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.
Treatments of Parkinson’
L-Dihydroxyphenylalanine LDopa which is converted into dopamine by remaining neurons. Not effective after too much of dopaminergic cells die as there are not enough neurons to make use of it.
Stereotaxic thalamotomy is the surgical interruption of the striatal output through the thalamus. This reduces the increased tone and tremor in the muscles. It is carried out by inserting a special probe into the brain to reach the relevant thalamic nucleus while the patient is awake. This enables the surgeon to see whether the probe is in the right place.
Stereotaxic thalamotomy is superceded by deep brain stimulation. In DBS electrodes are implanted to continously stimulate the sub-thalamic nucleus in the junction of the thalamus and the hypo-thalamus or alternatively the adjacent Zona incerta to reduce the severity of the symptoms.
None of these are treatments of the disease, but instead for reducing the symptoms.
Why is substantia nigra black ?
In fresh brain tissue, it contains significant quantities of pigment neuromelanin, which is a byproduct of dopamine
production. In PK dopamine synthesis is impaired therefore Substantia nigra loses its black color.
What is stroke ?
Stroke is most commonly caused by bursting or blocakge of an artery often referred to as cerebrovascular accident.
Symptoms of stroke
Depending on which artery is affected, it might be paralysis, loss of touch sensation, loss of ability to speak or all of these.Paralysis is on the opposite side of the body. An extensive damage to left cerebral hemisphere in an right hand person can cause aphasia due to damage to broca’s area. In very sever causes brain swellings may cause the hind brain respiratory centers o be pushed against the skull resulting in loss of breath and death. One of the areas that is particularly sensitive to damage is the INTERNAL CAPSULE.
How to diagnose stroke ?
Look for spasticity and hyper-reflexia in affected side.
What is Alzheimer’s disease ?
A neuro degenerative disorder that causes loss of neurons in the fore brain.
Symptoms of Alzheimer’s disease
Earlier symptoms - Minor episodes of memory loss.
But as the disease progresses, the person becomes incapacitated and cannot care for themselves.
What does Alzheimer’s disease cause
Dementia
Gradual blockage of cerebral arteries
Parkinson’s
What causes Alzheimer’s disease
Not yet known
- Genetic predisposition in some cases
- Loss of insulin receptors in the brain
- Damage to connectivity between neurons
Key feature of AD
- Reduction in level of acetyl choline in cerebral cortex
- Drugs sustaining acetylcholine has overall less impact and is costly
- Severe shrinkage of hippocampus, cerebral cortex , enlarged ventricles
- Hyperphosphorylation of protein Tau causing aggregation of abnormal proteins causing neurofibrillary tangles.
- Insoluble deposits of amyloid found in dead alzheimer patients.
What is epilepsy
Imbalance between excitation and inhibition of neurons most commonly causes hyperexcitation leading to epilepsy. Overreactive regions cause storms of electrical activity to spread over the cortex.
What is the cause of epilepsy
Mostly unknown
1. In temporal lobe epilepsy - difficult birth, pressure on the brain pushes the tip of the temporal lobe against the duramater. These areas of the scar tissues can cause electrical disturbances later in life.
Symptoms of epilepsy
- Seizure
- If temporal lobe epilepsy, people may experience olfactory hallucinations, feeling of dejavu or Jamaisvu, feeling of fear and terror, depersonalization and abnormal repetitive movements such as lips smacking, chewing , tooth grinding or aggressive actions
Treatment for epilepsy
If there is a known area for the start of the electrical disturbance, it can be removed surgically. However, if not not known it can be only controlled by anti-epileptic drugs. The anti-epileptic drugs can impair non epileptic regions to a certain extent.
regions affected in TLE
uncus(olfactory hallucinations), hippocamus(impairing in memory functions), amygdala(aggressive functions)
Brain trauma and death
Irreversible damage to the brain caused by severe blows to the head and even though the skull is not damaged. loss of cortical neurons.
Effects of brain trauma and death
Memory loss, headache, confusion
What is diffuse axonal injury?
Diffuse axonal injury is the slow degenerations of the fibres in the brain due to the twist and stretching of the axon during head trauma. It takes month for symptoms to appear after the acute injuries have healed.
What happens during brain hemorrhage?
Rise in inter cranial pressure.
What are some of the causes of intercranial pressure?
- hemorrhage
- swelling of the brain due to infection.
- Brain tumours
What is the result of increased inter cranial pressure?
Debilitating headache
Nausea caused by pressure stimulation of brainstem vomiting centres
.In severe causes the hind brain to be pushed against the foramen magnum, the exit hole from the skull where the hind brain joins the spinal cord, causing the person to lose consciousness or death.due to blood supply being cut to the respiratory systems.
Meaning of schizophrenia
Split mind. Splitting between internal thinking processes and the reality. It is different from multiple personality disorders.
What are the two major types of illnesses?
Neuroses(no split of reality) and psychoses(split in reality). Some neuroses symptoms are depression, distress and anxiety. Some psychoses are hallucinations, delusions, disordered thought patterns and bizarre behaviour.
When does schizophrenia occur?
Late adolescence
Symptoms of schizophrenia?
Disturbances in thinking Hallucination Delusion Decreased emotional responses Apathy Withdrawal from society
What causes Schizophrenia?
Unknown. Only some respond to drugs influencing serotonin and dopamine
What is bipolar affective disorder
bAD is a mood disorder characterised by presence of one or more episodes of abnormally elevated mood, referred to as mania. They may also have depressive episodes.
Treatments of BAD
Lithium chloride which affects intracellular sodium handling or sodium valproate which affects neurotransmission. These medications offer symptom relief for a period of time.
Causes of BAD
Unknown.
What is neurotic depression ?
Neurotic depression is a state of low mood and lack of interest in activity. It generally begins in early adulthood and affects third of the population at one point of time in their life. There is higher incidence of depression among women but it may be due to willingness of female to seek help.
What are some signs of neurotic depression
Changes in appetite or sleep.Loss of energy. decreased libido. Irritability. Feeling of worthlessness. Thoughts of suicide. In most severe cases patients may have delusional thoughts.
cause of depression
No single cause.
But rather contributing factors such as family history, trauma, stress and psychological problems.
Baseline of depression is due to imbalance in NT levels, not involved not known.
Treatments for depression
Drugs to increase effect of serotonin based on side effect profile
Electroconvulsive therapy and transcribing magnetic stimulation
Behavioural cognitive therapy
What is OCD?
Obsessive compulsive disorder is characterised by compulsions and obsessions. Obsession is recurring thoughts that is a source of anxiety and compulsion is repetitive thoughts triggered by anxiety. Common obsessions are worries about contamination by germs, thought of violent acts and constant doubt.
What is the treatment for OCD?
SSRI effective in 60% of OCD patients.
Surgical lesions to cingulate gyrus
Deep brain and vagus nerve stimulation
What is autism?
Autism is a neurodevelopment disorder. It affects males 4 times than female. It is a spectrum of disorders in which social, communication and cognitive skills are disordered. They are also characterised by repetitive behaviour.
What is the cause of autism?
There is no known cause.
What is known as savant syndrome?
Savant syndrome has some disabilities but also have improved functioning in other cognitive skills.
