Membrane practical discussion session
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Q1. What is the approximate concentration (in mM) of potassium ions inside a mammalian cell?
(Type your answer)
Q2. How do cells maintain this concentration gradient for potassium?
(Type your answer)
The mechanism that acts to maintain the cellular concentration gradient of potassium and sodium ions is the
Q3.
(Select one or more answers)
(a)
By convention, the reference side of the chamber is taken to be at 0 mV
(b)
The concentration gradient will favour movement of potassium ions from the right side to left side of the chamber
(c)
The electrical potential difference that develops between the reference and the left side of the chamber will have a negative value
(d)
The millivoltmeter will read +58 mV if the membrane is perfectly selective for potassium
If you need a calculator click here
Q4. With regard to movement of ions and the Nernst equation:
(Select one or more answers)
(a)
Ions always move across a membrane down their concentration gradient
(b)
The Nernst equation relates forces owing to concentration and electrical gradients
(c)
The Nernst equation is valid only for ions at electrochemical equilibrium
(d)
Nernst potentials are always positive values
(e)
If the measured membrane potential equals the value calculated using the Nernst equation then there will be no net movement of that ion.
Q5. The resting potential of most cells is most dependent on the transmembrane concentration gradient of:
(Select one answer)
(a)
Chloride
(b)
Potassium
(c)
Sodium
(d)
Calcium
(e)
Magnesium
Q6. The resting potential is dependent upon the electrochemical gradient for potassium ions because:
(Select one answer)
(a)
Cells contain largely potassium
(b)
The permeability to sodium ions is very small except during action potentials
(c)
The permeability of the resting membrane to potassium is higher than for other ions
(d)
Of the activity of the sodium/potassium ATPase
Q7. If the solution bathing a cell contains 80 mM potassium and the intracellular concentration is 140 mM, what do you expect the Nernst potential to be?
(Type your answer)
Q8. Given that there is a potential difference of 58 mV across a membrane that separates a solution containing 10 mM from another containing 100 mM potassium, what potential difference will you measure if the 2 solutions are changed to 120 and 12 mM?
(Type your answer)
Q9.
(Select one or more answers)
(a)
The formula above is a version of the Goldman equation
(b)
The formula above is the Nernst equation
(c)
The formula above normally includes a set of terms for chloride ions
(d)
The formula above can be used to calculate the membrane potential due to the electrochemical gradients and relative permeability for both sodium and potassium ions.
(e)
If the permeability to sodium is zero this equation will calculate values for membrane potential that are identical to the Nernst equation
Q10. A potential difference of -27 mV is measured in an artifical membrane practical (using a perfectly K selective membrane) when one side (the reference side) of the bath contains 120 mM potassium. What is the concentration of potassium on the other side?
(Type your answer)
Q11. If an artificial membrane is pemeable to calcium ions (remember that they have a 2+ charge) and one side of the chamber has 10 mM and the other has 100 mM, what is the expected Nernst potential?
(Type your answer)
Q12. Click on the part of the graph that allows you to estimate the concentration of K inside the muscle fibre
(Click on the image to select your answer)
Q13. Please fill in the gaps
(Type your answer)
Q14. If extracellular potassium is removed, what will happen to the activity of the sodium/potassium ATPase?
(Select one answer)
(a)
It will slow down
(b)
It will continue pumping but will move only sodium ions
(c)
It will stop working
Q15. Does the activity of the sodium potassium ATPase directly generate a membrane potential?
(Select one answer)
(a)
No
(b)
Yes
Q16. Which of the following statements about the conduction of a subthreshold depolarisation of a nerve or muscle cell is true
(Select one answer)
(a)
A subthreshold depolarisation is conducted by saltatory conduction.
(b)
It is conducted with decrement, which means that the depolarisation gets smaller as the depolarisation moves along the cell
(c)
The length constant is the distance over which the depolarisation decreases to 50% of its maximal size.
(d)
The length constant of myelinated nerves is far greater than in non-myelinated nerves
(e)
None of the above.
Q17. Which of the following statements about neuromuscular transmission are true
(Select one or more answers)
(a)
A miniature endplate potential occurs after an action potential in the nerve terminal.
(b)
Calcium influx into the nerve terminal initiates the chain of events that culminates in transmitter release.
(c)
The acetylcholine receptor protein is a voltage-gated ion channel that opens when it binds acteylcholine.
(d)
The desensitisation of the acetylcholine receptor normally terminates the endplate potential.
(e)
Only one action potential arriving at the presynaptic cell is sufficient to cause an action potential in the muscle fibre.
