Brain and the Nervous System Flashcards
The brain and spinal cord are protected by the _______ and ____
Meninges and Bone
What are the 3 meningeal layers?
Dura Mater, Arachnoid Mater, Pia Mater
Describe the Dura Mater?
A strong outer fibrous membrane that adheres to the skull and vertebrae
Describe the Arachnoid Mater?
The middle interposed membrane between the Dura and Pia
Describe the Pia Mater?
Inner thin membrane that adheres to the surface of the brain and spinal cord
Between the Pia and Arachnoid Maters is called the _____________
Sub-Arachnoid space
What is found in the sub-arachnoid space?
CSF - a watery fluid that nourishes and cushions the nervous system
The PNS is made up of all the nerves _______ the CNS
Outside
A group of nerve cell bodies in the PNS is called a _______
Ganglion
How many cranial nerves are there?
12 pairs
How many spinal nerves are there?
31 pairs
Nerves can be divided into the _______ or sensory pathways and the _______ or motor pathways
Afferent - Sensory
Efferent - Motor
How many cervical nerves are there?
8 pairs
How many thoracic nerves are there?
12 pairs
How many lumbar nerves are there?
5 pairs
How many sacral nerves are there?
5 pairs
How many coccygeal nerves are there?
1 pair
The brain is divided into 3 parts, what are they?
Cerebrum
Cerebellum
Brain Stem
The brain requires a rich blood and oxygen supply, how is this need met?
There are a large amount of blood vessels in the space between the cerebrum and the skull in the Circle of Willis
Shallow grooves in the cerebrum are called ______
Sulci
The raised regions surrounded by grooves are called _____
Gyri
Deep grooves in the cerebrum are called _______
Fissures
What are ventricles?
A series of spaces and tunnels within the center of the brain that secrete and house CSF which suspends the brain in the skull
The largest part of the brain is the ______ it is made of ____________ which are connected by the ____________
Cerebrum
2 Hemispheres
Corpus callosum
Nerve tracts ______ at the brain stem which results in ________________________
Cross over
Left side controls the right, Right side controls the left
The cerebral cortex is a thin layer, about _____ thick. It provides _______ and _______ for higher cognitive function. It houses _________ neurons
1.5-4mm thick
Connections and pathways
25 billion
The cerebellum is connected to the ________ and is responsible for ________________ and _______
Brain Stem
Coordination of movement and balance
The brain stem consists of the _______, ___ and _____________. It is responsible for ____________ and _______
Midbrain, Pons, Meddulla Oblongata
Basic Function and reflexes
What are the 2 main functions of the spinal cord?
- Conduct nerve impulses to and from the brain
- Process sensory information in a limited manner and perform reflex actions
Describe the structure of the spinal cord.
- Outer region is white matter(myelinated)
- The inner H-shaped region is grey matter (un-myelinated)
- A central canal is present which is continuous with the 4th ventricle in the brain
What are neuroglial cells?
Supportive cells found in the nervous system
What neuroglial cells are found in the CNS?
Astrocytes
Oligodendrocytes
Microglia
Ependymal cells
What neuroglial cells are found in the PNS?
Schwann cells
Satellite cells
Briefly describe the structure of a neuron
1 Cell body
Multiple processes on one end that receive impulses are called dendrites
A single process on the other end conducts impulses and is called an axon
Axons end is multiple processes called telodendria
Most axons are covered in a fatty sheath called _____. In the CNS axons are myelinated by _________, in the PNS axons are myelinated by ________.
Myelin
Oligodendrocytes
Schwann cells
A nerve is composed of the ____________________ joint together by a ______________
Processes of many neurons
Connective tissue sheath
Describe Astrocytes:
- Large star shaped cells
- Most abundant glial cell
- Has numerous processes that attach neurons to capillaries
- The provide nourishment for the neurons
Describe Oligodendrocytes:
- Smaller than Astrocytes with fewer processes
- Myelinate in CNS
Describe Microglia:
- Smallest glial cells
- Resident macrophages
Describe Ependymal cells:
- Line the ventricles and brain
- Involved in the production of CSF
There are more than __ types of neurotransmitters. What are some common examples?
