Physiology Problem Solving Homework
Spring 2016
Type in all your answers under each question using complete, grammatically correct sentences. Use Times 12 font and keep everything single-spaced. Even though tweeting and texting are normal practices with iPhones and such, this is NOT such an event. Full explanations and sentences are required.
Please put effort into this, as it will be graded according to effort and the correctness of your answer with respect to physiological/scientific logic.
Minimum effort and input on your end will be graded with minimum effort and output on my end. For example, when an explanation is asked for, you need to back up your statements with ‘evidence’. A blank statement is not an explanation unless you back it up with logic or with data.
Since this is a word document, items will shift as you type. It is your job to keep the organization of this assignment clean by using margins and common sense. For example, don’t start a new heading at the bottom of a page, with the starting paragraph on the next page (in editing, that is sometimes referred to as ‘orphaning’ or ‘decapitation’). I like to see a presentation as if you are applying for your dream job.
This is an individual effort. If a student copies work from another student, both students will receives a zero on this assignment.
Show me that you learned something this semester !
Type your name, aligned to the left, at the bottom of each page.
Name : ______
1. First set of questions
A. The following Table gives 3 solutions. If the osmolarity of blood is 290 milliOsmolor, which of the three solutions is iso-osmotic with blood ? Explain and back up your claim with your calculated data.
Solution 1 / Solution 2 / Solution 350 mM NaCl / 40 mM NaCl / 100 mM NaCl
25 mM KCl / 10 mM KCl / 5 mM KCl
25 mM MgCl2 / 20 mM CaCl2 / 5 mM CaCl2
100 mM Glucose / 110 mM Glucose / 25 mM Glucose
30 mM Fructose / 20 mM Fructose / 10 mM Fructose
Your answer:
B. What is the difference between Osmolority and Tonicity. In other words, compare and contrast the two. In addition, if a solution is iso-osmotic to another solution, will it also be isotonic ? Finally, explain what a physiological IV solution is. What is usually in it and why ? Explain this correctly. Do your research.
Your answer :
C. Earlier his year, it was reported that a teen slipped into a coma and almost died after drinking more than a quart of soy sauce on a dare. Apparently he developed a serious case of Hypernatremia. In a one page discussion, explain what hypernatremia is, how drinking the soy sauce caused this, how this relates to osmosis, and why it caused the person to slip into a coma. Finally, while this is extreme, give another example how one may develop hypernatremia .
Your Discussion :
2. Second set of Questions
Homeostasis requires that the total osmolarity of cells and extracellular medium needs to be the same ( i.e. isotonicity : the total number of non-permeable particles on either side of the membrane needs to be the same) AND that charge neutrality needs to be obeyed. This latter meaning that, the total sum of all negative ions and positive ions, needs to be the same on both sides of the membrane compartments.
A. Knowing this information, can you solve the following “puzzle” ? If the cell below is in a steady sate condition, what is the concentration of K+ inside the cell, and what is the concentration of Impermeable non-electrolytes outside the cell ? (understand the term non-electrolyte).
Na+ = 20 mM Na+ = 140 mM
K+ = unknown in mM K+ = 5 mM
Cl- = 5 mM Cl- = 145 mM
A- (non-permeable anions) = 165 mM Non-permeable Non-Electrolytes = ?
Your calculations and answers:
B. After solving for the missing information above, calculate the Equilibrium potential for the three different ions from the info above. Show your calculations.
Fill in the following table and answer the questions below :
Ion / Conc. Inside / Conc. Outside / Eq. PotentialNa+
K+
Cl-
(Note : make sure this table does not become cut in pieces when items in your document become shifted when you type in your answers.).
C. What is the physiological meaning of the equilibrium potential of a specific ion ? What does this tell us specifically ?
Your calculations and answers:
D. A neuro-physiologist does some experiments with this cell you been working with. His gadget is broken such that it cannot measure voltage, but it can measure current (in milli Amps). He sticks a specific Chloride electrode into this cell and measures the current for Chloride. There apparently seems to be no current for Chloride .
