Chapter 1. Cellular Physiology PDF

Chapter 1. Cellular physiology Assoc. Prof. Dr. Nguyen Trong Hong Phuc Learning outcomes: After studying this chapter, learners will be able to Understand the composition and volume of body fluids Describe the characteristics of membranes and the transport of mater...

Chapter 1. Cellular physiology Assoc. Prof. Dr. Nguyen Trong Hong Phuc Learning outcomes: After studying this chapter, learners will be able to Understand the composition and volume of body fluids Describe the characteristics of membranes and the transport of materials across cell membranes Present the ion distribution in the cell membrane, resting potential and action potential Present the mechanism of communication between neurons and between neurons and muscle cells through synapses Describe the mechanisms that couple the action potentials to contraction in muscle cells. Content 1. Volume and composition of body fluids 2. Characteristics of cell membranes 3. Transport across cell membranes 4. Diffusion potentials and equilibrium potentials 5. Action potentials 6. Synaptic and neuromuscular transmission 7. Skeletal muscle 8. Smooth muscle 1. VOLUME AND COMPOSITION OF BODY FLUIDS 1. VOLUME AND COMPOSITION OF BODY FLUIDS Composition of Body Fluid Compartments Composition of ICF and ECF Major ions in ECF: – Cation: Na+, – Anion: Cl-, HCO3- Major ions in ICF: – Cation: K+, Mg2+ – Anion: phosphate, protein  Composition of Body Fluid Compartments Units for Measuring Solute Concentrations Concentrations of solutes are expressed in - millimoles per liter (mmol/L): concentration - milliequivalents per liter (mEq/L): the amount of charged (ionized) solute and is the number of moles of the solute multiplied by its valence - milliosmoles per liter (mOsm/L): osmolarity Why don't we just use one form of unit? Composition of Body Fluid Compartments Electroneutrality of Body Fluid Compartments Must obey the principle of macroscopic electroneutrality: have the same concentration (mEq/L) of positive charges (cations) as of negative charges (anions)  Composition of Body Fluid Compartments Creation of Concentration Differences Across Cell Membranes The resting membrane potential of nerve and muscle: moving of K+ Action potential: differences in Na+ concentration across the cell membrane Composition of Body Fluid Compartments Creation of Concentration Differences Across Cell Membranes Ca2+ pumps embedded in the plasma membranes of erythrocytes move calcium out of the erythrocyte to prevent it from becoming rigid due to the accumulation of calcium Composition of Body Fluid Compartments Creation of Concentration Differences Across Cell Membranes Absorption of essential nutrients depends on the transmembrane Na+ concentration gradient  CHARACTERISTICS OF CELL MEMBRANES What is the structure of the cell membrane? What is its function? CHARACTERISTICS OF CELL MEMBRANES CHARACTERISTICS OF CELL MEMBRANES Phospholipid Component of Cell Membranes CHARACTERISTICS OF CELL MEMBRANES Protein Component of Cell Membranes  CHARACTERISTICS OF CELL MEMBRANES Protein Component of Cell Membranes ligand-binding Receptors transport proteins Pores Integral membrane Transmembrane proteins proteins Protein ion channels Peripheral protein Cell adhesion molecules GTP-binding proteins TRANSPORT ACROSS CELL MEMBRANES TRANSPORT ACROSS CELL MEMBRANES TRANSPORT ACROSS CELL MEMBRANES Simple Diffusion Net diffusion of the solute is depends on: – concentration gradient, – partition coefficient: water or oil – Diffusion coefficient: size of the solute molecule and the viscosity of the medium – thickness of the membrane – Surface area available for diffusion. What if the solvent is an electrolyte? TRANSPORT ACROSS CELL MEMBRANES Facilitated Diffusion Create better conditions for the diffusion process through the role of the carrier. Higher concentrations, the carriers → saturated and facilitated diffusion will level off. TRANSPORT ACROSS CELL MEMBRANES Primary Active Transport solutes are moved against an electrochemical potential gradient (uphill) Need ATP Pump: – Na-K ATPase – Ca2+ ATPase – H+ -K+ ATPase TRANSPORT ACROSS CELL MEMBRANES Primary Active Transport TRANSPORT ACROSS CELL MEMBRANES Primary Active Transport TRANSPORT ACROSS CELL MEMBRANES Secondary Active Transport Transport of two or more solutes is coupled Type: – Co-transport = symport – Anti-transport = counter transport TRANSPORT ACROSS CELL MEMBRANES Osmosis the flow of water across a semipermeable membrane because of differences in solute concentration.  