N154 at UCI (MOLECULAR NEUROBIOLOGY) - MIDTERM 1 PREP WITH
COMPLETE SOLUTIONS
1.1 Neurotransmitter - ANSWER
Synapses: - ANSWER Neurons are connected but not physically. They have on and off
connection. They are not always connected. 3 important components of a neuron
include 1) presyanptic neuron 2) synaptic cleft 3) postsynaptic membrane receptor
molecule
Neuron Communication - ANSWER 1) Electrical communication: Action potential
produced. We need a particular protein.
2) Chemical communication: Neurotransmitter binding to receptor.
How is electrochemical gradient maintained?
What is the significance of electrochemical graident produced by Na+/K+ pump? -
ANSWER Neurons have negative membrane potential. Outside the cell, Na+
concentration is higher. K+ concentration is also higher inside the cell. The
concentration gradient of ions such as Na+ and K+ make potential difference inside and
outside a cell. Due to this concentration gradient, ions want to move down their
concentration gradient. However, this electrochemical gradient is maintained by
Na+/K+ pump. Na+/K+ pump needs ATP to operate and maintain electrochemical
gradient.
Neurons use electrochemical gradient when Na+ channel opens. Na+ influx reduces
negative membrane potential and depolarizes the cell. This is the fundamental
mechanism for exciting neuron.
At rest, Na+ channel gate is closed. When AP is generated, voltage is sensed through
voltage sensor and because of the electrochemical gradient Na+ moves down their
concentration gradient and depolarize the cell.
Generation of action potential requires electrochemical gradient which is established by
Na+/K+ pump.
Why Na+/K+ pump is important? - ANSWER It is required to maintain electrochemical
gradient
What is the significance of electrochemical gradient? - ANSWER It is required to excite
, neurons and generate action potential or synaptic potentiation.
Ischemia-Lack of oxygen-Na+/K+ pump- Neurotransmitter transporter - ANSWER When
there is blockage of blood flow to the brain, there will be lack of o2 and glucose supply.
O2 and glucose are required to produce ATP. Na+/K+ pump requires ATP. Normally,
Na+/K+ pump brings K ion in the cell (from a high to a low concentration) and the pump
also takes out Na ions from inside the cell to the extracellular fluid (from high
concentration to low concentration). This concentration gradient is used by
neurotransmitter transporter as energy source.
Without o2 and glucose supply, Na+/K+ pump stops working. Thus, Na ion concentration
will accumulate within the cell and intracellular K ion concentration falls. Na+/K+ pump
cannot maintain concentration gradient and Neurotrasmitter transporter stop working.
Primary transporter, which pumps ions against concentration gradient, is ATP
dependent. Without o2 and glucose supply, primary transporters become dysfunctional
and stop working as well. Accumulation of Na+ ions inside the cell causes a
depolarization of the resting membrane potential. This depolarization causes release of
neurotransmitter such as glutamate. Glutamate concentration increases inside the cell.
Thus, we have more glutamate in synaptic cleft and this leads to excitotoxicity
(Excitatory postsynaptic response).
Which molecule are specific for norepinephrine neuron? - ANSWER norepinephrine
transporter is specific. But remember that vesicular monoamine transporter is not
specific to norepinephrine because other neurotransmitter such as Serotonin (5-HT)
and dopamine (DA).
(DBH): Dopamine-B-Hydroxylase - ANSWER dopaminergic neurons don't express DBH.
DBH is specific bio marker of NE.
Explain how TH (Tyrosine hydroxylase) can be either specific bio marker: - ANSWER TH
may be specific depending on how you use antibody against TH. TH can be a specific
bio marker under some conditions. NE is produced in brainstem. DA is produced in
midbrain. If we study midbrain area of the brain TH can be used as bio marker to identify
DA neurons. On the other hand, if we study brainstem, where NE is produced, TH can be
used to identify NE containing neurons.
