Functions and Disorders of the Nervous System

The Mechanics of Memory

Memory is a versatile cognitive process that allows us to acquire, store, and retrieve information. It involves various parts of the brain, including the association areas of the cerebral lobes and the limbic system. While motor skill memories are localized in the basal nuclei, cerebellum, and cerebral cortex, cognitive memories are categorized by their duration:

1. Sensory Memory: This is a fleeting "copy" of what is seen or heard, lasting only for a few seconds.
2. Short-term Memory: This has a limited capacity and a brief duration, typically lasting from seconds to hours.
3. Long-term Memory: This is the result of short-term memory being repeated, organized, and consolidated. It offers limitless storage capacity over time.

The process of moving information from short-term to long-term storage—known as consolidation—requires the hippocampus and the amygdaloid body.

Aging of the Nervous System

The nervous system undergoes significant changes throughout a person's lifespan. In the early years, the brain experiences rapid growth driven by the increase in neuron size and the proliferation of neuroglia.

However, as the nervous system ages, there is a gradual decrease in the capacity to transmit nerve impulses to and from the brain. This can lead to diminished information processing, slower voluntary motor movements, and increased reflex times.

Neurological Disorders and Injuries

When the delicate balance of the nervous system is disrupted by disease, trauma, or structural issues, various disorders can arise.

Structural and Electrical Disorders

• Hydrocephalus: This occurs when there is an abnormal accumulation of cerebrospinal fluid (CSF), often due to an obstruction in flow or abnormal production/reabsorption rates. This results in increased intracranial pressure.
• Cerebrovascular Accident (CVA/Stroke): Also known as a "brain attack," a CVA involves the destruction of brain tissue. This can be caused by intracranial hemorrhage, emboli, or atherosclerosis (the formation of cholesterol-containing plaques that block blood flow).
• Epilepsy: A disorder characterized by neurons that transmit electrical signals too frequently, unpredictably, and rapidly.

Sensory and Cognitive Impairments

Damage to specific cranial nerves or brain regions can lead to localized sensory losses:

• Anosmia: The loss of the sense of smell (olfaction).
• Ageusia: The loss of the sense of taste (gustation).
• Dysphagia: Difficulty in swallowing.
• Amnesia: A complete or partial loss of memory, often caused by psychological trauma or a blow to the head.
• Insomnia: Difficulty in falling or staying asleep.

Traumatic Brain Injury (TBI)

Physical trauma to the head can result in several types of injury:

• Concussion: An abrupt, temporary loss of consciousness following a blow to the head or a sudden movement of the head.
• Contusion: A physical bruising of the brain tissue caused by trauma, which leads to blood leaking from small vessels into the subarachnoid space.