Disorders of the Neurological System Flashcards
Where are action potentials initiated?
Junction between the cell body and the axon (if enough excitatory info)
Where does the action potential go from there?
Down the axon until the axon terminals, will then signal to release neurotransmitters
What are the two vessels that bring blood to the brain?
Internal carotid artery and the middle cerebral artery, form an anastomosis
What is the purpose of the blood brain barrier?
Serves as a physical barrier to chemicals
What elements compose the blood brain barrier?
Endothelial cells connected by tight junctions (rest on the basement membrane), astrocyte foot processes (surround the capillaries, help regulate) and pericytes (embedded within the basement membrane)
What are the meninges?
Layers of connective tissue that help to stabilize the brain and protect the structures from hitting surrounding bones
What are the components that make up the meninges?
Dura matter, arachnoid matter, pia matter
Which layer of the meninges is the thickest?
The dura matter which is the outermost region
What is found within the arachnoid matter?
Subarachnoid space which holds CSF
Where is the pia matter located?
On the surface of the brain itself, this layer is fine and delicate
What are the two types of ischemic stroke that can occur?
Thrombotic (more common, thrombus formed within the cerebrovasculature) and embolic (thrombus formed outside of the brain that breaks off and travels to, usually obstructs smaller vessels)
What are the two areas that develop when an infarction occurs?
Ischemic core (most severe area, neuronal and glial death within moments) and penumbra (surrounding area to this core, can survive for hours with full recovery)
Which area do therapeutic strategies target?
Penumbra!
Where does the ischemic cascade start?
Within the penumbra
What are the three elements of the ischemic cascade?
Excitotoxicity, oxidative stress, inflammation
What occurs during excitotoxicity in the ischemic cascade?
Sustained activation of neurons within penumbra, Ca2+ enters neurons, stimulates NT release, but when accumulates b/c cannot be pumped out= death signal. Neurons won’t have enough energy to maintain action potential, remain excited and cannot repolarize
How does inflammation impact the blood brain barrier?
Disrupts it and makes it more permeable= cerebral edema
What pathologic changes occur in hemorrhagic strokes?
Pooling of blood results in compression of surrounding tissues and this can disrupt blood flow= ischemic cascade activation. Hemoglobin is toxic to neurons!
What are common causes of hemorrhagic strokes?
Uncontrolled hypertension or ruptured aneurysms
What clears away the blood in a hemorrhagic stroke?
Macrophages and astrocytes, results in a cavity with dense glial scarring
What are oligodendrocytes?
Glial cells that produce a lipid-rich substance called myelin, wrap it around axon of the neuron
What is the purpose of myelin?
Serves as an insulator, prevents electrical information from leaking out
What are the Nodes of Ranvier?
Gaps in the myelin, allow ions to move in and out to propagate the action potential down the axon
What occurs in multiple sclerosis?
Autoimmune targets cells that produce myelin, resulting in myelin degeneration and loss of axons/killing off of oligodendrocytes
What are potential causes of MS?
Genetics, epigenetics, infectious component (infection may precipitate the autoimmune response–many positive for the EBV which has viral proteins that resemble myelin)
What is the pathophysiology in MS?
Immune cells attack oligodendrocytes, cytokines and ROS damage axons. Have Th1 and Th17 CD4+ cells involved, CD8+, macrophages and plasma cells
What are the types of MS?
Relapsing and remitting (65-80%), primary progressive (10-20%)
What are some of the clinical manifestations of MS?
Sensory or motor abnormalities- numbness, tingling, pain, weakness, slurred speech, etc., usually asymmetrical, can lead to brain atrophy, mood disorders, etc.
What region of the brain does Parkinson’s affect?
Primarily basal ganglia
What is Parkinson’s disease?
Chronic and progressive neurodegenerative disorder, results in motor deficits and lose neurons within the basal ganglia (less able to help coordinate movement)
Which gene places individuals at greater risk for Parkinson’s?
Abnormal a-synuclein gene
What occurs in Parkinsons?
Substantia nigra releases dopamine, there is a destruction of these neurons in the pars compacta of the substantia nigra
What are Lewy bodies in Parkinson’s disease?
