Before I move my arm the brain sends signals - what causes the brain to send signals?

Before I move my arm the brain sends signals - what causes the brain to send signals?

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  1. Please tell me what causes the brain to send signals, how does the brain send signals?

  2. can you tell me what happens between the point when you make an intention to pick up a glass of water, and before the brains sends signals to the body which excites the muscles.

So what happens at the moment when you make the intention to pick up a glass of water but before the brains sends signals after you reach to pick up a glass of water.

  1. Action potential - I haven't read through the entire Wikipedia article so I can't vouch for its accuracy (not that my neurophysiology is good enough to critique it), but it's probably a good start.
  2. Broadly speaking: the brain contains different regions that are each responsible for fairly specific tasks. In the case of picking up a glass of water we can, at a high level, describe the mechanism behind thirst. Your blood contains electrolytes in water; you can consider the electrolytes as being like cordial (reduce the water and you have a higher concentration of cordial / electrolytes). A sensing mechanism (beyond the scope of this answer) will trigger action potentials between the relevant areas of the brain (motor, memory, etc.) to result in the final movement.

1) There is always a persistent sodium current which is slowly inactivating in comparison with the fast transient sodium current that occurs when a neuron is depolarized. The effects of this persistent sodium current brings the resting membrane potential near the threshold. Furthermore, neurons do indeed fire and reach depolarization state due to these fluctuations in membrane potential, but those action potentials will not always cause a depolarization of the post-synaptic neurons, since those neurons have inputs of convergence from inhibitory neurons that produce inhibitory post-synaptic potentials. There is no moment or situations where all of your neurons are quiet. Further information about persistent sodium current can be read in French et al.,1990., "A Voltage-dependent Persistent Sodium Current in Mammalian Hippocampal Neurons"., J. Gen. Physiol., Vol 95;1139-1157

2) The brain center which is thought to play an important role, not only in decision making, but also in behavioral control of the decision making dependent on the reward and outcome, is the prefrontal cortex. Except for its associative learning capabilities prefrontal cortex is thought to have neuronal connections with many part of other brain structures and it must first gather information and integrate the information before deciding what to do. In your question the reward is the glass of water, the emotional response you would get to drink that cold water would aid to the decision making, and the motoric movement is initiated by the subsequent firing of neurons when you see the glass of water and when you recall/remember the feeling to drink it. Prefrontal cortex is therefore activated and can thereafter send action potentials to motor cortex and then to your peripheral nervous system and muscles, so you can pick up the glass of water.

More about this here:

Brain and Nervous System

The brain controls what we think and feel, how we learn and remember, and the way we move and talk. But it also controls things we're less aware of — like the beating of our hearts and the digestion of our food.

Think of the brain as a central computer that controls all the body's functions. The rest of the nervous system is like a network that relays messages back and forth from the brain to different parts of the body. It does this via the spinal cord, which runs from the brain down through the back. It contains threadlike nerves that branch out to every organ and body part.

When a message comes into the brain from anywhere in the body, the brain tells the body how to react. For example, if you touch a hot stove, the nerves in your skin shoot a message of pain to your brain. The brain then sends a message back telling the muscles in your hand to pull away. Luckily, this neurological relay race happens in an instant.

What Are the Parts of the Nervous System?

The nervous system is made up of the central nervous system and the peripheral nervous system:

  • The brain and the spinal cord are the central nervous system.
  • The nerves that go through the whole body make up the peripheral nervous system.

The human brain is incredibly compact, weighing just 3 pounds. It has many folds and grooves, though. These give it the added surface area needed for storing the body's important information.

The spinal cord is a long bundle of nerve tissue about 18 inches long and 1/2-inch thick. It extends from the lower part of the brain down through spine. Along the way, nerves branch out to the entire body.

