Brain basics 1
A Primer for Understanding Neuroplasticity
CNS, hemispheres, lobes, neurons and neurotransmsitters, neuromodulators
Learning changes the brain
Everything we feel, see, and hear, and every thought we think, is related to brain processes.
For viewers with a limited background in science, the illustrations and brief definitions on the pages Brain Basics 1 and Brain Basics 2 will help you
* identify some areas of the brain and learn some of their functions,
* understand how brain cells communicate,
* understand what neuroscientists mean by brain systems, and
* acquire a basic idea of how neuroscientists organize the brain to understand and study how it works.
Scroll down for Brain Basics 1 pages
Directional terms for the brain
Here's an interactive Web page from Get Body Smart forAnatomical Directional Terms for the Brain
Click here for a mind-mapped overview of this topic.
The central nervous system
Limit your focus to the pink and blue areas of this image and ignore the labels. The pink area is the central nervous system. The blue area is the peripheral nervous system.
The spinal cord is the pink area that extends from the brain. It is a long thin bundle of nerve fibers protected by the spinal column, which is made up of bones called vertebrae.
It is the main pathway of information connecting the brain and the peripheral nervous system.
It carries somatosensory information - i.e., information about the body - to the brain, and carries motor-control information from the brain to the peripheral nervous system.
The spinal cord and the brain together make up the central nervous system.
Hemispheres, lobes and brainstem
brain hemispheres
This image looks at the brain from the top. The cerebrum is the largest, most developed part of the human brain. It is divided down the middle into two brain hemispheres - a right and a left hemisphere.
The hemispheres connect to and communicate with each other through a thick bundle of nerve fibers called the corpus callosum.
The left hemisphere controls muscles on the right side of the body, and the right hemisphere controls muscles on the left side of the body. However, most brain functions are distributed across both hemispheres.
Generally speaking, however, the left hemisphere processes speech elements like grammar and vocabulary, and conscious probem solving.
And the right hemisphere generally processes nonverbal communication, such as recognizing faces, reading facial expressions, and connecting with people. It also processes the tone and emotion conveyed in speech. It dominates the brain during the first three years of childhood.
brain lobes
This image looks at the brain from the side.
The brain is divided down the middle into two hemispheres - the left and right hemispheres. Each cerebral hemisphere is divided into four lobes: the frontal, parietal, occipital, and temporal lobes. The frontal lobe is towards the front of the brain, and the occipital lobe towards the back. The parietal is towards the top and the temporal lobe towards the bottom.
Very generally speaking, the frontal lobe is associated, among other things, with reasoning, planning, problem-solving, and emotions, as well as motor functions; the parietal lobe is associated with movement, orientation, and the perception of sensory input from the body, such as touch, temperature, pain, etc.; the occipital lobe is associated with visual processing; and the temporal lobe is associated with memory, the perception and recognition of auditory stimuli (hearing), and speech.
Also labeled in this diagram are the brainstem, cerebellum, and spinal cord - their definitions are entered separately in this glossary.
brain stem
This inside view of the right hemisphere shows the brainstem. The front of the brain is to the left of this image. The cerebrum is the wrinkled area that resembles a cauliflower, and the brainstem is above the spinal cord.
The brainstem connects the cerebrum with the spinal cord. Electrical impulses from neurons in the motor (movement) and sensory areas of the cerebral cortex - the thin layer of cells that covering the cerebrum - travel through the brainstem to relay signals between the brain and the spinal cord.
The brainstem controls many important functions, including alertness, arousal, breathing, blood pressure, digestion and heart rate.
Neurons, synapses, and neurotransmitters
Neuron
Neurons are nerve cells in our brains and nervous systems. They process and transmit information through electrical impulses and chemical signals. They are the structural and functional units of the nervous system. They can either fire, or not fire. See neurotransmitters.
The three principal parts of a neuron are the cell body, the dendrites, and the axon.
Dendrites are the tree-like branches extending from the cell body of the neuron, coloured purple to the left of his image. Dendrites are extensions of the cell body of the neuron. Dendrites receive input, or chemical messages, from the axons of other neurons in its network or pathway.
