Physiology: Lecture 1 Flashcards
Study of normal function of the body and how the body maintains those normal functions
Physiology
Inputs change and produce error but outputs remain normal; requires input of energy
Homeostasis - steady state
How we sense and react to input changes
Feedback control
Output reduces initial error (reduces input)
System is generally good
Negative feedback
Output is the same as the initial change (leads to an EVENT)
System is generally bad
Positive feedback
Examples of positive feedback
Ovulation
Clot formation
What do feedback mechanisms regulate?
Health
What happens when errors exceed the ability of the control system to adjust?
Disease and pathology occur; body will attempt to compensate for any deviation from set point
(Ex: drinking more and more and more water where your body can’t get rid of it all anymore and it begins diluting your blood and everything else, causing many problems)
When is compensation never complete?
As long as the error signal still exists
What is the bodies best response?
Full compensation (normal function may not be restored)
What happens to compensatory mechanisms as time progresses?
They break down or initiate changes that lead to pathology and disease
Normal serum potassium levels
Roughly 4 mEq/L
Pathological range of normal serum potassium
3.5-5.0 mEq/L
Pathological potassium levels (death)
Less than 2.5 mEq/L
Greater than 5 mEq/L
What can cause pathological potassium?
- Progressive change in electrical activity (heart)
- As little as 1 mEq/L change can lead to death
Pt presents with macular edema; they are overweight, drink a lot of soda, and has diabetes. What’s the outcome?
Pt needs to get diabetes under control or he’ll lose his eyesight. This re establishes his normal homeostasis physiology and everything else gets better.
Q: What type of feedback is this?
A –> B –> C -x-> A
Negative feedback
Because output feeds back on A to stop release
Q: Pt presents with abnormally high levels of B and C, but low levels of A. What is the likely defect?
A –> B –> C-x-> A
Tumor secretion of B
Cut tumor out to come back to homeostasis
Water is about how much of body weight?
60%
Avg = 50% to 70%
Variations of water per body weight?
Age
Race
Gender (male’s have more, typically)
Fitness level
Average percent of water per body weight in males: Adult? Elderly?
Adult: 70% BW
Elderly: 50% BW
Average percent of water per body weight in females: Adult? Elderly?
Adult: 50% BW
Elderly: 45% BW
What is water weight inversely correlated with?
Body fat
What is the ratio of intracellular fluid (ICF) to total body water (TBW)?
IDF is 2/3 of TBW (27L)
What is intracellular fluid?
- Fluid inside ALL the cells of the body
- Maintained by the cell membrane
- Allows all salutes to be dissolved in the same medium (allows metabolic reactions to occur)
What is the ratio of extracellular fluid (ECF) to total body water (TBW)?
ECF is 1/3 of TBW (13L)
What is extracellular fluid?
- Fluid OUTSIDE of cells
- Split into 2 compartments by the capillary wall (Interstitial fluid and Plasma)
What are the 2 compartments of extracellular fluid that are split by the capillary wall? How much of the ECF do they account for?
1) Interstitial fluid - fluid around cells - 3/4 of ECF (10L)
2) Plasma - fluid portion of blood - 1/4 of ECF (3L)
What is the difference between ECF and ICF?
- They are different in composition
- -ICF is MOSTLY potassium and proteins
- -ECF is MOSTLY sodium and chloride
What are the similarities between ECF and ICF?
They are balanced in charge and amount of dissolved stuff (isotonic and electroneutroal=no charge differential)
Number of whole molecules in water
mM (1 mM NaCl = 1 mmol of NaCl in 1L of water)
Number of ions in water; When is it important?
mOsm (1 mM NaCl = 1 mOsm of Na and 1 mOsm of Cl = 2 total mOsm)
- Imp when considering concentration gradients
- If non-dissociable (glucose) then mMol = mOsm
Charge of dissociated ions; When is it important?
mEq (1 mOsm of Na = 1 mEq of Na, 1 mOsm of Ca2 = 2 mEq of Ca2)
-Imp when considering electrochemical gradients
Logarithmic scale used to measure H (ACID) ions
pH (pH = -log[H])
What is the basis for communication between ICF and ECF dependent on?
K (potassium) gradient
What is the proper absorption of nutrients between ICF and ECF dependent on?
Na (sodium) gradient
What does the movement of muscles between ICF and ECF require?
Movement of Ca2 (calcium)
What is compartment content based on?
