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Page 1: Physiology Notes

Chapter 1 & 6:Homeostasis 9/5/14 7:33 PM

Homeostasis- keeping internal environment stable relative to the outside

Law of mass balance- what comes in must equal what comes out

Two options:

Excretion- elimination of material from the body

Convert substances through metabolism

Mass flow=concentration of x * volume flow

Clearance-rate at which something leaves the body.

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Homeostasis is not equilibrium

Instead it’s a dynamic steady state

To maintain the body regulates certain variables at a setpoint

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There is an input signal, integrating center, output signal then a

response

Local control- starts in one tissue and is handled in that tissue

Reflex control uses long distance signaling

Two parts: a response and feedback loop

Three parts to a response loop: input signal, integrating center and

an output signal

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Negative feedback loops are homeostatic

Positive feedback loops are not homeostatic

Feedforward loops anticipate change

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Chapter 5: Membrane Dynamics 9/5/14 7:33 PM

Tonicity: how cell volume would be affected if placed in a certain solution

Hypotonic- cell gains water

Hypertonic-cell loses water

Isotonic-nothing happens

Tonicity depends on the concentration of non-penetrating particles

only

Diffusion:

Passive transport that uses kinetic energy of molecules

Higher to lower concentration-down concentration gradient

Occurs until the concentration is equal everywhere

Faster over short distances

Faster with high temperatures

Faster with smaller particles

Diffusion directly across a phospholipid bilayer is called simple

diffusion

o Only nonpolar lipophilic molecules can diffuse

o Exception is water-depends on concentration of membrane

o Rate of diffusion is determined by surface area

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o Fick’s law of diffusion and membrane permeability determine

diffusion rate

Protein-Mediated Transport-carried out by transporters

4 classes: structural proteins, enzymes, receptors and transporters

Structural proteins

o Connect membrane to cytoplasm

o Create cell junctions

o Attach cells to the extracellular matrix

Transport proteins are either channel or carrier

o Most channel ones are water filled

o Selectivity of a channel protein is determined by the diameter

and the amino acid charge of the protein its membrane

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Facilitated Diffusion uses carrier proteins

For example GLUT transporters

Takes advantage of concentration gradient

Active transport is opposite-requires energy

Down concentration gradient

Primary uses ATP, secondary “freeloads” by using the concentration

gradient potential energy of another molecule

Sodium-Potassium pump-primary active transport

SGLT transporter-secondary

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Vesicular Tranport

Phagocytosis-think amoeba

Endocytosis-creates smaller vesicles

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Chapter 8 9/5/14 7:33 PM