Intracellular accumulations of the a-synuclein protein, gets mutated and aggregates which is toxic to neurons
What pathophysiological processes occur in Parkinson’s?
Presence of Lewy bodies, dopaminergic neuron loss, mitrochrondrial dysfunction and ROS
What are some of the clinical manifestations of Parkinson’s?
Motor related- asymmetric, regular, rhythmic tremors, rigidity, bradykinesia (lack of ability to produce smooth motions), postural abnormalities, constipation, oil skin, impulse control, difficulty forming thoughts, other non-motor symptoms
What is Alzheimer’s disease?
Progressive neurodegenerative disorder that results in memory loss and overall decrease in intellectual function. Loss of neurons but in higher functioning areas
What characterizes Alzheimers?
Senile plaques, neurofibrillary tangles, neuronal death, loss of synapses
What are senile plaques?
Aggregation of AMYLOID-B PEPTIDES, toxic to neurons, can become surrounded by activated microglial and astrocytes coming to contain damage
What are neurofibrillary tangles?
Aggregate of TAU protein (insoluble, hyperphosphorylated), toxic, start to form insoluble masses
What prompts neuronal damage in Alzheimers?
Senile plaques and neurofibrillary tangles along with mitochondrial dysfunction and ROS, inflammation, cerebrovascular abnormalities (decrease in oxygen/nutrients, accumulation of aggregates around blood vessels, leaky BBB)
What are some clinical manifestations of Alzheimers?
Become progressively more forgetful, decline in concentration/problem solving/judgement, behavioural abnormalities, motor abnormalities
What is a protective measure against Alzheimers?
Estrogen- blocks some harmful effects of Amyloid-B protein
What are two infections of the CNS?
Meningitis and encephalitis
What occurs in viral meningitis?
Enters CNS, spreads through subarachnoid space and causes inflammation, resolves on its own and can be caused by numerous viruses (Enterovirus, measles, mumps, herpes, etc)
What occurs in bacterial meningitis?
More severe, high incidence in neonates, reaches the subarachnoid space through blood, causes severe inflammatory response, purulent exudate impairs the removal of CSF and cerebral edema occurs
What are the likely causes of bacterial meningitis?
In neonates= E.Coli and Group B strep, in adults= Streptococcus pneumoniae, Nesisseria meningitidis, H. Influenza
What occurs in encephalitis?
Inflammation of brain parenchyma (actual brain tissue), can occur alongside meningitis
How are traumatic brain injuries characterized?
Mild, moderate, severe concussion
What characterizes a severe TBI?
GCS <8, LOC >24 hours, brainstem involvement, permanent deficits
What characterizes moderate TBI?
GCS 8-13, LOC >30 min, no brainstem involvement, long duration amnesia, some permanent deficits
What characterizes a mild TBI?
GCS 13-15, may or may not have LOC (momentarily if anything), <24 hours amnesia
What is a TBI?
Traumatic brain injury, alteration in brain function caused by external force
What is a closed injury?
Striking of head on hard surface, rapidly moving object striking head, blast waves. Results in focal injury, may be coup or contrcoup, can result in contusions and hematomas
What types of hematomas can occur in TBI?
Epidural hematoma, subdural hematoma, intracerebral hematoma
What is an open injury?
Skull fracture, break in dura= exposure of cranial contents to environment
What two types of fractures can occur in an open injury?
Compound skull fracture, basilar skull fracture
What is often the cause of diffuse TBI?
Mechanical effects(whiplash, rotational forces) that result in stretching and shearing of axonal fibers
What are Schwann cells?
Provide support for neuronal processes in PERIPHERAL nervous system
What does the Wernicke area do?
Interpreting speech
What is the corpus callosum?
Transverse fiber tract that connects two cerebral hemispheres
What is the pons region in the brain?
Located below midbrain and above medulla- transmits info from cerebellum to brain stem and b/t two hemispheres
What is the vagus nerve?
A part of the PNS, stimulates results in PNS activity
Sympathetic motor neurons at the neuromuscular junction relase what?
Norepinephrine
What is an effect of Alpha-1 receptor stimulation?
Constriction of the coronary arterioles
