by a graded potential.
What are generator potentials?
Graded potentials that occur in sensory neurons.
How does the speed of conduction of action potentials relate to ion concentration?
The speed of conduction can be affected by ion concentration, but in this case, the lack of response is due to ion equilibration.
What occurs during the repolarization stage of the action potential?
K+ outflow through voltage-gated K+ channels, moving the membrane potential back toward RMP.
Which ion has a higher concentration outside the cell at rest?
Sodium (Na+).
What role do ion channels play in maintaining RMP?
They allow selective permeability to ions, influencing the membrane potential.
What is the refractory period?
A period during which a neuron cannot fire another action potential, ensuring unidirectional propagation.
What is the primary function of the Na+/K+ pump?
To actively transport sodium out of and potassium into the cell.
What happens during the depolarization phase of an action potential?
Sodium channels open, allowing Na+ ions to flow into the cell.
What is the significance of the axon terminal?
It releases neurotransmitters into the synapse.
What is the likely cause of no response after equilibrating ion concentrations in the axon?
Increased permeability for Na+ is not achieved, leading to no action potential generation.
What is a postsynaptic potential?
A graded potential that occurs in the dendrites or cell body of a neuron in response to a neurotransmitter.
What is the normal resting membrane potential for nerve cells?
-90 mV.
What happens during the depolarization stage of the action potential?
Threshold for voltage-gated Na+ channels is exceeded, leading to Na+ influx.
What primarily determines the resting membrane potential?
The distribution of ions across the cell membrane, particularly sodium (Na+) and potassium (K+).
What is the typical value of resting membrane potential in neurons?
Typically around -70 mV.
What role does membrane permeability (P) play in diffusion potential?
It determines how easily ions can pass through the membrane.
What is the second phase of action potential?
Repolarization.
How does the Nernst equation relate to ion permeability?
The Nernst equation shows how the concentration gradient of an ion affects its equilibrium potential, which influences the overall membrane potential based on permeability.
What characterizes an action potential?
A rapid but transient change in membrane potential.
What is the threshold potential typically around?
Approximately -55 mV.
What are synapses?
Junctions where neurons communicate with other neurons or cells.
How are graded potentials conducted?
Decrementally; amplitude decreases with distance.
What is a graded potential?
A change in membrane potential that varies in size depending on the strength of the stimulus.
What happens to graded potentials as they move away from the stimulus site?
They decrease in amplitude due to passive current flow.
What is the difference between absolute and relative refractory periods?
During the absolute refractory period, no action potentials can occur; during the relative refractory period, a stronger-than-normal stimulus can trigger an action potential.
What does it mean that graded potentials are graded?
It refers to the magnitude of the potential change, indicating that the signal can be reinforced.
What is the refractory period?
The time during which a neuron cannot fire another action potential.
Which statement correctly describes graded potentials and action potentials?
B. Graded potentials are proportional to the magnitude of the stimulus, whereas action potentials are 'all-or-none.'
What does the Nernst equation calculate?
The Nernst equation calculates the equilibrium potential for a specific ion based on its concentration gradient across the membrane.
What factors influence the resting membrane potential?
Ion concentrations inside and outside the cell, permeability of the membrane to different ions, and the activity of ion pumps.
What is the phase that follows repolarization?
Hyperpolarization.
What does a change in local membrane polarity indicate?
It indicates the transition from polarized to depolarized states.
What type of transport mechanism is the Na+/K+ pump?
Active transport.
What is the role of neurotransmitters?
Chemical messengers that transmit signals across synapses.
What is required for the generation of an action potential?
Specific voltage-gated ion channels.
What is the first phase of action potential?
Depolarization.
What occurs during the depolarization phase?
Sodium channels open, allowing Na+ ions to enter the neuron.
How is an action potential propagated along a nerve?
By the sequential opening and closing of ion channels along the axon.
Can suprathreshold stimuli depolarize a neuron during absolute refractory periods?
C. Suprathreshold stimuli are able to depolarize a neuron in absolute refractory periods.
What restores the resting membrane potential after an action potential?