Both the brain and the spinal cord are protected by bone: the brain by the bones of the skull, and the spinal cord by a set of ring-shaped bones called vertebrae. They're both cushioned by layers of membranes called meninges and a special fluid called cerebrospinal fluid. This fluid helps protect the nerve tissue, keep it healthy, and remove waste products.

What Are the Parts of the Brain?

The brain is made up of three main sections: the forebrain, the midbrain, and the hindbrain.

The Forebrain

The forebrain is the largest and most complex part of the brain. It consists of the cerebrum — the area with all the folds and grooves typically seen in pictures of the brain — as well as some other structures under it.

The cerebrum contains the information that essentially makes us who we are: our intelligence, memory, personality, emotion, speech, and ability to feel and move. Specific areas of the cerebrum are in charge of processing these different types of information. These are called lobes, and there are four of them: the frontal, parietal, temporal, and occipital lobes.

The cerebrum has right and left halves, called hemispheres. They're connected in the middle by a band of nerve fibers (the corpus callosum) that lets them communicate. These halves may look like mirror images of each other, but many scientists believe they have different functions:

  • The left side is considered the logical, analytical, objective side.
  • The right side is thought to be more intuitive, creative, and subjective.

So when you're balancing your checkbook, you're using the left side. When you're listening to music, you're using the right side. It's believed that some people are more "right-brained" or "left-brained" while others are more "whole-brained," meaning they use both halves of their brain to the same degree.

The outer layer of the cerebrum is called the cortex (also known as "gray matter"). Information collected by the five senses comes into the brain to the cortex. This information is then directed to other parts of the nervous system for further processing. For example, when you touch the hot stove, not only does a message go out to move your hand but one also goes to another part of the brain to help you remember not to do that again.

In the inner part of the forebrain sits the thalamus, hypothalamus, and :

  • The thalamus carries messages from the sensory organs like the eyes, ears, nose, and fingers to the cortex.
  • The hypothalamus controls the pulse, thirst, appetite, sleep patterns, and other processes in our bodies that happen automatically.
  • The hypothalamus also controls the pituitary gland, which makes the hormones that control growth, metabolism, water and mineral balance, sexual maturity, and response to stress.

The Midbrain

The midbrain, underneath the middle of the forebrain, acts as a master coordinator for all the messages going in and out of the brain to the spinal cord.

The Hindbrain

The hindbrain sits underneath the back end of the cerebrum. It consists of the cerebellum, pons, and medulla. The cerebellum — also called the "little brain" because it looks like a small version of the cerebrum — is responsible for balance, movement, and coordination.

The pons and the medulla, along with the midbrain, are often called the brainstem. The brainstem takes in, sends out, and coordinates the brain's messages. It also controls many of the body's automatic functions, like breathing, heart rate, blood pressure, swallowing, digestion, and blinking.

How Does the Nervous System Work?

The basic workings of the nervous system depend a lot on tiny cells called neurons. The brain has billions of them, and they have many specialized jobs. For example, sensory neurons send information from the eyes, ears, nose, tongue, and skin to the brain. Motor neurons carry messages away from the brain to the rest of the body.

All neurons, however, relay information to each other through a complex electrochemical process, making connections that affect the way we think, learn, move, and behave.

Intelligence, learning, and memory. As we grow and learn, messages travel from one neuron to another over and over, creating connections, or pathways, in the brain. It's why driving takes so much concentration when someone first learns it, but later is second nature: The pathway became established.

In young children, the brain is highly adaptable. In fact, when one part of a young child's brain is injured, another part often can learn to take over some of the lost function. But as we age, the brain has to work harder to make new neural pathways, making it harder to master new tasks or change set behavior patterns. That's why many scientists believe it's important to keep challenging the brain to learn new things and make new connections — it helps keeps the brain active over the course of a lifetime.

Memory is another complex function of the brain. The things we've done, learned, and seen are first processed in the cortex. Then, if we sense that this information is important enough to remember permanently, it's passed inward to other regions of the brain (such as the hippocampus and amygdala) for long-term storage and retrieval. As these messages travel through the brain, they too create pathways that serve as the basis of memory.

