pathophys 2 test 3 all pts combined
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Questions and Answers

Which of the following neurotransmitters is typically released with another transmitter into the synapse and modifies the effects of that neurotransmitter on the postsynaptic neuron?

  • Serotonin (correct)
  • Dopamine
  • Tryptophan
  • GABA

    • What is the primary function of GABA in the brain?

  • To excite the postsynaptic neuron
  • To release serotonin into the synapse
  • To increase respiratory rate
  • To inhibit the creation of an action potential (correct)

    • What is the effect of increased GABA signaling in the medulla?

  • Decreased respiratory rate (correct)
  • Increased heart rate
  • Decreased blood pressure
  • Increased respiratory rate

    • Why are benzodiazepines used in ETOH withdrawal?

    <p>Because they are indirect GABA agonists</p> Signup and view all the answers

    What is the effect of serotonin on muscle/motor pathways?

    <p>Excitatory</p> Signup and view all the answers

    Which of the following neurotransmitters is NOT a catecholamine?

    <p>Serotonin</p> Signup and view all the answers

    What is the primary function of acetylcholinesterase in the synapse?

    <p>Break down acetylcholine into its component parts</p> Signup and view all the answers

    Which of the following is an inhibitory neurotransmitter?

    <p>GABA</p> Signup and view all the answers

    What is the effect of increased levels of serotonin on the body?

    <p>Regulation of body temperature, sleep, and mood</p> Signup and view all the answers

    Which of the following diseases is associated with decreased levels of dopamine?

    <p>Parkinson's disease</p> Signup and view all the answers

    What is the effect of acetylcholine binding to its receptors on the postsynaptic membrane?

    <p>Opening of ion channels and depolarization of the neuron</p> Signup and view all the answers

    Which of the following is an excitatory neurotransmitter?

    <p>Acetylcholine</p> Signup and view all the answers

    What is the precursor to norepinephrine?

    <p>Dopamine</p> Signup and view all the answers

    Which of the following is a characteristic of catecholamines?

    <p>Synthesized from tyrosine</p> Signup and view all the answers

    What is the effect of increased levels of norepinephrine on the body?

    <p>Increased anxiety and depression</p> Signup and view all the answers

    What is the main function of microglia in the Central Nervous System?

    <p>To remove debris within CNS</p> Signup and view all the answers

    Which type of glial cell is responsible for creating and maintaining the myelin sheath in the Peripheral Nervous System?

    <p>Schwann Cells</p> Signup and view all the answers

    What is the main function of the thalamus?

    <p>Relay center for sensory information</p> Signup and view all the answers

    What is the term for the 'nerve glue' that makes up the support system of the nervous system?

    <p>Neuroglia</p> Signup and view all the answers

    What is the term for the unmyelinated cell bodies found in the Central Nervous System?

    <p>Gray matter</p> Signup and view all the answers

    What is the term for the group of gray matter nuclei deep in the forebrain that are connected with the cortex, thalami, and brain stem?

    <p>Basal ganglia</p> Signup and view all the answers

    What is the function of oligodendrocytes in the Central Nervous System?

    <p>To deposit myelin within CNS</p> Signup and view all the answers

    What is the term for the organized tracts of myelinated axons in the Central Nervous System?

    <p>White matter</p> Signup and view all the answers

    What is the main cause of ischemic stroke?

    <p>Atherosclerosis</p> Signup and view all the answers

    What is the percentage of ischemic strokes that are due to lacunar infarcts?

    <p>25%</p> Signup and view all the answers

    What is the term for the area of salvageable tissue surrounding the central core of irreversible ischemia?

    <p>Penumbra</p> Signup and view all the answers

    What is the goal of thrombolytic therapy in ischemic stroke?

    <p>To restore perfusion to the penumbra</p> Signup and view all the answers

    Which of the following types of neurons is responsible for transmitting impulses from the CNS to an effector organ?

    <p>Motor neurons</p> Signup and view all the answers

    What is the most common location for embolic strokes to occur?

