General Physiology

The study of the properties which are common to all cells and living beings (claude bernard). Among these common properties, there are the major metabolic pathway already studied during the general biochemistry lectures.

Learning outcomes of the course : 

• To be able to explain how the cell structure is maintained meanwhile this cell assume a particular function (cell membrane permeability, cellular volume regulation, muscle contraction, transmission of nervous information • To be able to give a molecular explanation to the phenomenon characterizing the living organisms. 

• To be able to give a global explanation about the complexity of the coordination system regulating the interactions between the various systems of the organism. 

• To be able to describe the relationships between specific metabolic pathways and the environmental properties. 

• To be able to use all these informations to start in good conditions the study of Human Physiology.

Recommended or required readings : 

Guyton

Marieb

Ganong

Supplemental 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 physiological system covered in class that day.

The entire presentation should be limited to 10 minutes; and include the following sections:

ackground: introduced the disease, how many are affected, who is affected, 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 the causative agent?

Treatment: how is the disease treated? Drugs, surgery, alternative therapy, lifestyle modifications, etc.

Current research: recent clinical trials and/or innovations on the topic.

Appropriate citations must be included on the last slide. The cited sources must be credible, scientific, and peer reviewed journals, or other publication. References may be subject to verification at the discretion of your lab instructor. Wikipedia is not allowed

HOMEOSTASIS & DIFFUSIONLab 1

• 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”

What is Homeostasis?

• 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.

Feedback Control Systems

ControlCenter

IMBALANCE

IMBALANCE

Receptor Effector

Components of Control Systems

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StimulusCauses a change inControlled variable

ResponseFed back to influence the effect of stimulus, either reduces it (negative) so controlled variable returns back to normal, or enhances it (positive) so the whole process continues at a faster rate.

Outputinformation sent along efferentpathway to effector

Inputinformation sent along afferentpathway to control center

BALANCE

• 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.

Negative Feedback Mechanism

Sweat glands activated

Shiveringbegins

StimulusBody temperaturerises BALANCE

StimulusBody temperature falls

ReceptorsTemperature-sensitivecells in skin and brain

ReceptorsTemperature-sensitivecells in skin and brain

EffectorsSweat glands

EffectorsSkeletal muscles

Control Centerthermoregulatory

center in brain

Control Centerthermoregulatory

center in brain

ResponseEvaporation of sweatBody temperature falls

ResponseContractions generate heatBody temperature rises

Figure 1.5 - Regulation of body temperature by a negative feedback mechanism.

Copyright © Pearson Education, Inc. Publishing as Pearson Benjamin Cummings. All rights reserved.

• 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

Positive Feedback Mechanism

MEMBRANE TRANSPORTPart II:

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Structure Of Plasma Membrane

• 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.

Selective Permeability

Membrane TransportPassive Transport – movement of a substance down its concentration gradient; does not require energy.

Active Transport – movement of a substance against its concentration gradient; requires energy (ATP).

Passive Transport

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

• 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)

Primary 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.

Secondary Active Transport

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

Normal cell volumeIntracellular fluid: 300 mOsm

nonpenetrating solutes

300 mOsmnonpenetrating solutes

200 mOsmnonpenetrating solutes

400 mOsmnonpenetrating solutes

H2O H2O

No net movement of H2O; no change in cell volume.

Water diffuses intocells; cells swell (lyse).

Water diffuses out ofcells; cells shrink (crenate).

(a) Isotonic conditions

(b) Hypotonic conditions

(c) Hypertonic conditions Copyright © 2010 Cengage Learning

Next meeting:

• Laboratory exercises on Homeostasis and Transport Mechanisms.