NeuroExplorer

The cell theory is a universally accepted principle of biology that sets the relationships between cell and livings things. The cell theory is composed of three basic principles that were established by three 19th-century German scientists – Matthias Schleiden, Theodor Schwann and Rudolph Virchow. The first principle of the cell theory is that all life is made of cells . All living organisms in the six kingdoms of life are made of cells. However, not all cells are alike. There are two categories of cells - prokaryotic and eukaryotic. Prokaryotic cells are simpler and lack a membrane-bound nucleus. In contrast, eukaryotes are larger and highly complex with a defined nucleus and several membrane-bound organelles. The second principle of the cell theory is that the cell is the basic unit of life . Some simpler organisms may by unicellular, meaning they only have one cell. However, these unicellular organisms still have remarkably complex structures – inside each cell are atoms

Neurons can transmit signals at astonishing speeds - some signals can travel as fast at 268 miles per hour! How are neurons capable of such speeds? Well, their axons, which transmit signals to other neurons, have a special covering known as the myelin sheath. Myelin, a lipid-rich substance, insulates the axon and increases the speed of signal transmission. As an action potential travels down the axon, some ions may cross the membrane and exit the cell. However, the presence of myelin prevents this escape. In the peripheral nervous system, myelin is found in the membranes of Schwann cells, a type of glial cell. Each Schwann cell forms one unit of myelin. In the central nervous system, oligodendrocytes, another type of glial cell, tightly wrap around the axon to form several layers of insulation. Each process of an oligodendrocyte can form one segment of myelin for several different cells. Myelin is not the only special feature of neurons that accelerates signal speeds. There are

You may be familiar with the branched out structure of the neuron - multiple, short dendrites and one long axon. But did you know that there are actually other neuron structures that differ in the number of processes? Processes are the project parts of an organic structure - in the case of the neuron, they are the dendrites and the axon. You are probably most familiar with the multipolar neuron , which has at least three processes extending from the soma - one axon and two or more dendrites. Multipolar neurons are the most abundant type of neurons and are usually motor neurons and interneurons. But did you know there are two other structures? Take a look at the picture below: The bipolar neurons  have two processes - one axon and one dendrite - that extend from opposite sides of the cell body. Bipolar neurons are rare and are only found in sensory organs - for example, the retina of the eye. Unipolar neurons  are sensory neurons that have one process extending from the soma. In

Neurons are highly specialized cells that respond to stimuli and transmit electrical and chemical signals to parts of the body. Their structure makes their function tremendously efficient. Take a look at the image below: Notice the branched out processes (projections). These processes, known as dendrites, receive electrical signals and transmit these signals down to the soma (cell body) and then the axon. Remember, electrical signals always travel from the dendrite end to the axon end . The soma contains organelles common to any other cell: the DNA-containing nucleus, cytoplasm, mitochondria, ribosomes, the endoplasmic reticulum, the Golgi Apparatus - just to name a few. Once the electrical signal is carried across the soma, it travels along the axon, a long fiber-like extension that transmits these impulses away from the cell body to other cells. The axon is covered in the myelin sheath, a special insulating envelope that increases the speed of signal transmissio

Did you know that there are actually three types of neurons - each corresponding to the three major functions of the nervous system? These major functions are sensory input, integration and motor output. What's the difference? The sensory input is carried out by sensory (afferent) neurons that detect a stimuli. Signals are then sent to the brain and spinal cord to be processed in the second stage known as integration. Integration is carried out by interneurons in the brain and spinal cord that interpret the messages from sensory neurons. After processing the input, interneurons relay the message to body parts, where a response is produced at the effector organ in the third and final stage known as the motor output. The motor output is carried out by motor (efferent) neurons that receive messages from interneurons and then activate certain body parts to respond to the stimuli. Afferent? Efferent? They sound so similar! A trick to remember the difference between the two is to loo

When you hear the term "brain cells", what first comes to mind? Neurons, of course! Well, turns out there are so many other types of cells in your nervous system that have critical roles. Which ones, you ask? NEUROGLIA! The little heroes of the nervous system! Of course, neurons play a crucial role in the nervous system. But the functions carried out by the nervous system could not  be achieved without neuroglia. The glial cells provide support, nutrition insulation and help with signal transmission. In the central nervous system, the four main types of glial cells are the astrocytes, microglia, ependymal cells and oligodendrocytes. Astrocytes  come from Greek for "star cell", given the name for its star-shaped appearance underneath a microscope. Astrocytes form the cellular glial scars , control the release of ions, form the blood-brain barrier and clear out neurotransmitters from the synapses. Microglia  ("small glue") are specialized macrophages

The Nervous System Central Nervous System (CNS) consists of the brain and spinal cord the main control center Peripheral Nervous System (PNS) consists of the nerves branching off from the brain and spinal cord allows the CNS to communicate with the rest of the body consists of the sensory division and the motor division Peripheral Nervous System Sensory Division also known as the afferent division picks up sensory stimuli transmits signals from the body to the brain Motor Division also known as the efferent division sends directions from the brain to effector organs and glands transmits signals from the brain to the body consists of the somatic and autonomic nervous system Motor Division Somatic Nervous System voluntary ⇒ skeletal muscle movement Autonomic Nervous System involuntary ⇒ internal organs example: heartbeat, lungs, stomach consists of the sympathetic and parasympathetic nervous system Autonomic Nervous System Sympathe

The human brain possesses amazing capabilities that make it the most amazing and powerful organ in the body. That is, when it's functioning properly. When it's not the effects can be devastating. Take a look at the diagram below (1) : The brain on the left side is normal, and the brain on the right has severe Alzheimer's (a neurodegenerative disease). Notice how the brain shrinks . The small seahorse-shaped hippocampus in the medial temporal lobe is crippled, thus losing the ability to store memories. But... how does this all happen? It all starts in the wrinkled cerebral cortex, where action potentials travel across the synapses of the billions of neurons in the brain. Chemical neurotransmitters jump across these synapses and carry the signals to other neurons (pictured below)(2) . The brain is functioning properly. However, in patients with Alzheimer's disease, proteins known as Beta-Amyloid begin to clump together and important Tau proteins begin to fall ap

Welcome to my blog! My goal is to share my excitement for the brain with you! I hope that, within time, you share this same fascination with me and realize that the human nervous system is a complex and fascinating structure whose capabilities are far-reaching. We still have only uncovered very little of the brain's secrets! I hope that, as we progress through this blog, we will  uncover more secrets about our fascinating nervous system that makes us who we are. Enjoy!

Hello! This is the beginning of my journey in neuroscience. Buckle up and enjoy!