Snapps week 2 Flashcards
You stimulate an axon at two separate points. How many action potentials are generated and what will happen when the two AP’s collide?
4, 3 of which will collide
increasing R of the membrane will cause?
increase conduction velocity of axon
less will leak out and AP will be stronger and faster
peak of AP, Vm is
positive
Alpha adrenergic receptor activation triggers peripheral vasoconstriction via which of the following second messengers?
IP3 and DAG
ACE-inhibitors decrease BP by inhibiting
peripheral vasoconstriction.
A beta cell in the pancreas receives a signal to close its potassium channels. The cell depolarizes and calcium enters the cell. Which of the following correctly describes the next step in this signaling pathway?
calcium influx triggers exocytosis of insulin
- GLUT 2 transporters on B cells uptake glucose
- glucokinases phos glucose (increases ATP;ADP ratio)
(signals K channels to close =depol) - ca channel opens =ca influx
- presence of calcium causes exocytosis of insulin
What is the function of K+ channel blockers as a treatment for MS?
K+ channel blockades enhance AP conduction by preventing rapid repolarization via K+ efflux
caffeine acts by
inhibiting phosphodiesterase
and increases PKA levels
Where in the cell can a high concentration of RAN-GTP be found?
nucleus
After the cholera toxin binds to the GM1 receptor on the cell’s membrane, what happens next?
The A subunit is cleaved, endocytosed, and cAMP is produced
two subunits to the cholera toxin:
A and B.
cholera A subunit:
The A is the active site
cholera B subunit:
the transport molecule.
cholera subunit binds to
GM1 receptor, but only A is cleaved and endocytosed.
This in turn activates adenylyl cyclase which produces cAMP.
This leads to activation of CFTR which leads to efflux of chloride ions.
At which point during an action potential is the driving force of sodium ions the smallest?
at peak
As a fourth year medical student you are doing a clinical rotation in Haiti. You see a patient that you suspect has cholera. What initial symptom does the patient report that leads you to think it is cholera?
voluminous diarrhea
Atropine is a drug administered to increase heart rate. How does atropine work?
M2 antagonist
atropine antagonizes the acetylcholine (Ach)pathway at the m2 muscarinic cholinergic receptor, which normally activates K+ channels to hyperpolarize heart muscle cells and decrease heart rate.
Binding of an agonist to a G-protein coupled receptor at its transmembrane domain causes a conformational change that results in which of the following functions?
activates the receptor and triggers signal transduction to begin
agonists activate GPCR’s and cause a conformational change that begins signal transduction. On the G alpha subunit GDP - GTP by a GEF GTP on G-alpha subunit allows it to go to effectors (enzymes that make 2nd messengers or ion channels that control perm) An intrinsic GTPase returns the GPCR back to its inactive state by hydrolyzing GTP to GDP.
myelin functions to
- decrease capacitance
- decrease resistance
- increase SA
- increase conduction velocity
Neurodegenerative diseases such as Alzheimers that result from the accumulation of plaques within the nucleus might be caused by:
a decreased ability of the NPCs to exclude molecules from nuclear entry as you age
An MRI on a patient shows lesions consistent with MS. You test the patient’s visual pathway using a Visually Evoked Potential, and notice a decrease in amplitude but not a delay in response. What is the most likely conclusion you can make at this time?
The patient has lost some neuronal axons
Decreased amplitude = loss of axons Decreased speed = demyelination Without additional studies and time, one cannot definitively conclude that this is or is not MS, or that this is autoimmunity
A seven year old female patient presents to your clinic with elevated k levels and a venous pH of 7.01. What other symptoms are to be expected in this patient?
nausea, decreased appetite, weight loss
When is asymmetry of NPC’s established?
during cell cycle
When G-protein coupled receptors are active, which components modulate their downstream effectors?
G beta-gamma and G alpha subunits
What role to B-cells play in MS?
They activate effector T-cells
You stimulate an AP in an axon and attempt to stimulate another 1 ms later but you do not get a response. What is happening in sodium channels during the refractory period?
m gates open but h gates remain shut
Directionality of protein transport is determined by:
RAN cycle
During accommodation, a slowly applied stimulus will cause:
activation gates to open after inactivation gates have already shut
Which of the following components of nucleoporin structure is highly conserved between species?
3 D archetecture
Which of the following transporters is located on the apical membrane and is the cause of the ionic efflux that leads to severe diarrhea:
CFTR channel
At the beginning of a relative refractory period, the k gates are in which position?
most are open
Which of the following people is at most risk for developing multiple sclerosis (MS)?
female 16-45
During G-protein coupled signaling, binding of GTP to G alpha subunits results in which of the following?
decreased binding affinity of G alpha and beta-gamma subunits
max concentration of urine solute
1200 mosM
Which of the following is correct regarding the Na/K/Cl exchanger of epithelial cell membranes?
drives the uptake of Cl into the cell that results in NaCl secretion
During conduction of an action potential down an axon, what determines outward membrane current?
Pk
During conduction of an action potential down an axon, what determines inward membrane current?
Pna
