Organelles

Introduction

When looking at the human body it is easy to break us down into structures. There is the skeletal structure that consists of bones, ligaments, tendons, cartilage, and muscles. With all these structures working together we are able to give our body the ability to move. Our Integument structure consists of our skin, hair, and nails. The main purpose of this structure is to protect our body from the outside world and the harmful toxins that we are exposed to on a daily basis. Our Nervous system is the structure that this textbook and neuroscience is focused on. It consists of the brain, spinal cord, and nerves. Its purpose is to send and receive impulses that are happening to keep your body in homeostasis.

Now there is a basic understanding of what makes up the body on a bigger scale it is time to look at what makes up those structures specifically on the cellular level. Cells are what make up the body and every part of your body consists of them. In the nervous system neurons are the primary cell that consist of and will be found when looking into those structures. In the human body there are over 80 billion neurons most of which

are located in the brain. ( Harvard Med). This chapter will focus on the organelles of the neuron and their functions.

Cell Membrane

The outermost layer of a cell is often called the cell membrane but could be referred to as the plasma membrane due to the consistency of the structure. In a deeper look of what makes up the cell membrane, phospholipids are what make up the membrane. Those phospholipids are packed closely together and consist of a round head and two tails. Different molecules make up the head then those who make up the tails. This is due to the portion of the phospholipid bilayer that is the head is hydrophilic and the area of the tails are hydrophobic this will allow the cell to maintain its shape and determine what will enter and exit the cell. In the membrane there are Ion channels whose purpose is to allow certain ions such as potassium and calcium to pass through and either enter or exit the cell. Proteins surround these ions to allow them to pass through with more ease.

Lysosome

The function of this organelle is to keep the cell clean. Lysosome in our cells are inherently with a pH of about 5 which if exposed to the rest of the organelles they would be broken down very quickly. In the lysosome there are enzymes that provide the ability to break down molecules and these are referred to as acid hydrolase.  The acid hydrolase breakdown primarily by using water molecules to breakdown a molecule. An example of this would be the cell is your dirty car and you could add soap but you need something to breakdown the dirt and get rid of it so you use a power washer with water.  To maintain an acidic environment the lysosome uses a ATP powered pump to push hydrogen into the cell. This pump is often referred to as the proton pump.

Mitochondria

One of the most well known organelles is the mitochondria. Often referred to as the powerhouse of the cell it is important to understand why that is the case.

Glucose is in the cytoplasm of a cell and through glycolysis ATP is produced and the final product is pyruvate.

Pyruvate is a three sugar that when it is taken in by a mitochondria and combined with oxygen it is able to be broken down and form two to three dozen ATP molecules per glucose molecule. This efficiency is why the mitochondria is the powerhouse of the cell.

Nucleus

The nucleus is the organelle that has one of the most important jobs.  DNA replication

takes place and through this process the cell is able to be divided into new healthy cells. More of this organelle will be covered in the next chapter, ” The Nucleus of Neurons“.

Rough Endoplasmic Reticulum

The Rough Endoplasmic Reticulum is surrounded by Ribosomes

and have the purpose of producing proteins that are found in vesicles or the outside of the cell. 

Neuron specific organelles

Dendrites

In a neuron there are branch like organelles whose primary purpose is to receive information from other neurons. These are referred to as  dendrites. The shape of a dendrite is dependent upon the area they are located and the type of neuron they are apart of.

Soma

Can also be referred to as the “Cell body” and depending on the location in the body it can process information.

Transport Vesicle

Its main purpose is to transport proteins synthesized in the soma.

Axon

The Axon is used to send information over a large distance. Action potentials are sent and depending on if they are anterograde or retrograde will determine their location.

Myelin Sheath

The purpose of the myelin sheath is to speed up the action potentials sent from the soma. Myelin is mostly consisted of lipid (fat).

Synaptic Vesicle

In the end of a neuron there is the presynaptic cell. In this area of the cell there are membrane surrounded circular neurotransmitters.  These are what are called synaptic vesicles. there is an important function of sending quick impulses to other neurons. they are consisted of proteins and lipids.