    <p>Middle cerebral artery</p> Signup and view all the answers

    What is the primary function of the somatic nervous system?

    <p>Regulation of voluntary motor control of skeletal muscle</p> Signup and view all the answers

    What is the term for the episode of neurologic dysfunction lasting less than 1 hour due to transient focal cerebral ischemia?

    <p>Transient ischemic attack (TIA)</p> Signup and view all the answers

    What is the percentage of all strokes that are due to atrial fibrillation?

    <p>15-25%</p> Signup and view all the answers

    Which type of glial cell is responsible for providing structural support and facilitating neurotransmission in the CNS?

    <p>Astrocytes</p> Signup and view all the answers

    What is the term for the process of cell death due to ischemia, leading to necrosis and swelling?

    <p>Infarction</p> Signup and view all the answers

    What is the term for the process by which nerve impulses jump from one node of Ranvier to the next, allowing for faster transmission of signals?

    <p>Saltatory conduction</p> Signup and view all the answers

    What is the window of opportunity for restoring perfusion to the penumbra to prevent necrosis and loss of function?

    <p>2-3 hours</p> Signup and view all the answers

    Which type of neuron is classified based on the number of processes extending from the cell body?

    <p>Multipolar neurons</p> Signup and view all the answers

    What is the term for the receptive portion of a neuron that receives signals from other neurons?

    <p>Dendrites</p> Signup and view all the answers

    What is the current standard of care for thrombolytic therapy in ischemic stroke?

    <p>Tenecteplase (TNK)</p> Signup and view all the answers

    Which type of neuron is responsible for transmitting impulses between neurons?

    <p>Interneurons</p> Signup and view all the answers

    What is the term for the division of the PNS that carries sensory information towards the CNS?

    <p>Ascending (afferent) pathway</p> Signup and view all the answers

    What is the term for the process by which one neuron receives many messages from several different cells at the same time?

    <p>Convergence</p> Signup and view all the answers

    What is the term for the autonomic nervous system division that is responsible for the 'rest and digest' response?

    <p>Parasympathetic nervous system</p> Signup and view all the answers

    What is the primary cause of small microaneurysms in hemorrhagic strokes?

    <p>Hypertension</p> Signup and view all the answers

    Which type of edema is most commonly seen in noncommunicating hydrocephalus?

    <p>Interstitial edema</p> Signup and view all the answers

    What is the percentage of the population with saccular (Berry) aneurysms?

    <p>2%</p> Signup and view all the answers

    What is the primary mechanism of cerebral edema due to tumors?

    <p>Increased permeability of capillaries</p> Signup and view all the answers

    What is the most common cause of spontaneous subarachnoid hemorrhage?

    <p>Trauma</p> Signup and view all the answers

    What is the primary mechanism of cytotoxic cerebral edema?

    <p>Damage to Na+/K+ membrane pumps</p> Signup and view all the answers

    What is the primary characteristic of arteriovenous malformations (AVM)?

    <p>Tangle of abnormal arteries and veins</p> Signup and view all the answers

    What is the primary consequence of massive intracerebral hemorrhage (> 150 mL)?

    <p>Cerebral perfusion falls to zero</p> Signup and view all the answers

    What is the primary characteristic of saccular (Berry) aneurysms?

    <p>Arises at forks of arteries in the base of the brain</p> Signup and view all the answers

    What is the primary mechanism of cerebral hemorrhage reabsorption?

    <p>Macrophages and astrocytes clear away blood</p> Signup and view all the answers

    Which of the following cognitive domains is NOT typically affected in Alzheimer's disease?

    <p>Motor control</p> Signup and view all the answers

    What is the main function of cholinesterase inhibitors in the treatment of Alzheimer's disease?

    <p>To decrease the breakdown of acetylcholine</p> Signup and view all the answers

    Which of the following meningeal layers is tightly adhered to the skull?

    <p>Dura mater</p> Signup and view all the answers

    What is the primary function of cerebrospinal fluid?

