[Biology Class Notes] on Diseases of the Nervous System Pdf

Definition

The complex network of nerve cells comprising neurones and fibres that transmits impulses from one part of the body to another is called the nervous system. Some of the commonly known nervous system diseases are Parkinson’s disease, Alzheimer’s disease, epilepsy, etc. 

The human nervous system is the most complex and important part of the body that acts as the powerhouse coordinating the actions and the sensory information. This system is also responsible for transmitting and recognizing signals to and fro different body parts. The nervous system has innumerable cells and nerves and their complicated network. They carry information and messages to and from the brain and spinal cord to different parts of the body. 

The Nervous System

The nervous system has two parts- the central nervous system (CNS) and peripheral nervous system (PNS). The central nervous system constitutes of the nerves in the brain and the spinal cord. The peripheral nervous system has the neurons, nerves and clusters of neurons called the ganglia. They are connected to each other and to the central nervous system. All these crucial parts of the nervous system receive and interpret the information. The other important function of the nervous system is the response to the stimuli inside and outside of the body.

Damage to the Nervous System

First of all, the neurons are very sensitive and fragile. In case of any injury to the neurons, signals from and to the brain can be stopped permanently or partially. The muscles in that particular area will not function properly and there will be numbness or loss of feeling. Injuries to the nerves will cause a serious impact on the brain, spinal cord and peripheral nerves. Along with the injuries, there are some infections like polio, meningitis and encephalitis that cause disorders in the nervous system.  The whole of the nervous system is responsible for a healthy full-functioning living being and in human beings, the central nervous system cannot repair itself and the damage to it will be permanent in the majority of the cases. The nerves in the peripheral system can heal after injuries and regain their function. Once the axons in the backbone are destroyed and the spinal cord is injured, paralysis occurs in varying degree of severity. 

Nervous System Diseases

The most common nervous system diseases are:

• Sciatica

• Parkinson’s disease

• Multiple sclerosis

• Neurofibromatosis

• Motor neuron disease

• Epilepsy

• Cerebral palsy

• Alzheimer’s disease

• Bell’s palsy

• Guillain- Barre syndrome

Elaboration of the Important Diseases:

Sciatica

In this condition, the patient has severe pain in the back and the legs. The sciatic pain occurs along the path of the nerve. The nerve beings at the lower spine and travels along the hip, buttocks and, back of the leg into the foot. Treatment over the years can provide relief from this pain.  

Most common causes of sciatica:

• Injury to the spinal cord

• Unwanted growth spurts in the bones

• Swelling of the muscles

• Ageing

• Prolonged pressure on the spine

• Obesity

• Diabetes

There will be pain and tingling sensation in the legs. This pain is felt mostly in the buttock region down the legs especially during coughing hard, sitting over a prolonged period in one position and while using the toilet. More serious complications like weakness, inability to control the bladder and bowels and numbness ought to be taken to the notice of medical professionals immediately. 

Parkinson’s Disease

This disease is a result of the damage to the nerve cells of a region of the brain that produces dopamine. This chemical is responsible for the effective functioning and movement of the muscles. It can also be inherited in rare cases and mostly affects people over 65. 

The main symptoms are:

There is no cure for this disease and a team of physiotherapist, neurologist, psychologist, occupational therapist and dietician can support a person suffering from this disease. 

Epilepsy

This is a long term condition in which the person has repeated seizures due to the damage in the brain. Seizures usually last for 1-3 minutes and the seizures lasting more than five minutes are fatal. A combination of conditions usually causes this disease. The main symptom is seizures and their duration and intensity depend on the part of the brain that has the damage. Their seizures are the result of disrupted electrical activity in the brain. The different kinds of seizures are:

All these kinds of seizures cause differences in feelings, behaviour, sensations, jerking and convulsions, consciousness sometimes. 

Cerebral Palsy

In this disease, the ability to control the muscles is lost or reduced due to the damage to the nervous system. There is an area in the brain that controls the muscles and their tone known as the muscle cortex. This area may be underdeveloped at the fetus stage or if the baby is deprived of oxygen in the womb or during the birth will be affected by this condition.  Prematurity, genetic mutation, injury to the brain and severe jaundice after birth are some of the reasons for cerebral palsy.  This phenomenon may occur before, during or after birth. There are many aftermaths of cerebral palsy:

• Involuntary muscle movements

• Stiff or floppy muscles

• Damage to the body position and movement

• Poor muscle tone and posture

• Impaired vision, hearing, speech and learning

• Eating difficulties

The doctors can diagnose babies with cerebral palsy by the age of 2. Most of these babies and toddlers miss important milestones. 

Alzheimer’s Disease

This disease is a form of Dementia and occurs due to d
amage to the cells and neurotransmitters in the brain. This damage affects the functions of the brain, the memory and the way of behaviour. This disease usually occurs due to ageing, severe head injuries, way of lifestyle and family history of people having this disease earlier. 

The main symptoms are:

• Forgetfulness

• Issues in speaking and understanding

• Issues in managing everyday chores

• Mood swings and changes in the personality

According to a survey, about 3 in 10 people above 85 years of age are affected by this disease in varying degree.

Guillain-Barre Syndrome

This syndrome occurs very rarely in which the own immune system of a person attacks the nerves causing extreme weakness and tingling sensations. This disease spreads rapidly in the body of the affected person and causes paralysis. Infections like gastrointestinal, respiratory and viruses like Zika occur prior to the symptoms in the patient. There is no cure or treatment but with therapies, many people recover partially or fully.  

Symptoms are:

• Difficulty in breathing

• Fluctuations in blood pressure

• Cramps/terrible aches at nights

• Difficulties in chewing, speaking and swallowing

• Issues in the vision

• Unsteady gait