Neurophysiology Flashcards
In a standard neuron, what is the threshold value that must be reached for an action potential to occur? A- -70 mv B- -55 mv C- -40 mv D- 0 mv E- +40 mv
B (-55mV)
EXPLANATION:
The threshold value for a standard neurone is –55mv; once this value is reached an action potential will occur.
A - -70mv is the resting potential of a neurone
E - +40mv is the maximum potential reached during depolarisation. Once +40mv is reached, the Na+ VG channels close
During the standard action potential, why does hyperpolarisation occur? A- K+ channels stay closed B - K+ channels are slow to open C - K+ channels stay open D - K+ channels are in an inactive state E- K+ channels are slow to close
E - K+ channels are slow to close
EXPLANATION: Hyperpolarisation occurs because after repolarisation, the K+ channels are slow to close, so there is a slight outward diffusion of K+, making the equilibrium potential more negative than the resting potential for a short period of time.
Which of the following factors would increase the conduction velocity along an axon? A – The absence of Schwann cells B – An increase in membrane resistance C – A decrease in membrane capacitance D – A larger axon diameter E – An unmyelinated axon
D – A larger axon diameter
EXPLANATION: A larger axon diameter is the only one out of these which would increase conduction velocity as this decreases resistance.
A - Schwann cells produce the myelin sheath which increases conduction velocity, so in their absence the CV would decrease
B – We want a low membrane resistance
C - We want a high membrane capacitance as this causes the VG channels to open quicker
E – An unmyelinated axon means that saltatory conduction can’t occur, so the conduction velocity decreases
What is the main event in the repolarisation stage of an action potential? A- Na+ voltage gated channels open. B- Na+ leak channels open. C- K+ voltage gated channels close. D- K+ voltage gated channels open. E- Na+/ K+ pump
D
The main event is the K+ VG channels opening - repolarisation
What does the Nernst equation calculate?
a. The threshold potential of a membrane.
b. The resting potential of a membrane.
c. The refractory period for an ion.
d. The threshold potential of an ion.
e. The resting potential of an ion.
E
The resting potential of an ion
Which one of these is an ABC Transporter (ATP-Binding Cassette)?
A- Na+-K+ ATPase
B- GLUT1
C- CFTR transporter
D- SGLT-1
C- CFTR transporter
How does cystic fibrosis affect mucus secretions?
An unfunctionable CFTR transporter is produced
Thus, Cl- ions cannot leave the cell and this leads to sticky secretions
What is the equilibrium potential of K+ ions?
a) +90 mV
b) -90 mV
c) +60 mV
d) -60 mV
e) -70mV
B-90mV
The following is the concentration of which ions (at rest) in an excitatory cell : Inside the cell = 150 mM / Outside cell = 5 mM
a) Na+
b) K+
c) Ca2+
d) Fe3+
e) Cl-
B- K+
Which of the following comparisons between myelinated and umyelinated neurones is true?
a) In both neurones the entire axon is in contact with the extracellular fluid
b) Saltatory conduction is a feature of unmyelinated axon
c) The conduction velocity of the fastest myelinated axons is about 100 m/s whereas the fastest unlyelinated axon has conduction velocity of about 1.5 m/s
d) Myelin sheath wraps around unmyelinated axon
C
Which of the following results in the repolarisation phase of the standard action potential curve?
a) Influx of Na+
b) Efflux of Na+
c) Influx of K+
d) Efflux of K+
e) Na+/K+ pump
D- Efflux of K+
Cystic fibrosis is caused by problem in the CFTR membrane protein. What type of transporter is this?
a) Antiporter
b) Uniporter
c) Symporter
d) ABC transporter
e) Aquaporin
D- ABC transporter
Which of the following receptors on the cells are located at a distance from the channels and require secondary intracellular messengers such as cAMP?
a) Ionotropic
b) Metabotropic (G-coupled receptors)
c) Agonist
d) Antagonist
e) All of the above
B- Metabotropic (G-coupled receptors)
