60 Questions
What type of potential exactly balances the tendency of an ion to diffuse down its concentration gradient?
Nernst potential
What is the driving force behind the movement of uncharged molecules across a membrane?
Concentration gradient
What is the typical value of the equilibrium potential for potassium ions (EK+)?
-85 mV
What is the primary factor that determines the diffusion potential across a membrane?
Concentration gradient
What would happen if the membrane was not permeable to the ion in question?
No diffusion potential would be generated
What type of cells undergo controlled changes in their membrane potential?
Neurons and muscle cells
What is the term for the difference in electric potential between the interior and exterior of a biological cell?
Membrane potential
What is the effect of a diffusion potential on the concentration of ions in bulk solution?
It has no effect on the concentration of ions
What is the typical value of the equilibrium potential for sodium ions (ENa+)?
+65 mV
What is the diffusion potential generated by?
The movement of a charged solute down its concentration gradient
What is the relationship between the diffusion potential and the concentration gradient?
The diffusion potential is directly proportional to the concentration gradient
What is the term for the membrane potential of a cell that remains relatively constant over time?
Resting potential
What is the resting potential of nerve fibers when not transmitting nerve signals?
-70 millivolts
What is the main contributor to the resting potential of nerve cells?
Potassium diffusion
What is the selectivity of the potassium leak channels?
100x higher for K than for Na ions
Why do potassium ions move into the cell?
Attracted to negative charges
What is the role of the Na-K pump?
To maintain the resting potential of nerve cells
Why is the membrane less permeable to sodium ions?
The membrane is more permeable to potassium ions
What is the minimal membrane potential required to trigger an action potential?
-55 mV
What happens to the membrane potential during depolarization?
It rises in the positive direction
What causes the rapid diffusion of K ions out of the cell during repolarization?
Voltage-gated potassium channels
What is the term for the state when neurons have a more negative membrane potential than normal?
Hyperpolarization
What is the absolute refractory period?
The time needed for the voltage-gated sodium channels to revert from the inactivated state to the resting closed state
What is the relative refractory period?
The time when the membrane is in a hyperpolarization state
What is the primary function of the Na-K pump?
To transport Na+ out and K+ in
What is the role of the ATPase function in the Na-K pump?
To activate the pump after binding of Na+ and K+ ions
What is the significance of the resting potential in neurons?
It is necessary for the transmission of nerve signals
What is the characteristics of an action potential?
A rapid change in the membrane potential that spreads rapidly along the nerve fiber
What are the five stages of an action potential?
Resting, threshold, depolarization, repolarization, and hyperpolarization
What is the significance of the Na-K pump in controlling the volume of a cell?
It helps to remove excess sodium ions from the cell
What is the primary driving force behind the movement of charged molecules across a membrane?
Electrical charges
What is necessary for a diffusion potential to be generated across a membrane?
A concentration gradient of charged molecules and membrane permeability
What is the effect of a diffusion potential on the bulk solution?
No effect on the concentration of ions
What determines the magnitude of the diffusion potential across a membrane?
Both the concentration gradient and permeability of the membrane
What would happen if a membrane was not permeable to the ion in question?
No diffusion potential would be generated
What is the relationship between the diffusion potential and the concentration gradient?
The diffusion potential increases with an increase in concentration gradient
What is the main factor that determines the equilibrium potential of an ion?
Both the electrical charge and concentration inside and outside the membrane
What is the characteristic of the membrane potential in most animal cells?
It does not vary with time
What is the term for the membrane potential that remains relatively constant over time?
Resting potential
What is the primary factor that determines the membrane potential of a cell?
The relative permeability of each ion
What is the difference between the electric potential inside and outside a biological cell?
Membrane potential
Which type of cells do not undergo controlled changes in their membrane potential?
Most animal cells
What is the primary contributor to the resting potential of nerve cells?
Diffusion of potassium through the nerve cell membrane
What determines the selectivity of potassium leak channels?
The protein structure of the channel
What is the direction of potassium ion movement in the resting state?
Out of the cell
What is the effect of the Na-K pump on the resting potential?
It maintains the resting potential
Why are potassium ions attracted to the inside of the cell?
Because of the negative charges inside the cell
What is the typical value of the resting potential of nerve fibers when not transmitting nerve signals?
-70 millivolts
What is the primary function of the Na-K pump in neurons?
To control the volume of the cell and maintain the resting potential
What is the characteristic of the action potential that allows it to spread rapidly along the nerve fiber membrane?
The sudden change from the resting negative membrane potential to a positive potential
What is the consequence of the dynamic changes in the membrane potential in neurons and muscle cells?
The generation of action potentials
What is the role of the ATPase function in the Na-K pump?
To activate the pump after binding of sodium and potassium ions
What is the significance of the resting potential in nerve cells?
It is essential for the transmission of nerve signals
How many stages are involved in the action potential?
5 stages
What is the minimum membrane potential required to initiate an action potential?
-55 mV
What type of channels are activated during depolarization?
Voltage-gated sodium channels
What is the term for the state when neurons have a more negative membrane potential than normal after an action potential?
Hyperpolarization
What is the primary function of the voltage-gated potassium channels during an action potential?
To slow down the depolarization process
What is the period during which the voltage-gated sodium channels are closed and cannot be reopened?
Absolute refractory period
What is the stage of the action potential during which the membrane potential becomes highly permeable to sodium ions?
Depolarization
This quiz covers the basics of muscle physiology, including the generation of resting membrane potentials and the phases of action potentials. It also explores the concepts of diffusion potential, concentration gradient, and the driving forces behind charged and uncharged molecules.
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