Movement. Different parts of the cerebrum move different body parts. The left side of the brain controls the movements of the right side of the body, and the right side of the brain controls the movements of the left side of the body. When you press your car's accelerator with your right foot, for example, it's the left side of your brain that sends the message allowing you to do it.

Basic body functions. A part of the peripheral nervous system called the autonomic nervous system controls many of the body processes we almost never need to think about, like breathing, digestion, sweating, and shivering. The autonomic nervous system has two parts: the sympathetic nervous system and the parasympathetic nervous system.

The sympathetic nervous system prepares the body for sudden stress, like if you witness a robbery. When something frightening happens, the sympathetic nervous system makes the heart beat faster so that it sends blood quickly to the different body parts that might need it. It also causes the at the top of the kidneys to release adrenaline, a hormone that helps give extra power to the muscles for a quick getaway. This process is known as the body's "fight or flight" response.

The parasympathetic nervous system does the exact opposite: It prepares the body for rest. It also helps the digestive tract move along so our bodies can efficiently take in nutrients from the food we eat.

The Senses

Sight. Sight probably tells us more about the world than any other sense. Light entering the eye forms an upside-down image on the retina. The retina transforms the light into nerve signals for the brain. The brain then turns the image right-side up and tells us what we are seeing.

Hearing. Every sound we hear is the result of sound waves entering our ears and making our eardrums vibrate. These vibrations then move along the tiny bones of the middle ear and turned into nerve signals. The cortex processes these signals, telling us what we're hearing.

Taste. The tongue contains small groups of sensory cells called taste buds that react to chemicals in foods. Taste buds react to sweet, sour, salty, bitter, and savory. The taste buds send messages to the areas in the cortex responsible for processing taste.

Smell. Olfactory cells in the mucous membranes lining each nostril react to chemicals we breathe in and send messages along specific nerves to the brain.

Touch. The skin contains millions of sensory receptors that gather information related to touch, pressure, temperature, and pain and send it to the brain for processing and reaction.

Eyelid Twitches

Eyelid feel like it's giving you Morse code? That's called myokymia. These random twitches, which can feel faint or really bug you, happen on the upper or lower lid. Triggers range from stress and smoking to wind, bright light, too much caffeine, and lack of sleep. Though annoying, the twitches are harmless and usually go away quickly, but they can come back over the next few days.


You may not have any symptoms of upper limb spasticity until weeks, months, or even years after you have a stroke or brain injury. The condition can cause:

  • Stiff arm muscles
  • Twitches or movements that you can’t control
  • Trouble using or moving your arms
  • Tightness in the muscles in your elbows, wrists, or fingers
  • Arms that get stuck in uncomfortable positions, such as pressed against your side.
  • Rotated shoulders
  • Bent elbows or wrists
  • Hands clenched into fists
  • Difficulty or pain when you move or straighten your arm, elbows, wrists, or fingers

Without treatment, your muscles can seem frozen in these positions. Spasms and stiffness can make it very hard to do normal tasks like dressing yourself.

If you notice muscle tightness, spasms, or stiff limbs at any time after you’ve had a stroke or brain injury, you should tell your doctor right away.


Written and Directed by
Christopher Rawlence

Produced by
Emma Crichton-Miller

Narrated by
Rena Baskin

Associate Producer
Barbara Park

Edited by
Rod McClean

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Nancy Linde

Simon Whiteside

Chris Morphet

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Greg Bailey

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Online Editor
Richard Craddock

Dubbing Mixer
Damian Reynolds

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Special Thanks
Professor Laurence Weiskrantz, Oxford University
Dr. Lance Stone, San Diego Rehabilitation Institute
Professor John Marshall, Oxford University
Professor Haydn Ellis, University of Wales

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8 Signs You Might Have Nerve Damage, According to Doctors

There are billions of nerves in your body. Most of them, your peripheral nerves, are like branches of a tree that spread out all over and transmit messages back to the trunk&mdashyour brain and spinal cord. When everything goes smoothly, your brain gets the info it needs so that you can move your muscles, recognize pain, and keep your internal organs working properly.