50 types Acetylcholine Adrenaline and Noradrenaline Glutamate Serotonin Dopamine
Neurotransmitters are synthesised by _______ and stored in small compartments called ______________
Neurons
Synaptic vesicles
When an impulse reaches the axon terminals ____ rushes into the cell and triggers ___________________________
Ca 2+
Exocytosis and release of neurotransmitters
What proteins regulate synaptic vesicle exocytosis?
70 Small GTP binding Rab proteins regulate vesicle transport
SNARE proteins regulate membrane fusion
Describe the embryological development of the Nervous System
- Thickening of ectoderm becomes known as the neural plate, it appears after the 2nd week
- Lateral regions of the neural plate begin to grow upwards forming neural folds
- Folds fuse forming a neural tube by the 4th week
Pathologies involving the neural tube occur if the tube has not _____________
Closed properly
What pathology occurs when the Cephalic region does not close properly?
Anencephaly
What pathology occurs when the Caudal region does not close properly?
Spina Bifida
Neural tube defects are the _____ common congenital malformation of the CNS. It follows a _____________ inheritance pattern and is related to deficiencies in __________
Most common
Multi-factorial inheritance
Folic Acid
Anecephaly is most common in ______ infants and _____ compatible with life
Female
Not compatible
In anencephaly, the brain initially protrudes through _________________ and is gradually _________ by ____________ and ________________. This results in the brain becoming a _____________ of ______ and _______ tissue
A defect in the cranial vault
Destroyed
Mechanical injury and vascular disruption
Vascularised mass of brain and connective tissue
What are the clinical manifestation of anecephaly?
- Infant has no brain
- Lacks soft tissue of the scalp and bone for skull vertex
- Malformation of the base of the brain cavity causing bulging eyes
- Short trunk, broad shoulders and absence of neck
- May extend to the upper region of the spinal cord
What are the 3 types of spina bifida?
- Occult spina bifida = failure of fusion in the lower lumbar regions, prevents few clinical features
- Meningocele = protrusion of the meninges
- Meningomyelocele = parts of the spinal cord and meninges protrude
In severe cases of meningomyelocele how does the spinal cord present?
Spinal cord presents as a flattened mass of nerve tissue that is continuous with adjacent skin and covered by a fine meninge
How do we treat Occult spinabifida?
Usually asymptomatic and requires no treatment
How do we treat Meningoceles?
Surgery that excises the sac and closes the spinal dura
How do we treat Large Meningoceles?
- Surgery like a small meningocele
- Surgey can result in lower motor function damage
- Often requires lifelong care
How do we screen for NTDs (Neural Tube Defects)?
- Amniocentesis aka Amniotic Fluid Test (AFT)
- Test for levels of α-foetoprotein (AFP)
- High levels of AFP are ussually diagnostic
- Can be detected on ultrasound by 20 weeks
What is Hydrocephalus?
The dilation of the cerebral ventricles that is ussually caused by an obstruction in CSF circulation
Causes compression atrophy of the brain
Explain how CSF is produced and circulated:
- 600-700mml produced every day in the lateral ventricles by the Choroid plexus
- Enters the 3rd ventricle then the 4th via the cerebral aqueduct where it exits into the SAS
- CSF is absorbed into the venous circulation in the sinuses of the dura
What are the 2 types of Hydrocephalus and what causes them?
Congenital - caused by ventircle malformation, causes enlargement of head
Aqquired - caused by blockage of the 4th ventricle ussualy due to fibrous adhesion or tumours
How do we treat Hydrocephalus?
- Insertion of a shunt that diverts flow away from the blockage
- Catheter end is inserted usually into a ventricle and other end usually goes to the peritoneal/abdominal cavity for drainage and reabsorption
What are shunts?
Sturdy and flexible plastic tube that consists of a shunt, catheter and valve
Voluntary muscle action is controlled by 2 systems; the _________ system controls voluntary motor function, the _________ system controls balance, posture and coordination.