Notice the nucleus, coloured green, within the main area of the cell body, in the purple area on the left of this image.
An axon is a part of a neuron. In this image, the axon is coloured yellow.
Neurons communicate with each other through electrical impulses and chemical messages. Electrical impulses travel down the axon to the axon terminals, the purple extensions to the right of this image.
There are many kinds of neurons with axons of varying lengths.
Nucleus
In biology, the nucleus of a cell is a subunit within a cell. For example, each neuron or brain cell contains a nucleus. In this image of a neuron, notice the nucleus of the cell, coloured green, within the main area of the cell body.
The term nucleus - plural, nuclei - also has a specialized use in neuroscience.
In neuroscience, nucleus refers to a group or collection of cells that form a structure identifiable by its unique characteristics and functions. For example, the amygdala is a group of nuclei located deep inside the temporal lobe - it is involved in processing emotions such as fear, anger and pleasure, and is responsible for determining what memories are stored, and where in the brain memories are stored.
The term nucleus and module are sometimes used interchangeably. Brain modules are units that change their structure, function and connections along neuronal pathways as people have adapted to and created cultural and technological changes in their environment.
Synapse
A synapse is the microscopic space between two neurons across which they connect to each other. Axons send or take information away from a neuron, and dendrites receive or bring information to a neuron.
Electrical impulses or signals travel down the axon of one neuron to its axon terminals, where chemicals called neurotransmitters are released into the synapse space to interact with receptors in the dendrites of another neuron.
Neurotransmitters are excitatory or inhibitory chemical messengers. They affect the receiving neuron in one of two ways. Neurons can either fire or not fire. Neurotransmitters can either excite a neuron, causing it to fire. Or they can inhibit a neuron, making it less likely to fire. See neurotransmitter.
Canadian behavioural neuropsychologist, Donald Hebb proposed, in 1949, that neurons firing together strengthen neuronal connections and pathways. His contribution led to the popular axiom - "neurons that fire together wire together."
Neurotransmitters
Neurotransmitters are chemicals or chemical messengers that are released from axon terminals of one neuron, and cross a synaptic gap to reach receptors in dendrites of another neuron.
Electrical impulses or signals travel down the axon of one neuron to its axon terminals, where chemicals called neurotransmitters are released into the synapse space to interact with receptors in the dendrites of another neuron.
A synapse is the microscopic space between two neurons across which they connect to each other. Axons send or take information away from a neuron, and dendrites receive or bring information to a neuron.
Neurotransmitters are excitatory or inhibitory chemical messengers. They affect the receiving neuron in one of two ways. Neurons can either fire or not fire. Neurotransmitters can either excite a neuron, causing it to fire. Or they can inhibit a neuron, making it less likely to fire.
Neurons "fire" when they're stimulated and become active. They "wire" when they connect to each other, and connect along neuronal pathways.
Canadian behavioural neuropsychologist, Donald Hebb, proposed in 1949 that neurons firing together strengthen neuronal connections and pathways. His contribution led to the popular axiom - "neurons that fire together wire together."
Known as the Hebb rule, it helps us to remember that practice and repetition, in thoughts or behaviours, result in synaptic changes, which are brain changes. These changes can be positive or negative.
Neuromodulators
Neuromodulators, are sometimes referred to as modulatory neurotransmitters. They are chemicals in the brain that affect how neurons respond to messages received from other neurons. For the most part, it is unnecessary to distinguish between neuromodulators and neurotransmitters. However, distinguishing them may help us better understand chemical transmission between neurons and what neuromodulation therapies attempt to achieve.
Neurotransmitters directly excite or inhibit partner receptors on the dendrites of receiving neurons. Neuromodulators, or modulatory neurotransmitters, enhance the excitatory or inhibitory responses of the receptors. In other words, neuromodulators increase or decrease the overall effectiveness of the synaptic connections. Examples of neuromodulators include dopamine, serotonin, and acetylcholine.