Snapps week 2

Question 1

You stimulate an axon at two separate points. How many action potentials are generated and what will happen when the two AP’s collide?

Answer 1

4, 3 of which will collide

Question 2

increasing R of the membrane will cause?

Answer 2

increase conduction velocity of axon

less will leak out and AP will be stronger and faster

Question 3

peak of AP, Vm is

Answer 3

positive

Question 4

Alpha adrenergic receptor activation triggers peripheral vasoconstriction via which of the following second messengers?

Answer 4

IP3 and DAG

Question 5

ACE-inhibitors decrease BP by inhibiting

Answer 5

peripheral vasoconstriction.

Question 6

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?

Answer 6

calcium influx triggers exocytosis of insulin

1. GLUT 2 transporters on B cells uptake glucose
2. glucokinases phos glucose (increases ATP;ADP ratio)
   (signals K channels to close =depol)
3. ca channel opens =ca influx
4. presence of calcium causes exocytosis of insulin

Question 7

What is the function of K+ channel blockers as a treatment for MS?

Answer 7

K+ channel blockades enhance AP conduction by preventing rapid repolarization via K+ efflux

Question 8

caffeine acts by

Answer 8

inhibiting phosphodiesterase

and increases PKA levels

Question 9

Where in the cell can a high concentration of RAN-GTP be found?

Answer 9

nucleus

Question 10

After the cholera toxin binds to the GM1 receptor on the cell’s membrane, what happens next?

Answer 10

The A subunit is cleaved, endocytosed, and cAMP is produced

Question 11

two subunits to the cholera toxin:

Answer 11

A and B.

Question 12

cholera A subunit:

Answer 12

The A is the active site

Question 13

cholera B subunit:

Answer 13

the transport molecule.

Question 14

cholera subunit binds to

Answer 14

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.

Question 15

At which point during an action potential is the driving force of sodium ions the smallest?

Answer 15

at peak

Question 16

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?

Answer 16

voluminous diarrhea

Question 17

Atropine is a drug administered to increase heart rate. How does atropine work?

Answer 17

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.

Question 18

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?

Answer 18

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.

Question 19

myelin functions to

Answer 19

1. decrease capacitance
2. decrease resistance
3. increase SA
4. increase conduction velocity

Question 20

Neurodegenerative diseases such as Alzheimer’s that result from the accumulation of plaques within the nucleus might be caused by:

Answer 20

a decreased ability of the NPCs to exclude molecules from nuclear entry as you age

Question 21

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?

Answer 21

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

Question 22

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?

Answer 22

nausea, decreased appetite, weight loss

Question 23

When is asymmetry of NPC’s established?

Answer 23

during cell cycle

Question 24

When G-protein coupled receptors are active, which components modulate their downstream effectors?

Answer 24

G beta-gamma and G alpha subunits

Question 25

What role to B-cells play in MS?

Answer 25

They activate effector T-cells

Question 26

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?

Answer 26

m gates open but h gates remain shut

Question 27

Directionality of protein transport is determined by:

Answer 27

RAN cycle

Question 28

During accommodation, a slowly applied stimulus will cause:

Answer 28

activation gates to open after inactivation gates have already shut

Question 29

Which of the following components of nucleoporin structure is highly conserved between species?

Answer 29

3 D archetecture

Question 30

Which of the following transporters is located on the apical membrane and is the cause of the ionic efflux that leads to severe diarrhea:

Answer 30

CFTR channel

Question 31

At the beginning of a relative refractory period, the k gates are in which position?

Answer 31

most are open

Question 32

Which of the following people is at most risk for developing multiple sclerosis (MS)?

Answer 32

female 16-45

Question 33

During G-protein coupled signaling, binding of GTP to G alpha subunits results in which of the following?

Answer 33

decreased binding affinity of G alpha and beta-gamma subunits

Question 34

max concentration of urine solute

Answer 34

1200 mosM

Question 35

Which of the following is correct regarding the Na/K/Cl exchanger of epithelial cell membranes?

Answer 35

drives the uptake of Cl into the cell that results in NaCl secretion

Question 36

During conduction of an action potential down an axon, what determines outward membrane current?

Answer 36

Pk

Question 37

During conduction of an action potential down an axon, what determines inward membrane current?

Answer 37

Pna