One of the possibilities of why there would not be a current for Chloride through this membrane is absence of chloride leakage channels. But, previous work by his lab partners has shown that this cell has leakage channels for the 3 ions discussed. Knowing this information, and the answers from the previous question, what can you tell me about the value of the actual resting membrane potential of this cell now ? Explain your reasoning !
Provide me with a small explanation and reasoning of what is going on .
3. Third set of Questions
A. Go to the following website :
http://www.physiologyweb.com/calculators/ghk_equation_calculator.html
Scroll down to where you will find a calculator table. Make sure all the mM radio buttons are highlighted and click “Fill Cells with Sample data”. Now make some changes. Change pNa to 0.01, change pCl to 0.05. Furthermore change the Chloride data to 108 mM outside, 8 mM inside. Change the Vm radiobutton to millivolts. You will get a value for the Resting Membrane potential (Vm) and values for the Equilibrium Potentials for K+, Na+ and Cl-.
Start filling in Column A. I have filled in the value for EK+ for Ko = 4 mM and Kin = 155 mM and the calculated Vm according to this calculator. Now, repeat this and only change the Ko values as shown in the table. Calculate the resulting EK+ and Vm values. Fill those into the table.
When finished with column A, hit the “clear all” button. Once again hit the “fill cells with sample data” button and adjust the data as follows : Keep pNa at 0.05, keep pCl at 0.45, change the Chloride data to 108 mM outside, 8 mM inside. Change the Vm radiobutton to millivolts.
Reat the calculations by only changing Ko from 1 to 12 and fill in the data in column B. Once again, the value at Ko = 4 mM has been filled in for you as an internal check ( make sure you get that same number).
Repeat this now with the following adjustments. Click the clear all button
If you look at the difference between Vm and EK+ at Ko = 4 mM, it is ( -69.4 – (-96.8)), which is equal to 27.4 mV. Fill in the 4th column by making the assumption that the Vm is always about 27.4 mV higher than the EK+ and thus apply that difference to every calculated value for EK+ (we are thus assuming that we don’t have the GHK equation).
KoExtracellular K+(in mM) / EK+ / Column A / Column B
1
2
3
4 / -97.7 mV / -88.5 mV / -70 mV
5
6
8
10
12
14
B. Create a nice ( !) graph that includes all these data in one graph ( with correct X-axis and Y-axis) and paste it in this document.
C. What does the abbreviation GHK equation stand for ? What is the difference between the Nernst Equation and the GHK equation ?
D. In the calculator, what does pNa, pK and pCl stand for and what are there respective ratios and what does it mean actually ?
E. In the calculator, what value and what temperature is actually being used ? And what does this temperature represent in Celsius ?
F. Go back to the calculator, clear all data and hit the Fill with sample data button. Now change the pNa to 1, pK to 0.05 and pCl to 0. What value to we now get for Vm and explain why that is ?
G. The data in column A above represent what happens in a cardio myocyte. The data in column B represents what happens in a skeletal muscle cell.
a) What extracellular value for K+ represent the normal condition ?
b) What can you tell me about the resting membrane potential between a cardiomyocyte and a skeletal muscle during normal condition ? Why that difference ?
c) What is the threshold value for action potentials in a skeletal muscle and a cardiomyocyte ? (look this up, or google it for example here http://www.pathophys.org/physiology-of-cardiac-conduction-and-contractility/ )
d) Voltage gated Na+ channels are important for action potentials. They have two gates, one of which closes the channel when it reaches about + 30 mV, and which will remain closed following an Action Potential IF the RMP does not drop below normal threshold values. Use this information now to explain why I made you create that table.
F. Your final job is to explain in at least 2/3 of a page what hyperkalemia is, and how one may get it. What are the symptoms and dangers ?
Hint 1: one of the links I gave you should help you with many of the answers.
Hint 2: the last question F will help you with answering item d) above.