Q18. Which of the following statements about the acetylcholine receptor protein of the neuromuscular junction are correct
(Select one or more answers)
(a)
The acetylcholine receptor protein is a voltage-gated ion channel.
(b)
The acetylcholine receptor is concentrated at neuromuscular junction.
(c)
The channel opened by acetylcholine is selective for sodium ions.
(d)
Depolarisation of the muscle cell promotes opening of the acetylcholine receptor protein?s ion channel.
(e)
Two molecules of ACh are required to bind to the receptor in order to open it.
Q19. Which of the following statements about synapses is true?
(Select one answer)
(a)
Gap junctions contain ligand-gated ion channels.
(b)
A neurotransmitter acts to increase or decrease the conductance of the postsynaptic membrane to one or more ions.
(c)
Synaptic delay is characteristic of chemical synapses.
(d)
Chemical synapses require influx of Na+ triggered by an action potential in the presynaptic nerve terminal
(e)
None of the above
Q20. The cartoon diagram is a membrane protein:
(Select one or more answers)
(a)
called the muscarinic acetylcholine receptor
(b)
that is involved in EC coupling in skeletal but not cardiac muscle
(c)
that is affected in Lambert-Eaton syndrome
(d)
that is both a receptor for an extracellular signalling molecule and an ion channel
(e)
that is inhibited by a toxin derived from the Puffer fish, tetrodotoxin
Q21. Click on either of the dorsal horns of the spinal cord
(Click on the image to select your answer)
Q22. In a relaxed skeletal muscle, the cross-bridges are:
(Select one or more answers)
(a)
Inhibited by tropomyosin.
(b)
a complex of myosin, actin, ADP, and Pi.
(c)
a myosin ATP complex.
(d)
dissociated from the thick filaments.
(e)
a high-energy complex of myosin, ADP, and Pi.
Q23. Using features present in the image, estimate the diameter (in micro meters) of the skeletal muscle fibers.
(Type your answer)
Q24. Each cross-bridge cycle:
(Select one answer)
(a)
moves the actin and myosin filaments by about 10 nm (nanometers) (1 nm = 10-9 m)
(b)
moves the actin and myosin filaments by about 2.2 um (micrometers) (1 um = 10-6 m)
(c)
uses 2 molecules of ATP per myosin head
(d)
Is equivalent to a muscle twitch response
(e)
Takes the same amount of time to complete in all striated muscles
Q25. Fine gradation of the force of contraction in a skeletal muscle is facilitated by:
(Select one answer)
(a)
mostly fast, glycolytic motor units.
(b)
large numbers of motor units with relatively few cells.
(c)
uniform excitability of motor nerves to fast and slow motor units.
(d)
high ATP synthetic rates
(e)
strength training and cellular hypertrophy.
Q26. The force of contraction in a skeletal muscle is normally graded by:
(Select one answer)
(a)
the amount of Ca++ released from the sarcoplasmic reticulum by an action potential.
(b)
a change in the affinity of troponin for Ca++
(c)
activation of fast, glycolytic motor units instead of slow, oxidative motor units.
(d)
summation of action potentials to prolong depolarisation.
(e)
recruitment.
Q27. Excellent performance in long distance running:
(Select one or more answers)
(a)
is accomplished by training of fast motor units.
(b)
is associated with an enhanced oxidative capacity of slow motor units.
(c)
is characterised by glycogen depletion.
(d)
is associated with cellular fatigue.
(e)
involves contraction of mainly slow motor units.
Q28. Click on the feature that enables you to identify this image as a section of skeletal muscle.
(Click on the image to select your answer)
Q29. Compared with a fast motor unit, a typical slow motor unit has:
(Select one or more answers)
(a)
fewer cells.
(b)
a higher force-generating capacity.
(c)
more mitochondria.
(d)
a less excitable motor nerve
(e)
a more rapid fatigue rate.
Q30. The force per cross-sectional area of a smooth muscle cell is
(Select one or more answers)
(a)
much greater than that of skeletal muscle.
(b)
similar to that of skeletal muscle
(c)
low because the cells are small.
(d)
Is developed more slowly than striated muscle
(e)
independent of the myoplasmic Ca++ concentration.
Q31. The membrane responsible for regulating the myoplasmic Ca++ concentration during sustained contractions in smooth muscle is:
(Select one answer)
(a)
the sarcoplasmic reticulum.
(b)
the caveoli
(c)
the motor endplate.
(d)
the sarcolemma.
(e)
the transverse tubule
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Copyright © 1999 University of Bristol. All rights reserved.
Author:
Phil Langton
Last modified: 20 Nov 2000 10:26
Authored in
CALnet