Steps of the Action Potential - Correct Answers Depolarization
Repolarization
Hyperpolarization
Depolarization - Correct Answers movement of the intracellular charge towards zero (more positive
charge)
Voltage gated Na channels open and allow Na to enter the cell -> voltage inside the cell moves towards
zero
Repolarization - Correct Answers Once the intracellular charge reaches zero, the negative polarity of the
inside of the cell is restored back to its baseline of -70 to -85 mV
-Na channels close, K channels open
Hyperpolarization - Correct Answers when the cell's resting membrane potential is greater than -85mV.
Is less excitable, because there is a greater distance between the resting membrane potential and the
threshold potential.
In order for the action potential to be sucessful - Correct Answers t has to depolarize by 15-20 mV
(threshold potential) to reach -55 to -65 mV.
An alteration in action potential may result from - Correct Answers neurologic diseases, muscle disease
or electrolyte imbalances.
What is the main protein responsible for maintaining the correct balance of extracellular Na and
intracellular K, which is needed for cellular excitation and membrane conductivity. - Correct Answers
Na+-K+ ATPase
Resting membrane potential - Correct Answers when the cell is in a nonexcited state and is at -70 to -85
mV.
,Refractory Period - Correct Answers is a period of time during most of the action potential which the
cell membrane resists stimulation and it cannot depolarize
Absolute refractory period - Correct Answers occurs when the membrane will not respond to ANY
stimulus no matter how strong.
Relative Refractory Period - Correct Answers occurs when the membrane is repolarizing and will only
respond to a very strong stimulus.
Hyperpolarized - Correct Answers when the cell's resting membrane potential is greater than -85mV.
Is less excitable, because there is a greater distance between the resting membrane potential and the
threshold potential.
Hypopolarized - Correct Answers when the cell's resting membrane potential is closer to zero, for
instance it is -65mV.
Is more excitable because the resting membrane potential is closer to the threshold potential, there is
less distance between them.
Action potential altered by hypokalemia - Correct Answers (serum outside of cell is low)
-Hyperpolarized (cell becomes more negative, ex: -100)
-Affects the resting membrane potential of cells
-The cell is less likely to depolarize and transmit impulses
Can cause a decrease in neuromuscular excitability and leads to weakness, smooth muscle atony,
paresthesias, and cardiac dysrhythmias
Action potential altered by hyperkalemia - Correct Answers Hypopolarized
-Also has an effect on the resting membrane potential
-If the ECF potassium increases without any change in the ICF potassium levels, the resting membrane
potential of the cell becomes more positive.
, -The cells are more excitable and conduct impulses more easily and more quickly because the resting
membrane potential is closer to the threshold potential. Therefore, the person will have peak T waves
on EKG.
-As potassium rises, the resting membrane potential will continue to become more positive and it will
eventually become equal to the threshold potential. As this happens the EKG will show a widening QRS
complex. If the resting membrane potential equals the threshold potential, an action potential will not
be generated and cardiac standstill will occur. Paralysis and paresthesias may also occur.
Action potential altered by hypocalcemia - Correct Answers -Causes an increase in the cell permeability
to Na causing a progressive depolarization
-Causes the RMP and the TP to be closer to one another & making it easier to initiate an action potential
- the cells are more excitable.
-Results in tetany, hyperreflexia, circumoral paresthesias, seizures, dysrhythmias
Action potential altered by hypercalcemia - Correct Answers -Causes a decrease in cell permeability to
Na
-Causes the RMP and the TP to increase in distance - the cells are less excitable and requires more of a
stimulus to initiate an action potential.
-Leads to weakness, hyporeflexia, fatigue, lethargy, confusion, encephalopathy, a shortened QT segment
and depressed widened T waves on EKG.
Atrophy - Correct Answers decrease or shrinkage in the size of the cell
-Imbalance between protein synthesis and degradation, , reduction of the intracellular contents, also
includes a self-eating process called autophagy.
-Example: aging brain cells, malnutrition, uterus decreasing in size after childbirth
Hypertrophy - Correct Answers increase in the size of cells, which ultimately increases the size of the
organ
-Etiology: triggers include repetitive stretching, chronic pressure, volume overload
-Pathophysiology: hormonal stimulation or increased functional demand, which increases the cellular
protein in the plasma membrane, endoplasmic reticulum, myofilaments, and mitochondria
Hyperplasia - Correct Answers -increase in number of cells, not the size of the cell, which results from
an increased rate of cell division, it can only happen in cells that are capable of mitosis *
Repolarization
Hyperpolarization
Depolarization - Correct Answers movement of the intracellular charge towards zero (more positive
charge)
Voltage gated Na channels open and allow Na to enter the cell -> voltage inside the cell moves towards
zero
Repolarization - Correct Answers Once the intracellular charge reaches zero, the negative polarity of the
inside of the cell is restored back to its baseline of -70 to -85 mV
-Na channels close, K channels open
Hyperpolarization - Correct Answers when the cell's resting membrane potential is greater than -85mV.
