Cardiac Muscle Action Potential

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What is the approximate resting potential of a cardiac muscle cell?

-85mV (correct)

-50mV

-60mV

-70mV

Which ion plays a crucial role in creating the resting potential of a cardiac muscle cell?

Potassium (K+) (correct)

Calcium (Ca2+)

Chloride (Cl-)

Sodium (Na+)

In a theoretical cell with an initial equal number of positive and negative charges, what creates the charge imbalance for the resting potential?

Diffusion of positively charged potassium ions out of the cell (correct)

Diffusion of sodium ions into the cell

Diffusion of negatively charged ions into the cell

Diffusion of chloride ions out of the cell

What is the primary form of negative charge inside cardiac cells contributing to the resting potential?

Organic phosphates Signup and view all the answers

Which pump is responsible for maintaining the ionic concentration gradients in cardiac muscle cells for resting potential?

Na+/K+ ATPase Signup and view all the answers

What happens to the sodium gates when the membrane potential reaches between +20 and +30 mV?

They are inactivated by the electric charge distribution. Signup and view all the answers

During which phase of the action potential does the K+ permeability begin to increase significantly?

Phase 1 Signup and view all the answers

What role do L-type voltage gated calcium channels play in the action potential?

They create a plateau phase in phase 2. Signup and view all the answers

Why does the membrane potential not immediately fall to the equilibrium potential for potassium despite increased K+ permeability?

Simultaneous opening of calcium channels and inward flow of calcium. Signup and view all the answers

When does the myocyte contraction occur in relation to the action potential phases?

During phase 2 Signup and view all the answers

Which phase of the cardiac action potential is characterized by the opening of sodium gates and a hundred-fold increase in sodium permeability?

Phase 0 Signup and view all the answers

What ion has its concentration gradient reversed in the Goldman equation used to calculate the true resting potential?

Sodium (Na+) Signup and view all the answers

During which phase of the cardiac action potential does the membrane potential depolarize to reach the threshold potential (-60 to -65mV)?

Phase 0 Signup and view all the answers

What is the primary characteristic of the plateau phase of the cardiac action potential?

Prolonged period of slow repolarization Signup and view all the answers

Which type of muscle tissue is primarily responsible for generating the wave of excitation that triggers the opening of sodium gates in cardiac muscle membranes?

Pacemaker tissue Signup and view all the answers

What is the main reason for the initial resting potential in the SAN being less negative compared to the rest of the heart?

Presence of 'inward rectifier' potassium channels Signup and view all the answers

What causes the pacemaker potential or 'prepotential' to drift upwards towards depolarization?

Influx of Na+ through funny channels Signup and view all the answers

Which ion channel type is responsible for the diastolic depolarization phase in pacemaker cells?

'Funny' sodium channels Signup and view all the answers

During which phase is there an inward calcium current that accelerates depolarization towards the threshold potential?

Phase 0: Depolarization phase Signup and view all the answers

What distinguishes the maximum depolarization level in the pacemaker cells from contractile myocardial cells?

+10 mV for pacemaker cells and +30 mV for contractile cells Signup and view all the answers

What triggers the opening of sodium ion channel gates in cardiac muscle, leading to rapid ion permeability rise and the generation of another action potential?

Depolarization to threshold potential Signup and view all the answers

Which parts of the heart exhibit automaticity, generating action potentials spontaneously?

Sinoatrial node Signup and view all the answers

What is the term used to describe the ability of the sinoatrial node (SAN) to have the fastest intrinsic rhythm in the human heart?

Pacemaker tissue Signup and view all the answers

Which type of muscle cells in the heart typically do not display automaticity?

Ventricular muscle cells Signup and view all the answers

What determines the rate of contraction in cardiac muscle?

Rate of depolarization of resting potential Signup and view all the answers

During which phase of the cardiac action potential do Na+ channels remain closed, leading to the 'absolute refractory' period of the myocytes?

Plateau phase Signup and view all the answers

What is the primary consequence of the 'absolute refractory' period in cardiac myocytes?

Inability to generate another action potential Signup and view all the answers

Where do some areas of the heart have particularly unstable 'resting potential'?

Pacemaker tissue Signup and view all the answers

What happens to many Na+ channels during the repolarization phase of the cardiac action potential?

They partially reopen Signup and view all the answers

Why is it harder to generate a subsequent action potential during the 'relative refractory period' of the cardiac action potential?

'Na' channels have partially recovered Signup and view all the answers

What concept is the Nernst equation based on?

Balance between diffusive and electrical gradients Signup and view all the answers

Why is the equilibrium potential for potassium in cardiac muscle cells slightly more negative than the resting membrane potential?

