This tiny nub acts as a memory indexer sending memories out to the appropriate part of the cerebral hemisphere for long-term storage and retrieving them when necessary. They are responsible for initiating and integrating movements. Parkinson s disease, which results in tremors, rigidity, and a stiff, shuffling walk, is a disease of nerve cells that lead into the basal ganglia. The brain and the rest of the nervous system are composed of many different types of cells, but the primary functional unit is a cell called the neuron. All sensations, movements, thoughts, memories, and feelings are the result of signals that pass through neurons.
Neurons consist of three parts.
The neuron is usually surrounded by many support cells. This sheath can include a fatty molecule called myelin, which provides insulation for the axon and helps nerve signals travel faster and farther. Axons may be very short, such as those that carry signals from one cell in the cortex to another cell less than a hair s width away. Or axons may be very long, such as those that carry messages from the brain all the way down the spinal cord. Image 6 Scientists have learned a great deal about neurons by studying the synapse the place where a signal passes from the neuron to another cell.