Afferent pathway “approaches” the control centerEfferent pathway “exits” the control center.
Figure 1.3 – The Big Picture Medical Physiology (Lange Series) – Jonathan Kibble and Colby Halsey (pg. 5)
In terms of the 2nd Law of Thermodynamics, the concentration difference represents an unstable state of high organization (low entropy) that changes to produce a uniformly distributed solution with maximum disorganization (high entropy)
The study of the properties whichare common to all cells and livingbeings (claude bernard).Among these common properties,there are the major metabolicpathway already studied duringthe general biochemistry lectures.
Learning outcomes of the course :•To be able to explain how the cell structure is maintained meanwhile thiscell assume a particular function (cell membrane permeability, cellularvolume regulation, muscle contraction, transmission of nervous information•To be able to give a molecular explanation to the phenomenoncharacterizing the living organisms.•To be able to give a global explanation about the complexity of thecoordination system regulating the interactions between the varioussystems of the organism.•To be able to describe the relationships between specific metabolicpathways and the environmental properties.•To be able to use all these informations to start in good conditions thestudy of Human Physiology.
Recommended or required readings :GuytonMariebGanongSupplemental laboratory modules (Dr. Bautista)
REQUIREMENTS:-Laboratory exercises-Journal Research Work-Laboratory exams/quizzes-Group Presentation
•Students will sign up for a group and topic on the first day of class.The presentation topic should be a disease related to the physiologicalsystem covered in class that day.The entire presentation should be limited to 10 minutes; and include thefollowing sections: ackground: introduced the disease, how many are affected, who isaffected, symptoms, complication, history of the disease, when discovered,etc. Diagnostic procedure: discuss how the disease is diagnosed. Mechanism: what is the causative agent? Bacteria, virus, fungus,autoimmune, hereditary, other? How does the disease result from thecausative agent? Treatment: how is the disease treated? Drugs, surgery, alternativetherapy, lifestyle modifications, etc. Current research: recent clinical trials and/or innovations on thetopic. Appropriate citations must be included on the last slide. The citedsources must be credible, scientific, and peer reviewed journals, or otherpublication. References may be subject to verification at the discretion of yourlab instructor. Wikipedia is not allowed
What is Homeostasis?• A dynamic constancy of the internal physiological environment. – the control of a vital parameter• Maintained by feedback control mechanisms.• The inability to maintain homeostasis indicates disease.Physiology: the study of biological functions and processes of the human body under normal conditions. – Function explains “why” – Process describes “how”
Feedback Control Systems• Feedback is the flow of information along a closed loop.• A single feedback loop does not operate in isolation, but rather as part of a large network of controls.Must be to perform the following functions: – The system must be able to sense the vital parameter. – The system must be able to respond to changes in the vital parameter by producing some sort of signal. – The signal must act in such a way as to produce an effect that controls the vital parameter.
Negative Feedback Mechanism• Action taken by the effectors to oppose changes in the controlled variable caused by a stimulus. – (e.g., thermostat regulation of room temperature) – Supports homeostasis – Most common feedback mechanism in nature.
Positive Feedback Mechanism• Actions taken by effector amplify the changes caused by the initial stimulus; therefore, resulting in further deviation from homeostasis. – (e.g., blood clotting, child birth, etc.)• Does not support homeostasis• Less common in nature
Selective Permeability• The plasma membrane is selectively permeable; allowing certain molecules to “penetrate” or “permeate” the membrane, while excluding others. – Hydrophobic, nonpolar molecules readily diffuse across the lipid bilayer membrane without the aid of membrane proteins. – Some very small, uncharged polar molecules, like water, are able to squeeze between tiny spaces created by the phospholipid tails as they sway in the fluid environment.
Membrane TransportPassive Transport – movement of a substance down itsconcentration gradient; does not require energy.Active Transport – movement of a substance against itsconcentration gradient; requires energy (ATP).
Simple Diffusion (diffusere means “to spread out”)• Passive transport across plasma membrane without assistance from a transporter protein.• The tendency for molecules within a particular space to become even distributed over time.• Molecules move down their own concentration gradient; from a region of [High] concentration [Low] concentration.• Continues until a dynamic equilibrium is reached.
Channel-mediated facilitated diffusion • Specialized channel proteins create hydrophilic tunnels in the lipid bilayer; thus facilitating the transport of small, polar molecules and ions across the membrane at much faster rates than in carrier-mediated transport. • Transport of solute passively down its concentration gradient; from [High] [Low] concentration. • Channel proteins are highly selective; allowing only specific molecules or ions of a certain size to cross the membrane • May be either entirely open or closed on both sides of the plasma membrane. Na+
Carrier-mediated facilitated diffusion • Specialized proteins that facilitate the transport of larger, hydrophilic (polar) molecules across the plasma membrane; generally too large to fit through channels. • Carrier proteins bind to the solute to be transported and move it through the membrane by undergoing a conformational change; this slows the transport of solute • Carriers are highly selectively • [High] [Low] concentration
Primary Active Transport• Carrier protein uses energy to move a substance against its concentration gradient. – Molecules are “pumped” against a concentration gradient at the expense of energy. – [Low] [High] concentration – Establishment of concentration gradient is a consequence of transport. – Direct use of energy (ATP)
Secondary Active Transport• Transport is driven by the energy stored in the concentration gradient of another molecule (Na+) – downhill movement of one molecule drive uphill movement of another molecule. – Utilizes established concentration of molecule A to power transport of molecule B – indirect use of energy (ATP)• Categories of Transport: – Cotransport (symport): driver ion and molecule move in same direction across plasma membrane. – Countertransport (antiport): driver ion and molecule move in opposite directions across plasma membrane.
Osmosis• The simple diffusion of water across a selectively permeable membrane; that allows water molecules to freely permeate the membrane but obstructs larger solute molecules.• Water moves down its own concentration gradient
Tonicity of Solutions• Isotonic solutions – both solutions have the same concentration of solutes. – No net movement of water• Hypotonic solution – lower concentration of solutes – Cells will lyse• Hypertonic solution – higher concentration of solutes. – Cells will crenate