If the aim of our study is to identify NE axon or DA axon in the cortex or hippocampus
and stain fibers in the cortex or hippocampus, we cannot distinguish two axons and
therefore, we cannot distinguish DA axons from NE axons based on TH. In this case, TH
COMPLETE SOLUTIONS
1.1 Neurotransmitter - ANSWER
Synapses: - ANSWER Neurons are connected but not physically. They have on and off
connection. They are not always connected. 3 important components of a neuron
include 1) presyanptic neuron 2) synaptic cleft 3) postsynaptic membrane receptor
molecule
Neuron Communication - ANSWER 1) Electrical communication: Action potential
produced. We need a particular protein.
2) Chemical communication: Neurotransmitter binding to receptor.
How is electrochemical gradient maintained?
What is the significance of electrochemical graident produced by Na+/K+ pump? -
ANSWER Neurons have negative membrane potential. Outside the cell, Na+
concentration is higher. K+ concentration is also higher inside the cell. The
concentration gradient of ions such as Na+ and K+ make potential difference inside and
outside a cell. Due to this concentration gradient, ions want to move down their
concentration gradient. However, this electrochemical gradient is maintained by
Na+/K+ pump. Na+/K+ pump needs ATP to operate and maintain electrochemical
gradient.
Neurons use electrochemical gradient when Na+ channel opens. Na+ influx reduces
negative membrane potential and depolarizes the cell. This is the fundamental
mechanism for exciting neuron.
At rest, Na+ channel gate is closed. When AP is generated, voltage is sensed through
voltage sensor and because of the electrochemical gradient Na+ moves down their
concentration gradient and depolarize the cell.
Generation of action potential requires electrochemical gradient which is established by
Na+/K+ pump.
Why Na+/K+ pump is important? - ANSWER It is required to maintain electrochemical
gradient
What is the significance of electrochemical gradient? - ANSWER It is required to excite
, neurons and generate action potential or synaptic potentiation.
Ischemia-Lack of oxygen-Na+/K+ pump- Neurotransmitter transporter - ANSWER When
there is blockage of blood flow to the brain, there will be lack of o2 and glucose supply.
O2 and glucose are required to produce ATP. Na+/K+ pump requires ATP. Normally,
Na+/K+ pump brings K ion in the cell (from a high to a low concentration) and the pump
also takes out Na ions from inside the cell to the extracellular fluid (from high
concentration to low concentration). This concentration gradient is used by
neurotransmitter transporter as energy source.
Without o2 and glucose supply, Na+/K+ pump stops working. Thus, Na ion concentration
will accumulate within the cell and intracellular K ion concentration falls. Na+/K+ pump
cannot maintain concentration gradient and Neurotrasmitter transporter stop working.
Primary transporter, which pumps ions against concentration gradient, is ATP
dependent. Without o2 and glucose supply, primary transporters become dysfunctional
and stop working as well. Accumulation of Na+ ions inside the cell causes a
depolarization of the resting membrane potential. This depolarization causes release of
neurotransmitter such as glutamate. Glutamate concentration increases inside the cell.
Thus, we have more glutamate in synaptic cleft and this leads to excitotoxicity
(Excitatory postsynaptic response).
Which molecule are specific for norepinephrine neuron? - ANSWER norepinephrine
transporter is specific. But remember that vesicular monoamine transporter is not
specific to norepinephrine because other neurotransmitter such as Serotonin (5-HT)
and dopamine (DA).
(DBH): Dopamine-B-Hydroxylase - ANSWER dopaminergic neurons don't express DBH.
DBH is specific bio marker of NE.
Explain how TH (Tyrosine hydroxylase) can be either specific bio marker: - ANSWER TH
may be specific depending on how you use antibody against TH. TH can be a specific
bio marker under some conditions. NE is produced in brainstem. DA is produced in
midbrain. If we study midbrain area of the brain TH can be used as bio marker to identify
DA neurons. On the other hand, if we study brainstem, where NE is produced, TH can be
used to identify NE containing neurons.
If the aim of our study is to identify NE axon or DA axon in the cortex or hippocampus
and stain fibers in the cortex or hippocampus, we cannot distinguish two axons and
therefore, we cannot distinguish DA axons from NE axons based on TH. In this case, TH