    <p>To provide a hydraulic skeleton to the brain</p> Signup and view all the answers

    What is the typical pH of cerebrospinal fluid?

    <p>7.3</p> Signup and view all the answers

    Which of the following is NOT a common cause of a subdural hematoma?

    <p>Ruptured aneurysm</p> Signup and view all the answers

    What is the function of the choroid plexus?

    <p>To produce cerebrospinal fluid</p> Signup and view all the answers

    Which of the following is a characteristic of cerebrospinal fluid?

    <p>pH of 7.3</p> Signup and view all the answers

    What is the function of arachnoid granulations?

    <p>To reabsorb cerebrospinal fluid</p> Signup and view all the answers

    What is the daily production of cerebrospinal fluid?

    <p>600 cc</p> Signup and view all the answers

    What is the primary difference between nerve repair in the Central Nervous System (CNS) and Peripheral Nervous System (PNS)?

    <p>CNS has a reduced ability to recover from injury, whereas PNS can repair</p> Signup and view all the answers

    What is the function of Nodes of Ranvier in myelinated neurons?

    <p>To increase the conduction velocity of nerve impulses</p> Signup and view all the answers

    What is the primary function of oligodendrocytes in the Central Nervous System?

    <p>To deposit myelin within the CNS</p> Signup and view all the answers

    What is the term for the degeneration of the distal nerve segment that occurs after injury to a peripheral nerve?

    <p>Wallerian degeneration</p> Signup and view all the answers

    What is the primary focus of multiple sclerosis treatment?

    <p>Slowing the rate of demyelination</p> Signup and view all the answers

    What is the common name for the 'JC' virus?

    <p>JC virus</p> Signup and view all the answers

    What is the primary characteristic of leukodystrophies?

    <p>Diseases caused by intrinsic factors such as genetic mutations</p> Signup and view all the answers

    What is the typical course of brain adaptation to hyponatremia?

    <p>Full adaptation within 2 days</p> Signup and view all the answers

    What is the result of the loss of the myelin sheath in demyelinating diseases?

    <p>Decreased conduction velocity of nerve impulses</p> Signup and view all the answers

    What is the result of rapid correction of chronic hyponatremia?

    <p>Shear forces and shifts in osmolytes cause injury to astrocytes and oligodendrocytes</p> Signup and view all the answers

    What is the primary cause of demyelination in Metachromatic Leukodystrophy?

    <p>Deficiency of the enzyme Arylsulfatase-A</p> Signup and view all the answers

    What is the primary difference between myelinated and unmyelinated neurons?

    <p>Myelinated neurons have a myelin sheath, while unmyelinated neurons do not</p> Signup and view all the answers

    What is the characteristic of Alzheimer's disease pathology?

    <p>Intracellular neurofibrillary tangles and extracellular beta-amyloid deposits</p> Signup and view all the answers

    What is the term for the process by which the proximal end of the injured neuron grows out to form a new axon?

    <p>Terminal sprouting</p> Signup and view all the answers

    What is the role of CD4+ T-cells in the pathophysiology of Multiple Sclerosis?

    <p>They present antigens to other immune cells and activate an immune response</p> Signup and view all the answers

    What is the result of the activation of B-cells in the pathophysiology of Multiple Sclerosis?

    <p>They produce antibodies against the oligodendrocytes</p> Signup and view all the answers

    What is the primary function of tau proteins in microtubules?

    <p>Microtubule stabilization</p> Signup and view all the answers

    What is the primary function of astrocytes in the Central Nervous System?

    <p>To fill spaces between neurons and surround blood vessels</p> Signup and view all the answers

    What is the term for the group of rare, inherited metabolic disorders that primarily affect the white matter of the Central Nervous System?

    <p>Leukodystrophies</p> Signup and view all the answers

    What is the characteristic pattern of symptoms seen in Relapsing-Remitting Multiple Sclerosis?

    <p>Periods of relapses with periods of full or partial recovery</p> Signup and view all the answers

    What is the clinical criteria for Alzheimer's disease diagnosis?

