Term
| Describe the structure of a sensory neuron. |
|
Definition
| Two axons, input and output section. Conducts inputs a long distance, hence the extra axon. Soma in the middle of the axons. Dendrites connect to one soma, synpases to the other. |
|
|
Term
| Normally the interior of the soma of a neuron is normalized to what voltage? |
|
Definition
|
|
Term
| What happens to the amplitude of the signal of a neuron as it progresses? |
|
Definition
|
|
Term
| What are typical internal/external resting solution levels of a cell? (e.g. high or low sodium) |
|
Definition
Intracellular: Low Sodium, High Potassium, Low Chloride,High concentratrion of neg. charged proteins Extracellular: High Sodium, Low Potassium, High Chloride |
|
|
Term
| What two forces can drive ions through channels/pores? |
|
Definition
| Concentration gradient, and ionic potential gradient |
|
|
Term
| What is the formula for the Nernst Equation? |
|
Definition
Ex = 61.6 * log10 (Xo/Xi) Where Ex is the potential required in mV, and Xo and Xi are extracellular concentation and intracellular concentration respectively. |
|
|
Term
| Why is the Nernst equation impractical? |
|
Definition
| Because it is unrealistic to isolate one ion from another. There will (almost) always be multiple ions affecting each other. |
|
|
Term
Define the elements in the diagram: [image] |
|
Definition
- GNa is a sodium ion channel, similarly for others
- VNa is the concentraction gradient, similarly for others
- C is the membrane itself (can hold a charge)
- Resistors on the inside and outside are the fluids inside and outside
|
|
|
Term
| Why doesn't chloride and potassium, which can freely transfer across the membrane via channels, diffuse? |
|
Definition
| Electric potential generated by other channels and the sodium/potassium exchanger |
|
|
Term
| What three ways can an electrode be used to measure an action potential? |
|
Definition
- Extracellular (Far Field) : Measures sodium concentration
- Extracelluar : Records local activity of sodium entering and potassium leaving the cell.
- Intracellular : Records electrically from the inside of the cell.
|
|
|
Term
| How does resistance/capacitance of the membrane change the time constant? |
|
Definition
| Low resistance/capacitance leads to a fast time constant, while high leads to a slow time constant. |
|
|
Term
| What is the formula fo the length constant of a membrane? |
|
Definition
L = sqrt[(RM / (Ra + Rx))] Where L is the length constant, RM is the leakage resistance of the membrane, Ra is the conducting cytoplasm axial resistance, and Rx is the extracellular fluid resistance. |
|
|
Term
| What causes sodium channels to close after an action potential? |
|
Definition
| The influx of sodium causes a large positive charge in the neuron which causes the inactivation gate to close. |
|
|
Term
| After an action potential how is the neuron's voltage potential returned to its resting state? |
|
Definition
| Efflux of potassium while sodium diffuses away. Actually overshoots resting potential and becomes more negative while potassium reaches its Nernst potential, then levels out thought sodium/potassium pump. |
|
|
Term
| How does a neuron create a signal strong enough to depolarize cells and create an action potential? |
|
Definition
| By summing signals from multiple dendrites. |
|
|
Term
| Describe the process of an action potential in terms of channels. |
|
Definition
| Neuron sums signals of its dendrites, the resulting signal is strong enough to open the activation gate of the sodium channel of a cell. Sodium rushes in, depolarizing the cell. Rapid positive charge closes the inactivation gate of the sodium channel, positive ions diffuse downstream to next channel (causing the same effect). Potassium leaves the cell causing repolarization and overshoot. Sodium/Potassium Exchanger corrects overshoot and returns cell to resting potential. |
|
|
Term
| Why does potassium leave the cell during repolarization? |
|
Definition
| Its flowing down its concentration gradient. It didn't leave before because the inside of the cell was more negative than the outside, which overcame the concentration gradient's drive to push potassium out. Once the action potential hit, the cell was no longer negative on the inside, and potassium flowed out. |
|
|
Term
| What causes the axon terminals to release its neurotransmitter vesicles? |
|
Definition
| Calcium enterring the cell. |
|
|
Term
| What determines if a neurotransmitter has an excitatory, inhibitory, or modulatory effect on a cell? |
|
Definition
|
|
Term
| What are the unique characteristics of Blood Brain Barrier Endothelial Cells? |
|
Definition
| Do not have gap junctions, instead form tight junctions - gives them much higher electrical resistance and lower permeability. Contain more mitochondria than other cells. Higher expression of some enzymes. |
|
|
Term
| What is the sole source of energy for neurons? |
|
Definition
|
|
Term
| What is the primary function of circumventricular organs (CVOs)? |
|
Definition
| Communicates between the brain and the peripheral organs |
|
|
Term
| How does radiation therapy related to CNS disease? |
|
Definition
| Patients who have a form of radiation therapy are much more likely to develop CNS diseases. |
|
|
Term
| What is the most common treatment for braint tumors? |
|
Definition
|
|
Term
| What effect can lead have on the CNS? |
|
Definition
- Penetrates blood brain barrier
- Induces physical damage primarily in the prefrontal cortex, cerebellum, and hippocampus.
- Blocks neurotransmitter development
- Inhibits myelin formation
- Decreases cognative function
- Associated with aggressiveness, delinquency, anti-social tendencies, and attention disorders
- Risk factor for Alzheimer's and senile dementia
- Increases oxidative stress and inflamation in the brain
|
|
|
Term
| How is aging related to CNS disease? |
|
Definition
| Decreases blood vessel density in the brain, and increases oxidative stress and inflammation in the brain. |
|
|