Is less excitable, because there is a greater distance between the resting membrane potential and the
threshold potential.
In order for the action potential to be sucessful - Correct Answers t has to depolarize by 15-20 mV
(threshold potential) to reach -55 to -65 mV.
An alteration in action potential may result from - Correct Answers neurologic diseases, muscle disease
or electrolyte imbalances.
What is the main protein responsible for maintaining the correct balance of extracellular Na and
intracellular K, which is needed for cellular excitation and membrane conductivity. - Correct Answers
Na+-K+ ATPase
Resting membrane potential - Correct Answers when the cell is in a nonexcited state and is at -70 to -85
mV.
,Refractory Period - Correct Answers is a period of time during most of the action potential which the
cell membrane resists stimulation and it cannot depolarize
Absolute refractory period - Correct Answers occurs when the membrane will not respond to ANY
stimulus no matter how strong.
Relative Refractory Period - Correct Answers occurs when the membrane is repolarizing and will only
respond to a very strong stimulus.
Hyperpolarized - Correct Answers when the cell's resting membrane potential is greater than -85mV.
Is less excitable, because there is a greater distance between the resting membrane potential and the
threshold potential.
Hypopolarized - Correct Answers when the cell's resting membrane potential is closer to zero, for
instance it is -65mV.
Is more excitable because the resting membrane potential is closer to the threshold potential, there is
less distance between them.
Action potential altered by hypokalemia - Correct Answers (serum outside of cell is low)
-Hyperpolarized (cell becomes more negative, ex: -100)
-Affects the resting membrane potential of cells
-The cell is less likely to depolarize and transmit impulses
Can cause a decrease in neuromuscular excitability and leads to weakness, smooth muscle atony,
paresthesias, and cardiac dysrhythmias
Action potential altered by hyperkalemia - Correct Answers Hypopolarized
-Also has an effect on the resting membrane potential
-If the ECF potassium increases without any change in the ICF potassium levels, the resting membrane
potential of the cell becomes more positive.
, -The cells are more excitable and conduct impulses more easily and more quickly because the resting
membrane potential is closer to the threshold potential. Therefore, the person will have peak T waves
on EKG.
-As potassium rises, the resting membrane potential will continue to become more positive and it will
eventually become equal to the threshold potential. As this happens the EKG will show a widening QRS
complex. If the resting membrane potential equals the threshold potential, an action potential will not
be generated and cardiac standstill will occur. Paralysis and paresthesias may also occur.
Action potential altered by hypocalcemia - Correct Answers -Causes an increase in the cell permeability
to Na causing a progressive depolarization
-Causes the RMP and the TP to be closer to one another & making it easier to initiate an action potential
- the cells are more excitable.
-Results in tetany, hyperreflexia, circumoral paresthesias, seizures, dysrhythmias
Action potential altered by hypercalcemia - Correct Answers -Causes a decrease in cell permeability to
Na
-Causes the RMP and the TP to increase in distance - the cells are less excitable and requires more of a
stimulus to initiate an action potential.
-Leads to weakness, hyporeflexia, fatigue, lethargy, confusion, encephalopathy, a shortened QT segment
and depressed widened T waves on EKG.
Atrophy - Correct Answers decrease or shrinkage in the size of the cell
-Imbalance between protein synthesis and degradation, , reduction of the intracellular contents, also
includes a self-eating process called autophagy.
-Example: aging brain cells, malnutrition, uterus decreasing in size after childbirth
Hypertrophy - Correct Answers increase in the size of cells, which ultimately increases the size of the
organ
-Etiology: triggers include repetitive stretching, chronic pressure, volume overload
-Pathophysiology: hormonal stimulation or increased functional demand, which increases the cellular
protein in the plasma membrane, endoplasmic reticulum, myofilaments, and mitochondria
Hyperplasia - Correct Answers -increase in number of cells, not the size of the cell, which results from
an increased rate of cell division, it can only happen in cells that are capable of mitosis *