The Na+/K+ pump and the closing of potassium channels.
What are the main components of a neuron?
Dendrites, cell body (soma), and axon.
What is the role of the sodium-potassium pump during action potential generation?
It helps restore the resting membrane potential after the action potential.
What is the threshold for action potentials?
Usually about 15 mV depolarized relative to the resting potential.
How does the change in sodium and potassium conductance affect the membrane potential?
Increased Na+ conductance depolarizes the membrane, while increased K+ conductance repolarizes it.
What is the effect of sodium channel inactivation during an action potential?
It prevents further influx of Na+, contributing to repolarization.
Why are the concentrations (C) of ions important for diffusion potential?
They dictate the gradient that drives the movement of ions across the membrane.
What do receptors recognize and bind to?
A particular ligand.
What is the 'All or None Response' in action potential generation?
The size and shape of the action potential are not influenced by the size of the stimulus.
How many potassium ions are transported into the cell by the Na+/K+ pump?
Two potassium ions.
What is myelin and its function in neurons?
A fatty substance that insulates axons, increasing signal transmission speed.
Do graded potentials have a refractory period?
No, they have no refractory period.
What is the refractory period?
The time during which a neuron cannot fire another action potential.
What is the significance of the reference electrode in membrane potential recording?
It provides a stable reference point for measuring the potential difference.
How does the action potential propagate along the axon?
Through a wave of depolarization and repolarization, often facilitated by myelin sheaths.
What is a specific molecule or cluster of molecules in the context of receptors?
A receptor that recognizes and binds a particular ligand.
How many sodium ions are transported out of the cell by the Na+/K+ pump?
Three sodium ions.
What occurs during the repolarization phase?
Potassium channels open, allowing K+ ions to flow out of the cell.
Can graded potentials be summed?
Yes, they can be summed.
What types of sensory modalities can receptors respond to?
Touch, pressure, cold, light, or sound.
What happens to the magnitude of action potential as it travels away from the point of generation?
E. Magnitude of action potential is in a gradual decreasing order as it travels away from the point of generation.
What is the Nernst equation used for?
To calculate the equilibrium potential for individual ions.
What are graded potentials?
Subthreshold electrical stimuli that do not produce a true action potential but generate electrical signals.
What happens during an action potential?
Complete depolarization occurs and is propagated down the axon to cause the release of neurotransmitters.
What is the all-or-nothing principle in action potentials?
Once the threshold is reached, an action potential will occur fully or not at all.
Do action potentials have a refractory period?
Yes, they have a refractory period.
What is the electrical signal generated by receptors called?
Generator or receptor potential.
What factors can affect the accuracy of membrane potential recordings?
Electrode placement, cell health, and external electrical noise.
What types of stimuli can produce graded potentials?
Electrical, chemical, or mechanical stimuli.
What is the function of dendrites in a neuron?
To receive signals from other neurons.
What is the refractory period?
The time during which a neuron cannot fire another action potential.
How are action potentials conducted?
Without decrement; the depolarization is amplified to a constant value at each point along the membrane.
What is the Goldman equation used for?
To calculate the resting membrane potential considering multiple ions.
What are the three states of membrane potential during action potential?
Polarized, depolarized, and then polarized again.
What is the significance of the Na+/K+ pump in maintaining cellular function?
It helps maintain the resting membrane potential and cell volume.
What is the nature of action potentials in terms of amplitude?
All-or-none; once the membrane is depolarized to threshold, amplitude is independent of the initiating event.
What is the threshold potential?
The critical level of depolarization that must be reached for an action potential to occur.
What initiates the action potential in a neuron?
A depolarization that reaches the threshold potential.
What is the purpose of the axon in a neuron?
To transmit electrical impulses away from the cell body.
Can action potentials be summed?
No, they cannot be summed.
What role does the cell body (soma) play in a neuron?
It contains the nucleus and organelles, integrating signals.
How does the amplitude of graded potentials vary?
Amplitude varies with conditions of initiating events.
