Must have detailed content, clarity, composition and formatting. this is a neurb

Question

Must have detailed content, clarity, composition and formatting. this is a neurbiology course upper level biology course for undergrad.

1. Why do neurons and other cells have a negative resting membrane potential? Draw a recording of a typical action potential. Label the axes and the key features of the action potential. Identify the underlying events for each of the following: rising phase overshoot peak falling phase undershoot

2. What is the purpose of myelin? Explain how myelin speeds the conduction of the action potential?

3. Diagram a neuron and label its components. In what ways are neurons specialized for communication? Do these specializations distinguish neurons from other types of cells?

Explanation / Answer

The resting potential is negative due to the accumulation of more sodium ions outside the cell than potassium ions inside the cell. This is due to.

a) Neurons have many more potassium leakage channels than sodium leakage channels. Therefore Potassium ions diffuse out of the cell at a much faster rate than sodium ions diffuse into the cell.

b) Sodium-potassium pumps move two potassium ions inside the cell and three sodium ions pumped out. This maintain the negatively-charged membrane inside the cell and maintain the resting potential.

i.)Depolarization (rising phase overshoot peak): A stimulus starts the depolarization of the membrane. Depolarization, also referred to as the "rising phase" is caused when positively charged sodium ions rush into a nerve cell. As these positive ions rush in, the membrane of the stimulated cell reverses its polarity so that the outside of the membrane is negative relative to the inside.

ii) Repolarization ( falling phase undershoot ); Once the electric gradient has reached the threshold of excitement, the "downswing" of repolarization begins. The channels that let the positive sodium ion channels through close up, while channels that allow positive potassium ions open, resulting in the release of positively charged potassium ions from the neuron. This expulsion acts to restore the localized negative membrane potential of the cell, bringing it back to its normal voltage.

2. The main purpose of a myelin sheath is to increase the speed of conduction of impulses.Myelin protect and insulate these axons and enhance their transmission of electrical impulses.

Myelin acts as an electrical insulator for the neurone and prevents the movement of ions into or out of the neurone. therefore signals in myelinated fibers, i or propagate by saltatory conduction from one node of ranvior (gap between myelin sheath) to other increasing the speed of conduction. This is called saltatory conduction.

3. Neurons have denrites which receives a signal and axons which send impuses to other neurons. Thus structure of neurons are specialised to receive and send signals from different parts of the body,

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