Pyramidal
Extrapyramidal
The axons of the Pyramidal system travel through fiber tracts called _______ or __________ tracts
Pyramidal
Corticospinal tracts
The neurons in Extrapyramidal system have connections with the _______ and ________
Cerebellum
Basal Ganglia
Both pyramidal and extrapyramidal systems are under _______ control and produce ____________________________.
Cortical control
Smooth, integrated function of muscle
A muscle is considered paralysed when it is __________________________________
No longer subject to voluntary control
What causes flaccid paralysis?
Diseases of the lower motor neurons
What causes spastic paralysis?
Diseases of the cortical motor neurons
What happens during flaccid paralysis?
- Lower motor neurons are destroyed or interrupted (e.g. Poliomyelitis)
- Reflex arcs needed for muscle tone are lost
- Muscle goes limp and atrophies
What happens during spastic paralysis?
- Cortical neurons are lost (Stroke,Cerebral Palsy) and voluntary control is lost
- Muscle tone is maintained so there is no atrophy
Stroke is defined as an injury the the brain tissue resulting from a ____________________. The most common type is called an ________ and acounts for __% of cases
Disturbance in blood supply
Ischemic Stroke
80%
What is an aneurysm?
Localised bulging of the wall of an artery due to weakening of the wall over time
Describe the characteristics of an Ischemic Stroke:
- Caused by a blood clot or blockage of arteries
- Lack of blood flow and oxygen causes necrosis and degeneration of brain tissue (Infarction)
- Blockages may be caused by thrombosis, arteriosclerosis or an embolism
Thrombotic strokes are caused by __________. They ____ blood flow to the brain and provide an area on which ________ can form
Sclerotic Plaques
Slow
Blood clots can form
Embolic strokes are caused by ____________ that have formed in __________________ and have blocked blood supply to the brain
Blood clots/thrombi
In another part of the body
Describe the characteristics of a Haemorrhagic Stroke:
- Occurs when a blood vessel supplying the brain ruptures
- Rupture prevents oxygen and nutrients from reaching the brain
- Common in patients with hypertension
- Very severe, often fatal
Manifestations of a stroke depend on the _____________________ and the _____________________
Location of the brain damage
Degree of the tissue damage
Strokes generally result in:
- Extensive brain injury
- Paralysis due to upper motor neuron damage
- Sensory disturbances
- Speech problems
- Hemiplegia
What is Hemiplegia?
A stroke involving one cerebral hemisphere often leads to weakness and paralysis down the opposite side
What are the risk factors for stroke?
Uncontrollable: Controllable:
- Age - Hypertension (Biggest risk)
- History of stroke - Smoking/Drugs/Alcohol
- Race - Obesity
- Heredity - Carotid Artery Disease
- High cholesterol
What are the signs and symptoms of stroke?
- 50% of cases are asymptomatic
- Sudden numbness
- Confusion or trouble speaking or understanding speech
- Loss of vision
- Dizziness and loss of balance
How do we treat strokes?
Treatment depends on cause, it is important that CT, MRI and Angiograms are done to determine cause ASAP
How do we treat Thrombotic Strokes?
- Clot dissolving drugs like TPA (Tissue plasminogen activator) lessen the severity of the stroke by restoring blood flow
- Endartectomy to remove a partially blocked area or implantation of a stent to widen the lumen
How can we prevent stroke?
- Control blood pressure
- Stop smoking
- Exercise
- Balanced diet
- Reduce alcohol consumption
- Control diabetes
- Take asprin, omega 3 and vitamin E
What is a Transient Ischemic attack (TIA)?
A “mini stroke” caused by a temporary interference with blood supply to the brain due to low BP, decreased heart function and over-medicating of hypertension
What are the symptoms of TIAs?
- Light-headedness
- Numbness
- Loss of balance
- Fleeting blindness
- Trouble swallowing or speaking
How are TIAs treated?
- Use of anti-platelet agents, mainly aspirin
- Some incidences require a carotid endartectomy
Aneurysms most commonly occur in the _____________ at the base of the bain and the _____
Circle of Willis
Aorta
What are the 3 types of aneurysms?