TRANSPORT ACROSS CELL MEMBRANES Osmosis Osmolarity = concentration of particles (mOsm/L) Osmolality = concentration of osmotically active particles per kilogram of water TRANSPORT ACROSS CELL MEMBRANES Osmotic pressure DIFFUSION POTENTIALS AND EQUILIBRIUM POTENTIALS Ion Channels Selective, allow ions with specific characteristics – Size – Charges Gates  DIFFUSION POTENTIALS AND EQUILIBRIUM POTENTIALS Ion Channels Selective, allow ions with specific Voltage-gated Na+ channel characteristics Gates – Voltage-gated channels – Second messenger–gated channels – Ligand-gated channels DIFFUSION POTENTIALS AND EQUILIBRIUM POTENTIALS Diffusion Potentials Diffusion potential is caused by diffusion of ions The membrane must be permeable to that ion Magnitude (mV): depends on the size of the concentration gradient Sign of the diffusion potential depends on the charge of the diffusing ion DIFFUSION POTENTIALS AND EQUILIBRIUM POTENTIALS Equilibrium Potentials The equilibrium potential is the diffusion potential that exactly balances or opposes the tendency for diffusion down the concentration difference  DIFFUSION POTENTIALS AND EQUILIBRIUM POTENTIALS Nernst Equation the Nernst equation converts a concentration difference for an ion into a voltage DIFFUSION POTENTIALS AND EQUILIBRIUM POTENTIALS Driving force → RESTING MEMBRANE POTENTIAL RESTING MEMBRANE POTENTIAL exists across the membrane of excitable cells in the period between action potentials established by diffusion potentials of K+ range of −70 to −80 mV the Na+-K+ATPase is necessary to create and maintain ACTION POTENTIALS The action potential is a phenomenon of excitable cells such as nerve and muscle and consists of a rapid depolarization (upstroke) followed by repolarization of the membrane potential. The basic mechanism for transmission of information in the nervous system and in all types of muscle. ACTION POTENTIALS ACTION POTENTIALS ACTION POTENTIALS Characteristics of Action Potentials Stereotypical size and shape Propagation All-or-none response. ACTION POTENTIALS ACTION POTENTIALS Propagation of Action Potentials ACTION POTENTIALS Propagation of Action Potentials The spread of local currents from active regions to adjacent inactive regions Transmitting the action potential sequentially down the axon Two mechanisms that increase conduction velocity along a nerve: – increasing the size of the nerve fiber – myelinating the nerve fiber SYNAPTIC AND NEUROMUSCULAR TRANSMISSION Types of Synapses SYNAPTIC AND NEUROMUSCULAR TRANSMISSION SYNAPTIC AND NEUROMUSCULAR TRANSMISSION SYNAPTIC AND NEUROMUSCULAR TRANSMISSION Types of Synaptic Arrangements One-to-one synapses: causes a single action potential in the postsynaptic cell One-to-many synapses: causes a burst of action potentials in the postsynaptic cells → amplification of activity Many-to-one synapses: sum of the inputs SYNAPTIC AND NEUROMUSCULAR TRANSMISSION Synaptic Input—Excitatory and Inhibitory Postsynaptic Potentials The many-to-one synaptic arrangement: common configuration Excitatory postsynaptic potentials (EPSPs): opening Na+ channel → depolarize Inhibitory postsynaptic potentials (IPSPs): opening Cl− channels → hyperpolarize SYNAPTIC AND NEUROMUSCULAR TRANSMISSION Integration of Synaptic Information SYNAPTIC AND NEUROMUSCULAR TRANSMISSION Neurotransmitters SKELETAL MUSCLE SKELETAL MUSCLE SKELETAL MUSCLE SKELETAL MUSCLE SKELETAL MUSCLE Length-Tension Relationship SKELETAL MUSCLE SMOOTH MUSCLE SMOOTH MUSCLE About the cell