Nernst Equation in Cell Membrane Analysis

Podcast Beta

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What describes the relationship between resistance and pressure in the vasculature?

Increased resistance causes decreased pressure. (correct)

Higher resistance leads to lower flow velocity.

High resistance is found in the capillaries.

Lower resistance results in lower pressure.

Which factor is pulse pressure primarily determined by?

High resistance in arterioles

Stroke volume (correct)

Total blood volume

Mean arterial pressure

What is the primary intracellular ion that correlates with myocardial contractility?

Sodium (Na+)

Chloride (Cl–)

Potassium (K+)

Calcium (Ca2+) (correct)

Which receptor's blockade results in decreased cardiac output when treated with propranolol?

β1 Receptors Signup and view all the answers

What is a known effect of propranolol on the heart?

Decreases heart rate Signup and view all the answers

In regards to the cardiovascular system, which area experiences the highest resistance?

Arterioles Signup and view all the answers

At which point on the action potential is K+ closest to electrochemical equilibrium?

Point 5 Signup and view all the answers

What is responsible for the change in membrane potential from point 1 to point 3?

Movement of Na+ into the cell Signup and view all the answers

What primarily causes the membrane potential change from point 3 to point 4?

Movement of K+ out of the cell Signup and view all the answers

During which part of the action potential is Na+ permeability highest?

Between points 2 and 3 Signup and view all the answers

What role does the Na+–K+ pump play during the action potential?

It helps maintain resting membrane potential after repolarization. Signup and view all the answers

What change in the membrane potential occurs immediately upon the opening of Na+ channels?

The potential becomes more positive. Signup and view all the answers

What is expected to happen to the K+ concentration inside the cell during repolarization?

It decreases. Signup and view all the answers

What is the main driving force for K+ to exit the cell at point 4?

Electrical gradient towards the extracellular fluid Signup and view all the answers

What effect does the opening of K+ channels have on the membrane potential?

It hyperpolarizes the membrane. Signup and view all the answers

Which of the following drugs is a β2 agonist used to treat asthma?

Albuterol Signup and view all the answers

Which type of receptor is contraindicated in asthma treatment due to its bronchoconstrictive effects?

β2 Antagonists Signup and view all the answers

What is the primary action of α1 receptors in the body?

They stimulate the formation of IP3. Signup and view all the answers

Which receptor mediates the secretion of epinephrine by the adrenal medulla?

Cholinergic nicotinic receptors Signup and view all the answers

Which of the following autonomic drugs activates adenylate cyclase?

Norepinephrine Signup and view all the answers

Which receptor type acts by inhibiting adenylate cyclase in the body?

α2 Receptors Signup and view all the answers

Which adrenergic receptors are responsible for causing vasodilation when activated by low concentrations of epinephrine?

β2 Receptors Signup and view all the answers

What physiological effect does the activation of β1 receptors have?

Increase in heart rate Signup and view all the answers

Which type of autonomic receptor is primarily cholinergic?

Muscarinic receptors Signup and view all the answers

Which substance is released into circulation when the adrenal medulla is stimulated?

Epinephrine Signup and view all the answers

What is the effect of an inhibitory postsynaptic potential on the postsynaptic membrane?

It hyperpolarizes the postsynaptic membrane by opening Cl− channels. Signup and view all the answers

What happens to intracellular calcium concentration when Na+, K+-ATPase is inhibited?

Increased intracellular calcium concentration. Signup and view all the answers

Which of the following events in skeletal muscle excitation–contraction coupling occurs first?

Action potential in the muscle membrane. Signup and view all the answers

What is the role of Cl− channels in an inhibitory postsynaptic potential?

They hyperpolarize the membrane by allowing Cl− influx. Signup and view all the answers

What occurs immediately after the depolarization of the T tubules during excitation–contraction coupling?

Release of Ca2+ from the sarcoplasmic reticulum. Signup and view all the answers

How does an increase in intracellular Na+ concentration affect Na+–Ca2+ exchange?

It decreases the Na+ gradient, inhibiting the exchange. Signup and view all the answers

Which ion's channels must open to achieve hyperpolarization during an inhibitory postsynaptic potential?

Chloride (Cl−) Signup and view all the answers

Which sequence correctly describes the events of excitation–contraction coupling?

Action potential; depolarization of T tubules; release of Ca2+ from SR. Signup and view all the answers

What is the equilibrium potential of Cl− approximately in mV, influencing hyperpolarization?

