2010 exam 1

Question 1

The Nernst equilibrium potential for K+ is determined by: (3 factors)

Answer 1

:: Extracellular concentration of K+
:: Intracellular concentration of K+
:: Temperature of the cell

- The Nernst equation describes the equilibrium potential for any individual ion
// Z = valence

Question 2

What is the best answer regarding the concentrations of following ions inside and outside the cells: (3 ions)

Answer 2

:: [K+]: inside > outside
:: [Na+]: inside < outside
:: [Ca++]: inside < outside

Question 3

Na+,K+-dependent ATPase…

Answer 3

:: Largely determines the intracellular concentration of Na+
:: Largely determines the intracellular concentration of K+
:: Utilizes ATP hydrolysis to transport ions against their gradients

Question 4

At resting membrane potential…

Answer 4

:: K+ flows from inside to outside of the cell.

Question 5

Action potentials…

Answer 5

Are fired in an all-or-none fashion, depending on whether a threshold is passed.

Question 6

Action potentials:

Answer 6

In the same train have the same amplitude and encode information in their frequency (The frequency of the AP provides information about the strength of the stimulus)

Question 7

Which is the best answer about the conduction velocity of action potentials?

Answer 7

Myelination increases it and it is reduced in multiple sclerosis

Question 7

A neuron is firing action potentials at 200 Hz, this means that:

Answer 7

The total refractory period is less than 5msec.

Question 8

Which is the best answer about the nodes of Ranvier?

Answer 8

They have enriched expression of Na+ channels and they relay action potentials in a saltatory manner

Question 10

How does novocaine work?

Answer 10

It blocks Na+ channels and it blocks action potential so your brain does not perceive pain (TTX blocks AP generation by blocking Na+ entry into axons and skeletal muscle cells)

Question 11

At neuromuscular junction, acetylcholine…

Answer 11

Is sequestered in synaptic vesicles at very high concentration

Question 12

Which is the best answer about the end plate potential?

Answer 12

It propagates in the skeletal muscle cells with decrement and it always triggers an action potential in the muscle cell in normal situation

Question 13

How does EPSP make a neuron fire action potentials?

Answer 13

A neuron has thousands of EPSPs that can summate. Spatial and temporal summation of many EPSPs can produce a suprathreshold stimulus at the axon hillock

Question 14

Botox (diluted botulinum toxin) blocks the action of acetylcholine at NMJ by:

Answer 14

Inactivating the SNARE proteins responsible for the fusion of synaptic vesicles with the presynaptic membrane

:: SNARE proteins: targets of botulinum toxins
:: V-SNARE: synaptobrevin
:: T-SNARE: syntaxin and SNAP-25
:: Calcium sensor: synaptotagmin

Question 15

Acetylcholine is sequestered into synaptic vesicles by:

Answer 15

Vesicular acetylcholine transporter

Question 16

In the stretch reflex induced by tendon tap,

Answer 16

:: Action potentials are fired if the generator potential is suprathreshold.
:: A DRG neuron directly synapses on the alpha-motor neuron that innervates the rectus femoris muscle.
:: An interneuron inhibits AP firing in the alpha-motor neuron that innervates the semitendinosus muscle.

Question 17

One of the side effects of Viagra, cGMP-specific phosphodiesterase (PDE) inhibitor, is on color vision. Why?

Answer 17

:: Because a cGMP-gated cationic channel regulates Vm of cone cells.
:: Because Viagra also inhibits the PDE in retina cells.

Question 18

Autonomic nervous system (ANS) differs from Somatic Nervous System (SNS) in that:

Answer 18

:: ANS largely controls involuntary responses whereas SNS largely controls voluntary responses.
:: ANS controls internal organs while SNS controls skeletal muscles.

Question 18

Resting membrane potential of neurons are largely determined by K+ conductance.

Answer 18

True.

(RMPs and APs result from the movement of Na+ and K+ through voltage-dependent channels).

Question 19

Sympathetic and parasympathetic nervous systems differ in that:

Answer 19

:: Sympathetic nervous system generally produces widespread responses while parasympathetic nervous system generally produces localized responses.
:: Locations of preganglionic cell body are different.

Question 20

An alpha-motor neuron can only innervate one skeletal muscle cell because a skeletal muscle cell can only be innervated by a single alpha-motor neuron.

Answer 20

False.

Question 21

Synaptotagmin senses the increase of intracellular calcium level to trigger the release of neurotransmitters.

Answer 21

True.

Question 22

GABA can only work on ligand-gated channels.

Answer 22

False.

Question 23

Generator potentials produced by external stimuli always produce action potentials.

Answer 23

False.

Question 24

All odorant receptors belong to the same family of protein and use the same second messenger to change Vm by altering the conductance of ion channels.

Answer 24

True.