    <p>Insidious onset and progressive course of cognitive decline</p> Signup and view all the answers

    What is the role of regulatory T-cells in the remission phase of Relapsing-Remitting Multiple Sclerosis?

    <p>They release cytokines to shut down the immune response</p> Signup and view all the answers

    What is the result of slow correction of chronic hyponatremia?

    <p>Cells acclimate to osmotic changes and prevent damage</p> Signup and view all the answers

    What is the term for the formation of scar tissue in response to the injury of oligodendrocytes in Multiple Sclerosis?

    <p>Plaque formation</p> Signup and view all the answers

    What is the characteristic of Central Pontine Myelinolysis?

    <p>Demyelination due to rapid correction of hyponatremia</p> Signup and view all the answers

    What is the effect of correcting hyponatremia on brain cells?

    <p>Water moves out of the cells, causing them to shrink</p> Signup and view all the answers

    What is the characteristic imaging finding in Multiple Sclerosis?

    <p>White matter lesions on the brain and spinal cord</p> Signup and view all the answers

    What is the term for the first acute neurologic episode in Multiple Sclerosis?

    <p>Clinically isolated syndrome</p> Signup and view all the answers

    What is the result of the re-myelination process in Multiple Sclerosis?

    <p>The myelin sheath is repaired</p> Signup and view all the answers

    What is the role of macrophages in the pathophysiology of Multiple Sclerosis?

    <p>They phagocytose dead cells and debris</p> Signup and view all the answers

    What is the primary mechanism of injury in diffuse axonal injury?

    <p>Shifting/rotation of the brain within the skull during trauma</p> Signup and view all the answers

    Which type of lesions are commonly seen in the basal frontal and temporal areas due to acceleration/deceleration injuries?

    <p>Focal cerebral contusions</p> Signup and view all the answers

    What is the characteristic of mild traumatic brain injury (mTBI)?

    <p>Temporary impairment of neurologic function</p> Signup and view all the answers

    What is the primary risk factor for secondary brain insults after an initial traumatic brain injury?

    <p>Vulnerability of cells to further damage</p> Signup and view all the answers

    What is the hallmark symptom of chronic traumatic encephalopathy?

    <p>Progressive neurological disorder</p> Signup and view all the answers

    What is the most common cause of meningitis?

    <p>Viral</p> Signup and view all the answers

    What is the primary mechanism of bacterial meningitis?

    <p>All of the above</p> Signup and view all the answers

    What is the classic triad of clinical manifestations of meningitis?

    <p>Fever, neck stiffness, and altered mental status</p> Signup and view all the answers

    What is the primary goal of treatment in bacterial meningitis?

    <p>Eliminating the bacterial pathogen</p> Signup and view all the answers

    What is the role of steroids in the treatment of bacterial meningitis?

    <p>Reducing inflammation</p> Signup and view all the answers

    What is the primary indication of a lumbar puncture?

    <p>Measuring intracranial pressure (ICP)</p> Signup and view all the answers

    What is the characteristic CSF finding in meningitis?

    <p>Elevated WBCs, bacteria, and decreased glucose</p> Signup and view all the answers

    What is the primary cause of increased intracranial pressure (ICP)?

    <p>Space-occupying lesions</p> Signup and view all the answers

    What is the primary goal of an external ventricular drain?

    <p>Monitoring ICP</p> Signup and view all the answers

    What is the characteristic of obstructive hydrocephalus?

    <p>Blockage of CSF flow</p> Signup and view all the answers

    What is the primary treatment option for obstructive hydrocephalus?

    <p>VP Shunt</p> Signup and view all the answers

    What is the characteristic CSF finding in viral meningitis?

    <p>Elevated WBCs, normal glucose</p> Signup and view all the answers

    What is the primary cause of hydrocephalus ex vacuo?

    <p>Loss of surrounding brain tissue</p> Signup and view all the answers

    What is the primary mechanism of traumatic brain injury (TBI)?

