2013 exam 1

Question 0

A reflex is a voluntary response controlled by the brain.

Answer 0

False.

Question 1

Why can atropine, an antagonist for muscarinic receptors, be used as an antidote to the nerve gas sarin? (3 reasons)

Answer 1

:: Because sarin inhibits the breakdown of acetylcholine
:: Because sarin increases the concentration of acetylcholine in the synaptic cleft
:: Because atropine blocks the action of acetylcholine on muscarinic receptors

Question 2

A train of action potentials encode information in the amplitude of action potentials.

Answer 2

False.

• APs encode information in their FREQUENCY
• APs in the same train have the same amplitude
• AP amplitudes provide NO information on the stimulus strength

Question 3

During the entire refractory period:

Answer 3

An action potential can be fired only during the relative refractory period if the stimulation is strong enough.

Question 4

It is hard to see colors under dim moon light. Why?

Answer 4

Cone cells are not strongly activated under dim light.

Question 5

AP-dependent neurotransmitter release is blocked in extracellular solution with no calcium. Why?

Answer 5

Calcium entry through voltage-dependent calcium channels triggers the fusion of synaptic vesicles with plasma membrane at the nerve terminal.

Question 6

What neurotransmitter(s) is (are) used by the sympathetic nervous system?

Answer 6

Acetylcholine and norepinephrine

Question 7

Knowing that Viagra is a PDE inhibitor and nitroglycerin produces NO, can you tell why it is very dangerous to take nitroglycerin and Viagra together?

Answer 7

:: NO activates guanylate cyclase to increase cGMP (which can lead to protein kinases)
:: cGMP dilate blood vessels
:: Blocking PDE increases cGMP

• NO diffuses out of postsynaptic space from one neuron to another
• NO occurs in the retrograde direction (axon terminal to cell body)
• NO action is restricted to a limited area
• NO does not need enzymatic breakdown or reuptake
• NO action quite important in a wide array of functions
• NO mechanism of action in smooth muscle is to increase cGMP in the recipient cell; dephosphorylate myosin light chain; relax smooth muscle

Question 8

Action potentials are propagated from the axon hillock to the nerve terminal because:

Answer 8

Propagation in the opposite direction is blocked by the inactivation of Na+ channels

Question 9

The resting membrane potential of a neuron is:

Answer 9

:: Largely determined by gK+
:: Closer to Ek+ then to Ena+
:: Affected by temperature

• At RMP, K+ flows from inside to outside of the cell

Question 10

Receptor potentials cannot be generated in humans by:

Answer 10

X-Ray

• But CAN BE generated by: touch, heat, perfume, sugar

Question 11

Most antidepressants are selective serotonin reuptake inhibitors. They work by:

Answer 11

Prolonging the action of serotonin in the synaptic cleft

Question 12

Why can’t the peak of an action potential reach Ena+?

Answer 12

:: Because of the inactivation of Na+ channels
:: Because K+ channels are highly active at the peak of an action potential

• At the peak of the AP:
  1. Membrane polarity is reversed
  2. Delta E and delta C for Na+ become opposite to each other
  3. Delta E and delta C for K+ both drive out K+ from the cell

Question 13

GABAa (and GABAc) receptors are different from GABAb receptors in that:

Answer 13

GABAa receptors are ion channels.

• GABA can work on more than just ligand-gated channels

Question 14

Curare blocks muscle contractions because:

Answer 14

It blocks acetylcholine receptors.

Question 15

Acetylcholine receptors at the neuromuscular junction:

Answer 15

:: Allow K+ to exit the muscle cell

:: Allow Na+ to enter the muscle cell

Question 16

Choline acetyltransferase is expressed in:

Answer 16

Alpha-motor neurons

Question 17

For a neuron that has an RMP of -70 mV, what has likely happened when this neuron does not fire an action potential?

Answer 17

The summation of all EPSPs and IPSPs is -65 mV at the axon hillock.

Question 18

Dopamine transporters are located on:

Answer 18

The plasma membrane of dopaminergic neurons.

Question 19

In hyperkalemia:

Answer 19

Ek+ is increased

• Excessive perspiration can lead to mild Hypokalemia (decreased blood level of K+); readily treated with Gatorade or foods high in potassium

Question 20

Voltage-gated K+ channels:

Answer 20

Allow K+ to exit a neuron.

Question 21

Action potentials are conducted in a saltatory (leap) fashion on myelinated axons to:

Answer 21

:: Increase conduction velocity

:: Minimize the use of Na+,K+-ATPase

Question 22

How do we perceive the sweetness of sugar?

Answer 22

Sugar activates a GPCR to increase neurotransmitter release from taste receptor cells.

Question 23

Most antipsychotic drugs inhibit the dopamine D2 receptors. They work by:

Answer 23

Blocking the activation of G-proteins coupled to the D2 receptors.

Question 24

Most preganglionic parasympathetic neurons have their cell bodies in the thoracic and lumbar regions.

Answer 24

False.

Question 25

Valium primarily acts at which receptor, as an agonist or an antagonist, to alleviate anxiety?

Answer 25

GABAa receptor, as an agonist. (Increase Cl- flux)

• GABA and glycine (strychnine is a glycine receptor blocker) are two examples of inhibitory NTs
• GABA is the major inhibitory NT in the CNS
• GABA are small interneurons that normally dampen activity within neuronal circuits
• Two main types of GABA are GABAa and GABAb

Question 26

Intracellular fluid has a _________ charge relative to outside of the cell.

Answer 26

Negative

Question 27

The charge difference between the intracellular fluid and the extracellular fluid creates…

Answer 27

An electrical potential across the membrane (for example, a membrane potential).

Question 28

By convention, extracellular fluid is assigned a voltage of:

Answer 28

Zero

Question 29

Neurons under resting conditions have a membrane potential of…

Answer 29

-40 to -90 mV

The typical resting membrane potential is -70 mV

Question 30

What is the ratio of Na+ ions to K+ ions during the Na+/K+ ATPase pumps action?

Answer 30

3 Na+ ions move out of the cell for every 2 K+ ions that are pumped in

Question 31

Equilibrium potential can be described as:

Answer 31

:: The membrane potential at which the flux produced by the electrical gradient exactly offsets the flux produced by the concentration gradient
:: No net flux
:: Membrane potential flux = concentration gradient potential flux

Question 32

The equilibrium potential of K+ is:

Answer 32

-90 mV

Question 33

The equilibrium potential of Na+ is:

Answer 33

-90 mV

Question 34

Both concentration and electrical gradients favor:

Answer 34

Na+ influx

• Only a concentration gradient favors K+ efflux