Describe the structure of a typical neuron (multipolar) and give the function of

Question

Describe the structure of a typical neuron (multipolar) and give the function of each of its parts : Cell Body (Soma) Dendrites- Axon - Axon Hillock - Myelin Sheath - Nodes of Ranvier - Synapse - Compare and contrast an absolute refractory period with a relative refractory period: What is the difference between an Ipsilateral and Contralateral reflex? Describe what is happening during the following events in an action potential: Resting Potential - Depolarization - Repolarization - Hyperpolarization - Name the neuro transmitters of the peripheral nervous system and describe Cholinergic/Adrenergic receptors: Describe cocaine's mechanism of action:

Explanation / Answer

1. Soma: General body of a neuron. It contains cell nucleus and dendrites.

Dendrites: The branched projections of the soma which transmit electric stimulation

Axon: It is a nerve fiber which conducts the electrical impulses away from the cell body. It is covered by myelin.

Axon hillock: the part of the soma which connects to the axon

Myelin sheath: A substance which surrounds the axon. it is an electric insulating substance.

Nodes of Ranvier: The gaps in the myelin sheath on the axon is called a node of Ranvier.

Synapse: a synapse is a junctions between two nerve cells where the electric impulse is transmitted.

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2. The absolute refractory period refers to the period where both depolarization and repolarization occur. In this period most of the sodium channels are in an inactive state.

The relative refractory period refers only to the period when hyperpolarization occurs. In this period potassium channels remain open in response to repolarization.

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3. When a response occurs on the same side of the body which is stimulated, it is called ipsilateral reflex. When the response is on the opposite side of the body as the stimulus, it is called contralateral reflex.

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4. Resting potential: The resting state when the membrane is not transmitting any impulses

Depolarization: The charge in the cell changes from an negative charge to a positive charge. Voltage gated ion channels open to allow sodium ions into the cell.

Repolarization: The voltage gated sodium channels close and the potassium channels open. The potassium ions then move out of the cell to bring the charge of the cell back to resting state.

Hyperpolarization: This happens when the outflow of potassium ions is much more than necessary. This causes the charge in the cell to become more negative than the resting potential.

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