    <p>All of the above</p> Signup and view all the answers

    What is the characteristic of subarachnoid hemorrhage?

    <p>All of the above</p> Signup and view all the answers

    What is the primary function of the peripheral decarboxylase inhibitor Carbidopa in the treatment of Parkinson's disease?

    <p>To prevent the peripheral metabolism of Levodopa, reducing side effects</p> Signup and view all the answers

    What is the characteristic of the 'pill-rolling' tremor seen in Parkinson's disease?

    <p>It is a slow, rhythmic movement at rest</p> Signup and view all the answers

    What is the primary mechanism of action of Riluzole in the treatment of Amyotrophic Lateral Sclerosis (ALS)?

    <p>It blocks the release of glutamate, which is believed to play a role in neuronal injury</p> Signup and view all the answers

    What is the term for the group of neurons that are affected in the early stages of Amyotrophic Lateral Sclerosis (ALS)?

    <p>Upper motor neurons</p> Signup and view all the answers

    What is the primary function of the basal ganglia?

    <p>Initiating voluntary motor movement</p> Signup and view all the answers

    What is the primary function of the autonomic nervous system (ANS)?

    <p>To maintain homeostasis</p> Signup and view all the answers

    What is the role of the substantia nigra in the basal ganglia?

    <p>Producing dopamine and regulating movement</p> Signup and view all the answers

    What is the difference between upper and lower motor neurons?

    <p>Upper motor neurons transmit signals from the cortex to the spinal cord, while lower motor neurons transmit signals from the spinal cord to the peripheral nervous system</p> Signup and view all the answers

    What is the term for the 'nerve glue' that makes up the support system of the peripheral nervous system?

    <p>Glia</p> Signup and view all the answers

    What is the term for the type of nerve fibers that are affected in diabetic neuropathy?

    <p>Large myelinated fibers</p> Signup and view all the answers

    What is the result of dysfunction in the indirect and direct pathways of the basal ganglia?

    <p>HYPERkinetic disorders, such as Huntington's disease</p> Signup and view all the answers

    What is the term for the sensation of pain that is mediated by the spinothalamic tract?

    <p>Second pain</p> Signup and view all the answers

    What is the primary characteristic of chorea, a symptom of Huntington's disease?

    <p>Involuntary, non-rhythmic movements</p> Signup and view all the answers

    What is the term for the division of the peripheral nervous system that carries sensory information towards the CNS?

    <p>Afferent division</p> Signup and view all the answers

    What is the genetic mutation responsible for Huntington's disease?

    <p>Triplet repeat expansion of a DNA sequence responsible for coding for glutamine</p> Signup and view all the answers

    What is the primary effect of the accumulation of abnormal protein in Huntington's disease?

    <p>Neuronal death and dysfunction</p> Signup and view all the answers

    What is the primary function of the spinal cord in the peripheral nervous system?

    <p>To transmit sensory information to the CNS</p> Signup and view all the answers

    What is the primary characteristic of Parkinson's disease?

    <p>Progressive degeneration of dopamine-producing neurons in the substantia nigra</p> Signup and view all the answers

    What is the term for the 'relay station' for sensory and motor signals in the brain?

    <p>Thalamus</p> Signup and view all the answers

    What is the result of damage to the putamen and caudate nucleus in the basal ganglia?

    <p>Diffuse atrophy of the corpus striatum</p> Signup and view all the answers

    What is the primary function of the median nerve in the hand?

    <p>Motor and sensory innervation</p> Signup and view all the answers

    What is the characteristic of the carpal tunnel?

    <p>Formed by the transverse carpal ligament superiorly and the carpal bones inferiorly</p> Signup and view all the answers

    What is the effect of compression of the median nerve?

    <p>Ischemia and mechanical disruption</p> Signup and view all the answers

    What is the characteristic of Charcot-Marie-Tooth Disease (CMT)?

    <p>A demyelinating disorder of the peripheral nervous system</p> Signup and view all the answers

    What is the pathogenic mechanism of CMT?

