Brain+and+nervous+system

[[file:hemispheric specialisation.doc]][[file:hemispheric specialisation.doc]]Anatomy of the Nervous System
If you think of the brain as a central computer that controls all bodily functions, then 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 and 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 accidentally 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 takes a lot less time than it just took to read about it.

Considering everything it does, the human brain is incredibly compact, weighing just 3 pounds. Its many folds and grooves, though, provide it with the additional surface area necessary for storing all of the body's important information.

The spinal cord, on the other hand, is a long bundle of nerve tissue about 18 inches long and ¾ inch thick. It extends from the lower part of the brain down through spine. Along the way, various nerves branch out to the entire body. These are called the peripheral nervous system. 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 as well as a special fluid called cerebrospinal fluid. This fluid helps protect the nerve tissue, keep it healthy, and remove waste products. The brain is made up of three main sections: the forebrain, the midbrain, and the hindbrain.



1. 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 beneath 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.

The cerebrum has right and left halves, called hemispheres, which are connected in the middle by a band of nerve fibers (the corpus collosum) that enables the two sides to communicate. Though these halves may look like mirror images of each other, 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 the 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 from the spinal cord 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 pituitary gland. 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. It also controls the pituitary gland, which makes the hormones that control our growth, metabolism, digestion, sexual maturity, and response to stress.

2. The Midbrain
The midbrain, located 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.

3. The Hindbrain
The hindbrain sits underneath the back end of the cerebrum, and 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 all of the brain's messages. It is also controls many of the body's automatic functions, like breathing, heart rate, blood pressure, swallowing, digestion, and blinking.

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Related web-sites [|Left Brained/ Right Brained]

http://frank.mtsu.edu/~studskl/hd/learn.html






 * Primary Somatosensory Cortex and Primary Motor Cortex**

The size of the area on the Primary Somatosensory Cortex and the Primary Motor Cortex that is responsible for a particular body part is relative to the sensitivity of that body part and the amount of use, not the size of the body part. Therefore the your lips and fingers have a greater cortical area than the back of your legs or the soles of your feet.





** Brain research methods ** These methods are listed in order of invention so you can try and remember them by remembering that they get more sophisticated as you progress down the list and the information they give generally becomes more useful. **Case Study (clinical studies)** – used to study rare or unusual phenomena. Findings from case studies are often used as the basis for creating a hypothesis for further study. Limitations – time consuming, cannot generalise results **Electrical stimulation of the brain (EBS)**- involves stimulating the brain with an electrical current to see what response that triggers in the body. Used to determine which part of the brain controls which body function. Limitations – extremely invasive as it involves opening up the skull and using an electrical probe to stimulate the brain. Would not be acceptable today except on animals. Hard to generalise results as a lot of the research was carried out on epileptic patients. **Electroencephalograph (EEG) –** detects activity in the brain using electrodes attached to the scalp. Non invasive, used to detect patterns during sleep, inexpensive, can be used over long periods of time. Limitations – does not give detailed information about which particular structures of the brain are activated and what their specific function might be. **Computerised tomography (CT) –** developed in the 1970’s it uses x-rays to produce an image of a cross section or slice of the brain. Iodine is injected into the patient to help highlight the brains blood vessels. A 2 dimensional image is produced and is useful for determining structural abnormalities. Limitation – does not show brain functioning. **Magnetic resonance imaging (MRI**) – developed in 1977 it uses magnetic fields to vibrate atoms in the brain’s neurons to produce an image of the brain. Can be used to produce 3 dimensional pictures. Is non-invasive. Is more precise than a CT scan. Limitation – shows only brain structure not function. Cannot be used on people with metal in their body ie pace makers **Positron emission tomography (PET) –** is the first method to produce information about brain functioning. A harmless radioactive/glucose substance is injected and increased activity in the brain is monitored as the patient carries out varies cognitive or behavioural tasks. Limitations - 2 dimensional only. 40 second interval between scans so cannot pick up rapid changes. **Functional Magnetic Resonance Imaging (fMFI)** – is one of the more advanced brain neuroimaging techniques. Detects changes in oxygen levels in the brain as various tasks are carried out. A computer creates an image with colour variations to indicate which area of the brain is activated during various activities. Can take images in rapid succession. Produces 3 dimensional images. Limitations - Cannot be used on people with metal in their body ie pace makers