Membrane permeability
Is the capillary membrane selective or non selective? Explain why
Non-selective
- It filters based on size
- No proteins (albumin, RBC’s, etc) in interstitial fluid because THEY STAY INSIDE THE CELLS!!!
Is the cell membrane selective or non selective? Explain why
VERY selective (few things cross without help) -Small, non-polar salutes can diffuse across the membrane
What small, non-polar salutes can diffuse across the cell membrane?
- O2
- CO2
- Ethanol
- Steroid hormones
- Water (polar, but is special)
- *Everything else needs help
How do materials (except for the small, non-polar solutes that diffuse across) cross the cell membrane?
- Use channels
- Utilize transport proteins
What are channels (in the cell membrane)?
Holes in the membrane for specific solutes to move ALONG THE GRADIENT
How do materials utilize the transport proteins in the cell membrane?
- Large solutes/proteins can move WITH THE GRADIENT
- Solutes/proteins can also move AGAINST THE CONCENTRATION GRADIENT
Movement of stuff that is with the gradient. Is there energy used or no? Give examples
- Passive transport
- No
- -Diffusion
- -Facilitated diffusion
- *Pass with
Movement of stuff that is against the gradient. Is there energy used or no? Give examples
- Active transport
- Yes; enzymes are required
- -Primary active
- -Secondary active
- *Active against
Movement of solutes from area of higher to lower concentration; random movement; faster with temp and concentration gradient; can utilize a channel if non-permeant
Diffusion (passive transport)
Type of transport when carrier proteins bind to and move specific non-permeant solutes across membranes.
Facilitated diffusion (passive transport)
J=PA(Ca-Cb)
Rate of diffusion calculation (Diffusion Gradient)
J = rate of diffusion (cm/sec) (“amt of movement per sec”)
P = permeability (cm/sec)
A = surface area for diffusion
Ca-Cb = difference in concentration of two solutes (mmol/L)
EXAMPLE:
Solution A&B are separated by 2 cm^2 of membrane that is permeable only to urea. Its permeability was measured at 5x10^-5 cm/sec. The partition coefficient of urea is 10^-3, as measured in an oil-water mixture. The urea concentration of solution A is 10 mg/ml while solution B is 1 mg/ml. What is the initial diffusion rate of urea and in what direction will it move?
J=PA(Ca-Cb)
J=5x10^-5cm/sec X 2cm^2 (10mg/ml - 1mg/ml)
J=9x10^-4mg/sec and the urea will move from Soln A to Soln B
QUESTION:
Solution A&B are separated by 4 cm^2 of membrane that is permeable only to calcium. Its permeability was measured at 2.76x10^-5 cm/sec. The partition coefficient of calcium is 10^-8, as measured in an oil-water mixture. The urea concentration of solution A is 10 mg/ml while solution B is 1 mg/ml. What is the initial diffusion rate of urea and in what direction will it move?
No movement will occur!!
If the membrane is not permeable to a solute, it can NOT diffuse across the membrane! Pay attention to the solutes being used!
Active transport:
1) Does or does not require energy?
- If it does, what does it use for this energy?
2) Includes what names?
3) Moves a solute how?
1) Requires energy!!
- Uses ATP
2) Names usually include ATPase, -porter or exchanger
3) Always moves a solute AGAINST its gradient
Directions that active transporters can move one or more molecules in varying directions
- Symport (cotransport)
- Antiport/exchanger (contertransport)
Moves Na and glucose into cell in small intestine and kidney; movement is in same direction; SGLT (Na-glucose transporter 1)
***VERY IMPORTANT!!!!
Symport (Cotransport)
Moves Ca2 out and Na into cell; Usually in excitable cells (retina); moves in opposite direction; NCX (Na - Ca2 exchanger)
Antiport/exchanger (cotransport)
How are distinctions made for active transport?
They are made on WHERE energy is expended
The type of active transport where ATP is used to directly move solutes - pumps and ATPases usually
Primary active transport
The type of active transport where the gradient set up by primary transport is used to move solutes.
Secondary active transport
The type of active transport that uses cargo brought in by secondary to bring in another solute
Tertiary active transport
What is the ionic movement with primary active transport?
- 3 Na in
- 1 Ca out
EXAMPLE:
Digitalis (glycoside) is a Na/K ATPase inhibitor. It increases the strength of cardiac contractions. How?
- Need Ca for muscle contraction. To make heart beat harder, you’d need more Ca.
