2009 exam 1

Question 0

Subthreshold depolarizations in axons:

Answer 0

Are graded- non-regenerative potentials and are conducted with decrement.

Question 1

Which of the following is true about sympathetic and parasympathetic nervous systems?

Answer 1

Both systems work in a coordinated manner to meet the needs of the body in response to changes in environment.

Question 3

Metabotropic neurotransmitter receptors differ from ionotropic neurotransmitter receptors in that: (4 reasons)

Answer 3

:: Metabotropic receptors are not channels.
:: Metabotropic receptors change the properties of other channels through intracellular signaling pathways.
:: Metabotropic receptors are G-protein coupled receptors.
:: Metabotropic receptors mediate slow neurotransmitters.

• Metabotropic glutamate receptors work via a ligand-gate; 2nd messengers; opening of an ion channel pore
• Ionotropic glutamate receptors (AMPA and NMDA) work via ligand-gated channels that form an ion channel pore by binding to a receptor pore

Question 3

Which of the following is true about vision?

Answer 3

Color is interpreted by cone cells in the photoreceptors layer of the retina.

Question 4

Which of the following is true about a motor unit?

Answer 4

:: All muscle fibers in the same motor unit are innervated by a single alpha-motor neuron.
:: The alpha-motor neuron uses acetylcholine to control muscle contraction.

Question 5

An action potential:

Answer 5

Can be generated more easily (readily) if the concentration of extracellular K+ is increased.

Question 6

Which of the following is true about the decision to fire action potentials?

Answer 6

:: It is made at axon hillock.

:: Both spatial summation and temporal summation contribute to the decision.

Question 7

NMDA receptors differ from AMPA receptors in that:

Answer 7

NMDA receptors are blocked by Mg++, while AMPA receptors are not.

• When AMPA opens, Na+ influx
• When NMDA opens, Ca++ influx
• NMDA receptor is a molecular coincidence detector. It only opens with glutamate binding and depolarization

Question 8

When an axon is at its RMP:

Answer 8

The membrane is more permeable to K+ than to Na+.

Question 9

Which of the following happens in the stretch reflex? (4 events)

Answer 9

:: The tendon tap induces stretch of muscle spindles, which produces generator potentials.
:: Action potentials travel along Ia fiber of a DRG neuron to the spinal cord.
:: An alpha-motor neuron is activated by neurotransmitters released from the DRG neurons.
:: Release of acetylcholine by the alpha-motor neuron triggers contraction of the rectus femoris muscle.

Question 11

Which of the following is true about the autonomic nervous system? (2 facts)

Answer 11

:: Autonomic nervous system deals with involuntary sensory and motor responses of the internal organs.
:: Autonomic nervous system relies on autonomic ganglionic neurons to relay the output from the central nervous system to target organs.

Question 11

At the NMJ:

Answer 11

Two molecules of Ach are required to activate ligand-gated channels in the postsynaptic membrane.

…acetylcholine is sequestered in synaptic vesicles at very high concentration

Question 12

At the peak of the AP:

Answer 12

:: Both chemical and electrical potentials act to force K+ out of the cell.
:: Na+ inactivation occurs and closes Na+ voltage-gated channels.

Question 13

Botulinum toxins block GABAa receptors so that synaptic transmission is halted

Answer 13

False.

Question 14

Local anesthetics prevent AP production by blocking Na+ channels only in unmyelinated neurons.

Answer 14

False.

Question 15

An increase in the gNa+ of the resting cell membrane will depolarize the cell membrane.

Answer 15

True.

Question 16

Inhibitory postsynaptic potentials (IPSPs) are inhibitory because they lower the probability of firing an action potential.

Answer 16

True.

Question 17

A decrease in [K+o] will stabilize the membrane (make it less excitable) by depolarizing the cell membrane.

Answer 17

False.

Question 18

Excitatory postsynaptic potentials (EPSPs) bring membrane potential closer to the threshold of firing action potentials.

Answer 18

True.

Question 19

Axons with a lower arm and a smaller diameter will have shorter length constants and thus slower conduction velocities.

Answer 19

True.

Question 20

For sensory transduction, all external and internal stimuli are converted to receptor potentials whose summation determines the production of action potentials.

Answer 20

True.

Question 21

Glutamate can mediate both fast and slow synaptic transmission.

Answer 21

True.

Question 22

A dorsal root ganglion neuron extends a dendrite to a sensory organ such as skin.

Answer 22

False.

Question 23

In resting axon terminals at the NMJ, both chemical and electrical forces act to force Ca++ into the cell through ligand-gated channels.

Answer 23

False.

Question 24

Oligodendrocytes

Answer 24

Myelin-producing cells in the CNS. 1 oligodendrocyte is responsible for 40 axons (vs Schwann cells in the PNS are responsible for 1 axon)