Saccular - resembles a small sack
Fusiform - spindle shaped
Berry - berry-like in appearance
What is the difference between a True and False (psuedoaneurysm) Aneurysm?
True aneurysms involve out pouching of all layers of the arterial wall, may be due to infection, hypertension or be congenital
False/Pseudoaneurysm involve out pouching only of the adventitia, may be caused by trauma involving the intima
The most common type of aneurysm is a ______________________, it results from a _______ defect in the muscular and elastic tissue and is found particularly around the ________. It is associated with _______________
Congenital Cerebral Aneurysm (CCA)
Congenital defect
Circle of Willis
Polycystic Kidney Disease
How are aneurysms located?
Via an angiogram
How do we treat aneurysms?
- Fixing a titanium clip around the aneurysms
- Coil Embolisation is done by filling of the swelling with a coil to prevent blood entering the aneurysm
What are the risk factors for developing aneurysms?
- Hypertension
- Diabetes
- Smoking
- Alcoholism
- Insomnia
What are the 4 types of infection found in the nervous system?
Meningitis - Infection of the meninges of the brain or spinal cord
Encephalitis - Infection of the brain tissue
Meningoencephalitis - Infection of both the brain and meninges
Myelitis - Infection of the spinal cord
What are the manifestations of CNS infections?
Fever
Stiffness of neck
Headache
Alteration of conciousness
Meningitis is caused by ______ and ______ infections, with _____ being the most common at 90% of cases
Bacterial or viral
Viral is most common
Bacterial meningitis is caused mainly by either ____________ or ____________. __________ is the only one known to cause epidemics
Pneumococcus
Meningococcus
Meningococcus
Meningococcus is a gram-________ bacteria. There are __ types of meningococcus. ___ serous groups are responsible for all cases in humans
Negative
13
5
How are meningococci transmitted between patients? How long is the average incubation period?
Through droplets of respiratory or throat secretions
4 days
Meningococcal may present as ________ or the more severe __________
Meningitis
Septicaemia
How do meningococci infect patients?
- They enter the blood through the epithelial cells of the nasopharynx
- They avoid immune clearance due to their polysacchirde capsule
- Enter the ventricles of the brain and .’. the CSF
- Bacteria lyse releasing it’s cell wall products into the subarachnoid space causing inflammation and purulent exudate to form
What are the signs and symptoms of Meningococcal infection?
- Severe headache
- Fever
- Fatigue
- Stiff/painful muscles and joints, especially neck
- Sensitivity to light
- Purple bruise like rash
- Rapid breathing
- Cold hands and feet and shivers
How is meningococcal diagnosed?
Lumbar punctures showing purulent CSF
Sometimes bacteria can be see in microscopic examination of CSF
How do we treat meningococcal?
Antibiotics like penicillin, ampicillin, cloramphenicol and ceftriaxone
How can we prevent meningococcal?
Polyssachiride vaccinations for the Serous groups A, C, Y and W135
No vaccine for Serous group B
A prion is a _____________________ particle and is a type of ________ agent
Proteinaeceous infectious particle
Infectious
Prions are able to convert _______ from ______ conformations to _______ conformations
Proteins
Normal
Abnormal
Prions are responsible for ___________________________ and these diseases are fatal and untreatable
Transmissible Sponfigiform Encephalopathies
__________________ is the most common human prion disease. It is fatal within ________. The symptoms are caused by _____________ associated with excessive __________
Creutzfeldt-Jakob disease (CJD)
6 months
Progressive neural cell death
Prion build up
What are the symptoms of CJD?
- Rapid dementia leading to memory loss, personality changes and hallucinations
- Speech impairment
- Jerky movements
- Seizures
- Loss of balance
Explain the histology of CJD:
- Affected individuals brains appear spongy because they have large vacuoles that look like holes
- Neurons degenerate and astrocytes proliferate in response
How is CJD transmitted?
- Contact with infected tissues or biological material
- Can be inherited or sporadic
- Cannibalism
What is Alzheimer’s Disease?
