From eating, breathing to thinking, analyzing various scenarios and feeling, everything is controlled by your brain. This jelly-like mass of tissue weighs around 3 pounds and is very susceptible to injury. Thus it is protected by the bones of vertebrae and cranium and then by cerebrospinal fluid. As human evolved over generations, the mass of the brain increased tremendously but our skull didn't grow resulting in the wrinkles that one can observe in the human brain.
Deep within the brain, lie structure that acts as the gatekeeper between spinal cord and cerebrum. This region is responsible for feeling various emotions such as fear, safe etc. Like the lobes in the cerebrum, they also come in a pair with one on each side of the brain. The hypothalamus, about size of a pearl, is the emotional center of the brain and is responsible waking you up in the morning and getting your adrenalin
The other important part of the inner brain is the hippocampus, which is used to send information to appropriate part of the cerebrum for long term storage and retrieving them whenever needed.
How do the brain and the rest of body communicate:
Before we understand, how the communication takes place between various body parts and brain, let me allude to central nervous system (CNS) and peripheral nervous system (PNS). CNS comprises the brain and the spinal cord whereas PNS comprises all the nerves that come out of CNS. Now the prime function of CNS is to integrate various sensory input coming from PNS and then responding to it both consciously and unconsciously.
|Image courtesy: publi.cz|
Also, all the communication takes place by relaying signals to and from the neurons. These neurons comprise of 3 parts namely cell body, dendrites and axon. Dendrites are called listeners which get the message from the neighboring neuron and pass it towards the axon. Axons are called talkers which in turn pass the coming message to the neighboring neuron. The place where the exchange of message occurs is called synapse. These messages are passed via the release of chemicals called neurotransmitters, these neurotransmitters pass the synapse and attaches to receptors thereby creating a potential difference and hence the new neuron passes these signal further.
Now any communication can be broken into simple blocks. Input block will be the sensory input collected by the receptors (sensory neuron) in the PNS and then it is forwarded to the spinal cord and then finally to the brain. Now, upon reaching CNS , these information are then processed by the appropriate parts of the brain. Finally, the output is motor output where there is some movement in one or more parts of your muscles, these responses are carried to the muscles through motor neurons.
|Image Courtesy: urbanchildinstitute.org|
Now I will try to illustrate all these points with an example. Suppose you are walking in the garden on bare feet. Suddenly a thorn pierces your skin and you feel a lot of pain. The mechanoreceptors in the skin of your leg are activated and an electric signal is passed via these neurons to CNS. Once it reaches the spinal cord, the spinal cord sends a response via the motor neuron which causes you to lift your leg at once. At the same time, this signal is passed to various parts of your brain like the hypothalamus which makes you emotional and you start to think why did this happen to me, is this the punishment from God for not doing my chores. Finally, the signal reaches to frontal cortex which starts to analyze the situation and then you start to think that you shouldn't have come bare feet to the garden and also start to think of the ways to stop the bleeding.