-90 mV Signup and view all the answers

What effect do adrenergic β2 receptors have on vascular smooth muscle when stimulated by low doses of epinephrine?

Vasodilation occurs Signup and view all the answers

Which type of receptor potentials are graded in size based on stimulus intensity?

Receptor potentials Signup and view all the answers

How does an increase in contractility affect cardiac output on a Frank-Starling curve?

It increases cardiac output for a given end-diastolic volume Signup and view all the answers

What primarily causes the greatest pressure decrease in the circulation across the arterioles?

Their greatest resistance Signup and view all the answers

Which receptor type is more sensitive to epinephrine, leading to vasodilation at low doses?

Adrenergic β2 receptors Signup and view all the answers

What is the relationship between resistance and pressure in the cardiovascular system?

Higher resistance leads to greater pressure drop Signup and view all the answers

What happens to receptor potentials if they are hyperpolarizing?

They bring membrane potential away from threshold Signup and view all the answers

What does the Frank-Starling Law state regarding cardiac output and venous return?

Cardiac output matches venous return Signup and view all the answers

What is the nature of action potentials compared to receptor potentials?

Action potentials are all-or-none events Signup and view all the answers

Which statement about α receptors in vascular smooth muscle is correct?

They induce vasoconstriction Signup and view all the answers

Study Notes

Nernst Equation and Membrane Potential

Membrane permeability to single ions is assumed in the Nernst equation.
For sodium (Na+), the equilibrium potential (ENa+) is calculated as +60 mV using extracellular (Ce) and intracellular (Ci) concentrations.
Na+ diffuses into the cell, causing depolarization which makes the interior of the cell positive.

Nerve Action Potential

Point 5 of the action potential diagram shows K+ closest to electrochemical equilibrium due to hyperpolarization.
The driving force for K+ movement out of the cell balances chemical and electrical gradients during repolarization.
Between points 1 and 3, Na+ influx caused by opening Na+ channels generates the upstroke of the action potential.
Between points 3 and 4, K+ efflux occurs through opened K+ channels, leading to repolarization.

Inhibitory Postsynaptic Potential

Hyperpolarization of the postsynaptic membrane results from opening Cl− channels, which moves the membrane potential toward -90 mV.
Inhibitory postsynaptic potential (IPSP) takes the membrane further from the threshold for action potential initiation.

Na+, K+-ATPase Inhibition Effects

Inhibition leads to increased intracellular Na+ concentration, subsequently increasing intracellular Ca2+ by impairing Na+ gradient for Na+–Ca2+ exchange.
Increased intracellular Na+ concentration also inhibits Na+–glucose cotransport.

Excitation-Contraction Coupling in Skeletal Muscle

The correct sequence involves action potential in the muscle membrane, T-tubule depolarization, and subsequent Ca2+ release from the sarcoplasmic reticulum.
Ca2+ binds to troponin C to initiate cross-bridge formation after freeing actin from inhibition.

Adrenergic Receptors

α1 adrenergic receptors stimulate the formation of inositol 1,4,5-triphosphate (IP3), causing increased intracellular Ca2+ levels.
Cholinergic nicotinic receptors mediate epinephrine secretion from adrenal medulla.
β2 receptors mediate vasodilation in response to low doses of epinephrine; higher doses cause vasoconstriction.

Sensory Receptor Potentials

Receptor potentials are graded potentials that depend on stimulus intensity, in contrast to action potentials which are all-or-none.

Cardiac Function and Pressure Dynamics

Increased contractility demonstrates increased cardiac output for a given end-diastolic volume on a Frank-Starling diagram.
The greatest pressure drop in circulation occurs across arterioles due to their highest resistance.
Pulse pressure is the difference between systolic and diastolic pressures, indicative of stroke volume.

Myocardial Contractility

Myocardial contractility is dependent on intracellular Ca2+ concentration, which regulates actin-myosin interactions.
Propranolol, a β1 and β2 adrenergic antagonist, decreases cardiac output by inhibiting β1 receptors, affecting heart rate and contractility.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz explores the applications of the Nernst equation, particularly in the context of ionic gradients across cell membranes. It covers the calculation of the equilibrium potential for sodium ions (ENa+) and how concentration differences influence ionic diffusion. Understanding these principles is essential for studying cellular electrochemistry.