16.26: Disorders of the Nervous Tissue

Nervous tissue is a vital component of the human body's communication system, enabling us to perceive and respond to stimuli. However, like all other tissues, it is vulnerable to disorders and diseases that can significantly impact our neurological functioning.

Homeostatic Imbalances:

Alzheimer's disease manifests as a gradual decline in memory and cognitive abilities, attributed to the buildup of amyloid plaques and neurofibrillary tangles in the brain.

Parkinson's disease arises from the degeneration of dopaminergic neurons that play a vital role in motor function. This degeneration leads to tremors, rigidity, and challenges in initiating voluntary movements.

Multiple sclerosis is a condition where the immune system mistakenly attacks and damages the myelin sheath, a protective covering of nerve fibers in the brain and spinal cord. This process, known as demyelination, leads to compromised communication between nerve cells.

Infections:

Meningitis is a disease that results from an infection, causing the meninges - the protective layers around the brain and spinal cord - to become inflamed. This often leads to symptoms like a high temperature, headaches, and a stiff neck.

Poliomyelitis, a viral infection, targets the motor neurons in the spinal cord, resulting in muscle weakness and paralysis.

Toxicity:

Lead poisoning: High levels of lead exposure can cause brain and nervous system damage, leading to developmental delays, seizures, and behavioral issues.

Carbon monoxide poisoning: Carbon monoxide is a poisonous gas that can affect the brain and nervous systems, leading to symptoms such as headache, dizziness, and confusion.

Genetics:

Huntington's disease: an inherited disorder that causes the destruction of acetylcholine and GABA (gamma-aminobutyric acid) producing neurons, leading to involuntary movements, cognitive problems, and behavioral changes.

Tourette Syndrome: a genetic disorder that results in repetitive, involuntary movements and vocalizations called tics.

Nervous tissue disorders are caused by several factors.

Homeostatic imbalances include cerebral hypoxia  — or reduced oxygen supply to the nervous tissue; cerebral ischemia  — or disrupted blood flow to the brain; or electrolyte imbalance.

For instance, homeostatic imbalances can cause epilepsy, characterized by short and recurrent seizures. In addition, epilepsy is also caused by head injuries, infections, or brain damage at birth.

Infections in nervous tissue often result in serious diseases.

For example, the Poliovirus infects motor neurons, causing poliomyelitis. Diphtheria is caused by the bacterium Corynebacterium diphtheriae that destroys Schwann cells and the myelin sheath in the PNS.

Chronic exposure to heavy metals such as lead, arsenic, or mercury causes progressive demyelination of neurons.

Physical injuries, such as traumatic brain injury or spinal cord injuries, often cause permanent damage to nervous tissue, leading to paralysis.

Genetic mutations often play a role in developing nervous tissue disorders such as multiple sclerosis, Huntington's disease, Parkinson's disease, and Alzheimer's disease