Neurophysiology Midterm 1 Review

Which of the following ions have an INWARD concentration gradient rather than outward? (Assuming that the ion’s respective channels are opened) (SELECT ALL THAT APPLY)

• Sodium (Na+) 

• Potassium (K+)

• Calcium (Ca2+)

• Chloride (Cl-) 

Answer explanation

These ions are more concentrated OUTSIDE of the cell; therefore, they will have an INWARD concentration gradient!

GABA is an inhibitory neurotransmitter found in the CNS. How is it removed from the synaptic cleft?

• Astrocytes

• Microglia

• Diffusion

• Reuptake to the presynaptic terminal

Answer explanation

GABA is removed through active uptake into astrocytes.

Which of these are secondary vesicles? (select all that apply)

• Metencephalon

• Prosencephalon

• Telencephalon

• Myelencephalon

• Diancephalon

Can another action potential occur during the relative refractory period (hyperpolarization / undershoot)? 

• This is a trick question, because there’s only absolute refractory period, and there is no such thing as relative refractory period. 

• No, because no amount of stimulation can trigger an action potential due to sodium voltage channels being inactivated. 

• Yes, because the sodium voltage channels are no longer inactivated during this time and can be activated, but a stronger stimulus will be required to stimulate an action potential

• Yes, because the potassium voltage channels are no longer open during this time, so the K+ ions cannot move outside of the cell; therefore, preventing hyperpolarization. 

• Yes, but a stronger stimulus will be required to stimulate an action potential, because the membrane potential is more positive than the resting membrane potential during this time. 

Answer explanation

Sodium channels can be activated at this time, BUT a stronger stimulus will be needed, because potassium ions are slow to close This still allow K+ to move outside of the cell – resulting in a more negative membrane potential. Choice A is simply false. Choice B describes absolute refractory period. Choice D is false, because potassium channels are still OPEN at this time and are slow to close. Choice E is false. The first half of the statement is true (a stronger stimulus is required), but the second half is false. The membrane potential is more NEGATIVE than the resting membrane potential at this time, because potassium channels are still open, which allow K+ efflux. 

What part of the neuron "integrates signals"?

• Axon

• Soma (cell body)

• Axon terminal

• Dendrites

Answer explanation

Signal integration happens throughout the cell body and then propagates along the axon if threshold for an action potential is met.

The pictured vesicles are round and electron lucent. What is the most likely neurotransmitter contained in this type of synapse vesicle?

• Inhibitiory

• Acetylcholine

• GABA

• Catecholamines

Answer explanation

Grays Type I: round clear vesicles, usually excitatory

What percentage of signal is lost 200 microns from the axon hillock?

• 86

• 13

• 63

• 37

Answer explanation

Let's say you have 100 units of signal strength. 100 microns form the axon hillock you lose 63% of the strength, so 63 units. 100 microns away you have 37 units left. Then you move away another 100 microns and lose 63% of the 37 units you have left. 37-(.63X37)=~14

100-14=86 units of signal lost 200 microns from the axon hillock.

Which type of Axonal transport is the fastest?

• Retrograde small particles

• Retrograde large particles

• Dissolved Substances

• Orthograde Large Particles

Answer explanation

The decarboxylation of Glutamate forms what neurotransmitter?

• Gamma-aminobutyric acid

• Substance P

• Glycine

• Norepinephrine

Answer explanation

GABA is formed by the decarboxylation of Glutamate.

The neural ______ gives rise to the PNS

• Crest

• Basal Plate

• Tube

• Alar Plate

Answer explanation