A chronic neurodegenerative disease characterised by progressive cognitive deterioration and behavioral changes
What are the symptoms of AD?
- Short term memory loss
- Decreasing cognitive function
- Emotional disturbances
Describe the histopathology of AD:
Neurofibillary tangles form:
- Degenerative changes in the neuron microfillaments
- Fibrils become a thickened tangled mess
- Disrupts axonal transport
Amyloid plaques form:
- Masses of broken down filaments form amyloid plaques that are insoluble to microglia
- Scarring occurs due to insolubility
What is amyloid?
The general term for protein fragments that the body produces normally
___________ levels decrease during AD
Acetylcholine
Macroscopically, AD causes atrophy of the __________
Cerebral cortex
What causes AD?
- Unknown, but thought to be due to disruption of brain metabolism
- Genetic factors: Autosomal dominant mutations in Presenilin 1 and 2 and Amyloid precursor protein
What are the risk factors for developing AD?
- Advancing age
- ApoE epsilon 4 genotype in some populations
- Head injury
- Poor CVS health
- Exposure to heavy metals
What reduces to risk of developing AD?
- Intellectual stimulation
- Social interaction
- Physical exercise
- Healthy diet low in saturated fats
How do we treat AD?
- No cure
- Medications offer small symptomatic benefit
- Research in medications aimed at reducing β-amyloid accumulation
What is multiple sclerosis?
A chronic inflammatory disease that affects the central nervous system characterised by periodic and random focal degeneration of myelin sheath
What causes the myelin sheath to break down in MS?
- Immune cells react to the myelin
- Astrocytes attempt to heal the cells but cause glial scarring
- The local ares of scar formation are called multiple sclerotic plaques
Constant glial scarring causes _______ of the neurons and _____________________________.
Hardening
Disrupts the action potential conduction
Multiple sclerotic plaques can be seen by using ______
MRI
MS appears in people between __ and __ years old. It is more common in _____ than _____
20 - 40 years old
Women than men
What are the signs and symptoms of MS:
The nature of symptoms depend on the region that has been scarred
- Change in sensation
- Visual problems
- Muscle weakness
- Depression
- Coordination and speech difficulties
- Severe fatigue and pain
What causes MS?
The precise cause is not really known
- Multi-factorial
- Possibly genetic
- Possibly viral infection
T-cells are known to play a key role in the development of _____________. This means that the disease can be classed as ___________.
Multiple Sclerosis
Autoimmune
Explain how T-lymphocytes have a role in the degeneration of myelin
- T-cells recognise myelin as harmful
- T-cells release cytokines to attract macrophages, antibodies and cytokines
- Macrophages, cytokines and antibodies attack and degenerate the myelin
What cells attempt to remyelinate fibers affected by MS?
Oligodendrocytes
How do we treat MS?
- No cure
- Treatments aim to halt acute attacks and restore function
- Glucocorticoids halt acute attacks
- Interferons IFN-1 a/b regulate the immune system involvement
What is Parkinson’s disease?
A chronic debilitating disease characterised by excessive muscle contraction
What are the symptoms of Parkinsons?
- Muscle Rigidity
- Tremors
- Bradykinesia (slowing of physical movement)
- Akinesia (loss of physical movement in extreme cases)
The primary symptoms of Parkinson’s disease are caused by insufficient production of ________ which is produced by _______________ found in the ________.
Dopamine
Dopaminergic Neurons
Substantia Nigra
What are the secondary symptoms of Parkinson’s disease?
High level cognitive function impairment and subtle language problems
Parkinson’s is both __________ and _________
Chronic and progressive
How does Parkinson’s disease develop?
- Progressive loss of Dopaminergic neurons in the substantia nigra
- The synapse between these neurons and the basal ganglia no longer synapse correctly
- Decrease in neurons and dopamine
What does a decrease in dopamine do?
Increases muscle rigidity
Increases tone
Abnormal involuntary movements
What is the cause of Parkinson’s?