But when peripheral nerves get damaged, it&rsquos another story: Walking could become challenging, you might experience unrelenting pain, or you could end up with a serious injury because you had no idea how hot that stove was.

An estimated 20 million Americans suffer from peripheral nerve damage, a.k.a. neuropathy, according to the National Institute of Neurological Disorders and Stroke. &ldquoDiabetes is the number one cause. Bad luck [meaning you inherited an anatomical defect] is number two. Repetitive motion and Lyme disease follow,&rdquo says Andrew Elkwood, M.D., a surgeon who specializes in nerve reconstruction at The Institute for Advanced Reconstruction in New York and New Jersey.

Other causes include sudden trauma (like a car accident), aging, vitamin deficiencies, heavy exposure to toxins (including alcohol, cancer medications, lead, mercury, and arsenic), and infections and autoimmune disorders like hepatitis C, diphtheria, HIV, Epstein-Barr, rheumatoid arthritis, and Guillain-Barré Syndrome. In some cases, there&rsquos no known cause.

The Brain and Nervous System

The basic element of the nervous system is the nerve cell, or neuron. In combination, neurons form nerves, fibers that transmit impulses throughout the body. A protective covering of myelin, a fatty substance, insulates parts of the fibers.

The action of nerve cells is both electrical and chemical. At the ends of each nerve cell there are specialized regions called synaptic terminals, which contain large numbers of tiny membranous sacs that hold neurotransmitter chemicals. These chemicals transmit nerve impulses from one nerve cell to another. After an electrical nerve impulse has traveled along a neuron, it reaches the terminal and stimulates the release of neurotransmitters from their sacs.

The neurotransmitters travel across the synapse (the junction between the neighboring neurons) and stimulate the production of an electrical charge, which carries the nerve impulse forward. This process is repeated over and over again until a muscle is moved or relaxed or a sensory impression is noted by the brain. These electrochemical events can be considered the "language" of the nervous system, by which information is transmitted from one part of the body to another.

­ There are two major divisions of the nervous system: the central nervous system and the peripheral nervous system. The central nervous system consists of the brain and the spinal cord. The brain lies within the skull and governs body functions by sending and receiving messages through the spinal cord. Protecting the brain and spinal cord are bones, layers of tissue, and cerebrospinal fluid.

Once messages leave the central nervous system, they are carried by the peripheral nervous system. The peripheral system includes the cranial nerves (nerves branching from the brain) and the spinal nerves (nerves branching from the spinal cord). These nerves convey sensory messages from receptor cells in the body to the central nervous system. They also transport motor impulses from the central system out to the body, where muscles and glands can respond to the impulses.

The autonomic nervous system, which is part of the peripheral nervous system, reg-ulates all activity that is involuntary but necessary for life, including activity of the internal organs and glands.

Working together, these divisions coordinate adjustment and reaction of the body to internal and external environmental conditions.

Now that we've covered the nervous system, let's discuss the brain, cerebrospinal fluid, and other related elements in the next section.

MRI machines are commonly used to investigate the brain. See how much you know about them in our MRI Quiz.

The Brain and Cerebrospinal Fluid

The brain is the body's control center. The brain sends messages to and receives stimulation from all parts of the body. More than 10 billion interlinked brain cells regulate the functioning of the body during sleep and wakefulness.

Different areas of the brain control different body functions. At the back of the skull is the cerebellum, which controls coordination of movements, balance, and posture. Deep inside the brain is the thalamus, which is the relay station for incoming impulses from the rest of the body, conveying sensations of pain, touch, and temperature to other parts of the brain.

