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Visual Guide to Your Nervous System
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Your Command Central
Made up of billions of
nerve cells called neurons, your nervous system is what lets you do everything
from breathe to walk to dream. It has two main parts: the central nervous
system, which includes the brain and spinal cord, and the peripheral nervous system
(all the other nerves in your body).
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Who's Running the Show?
Your nervous system
works both on autopilot and with you in control. A voluntary action is
something that takes conscious thought, like when you walk or clap your hands.
That uses the somatic nerves. Involuntary actions are things like your
heartbeat that happen whether or not you're thinking or doing anything about
it. That's the autonomic system.
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Sympathetic Nervous System
This part of your
autonomic system is in charge of your body's "fight or flight"
response. When you come across a threat, your sympathetic nervous system kicks
into gear, quickly changing body processes like your breathing and heart rate
so that you have extra energy and are ready to face the danger or run away.
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Parasympathetic Nervous System
The other part of your
autonomic system has the opposite effect. It's the brake pedal to the
sympathetic nervous system's gas pedal. It takes over with the "rest and
digest" response to bring you back to normal after the danger has passed.
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Don't Drain Your Brain
Stress that doesn't let
up leaves your sympathetic nervous system on alert. And over time, that can
lead to you losing your mental sharpness. You may take longer to react to
things and make more errors. (High levels of stress also affect your physical
health, including weakening your immune system and raising your chance of heart
disease.)
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Neurons
They're how your brain
and body "talk" to each other. These nerve cells use special parts to
communicate. The axon releases a chemical called a neurotransmitter that's
picked up by the dendrite of another neuron, where it's turned into an electrical
signal. Sensory neurons respond to things like sound, smell, and touch and
deliver the info to your brain. Motor neurons bring messages from your brain to
your muscles.
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Glial Cells
These cells get their
name from the Greek word for "glue." They surround, support, and
cushion the neurons in your brain and spinal cord. But that's not all they do.
Researchers are only beginning to understand the role glial cells play in how
the brain works, neurological diseases, and more.
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Brain
This incredibly complex
and vital organ is made up of 100 billion or so neurons. It controls your
movement, speech, heartbeat, and breathing. And it's the root of all your
thoughts and feelings. Around the size of two clenched fists and weighing in at
about 3 pounds, it's protected by your skull and the fluid it floats in.
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Cerebrum
The largest part of the
brain is divided into two halves called hemispheres. The left one, which
controls the right side of your body, handles speech, logic, math calculations,
and pulling facts from your memory, too. The right hemisphere, which controls your
left side, is also in charge of music, recognizing faces, and understanding
your body's position relative to what's around you, what's known as spatial
awareness.
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Cortex
The outermost layer of
the cerebrum has many wrinkles and folds. This is where you'll find your
brain's "gray matter," which processes information.
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Basal Ganglia
You'll find this network
of circuits deep inside the hemispheres of your brain. The basal ganglia
coordinate movement, behavior, and emotions. They make things that happen in
sequence possible, like walking and dancing, learning patterns, forming habits,
and stopping activities then starting new ones. Damaged basal ganglia cause
Parkinson's and Huntington's diseases.
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Cerebellum
Your cerebellum oversees
complicated movements, posture, and balance. It coordinates different muscle
groups and fine-tunes movements with practice, like hitting a golf ball or
hockey puck. Because of it, walking can be a smooth, continuous motion. It's also
important for language and speech.
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Amygdala
This almond-shaped area
is responsible for your emotions and some behavior. It's believed your amygdala
helps you do everything from form memories to pick up on social cues. It sounds
the alarm that triggers your body’s "fight or flight" response to
danger.
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Hippocampus
You have one on each
side near the center of your brain. They help you learn and remember important
who, what, and where details -- like your boss's name and the location of your
house -- and turn short-term memories into long-term ones. It's one of the
first areas damaged by Alzheimer's disease.
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Thalamus
The top part of your
brain stem is kind of like a post office for your senses. It gets signals
related to sight, smell, hearing, taste, and touch and passes the information
to other parts of your brain.
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Pons
This key relay station
is the middle part of your brain stem and a bridge between the cerebrum
and the cerebellum. It's the origin of nerves that control facial expressions,
eye movement, chewing and swallowing, and bladder control. It plays a role in
breathing. And it's probably where your dreams happen.
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Medulla Oblongata
Your medulla handles the
autonomic things you don't think about, like your breathing, blood pressure,
and heart rate. It's found at the bottom of the brain stem, where it helps
transfer signals between the brain and spinal cord, too.
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Spinal Cord
It's probably smaller
than you think: about 17 inches long (the diagonal of a large laptop screen)
and less than 1/2-inch wide, thinner than an adult's finger. It runs from the
base of your brain down your back, surrounded by bones called vertebrae.
Bundles of nerve fibers, protected by tissue and fluid, carry information back
and forth from your brain to your body.
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Peripheral Nerves
If the central nervous
system is the main office, the peripheral nervous system is the workers out in
the field. There are 12 cranial nerves that connect to the brain, including
ones that let you smell, see, smile, and swallow. Another 31 pairs of nerve
roots (one sensory, one motor) branch out from your spinal cord between the
vertebrae. The sciatic nerve is the largest single nerve. It goes from your
pelvis down the back of your thigh.
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Enteric Nervous System
When someone talks about
your "second brain," this is what they're referring to. It's a
separate network of more than 100 million nerve cells that line your
gastrointestinal tract and control the process of digestion, like moving stuff
into your stomach (and out at the end), breaking down food, and absorbing
nutrients.
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Diseases and Conditions
Infections, injuries,
poisons, even high blood sugar can harm parts of your nervous system. Stroke,
meningitis, polio, migraine, carpal tunnel syndrome, epilepsy, MS, and shingles
are all nervous system disorders. Doctors who treat them are called
neurologists.
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Healthy Habits
Taking care of yourself
in general will also help your nervous system. Get plenty of sleep. Don't
smoke. Find ways to relax. Exercise has an anti-aging effect on the brain and
can protect against memory loss. Eat well, with lots of veggies, fruits, and omega-3s;
cut back on carbs, and avoid sugary foods and saturated and trans fats. Spend
time with friends and learn new skills to help your brain work better.
UP NEXT
This tool does not provide medical advice.
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