Influence from movements of ions other than potassium Signup and view all the answers

What is the primary ion influencing the magnitude of the resting potential in cardiac muscle cells?

Potassium Signup and view all the answers

Why is the membrane potential far from the Na+ equilibrium potential of +60 mV at rest?

Low permeability to sodium ions Signup and view all the answers

What is responsible for maintaining the ionic concentration gradients in cardiac muscle cells?

Sodium-potassium pump Signup and view all the answers

What contributes to the resting membrane potential being slightly more negative than the potassium equilibrium potential in cardiac muscle cells?

Movement of ions other than potassium Signup and view all the answers

What is the role of the Na+/K+-ATPase pump in relation to ion gradients and membrane potential?

Creates and maintains ionic concentration gradients Signup and view all the answers

Why is sodium far from electrochemical equilibrium at rest in cardiac muscle cells?

Low sodium permeability at rest Signup and view all the answers

Why does potassium have a substantial influence on the resting membrane potential?

Low permeability to other ions Signup and view all the answers

What determines the slightly more negative equilibrium potential for potassium in cardiac muscle cells compared to the RMP?

Other ion movements besides potassium Signup and view all the answers

Cardiac Muscle Action Potential

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Questions and Answers

What is the approximate resting potential of a cardiac muscle cell?

Which ion plays a crucial role in creating the resting potential of a cardiac muscle cell?

In a theoretical cell with an initial equal number of positive and negative charges, what creates the charge imbalance for the resting potential?

What is the primary form of negative charge inside cardiac cells contributing to the resting potential?

Which pump is responsible for maintaining the ionic concentration gradients in cardiac muscle cells for resting potential?

What happens to the sodium gates when the membrane potential reaches between +20 and +30 mV?

During which phase of the action potential does the K+ permeability begin to increase significantly?

What role do L-type voltage gated calcium channels play in the action potential?

Why does the membrane potential not immediately fall to the equilibrium potential for potassium despite increased K+ permeability?

When does the myocyte contraction occur in relation to the action potential phases?

Which phase of the cardiac action potential is characterized by the opening of sodium gates and a hundred-fold increase in sodium permeability?

What ion has its concentration gradient reversed in the Goldman equation used to calculate the true resting potential?

During which phase of the cardiac action potential does the membrane potential depolarize to reach the threshold potential (-60 to -65mV)?

What is the primary characteristic of the plateau phase of the cardiac action potential?

Which type of muscle tissue is primarily responsible for generating the wave of excitation that triggers the opening of sodium gates in cardiac muscle membranes?

What is the main reason for the initial resting potential in the SAN being less negative compared to the rest of the heart?

What causes the pacemaker potential or 'prepotential' to drift upwards towards depolarization?

Which ion channel type is responsible for the diastolic depolarization phase in pacemaker cells?

During which phase is there an inward calcium current that accelerates depolarization towards the threshold potential?

What distinguishes the maximum depolarization level in the pacemaker cells from contractile myocardial cells?

What triggers the opening of sodium ion channel gates in cardiac muscle, leading to rapid ion permeability rise and the generation of another action potential?

Which parts of the heart exhibit automaticity, generating action potentials spontaneously?

What is the term used to describe the ability of the sinoatrial node (SAN) to have the fastest intrinsic rhythm in the human heart?

Which type of muscle cells in the heart typically do not display automaticity?

What determines the rate of contraction in cardiac muscle?

During which phase of the cardiac action potential do Na+ channels remain closed, leading to the 'absolute refractory' period of the myocytes?

What is the primary consequence of the 'absolute refractory' period in cardiac myocytes?

Where do some areas of the heart have particularly unstable 'resting potential'?

What happens to many Na+ channels during the repolarization phase of the cardiac action potential?

Why is it harder to generate a subsequent action potential during the 'relative refractory period' of the cardiac action potential?

What concept is the Nernst equation based on?

Why is the equilibrium potential for potassium in cardiac muscle cells slightly more negative than the resting membrane potential?

What is the primary ion influencing the magnitude of the resting potential in cardiac muscle cells?

Why is the membrane potential far from the Na+ equilibrium potential of +60 mV at rest?

What is responsible for maintaining the ionic concentration gradients in cardiac muscle cells?

What contributes to the resting membrane potential being slightly more negative than the potassium equilibrium potential in cardiac muscle cells?

What is the role of the Na+/K+-ATPase pump in relation to ion gradients and membrane potential?

Why is sodium far from electrochemical equilibrium at rest in cardiac muscle cells?

Why does potassium have a substantial influence on the resting membrane potential?

What determines the slightly more negative equilibrium potential for potassium in cardiac muscle cells compared to the RMP?

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