Around the thalamus is the hypothalamus, which governs involuntary (automatic) body operations, such as heartbeat and blood circulation. The pituitary gland is attached to the hypothalamus by a thin stalk. Because the pituitary gland controls most of the hormones in the body, the hypothalamus is considered a major influence on primary drives governed by hormones, such as hunger, thirst, and sexual desire.

Covering the inner parts of the brain is the cerebral cortex, which consists of two cerebral hemispheres. Located in these hemispheres are the nerve centers that regulate thought and voluntary action. Connecting the left and right cerebral hemispheres is a broad band of fibers called the corpus callosum. Because nerve fibers from the two cerebral hemispheres cross one another in a structure called the medulla at the base of the brain before progressing down the spinal cord, each hemisphere generally controls functions in the opposite side of the body. For example, a region in the left hemisphere governs movement of the right arm.

The brain is the most complex organ in the body. Although research has identified many of its capabilities in memory, reasoning, and creative thought processes, many functions of the brain continue to remain a mystery.

Cerebrospinal fluid

Cerebrospinal fluid (CSF) is a clear, colorless fluid that surrounds the brain and spinal cord, cushioning them against injury.

The CSF is made of water containing small amounts of minerals and organic substances (especially protein). It is continually being produced by a specialized network of capillaries (tiny blood vessels) known as the choroid plexus, located in the ventricles (chambers) of the brain. About one pint is produced every 24 hours, and approximately five ounces is circulating at any one time.

From the two lateral ventricles, the CSF flows into the third and fourth ventricles of the brain. It then passes into the space between the innermost and second layers of the tissue covering the brain, bathing the entire outer surface of the brain in fluid before passing downward around the spinal cord. Eventually the fluid returns upward, is absorbed into special tissue between the linings of the brain, and passes into the blood vessels.

Samples of CSF (drawn from around the spinal cord with a needle inserted in the lower back -- a procedure known as a lumbar puncture) can be valuable in diagnosing disorders of the brain and spinal cord. The samples may indicate a hemorrhage or blood clot in the brain, various types of meningitis, a brain abscess, or a tumor of the brain or spinal cord.

©Publications International, Ltd.

This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Consumer Guide (R), Publications International, Ltd., the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.

Exercise for Stroke Patients with Paralysis

Passive exercises can be adapted from any active exercises by assisting your affected muscles through the movements.

Here’s another exercise for stroke patients with paralysis. It’s called “Punching Movement” and it targets the entire arm:

To perform this exercise, slide your arm across the table to ‘punch’ the water bottle, and then pull your arm back, using your other arm to assist with the movement. It can also become an active exercise by initiating the whole movement with your affected arm.

These exercises help restore movement after post stroke paralysis by reconnecting your mind to your muscles.

Mental practice involves imagining (or visualizing) yourself doing the movements you want to get better at. This helps activate neuroplasticity just as physical practice does.

Stroke patients who struggle with paralysis can benefit from combining mental practice with passive exercises since the mind and body are connected and both require healing.

For example, if you want to regain movement in your arm, spend time visualizing yourself doing the Punching Movement above. Then, after your visualization, practice the movement in real life.

Combining mental practice with physical practice leads to even better results.

Mind Messaging: Thoughts Transmitted by Brain-to-Brain Link

In an experiment that sounds more like science fiction than reality, two humans were able to send greetings to each other using only a digital connection linking their brains.

Using noninvasive means, researchers made brain recordings of a person in India thinking the words "hola" and "ciao," and then decoded and emailed the messages to France, where a machine converted the words into brain stimulation in another person, who perceived the signals as flashes of light. From the sequence of flashes, the French recipient was able to successfully interpret the greetings, according to a new study published today (Sept. 5) in the journal PLOS ONE. [Inside the Brain: A Photo Journey Through Time]

The researchers wanted to know if it is possible for two people to communicate by reading out the brain activity of one person and injecting that activity into a second person.

