The Nervous System

What is it?

The nervous system is the body’s command center and is made up of the brain, spinal cord and nerves. It functions through electrical signals sent between the brain and other parts of the body. It is the decision maker for how your body responds to situations, and tracks what is happening in your surroundings

Astrocytes are a type of glial cell in the brain that play several roles in maintaining neuron health and function. They provide nutrients to neurons, regulate the balance of cellular ions such as sodium chloride, potassium, and phosphate, and contribute to the physical structure of the brain. Astrocytes are also involved in the secretion or absorption of neurotransmitters and the maintenance of the blood-brain barrier.

Oligodendrocytes are a type of neuroglia that support and insulate axons in the central nervous system (CNS) . They produce myelin, an insulating sheath for nerve fibers, and contribute to axonal maintenance by providing sustenance to neurons. By insulating the nerves in the brain and spinal cord, oligodendrocytes accelerate neural signaling.

 How Does it function?

The main function is to send messages from multiple areas of the body to the brain and back to the body correct body part. These electrical signals travel in the brain, skin, organs, glands and muscles.

These messages help to move limbs and feel sensations. The eyes, ears tongue, nose and nerves examine information about your environment then carries that data to and  the brain

These messages are made of electrical signals from various different neurons such as:

 Motor Neurons- Take signals from your brain and spinal cord to your muscles. Motor Neurons are responsible for helping you move, assist with breathing, swallowing and speaking. These facilitate motor function

Sensory Neurons – Take information from your senses to the brain. They detect light, sound, odor, taste, pressure, and heat and send messages about those things to the brain

Interneurons – Communicate between motor and sensory neurons. Interneurons regulate your movement in response to sensory information and play a role in how you, think and remember

The most basic unit of the nervous system is a nerve cell or neuron. A neuron has a cell body include the nucleus, special extensions called Axons and dendrites. Bundles of Axons make up the nerves. Axons and Dendrites are the mechanisms that allow neurons to communicate throughout the body.

When a neuron communicates with another neuron, it sends an electrical signal along its axon. At the axon's end, this electrical signal transforms into a chemical signal. The axon then releases this chemical signal using neurotransmitters into the synapse —the gap between the axon's end and the dendrite tip of another neuron. The neurotransmitters carry the signal across the synapse to the neighboring dendrite, which converts the chemical signal back into an electrical signal. This electrical signal then travels through the neuron and undergoes the same conversion processes as it moves to other neurons.

The nervous system also comprises non-neuron cells known as glia (pronounced GLEE-uh). Glia play several crucial roles in maintaining the proper functioning of the nervous system. For instance, glia:

• Support and stabilize neurons

• Protect neurons

• Form myelin insulation to facilitate nerve impulse transmission

• Repair neurons and restore their function

• Remove dead neurons

• Regulate neurotransmitters

Anatomy of the nervous System

Parts of the nervous system

The 2 MAIN parts of the nervous system

-        Central Nervous system houses the brain and spinal cord. The brain reads signals from your nerves to regulate how you think, move and feel.

-        Peripheral Nervous system houses the network of nerves. Nerves branch out from the spinal cord to your organs, arms, legs, fingers and toes.

There are then 2 parts to the Peripheral Nervous system

-        Somatic Nervous system which guides your voluntary movements

-        Autonomic nervous system which guides the involuntary movements

o   Parasympathetic Nervous system – controls the body’s response during times of rest. Uses 4 of the 12 cranial nerves, these nerves are connected directly to the brain, 3 of the 4 cranial nerves involved only interact with your senses and glands connected to your eyes, nose and mouth. The 4th is your vagus nerve (see the vagus nerve page for more information). It does utilize some of the 31 nerves that connects directly to your lower spine, these send signals to your bladder and bowels

o   Sympathetic Nervous system – controls the body’s function during times of stress or the fight or flight response. The SNS uses neurotransmitters to communicate such as norepinephrine, epinephrine and acetylcholine.

The important thing to grasp with the PSNS and the SNS is that they work together while maintaining opposite roles. While the Sympathetic NS carries the signals that puts the body on alert, your Parasympathetic NS carries the signals that relax those systems.

You can imagine the nervous system like a tree. The CNS is the trunk of the tree while the PNS is the branches that spread out from the tree. The SNS and PSNS fall within the tree.

Ganglia are clusters of nerve cell bodies located outside the central nervous system (CNS). They act as relay stations, processing and transmitting nerve signals between different parts of the body and the CNS. Ganglia play a crucial role in the peripheral nervous system, helping to coordinate and regulate various bodily functions.