Electroneutrality in Body Fluids

Study Notes

Body Fluid Compartments

Body fluids maintain macroscopic electroneutrality, equal concentrations of cations and anions.
Major ions in extracellular fluid (ECF): Sodium (Na+), Chloride (Cl-), Bicarbonate (HCO3-).
Major ions in intracellular fluid (ICF): Potassium (K+), Magnesium (Mg2+), Phosphate, and Proteins.

Membrane Potential and Transport

Resting membrane potential in nerve and muscle cells is primarily influenced by K+ movement.
Action potentials arise from Na+ concentration differences across cell membranes.
Calcium (Ca2+) pumps in erythrocytes prevent rigidity by removing excess calcium.
Nutrient absorption relies on the transmembrane sodium (Na+) concentration gradient.

Cell Membrane Characteristics

Composed of phospholipids and proteins.
Integral membrane proteins serve as transport proteins, ion channels, receptors, and adhesion molecules.
Peripheral proteins assist in signaling and communication.

Transport Mechanisms

Simple Diffusion: Driven by concentration gradients, influenced by solute size, viscosity, and membrane thickness.
Facilitated Diffusion: Involves carrier proteins; saturation occurs with higher solute concentrations.
Primary Active Transport: Moves solutes against their gradient using ATP (e.g., Na-K ATPase, Ca2+ ATPase).
Secondary Active Transport: Involves co-transport (symport) and counter-transport (antiport) of solutes.
Osmosis: Water movement across membranes due to solute concentration differences.

Ion Channel Functions

Ion channels allow selective passage based on size and charge.
Voltage-gated, ligand-gated, and second messenger-gated channels regulate ion flow.

Diffusion and Equilibrium Potentials

Diffusion potential arises from ion movement; depends on concentration gradients.
Equilibrium potential is achieved when diffusion potential opposes the concentration difference.
The Nernst equation converts ion concentration differences to voltage.

Resting and Action Potentials

Resting membrane potential ranges from -70 to -80 mV, maintained by Na+-K+ ATPase.
Action potentials involve rapid depolarization followed by repolarization; crucial for nerve and muscle signaling.
Propagation of action potentials is facilitated by local currents and increases with fiber size and myelination.

Synaptic Transmission

Synapses can be classified as one-to-one, one-to-many, or many-to-one, affecting signal transmission amplitude.
Excitatory postsynaptic potentials (EPSPs) lead to depolarization via Na+ channel opening.
Inhibitory postsynaptic potentials (IPSPs) cause hyperpolarization through Cl- channel opening.

Muscle Excitation and Function

Skeletal muscles operate under the length-tension relationship, essential for optimal contraction force.
Smooth muscle exhibits different contraction and signaling properties.

Learning Outcomes

Understand body fluid composition and volumes, membrane characteristics, and transport mechanisms.
Explain ion distributions, resting and action potentials, and synaptic communication.
Describe skeletal and smooth muscle mechanics and their physiological implications.

Description

This quiz delves into the composition and electroneutrality of body fluid compartments, emphasizing the principles of macroscopic electroneutrality. It covers essential concepts like resting membrane potential and action potential in nerve and muscle cells, highlighting the role of cations and anions. Test your understanding of these fundamental physiological principles.

Electroneutrality in Body Fluids

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Questions and Answers

What principle must body fluid compartments obey?

What is primarily responsible for the resting membrane potential in nerve and muscle cells?

What role do Ca2+ pumps play in erythrocytes?

Which factor does NOT influence the net diffusion of a solute across a membrane?

Which component is NOT typically associated with cell membrane functions?

Which cation is primarily found in the extracellular fluid (ECF)?

What unit is used to express the amount of ionized solute based on its valence?

Which of the following ions is predominantly found in the intracellular fluid (ICF)?

What is the primary reason for using multiple units for measuring solute concentrations?

What type of ions are predominantly found in the extracellular fluid (ECF)?