Glial cells
also known as glia, outnumber neurons ten to one, and are traditionally thought to play a supportive role to neurons, both physically and metabolically. They provide scaffolding on which the nervous system is built, help neurons line up closely with each other to allow neuronal communication, provide insulation to neurons, transport nutrients and waste products, and mediate immune responses.
Neurons
serve as interconnected information processors that are essential for all of the tasks of the nervous system.
Cell Membrane
A semipermeable membrane that makes out a neuron’s outer surface. This membrane allows smaller molecules and molecules without an electrical charge to pass through it, while stopping larger or highly charged molecules.
Soma
The cell body where the nucleus of the neuron is located. The soma has branching extensions known as dendrites, as well as a major extension known as the axon. Electrical and chemical signals travel across the soma from the dendrites to the axon.
Dendrite
Branching extensions of the soma. The neuron is a small information processor, and dendrites serve as input sites where signals are received from other neurons.
Axon
A major extension of the soma which receives signals that are transmitted electrically across the soma from the dendrites. The axon ends in multiple terminal buttons. Axons range in length from a fraction of an inch to several feet.
Myelin Sheath
Glial cells that form a fatty substance around some axons. It coats the axon and acts as an insulator, increasing the speed at which the signal travels. The myelin sheath is crucial for the normal operation of the neurons within the nervous system: the loss of the insulation it provides can be detrimental to normal function. Disorders such as Multiple Sclerosis (MS) involve a large-scale loss of the myelin sheathe on axons throughout the nervous system, resulting in loss of motor control, dizziness, and fatigue. There are treatments to modify the course of the loss of the myelin sheathe exist, but there is no known way to recover a myelin sheathe that has been lost.
Terminal buttons
Found at the end of the axon. The terminal buttons contain synaptic vesicles that house neurotransmitters, the chemical messengers of the nervous system.
membrane potential
This difference in charge across the membrane
provides energy for the signal
The Frontal Lobe
The frontal lobe is located in the forward part of the brain, extending back to a fissure known as the central sulcus. The frontal lobe is involved in reasoning, motor control, emotion, and language. It contains the motor cortex, which is involved in planning and coordinating movement; the prefrontal cortex, which is responsible for higher-level cognitive functioning; and Broca’s area, which is essential for language production.
People who suffer damage to Broca’s area have great difficulty producing language of any form. There is nothing wrong with their mouths or vocal cords, but they are unable to produce words. They can follow directions and do routine tasks but can’t respond verbally, and they can read but no longer write.
The Parietal Lobe
The brain’s parietal lobe is located immediately behind the frontal lobe, and is involved in processing information from the body’s senses. It contains the somatosensory cortex, which is essential for processing sensory information from across the body, such as touch, temperature, and pain. The somatosensory cortex is organized topographically, which means that spatial relationships that exist in the body are maintained on the surface of the somatosensory cortex. For example, the portion of the cortex that processes sensory information from the hand is adjacent to the portion that processes information from the wrist.
The Occipital Lobe
The occipital lobe is located at the very back of the brain, and contains the primary visual cortex, which is responsible for interpreting incoming visual information. The occipital cortex is organized retinotopically, which means there is a close relationship between the position of an object in a person’s visual field and the position of that object’s representation on the cortex. You will learn much more about how visual information is processed in the occipital lobe when you study sensation and perception.
The following video is a great summation of the materials presented thus far in this section. It provides a great memory tool and description towards the back end of the video that will help you to remember the functions of the four lobes.
The Temporal Lobe
There are two temporal lobes, located on either side of the head (temporal means “near the temples”). The temporal lobe is associated with hearing, memory, emotion, and some aspects of language. The auditory cortex, the main area responsible for processing auditory information, is located within the temporal lobe. Wernicke’s area, important for speech comprehension, is also located here. Whereas individuals with damage to Broca’s area have difficulty producing language, those with damage to Wernicke’s area can produce sensible language, but they are unable to understand it.