- Less of Na concentration gradient coming into cell, so there is holding onto more Ca inside cell, helping muscles contract more.
If a form of transport utilized a carrier protein that binds to the substrate, it can become saturated. (T/F)
True
When does saturation occur?
When the concentration of a solute is greater than the number of available transporters can handle
(“Once you reach this point, no matter how much more solute [ex: Glucosuria in Diabetes] you add, it will not increase anymore)
Maximal rate of transport movement is what?
Transport maximum (Tm)
Do transport proteins have specificity?
***IMPORTANT!
Yes; they have stereospecificity
Which type of glucose is bound and transported?
D-glucose
Bound & Transported = The D!!!!
Which type of glucose is not bound or transported?
L-glucose
Transporters recognize closely related molecules. What do these do?
Compete for binding sites and can affect Tm (transport maximum)
How does Farxiga affect the binding site?
Farxiga blocks SGLT1 by occupying the binding site, causing the transporter to reach Tm at a lower actual concentration
(It will artificially lower blood glucose levels, which can cause UTI’s because you’re excreting blood glucose)
QUESTION:
Predict how the movement rate of sodium through a channel would change if the concentration gradient of sodium was increased 100%.
Rate would be doubled
*Remember, this is a channel!
QUESTION:
Predict how the movement rate of glucose would change if the concentration gradient of glucose was increased 100%.
Insufficient Data; It depends. He will never ask a question like this.
QUESTION:
Which of the following could exhibit a transport maximum?
A) movement of sodium through Nav (voltage-gated Na channel)
B) movement of oxygen into the blood
C) movement of potassium via Na-K ATPase
D) movement of CO2 out of tissues
C) movement of potassium via Na-K ATPase
Process where water can freely pass through MOST cell membranes - channels called aquaporins
Osmosis
What happens for osmosis to occur?
- Difference in concentration of solutes that cannot pass generates a pressure difference
- Pressure difference pushes water from area of low solute concentration to area of high concentration
- Positive correlation with temperature
- THIS IS NOT DIFFUSION OF WATER…but This is basically diffusion
Pressure that stops movement during osmosis
Osmotic pressure
gC = ?
Osmolarity (mOsm/L)
g = number of particles per molecule
C = concentration (mmol/L, mM)
How do you measure osmolality?
Per Kg of water instead of per L like in osmolarity
1 L water = 1 Kg water
Basically the same number
(gCoRT)/(pi) = ?
Osmotic pressure
R = gas constant
T = temp in Kelvin
o = reflection coefficient of membrane
**the more restrictive an enzyme gets, the higher the pressure gets
Comparison of two fluids separated by a semi-permeable membrane, with respect to the bathing solution
**IMP!!
Tonicity
Type of tonicity where the inside of the cell has more dissolved solutes; water rushes in, cell bursts
Hypotonic (hyposmotic)
Type of tonicity where dissolved solutes are equal; no net water movement
Isotonic (Isomotic)
Type of tonicity where there is less solute inside; water rushes out, and the cells shrivel
Hypertonic (Hyperosmotic)
Pressure difference between water and blood
7 atm of pressure
QUESTION:
68 yr old woman comes down with heat stroke and rains; they administer cold saline via IV and transport her to hospital while applying cold compresses to her head and neck;
Q: What did she lose in her sweat?
Lots of water and some NaCl (sodium/salt)
-more water than NaCl
QUESTION:
68 yr old woman comes down with heat stroke and rains; they administer cold saline via IV and transport her to hospital while applying cold compresses to her head and neck;
Q: How did sweating effect the Osm of ECF and ICF?
ICF Osm went up, ECF Osm went up
-less water in blood to dissolve stuff that was there, so Osm in ISF goes up too because it tries to help out the ICF
QUESTION:
68 yr old woman comes down with heat stroke and rains; they administer cold saline via IV and transport her to hospital while applying cold compresses to her head and neck;
Q: Why did they give her I.V. cold saline instead of I.V. cold water?
They didn’t want to lose her RBC’S
1) What are the Darrow-Yannett diagrams used for?
2) What’s on the X axis? On the Y axis?
3) What’s it split into?
1)Used to visualize how osmolality and volume changes
2)X axis = volume
Y axis = osmolality (concentration)
3) Split into ECF and ICF
Where do all fluid changes that occur in the body originate?
In ECF and may or may not affect ICF