- Idiopathic
- Possibly links to genetics, drugs, head trauma
How is Parkinson’s treated?
- No cure
- Medications relieve symptoms
- L-dopa is a drug that gets converted to dopamine in the dopaminergic neurons
- Dopamine agonists
- Research in stem cell therapy
What are the common tumours that occur in the PNS
- Schwannomas, tumour of the schwann cells that can be singular or multiple and benign or malignant
- Neuromas or neurofibromas are solitary benign tumours that are often attached to nerve trunks
What is multiple neurofibromatosis?
- Autosomal Dominant trait
- Skin is disfigured by multiple tumours in the cutaneous nerves
- 10-15% become malignant Schwann Sarcomas
- Surgical intervention is required
What kind of tumours can occur in the brain?
Primary tumour, less common
Metastatic tumour from other cancers (i.e. breast and lung cancer)
Tumours in the brain can arise from:
Meninges = Meningioma
- Benign tumour of the Arachnoid cells attached to the Dura
Glial cells = Glioma
- Astrocytoma
- Oligodendroglioma
Ventricular lining = Ependymoma
Rarely blood vessels
Lymphomas may occur
Primary tumours in the brain ______________ metastasise outside of the nervous system
do not normally
Symptoms of brain tumours are dependent on _________________ but are commonly associated with __________
The size and location
Headaches
How do we treat brain tumours?
- Surgical resection
- Chemotherapy
- Radiotherapy
What types of tumours affect the spinal cord?
Ependymomas of the thin filament of tissue at the end of the caudal end of the spinal cord (filum terminale)
Multiple Myeloma (Metastatic tumour) is a tumour of the plasma cells in the bone marrow that may extend into the spinal cavity
Tumours involving the spine usually result in ___________________
Loss of motor function below the level of injury
Peripheral nerve diseases are caused by _________ and vary degrees of ______________. The effects depend largely on the extend of these issues
Demyelination
Axonal degeneration
Peripheral nevre injuries may result from __________, ______ or a ___________. They can also be caused by __________________ of the nerve by a ___________, this is called ____________.
Deep lacerations Fracture Crushing injury External compression by a fibrous band/ligament Nerve entrapment Neuropathy
What is Carpal Tunnel Syndrome (CTS)?
A medical condition in which the median nerve is compressed at the wrist causing tingling, pain, weakness and coldness in parts of the hand
How do we treat CTS?
Surgical resection of the ligament compressing the median nerve
What is polyneuritis?
A peripheral nerve disorder characterised by progressive muscle weakness, numbness and tingling. Muscles may show a degree of atrophy.
Polyneuritis is caused by ______________, ___________ and __________.
Systemic diseases like diabetes, exposure to heavy metals, alcoholism
What is Guillain Barre’s syndrome?
An idiopathic form of polyneuritis characterised by widespread, patchy demyelination of nerves with mild inflammatory changes
Guillain Barre’s syndrome usually occurs after _____________ and is due to an autoimunne reaction to _____. It is associated with progressive _________________ and can also affect ________.
Viral infections (like measels and mumps)
Myelin
Weakness in the leg
Breathing
Symptoms of Guillain Barre’s syndrome are usually _______ and patients generally ______ in 1 month
Transient
Recover
The affects that HIV has on the nervous system are classifed into 3 groups:
- Infections directly associated with the virus
- Infections caused by opportunistic pathogens
- AIDS-related tumours
In addition to infecting T-cells, AIDS can infect ________ that can transport the the virus to the CNS
Monocytes
AIDS viral infection in the nervous system may lead to:
CNS:
- Acute viral meningitis
- AIDS related dementia (Similar to Alzheimers)
PNS:
- Peripheral nerve disorders e.g. Polyneuritis
Common opportunistic pathogens that affect the nervous system associated with AIDS infection are:
Herpes Virus Infection
CMV
Toxoplasma Gondii
AIDS sufferers are predisposed to various _______ neoplasms like ___________ and ________. These may _________ the nervous system. They carry a ____ prognosis.
Malignant Kaposi's sarcoma Lymphoma Metastises to Very poor