"Could we develop an experiment that would bypass the talking or typing part of [the] Internet and establish direct brain-to-brain communication between subjects located far away from each other, in India and France?" co-author Dr. Alvaro Pascual-Leone said in a statement. Pascual-Leone is a neurologist at Beth Israel Deaconess Medical Center in Boston, and a professor at Harvard Medical School, in Cambridge, Massachusetts.

To answer that question, Pascual-Leone and his colleagues at Starlab Barcelona, in Spain, and Axilum Robotics, in Strasbourg, France, turned to several widely used brain technologies.

Electroencephalogram, or EEG, recordings are taken by placing a cap of electrodes on a person's scalp, and recording the electrical activity of large regions of the brain's cortex. Previous studies have recorded EEG from a person thinking about an action, such as moving his or her arm, while a computer translates the signal into an output used to move a robotic exoskeleton or drive a wheelchair.

In other studies, a method called transcranial magnetic stimulation (TMS) has been used to stimulate parts of the brain by applying tiny electrical currents to the scalp. This causes the neurons in a certain area to fire. For example, TMS can make a person's muscles twitch or can produce flashes of light in his or her visual field.

In the current study, the researchers linked these two processes, EEG recording and TMS. Four healthy volunteers took part in the mind-messaging experiment. One person, (the word sender) was hooked up to an EEG-based brain-computer interface the other three people (the word recipients) received the messages in the form of TMS, and had to interpret the words based on the flashes they saw.

Using the system, the message sender, in India, transmitted the words "hola" (Spanish for "hello") and "Ciao" (Italian for "hello"/"goodbye") to the message recipients in France, located 5,000 miles (8,000 kilometers) away. All three recipients correctly translated the message, the researchers said.

In a second experiment, with volunteers in Spain and France, the total error rate for message transmission was 15 percent, and more of the error came from decoding the words than from encoding them, the researchers said.

The findings show it is possible to transmit a thought (albeit a very basic one) from one person to another without requiring the transmitter to speak or write, the researchers said.

"We believe these experiments represent an important first step in exploring the feasibility of complementing or bypassing traditional language-based or motor-based communication," Pascual-Leone said.

But the researchers stop short of calling it telepathy. The dictionary defines telepathy as communicating thoughts directly from one mind to another without using words or signals, but most scientists probably have something more sophisticated in mind than producing a light flash that means "hello."

Scientists previously demonstrated a human brain-to-brain connection that allowed one person to transmit a command to move another person's finger. And other experiments have demonstrated a kind of brain-to-brain connection between two rats and between two monkeys. Still, the technology remains in its early stages, most experts agree.

How Your Brain Works

Neurons come in many sizes. For example, a single sensory neuron from your fingertip has an axon that extends the length of your arm, while neurons within the brain may extend only a few millimeters.

They also have different shapes depending on their functions. Motor neurons that control muscle contractions have a cell body on one end, a long axon in the middle and dendrites on the other end. Sensory neurons have dendrites on both ends, connected by a long axon with a cell body in the middle. Interneurons, or associative neurons, carry information between motor and sensory neurons.

These fundamental members of the nervous system also vary with respect to their functions.

  • Sensory neurons carry signals from the outer parts of your body (periphery) into the central nervous system.
  • Motor neurons (motoneurons) carry signals from the central nervous system to the outer parts (muscles, skin, glands) of your body.
  • Interneurons connect various neurons within the brain and spinal cord.

The simplest type of neural pathway is a monosynaptic (single connection) reflex pathway, like the knee-jerk reflex. When the doctor taps the right spot on your knee with a rubber hammer, receptors send a signal into the spinal cord through a sensory neuron. The sensory neuron passes the message to a motor neuron that controls your leg muscles. Nerve impulses travel down the motor neuron and stimulate the appropriate leg muscle to contract. The response is a muscular jerk that happens quickly and does not involve your brain. Humans have lots of hardwired reflexes like this, but as tasks become more complex, the pathway circuitry gets more complicated and the brain gets involved.