Membrane physiology, nerves and muscle: cellular and muscular foundations

Membrane Physiology, Nerves and Muscle

Bio. Juan M. AyalaSubstance transport through cell membranesIntro

• Intracellular fluid (ICF)
• Extra cellular fluid (ECF)

Phosphate ATP ADP

Membrane Structure

Extracellular fluid Intracellular fluid H2O 2 High osmotic pressure

Transport Proteins

Carrier Protein Channel Protein

Diffusion and Active Transport

• Diffusion: Trough kinetical or random movements trough the membrane
• Active: Transport proteins move substances trough the membrane against the current.

A B C Ca2+ Ca2 Ca2+ Ca2+ Ca2+ CO2 Ca2+ Na+ Na+ Na+ Na+ .. ... K K+ K+ CO2 Ca2+ K+ K+ K+ Difusión pasiva Difusión facilitada Transporte activo

Diffusion Mechanisms

• Simple and facilitated (specific)
• Simple: The kinetic movement of molecules happen through openings in membranes.
• The speed is determined by the quantity of substance available the speed of kinetic movement, number and size of the openings in the membrane.
• Facilitated (Specific): Facilitated by membrane proteins.
• Helped by a chemical union with the molecules.

Acuaporina G A O 4 B BYJU'S The Learning App Container Byjus.com C

Diffusion of Fat-Soluble Substances

A factor to determine the speed of diffusion Blood plasma Interstitial fluid CO2 CO2 CO Tissue cell CO2 CO2 Detached from hemoglobin CO2 Red blood cell O2 O2 O2 (dissolved in plasma)

Diffusion of Water and Other Not Fat-Soluble Substances

• Aquaporins
• 13 types
• Large water-soluble molecules

Espacio extracelular Water channel Canal de proteína Cell membrane ++ Cell membrane + Membrana celular 6 Espacio intracelular

Diffusion Through Protein Channels

Carrier Proteins Characteristics

1. Selective Permeable
2. Some can be activated (Carrier proteins activated by voltage) o chemical substances that become attached to the protein (Carrier proteins activated by ligands)

+ DIFUSIÓN FACILITADA POR CANES IÓNICOS Iones Iones I DE GRADIENTE PASAJE A FAVOR Canal iónico no regulado Canal iónico regulado .......................... Molécula señalizadora lones Canal abierto Sitio de unión de la molécula señalizadora

Facilitated Diffusion and Proteins

• Main difference between facilitated and simple, facilitated comes close to V max.
• The main substances are glucose and amino acids

Difusión simple Velocidad de difusión Vmáx Difusión facilitada Concentración de la sustancia FIGURA4-7 Efecto de la concentración de una sustancia sobre la velocidad de difusión a través de una membrana mediante difusión simple y difusión facilitada. Este gráfico muestra que la difusión facitada se aproxima a una velocidad máxima denominada Vár

Factors That Influence the Net Rate of Diffusion

• Net rate of diffusion is proportional to the difference in concentration through the membrane

Exterior Interior Ci Membrana

Osmosis (Selective) Net Diffusion

• Cero movement The necessary pressure needed to stop Osmosis is called osmotic pressure determine by the number of particles per unit of volume.
• Osmolarity: Osmolar concentration expressed in osmoles per litter.
• C=(mv^2)/2

Hypoosmotic solution Hyperosmotic solution H2O Selectively permeable membrane

Active Transport

• Transport proteins move substances trough the membrane against the current.
• Two types Primary and secondary according to the origin of the energy either by the presence of any phosphatide molecule or ionic concentrations.

Cotransportador sodio-glucosa Fluido extracelular Na+ - + Membrana plasmática Concentración + Glucosa Glucosa Citoplasma

Primary Active Transport

The substances transported primarily by this are Sodium, Potassium, Calcium, and hydrogen to name some Ions.

• The one we know the most is Na+-K+ Bomb or pump

BOMBA DE Na+ y K+ LEC 3 Na+ K Na+ Gradiente Gradiente K+= Na+ ATP 2 K+ LIC ADP + P

Na+-K+ Bomb or Pump Functions

• Controls Na concentration I cytoplasm
• Stablish the negative voltage in the cell
• Controls cellular volume (electrogenic nature)
• Basic components Subunit alfa and subunit Beta

Subunit Alpha Characteristics

• 3 receptor points for the union of Na ions
• 2 receptor points for the union of K Ions
• 1 Phosphate receptor

ADP.AIF A P Cytoplasm .3Na+ -Oligomycin B Plasma membrane a Extracellular FXYD B Na+/K+ pump ATP ADP Cytosol P P Na+ Cytoplasmic Na+ binds to the Na+/K+ pump 2 The Na+/K+ pump is phosphorylated by ATP 3 The pump changes its conformation, causing Na+ release K+ + P P 6 K* is released from the pump The pump returns to 5 its original conformation 4 Extracellular K+ binds to the pump, leading to dephosphorylation

Calcium Pump

• Controls the concentration of calcium
• Works as a ATPasa

Ca2+ PMCA Caveolin-3 syntrophin nNOS Low [Ca2+] NO signalling Contractility Hypertrophy Cardiomyopathy Heart Failure

Energy for Primary Active Transport

• Energy (In calories for osmol)= 1.400Lognat(C1/C2)
• How much concentration we have before transport

NH2 O N. N HO-P-O-P-O-P-O 1 I N N OH OH OH 0 OH OH

Secondary Active Transport

+ Na Extracellular space ++ Cell membrane concentration Amino Acid/ Intracellular space

Membrane Potential Due to Ion Concentration

• Stablish the electronegativity of cells

Potencial De Membrana Potenciales E. Potencial de Nernst: Potencial de Difusión - 94 mv + - K+ - + - ++ + Na+ Na + ++ Tu Uvirtual

Membrane Potential in Neurons

• Nervous signals are transmitted through action potential.

+ + + + + + + - - - - - - + + + + + + + + Dendrite Nucleus Cell body Axon Myelin sheath Node of Ranvier Direction of Impulse Axon terminal Synapse

Contraction of Skeletal Muscle

Muscle Cell Anatomy

MUSCLE FIBER NUCLEUS MYOFIBRIL SARCOLEMMA MITOCHONDRIA SARCOPLASMIC RETICULUM

Functional Anatomy of Skeletal Muscle

muscle Z line actin tendon myosin sarcomere bone muscle bundle HH HH HH HH myofibril fascicle muscle fibre (muscle cell) @ 2015 Encyclopædia Britannica, Inc.

General Mechanism of Muscle Contraction

• Action potential
• Acetylcholine secretion
• Chanels activated by Acetylcholine
• Local depolarization
• Action potential travels trough the uscle fiver

Z disc I band A band I band disc UT M line Relaxed Thin filament (actin) Thick filament (myosin) H zone Elastic filament (titin) Upon contraction + ATP, Ca2+ Contracted H zone Actin Myosin pulls the actin along its length. The cross-bridges of the myosin filaments attach to the actin filaments and exert Z