Chapter 9 Flashcards
Why is damage to CNS serious ?
Bcos neurons cannot be replaced unlike other organs.
How does polio enter the nervous system ?
Via the nerve muscles synapses and travels along the motor neuron axons to reach the spinal cord or the hind brain.
Symptoms of polio / affected areas
It is more commonly the symptom of Summer diarrhea, but when it invades CNS, it causes severe paralysis. If the motor neuron affected is below the mid cervical region, the paralysis is either one or more of the limbs and if in upper cervical region or hind brain, result is paralysis of swallowing and breathing muscles. Unless supported by mechanical respirator, patient may die.
Polio epidemic year
1950
Polio treatments
NO treatment. Protective vaccines have eliminated polio almost across the world. 4 countries still report.
How does rabies affect the CNS ?
Rabies virus also enter peripheral nerves to enter CNS, it is usually transmitted by fluids from an infected animal. The virus enters the synapses, goes through the axons to reach the neuron body. Special feature of rabies allows it to multiply and pass through the synapses , can affect the whole NS. Cell death usually occurs years after initial bite followed by death.
Can rabies be prevented ?
It can be interrupted if a special vaccination is administered within few days of initial bite.
How is the ability of rabies virus to cross synapse useful ?
It let to the development of nerve tracing techniques using pseudo rabies virus , a non-dangerous relative of rabies. It travels retrograde direction therefore it can be used to trace multi-synaptic pathway.
What is a prion ?
Mis-configured version of normal protein which can cause normal proteins to change to abnormal form.
What is CJD ?
Creutzfeldt Jakob Disease. It is a prion disease in which the abnormality is present in the new host causing widespread brain damage and death. CJD appears spontaneously in 1 in million people.
How was the characteristics of prion disease unraveled ?
It was unraveled by the study of the kuru epidemic in Papa New Guinea. Kuru is a variant of CJD that causes severe cerebellar and cerebral damage. It results in death one year after the symptoms. It was investigated by Gadjusck, he showed that the prion could be transmitted to chimpanzees in laboratories and epidemic was caused by the ritual cannabalism of deceased relatives in the affected community. He was awarded nobel prize 1976.
How can prions replicate ?
They take over the machinery of the cell to replicate.
What is the variant of CJD that affects sheeps ?
Scrapie
What is the variant of CJD that affect cows?
Mad cow disease or Bovine spongiform encephalopathy
Can scarpie or BSE be transmitted to humans ?
Yes. Causes vCJD’s. Despite the eradication of disease from farm cattle, new cases of vCJD continue to appear, the reason could be prion disease having longer incubation period perhaps 20 years or more.
What is MS
MS is a progressive degenerative disease of the nervous system resulting in CNS inflammation and demylienation of axons.
Who is MS common in
Young adults, 3 times more common in young woment than men.
What causes damage to myelin sheath and inflammation ?
It is an autoimmune reaction where the body becomes deregulated and starts attacking the other cells in its own body. The inflammation causes proliferation of astrocytes to form scars around the outside of the axons called the plaques.
What is the characteristic sign of MS?
Appearance of the plaques
How does the demyelination affect ?
It interrupts the transmission of the nerve impulses and slows them down causing abnormalities in motor control or vision.
What are the features of MS ?
Muscle weakness Lack of Coordination Intention tremor sometimes paralysis Sensory abnormalities like blurred vision or blindness Immense fatigue Heat sensitivity Electric shock like sensation
How does MS progress
There are episodes of damage separated by months without new symptoms. The symptoms are often caused by inflammation and they gradually resolves as inflammation subsides. Episodes of damage become more frequent and there is overall gradual decline the health of the person. In rare cases symptoms may progress rapidly without resolving incapacitating the person.
Who are prone to Parkinson’s ?
Older adults
Main features and symptoms of parkinson’s
Tremor in the hands
Shuffling walk
Muscular rigidity
Slow movements due to rigidity and because of this the patient may appear emotionless and apathetic
What is the cause and where is the damage for PK
No known cause.
Underlying damage is most often in the substantia nigra.
The Substantia nigra sends dopaminergic axons to the striatum, due to this there is disruption in the normal role of posture and movement.