    <p>Abnormalities in the axons or production/maintenance of the myelin sheath</p> Signup and view all the answers

    What is the clinical manifestation of Myasthenia Gravis?

    <p>Generalized proximal limb weakness and fatigability with repeated activities</p> Signup and view all the answers

    What is the pathogenic mechanism of Myasthenia Gravis?

    <p>Autoimmune disorder of the neuromuscular junction</p> Signup and view all the answers

    What is the treatment of Myasthenia Gravis?

    <p>Acetylcholinesterase inhibitors, immunosuppressants, and plasmapheresis</p> Signup and view all the answers

    What is the characteristic of the carpal tunnel syndrome?

    <p>Most common compressive focal mononeuropathy</p> Signup and view all the answers

    What is the effect of chronic neuropathy in CMT?

    <p>Muscle atrophy and secondary skeletal deformities</p> Signup and view all the answers

    What is the primary mechanism by which Campylobacter jejuni triggers an autoimmune response in Guillain-Barré syndrome?

    <p>Molecular mimicry between bacterial peptides and peripheral nerve gangliosides</p> Signup and view all the answers

    What is the typical presentation of Guillain-Barré syndrome?

    <p>Symmetric, ascending weakness starting in the legs</p> Signup and view all the answers

    What is the primary treatment for Guillain-Barré syndrome?

    <p>Intravenous immunoglobulin (IVIG)</p> Signup and view all the answers

    What is the underlying anatomic issue that contributes to Carpal Tunnel Syndrome?

    <p>Compression of the median nerve by the carpal tunnel</p> Signup and view all the answers

    What is the characteristic pattern of weakness in Guillain-Barré syndrome?

    <p>Ascending, symmetric weakness starting in the legs</p> Signup and view all the answers

    What is the primary role of the immune system in Guillain-Barré syndrome?

    <p>To activate T cells that attack the peripheral nerves</p> Signup and view all the answers

    What is the common preceding infection associated with Guillain-Barré syndrome?

    <p>Campylobacter jejuni</p> Signup and view all the answers

    What is the primary goal of supportive care in Guillain-Barré syndrome?

    <p>To manage symptoms and prevent complications</p> Signup and view all the answers

    Study Notes

    Central Nervous System

    • Consists of brain and spinal cord

    Peripheral Nervous System

    • Consists of cranial nerves (project from brain) and spinal nerves (project from spinal cord)
    • PNS pathways can be divided into:
      • Ascending (afferent) pathways: carry sensory information towards CNS
      • Descending (efferent) pathways: carry motor signals away from CNS to innervate effector organs (skeletal, cardiac, smooth muscle, glands, etc.)

    Descending (Efferent) Pathways

    • Can be divided into:
      • Somatic nervous system: regulates voluntary motor control of skeletal muscle
      • Autonomic nervous system: involuntary control of organ systems/internal viscera, further divided into:
        • Sympathetic nervous system ("fight or flight")
        • Parasympathetic nervous system ("rest and digest")

    Cells of the Nervous System

    • Neurons:
      • Electrically excitable cells that transmit electrical or chemical information between other neurons to an effector organ
      • Have three main components:
        • Cell body
        • Dendrites
        • Axons
      • Can be classified structurally (unipolar, pseudounipolar, bipolar, multipolar) or functionally (sensory, motor, interneurons)
    • Neuroglia (support cells):
      • Provide structural support, nutrition, protection for neurons, and facilitate neurotransmission
      • Types:
        • Oligodendrocytes (CNS): produce myelin
        • Astrocytes (CNS): fill spaces between neurons and surround blood vessels
        • Microglia (CNS): remove debris
        • Ependymal cells (CNS): line CSF-filled cavities
        • Schwann cells (PNS): form myelin
        • Satellite cells (PNS): provide support for neurons

    White and Gray Matter

    • White matter: myelinated axons organized into tracts
    • Gray matter: unmyelinated cell bodies and dendrites, found on the cortical surface and in certain deeper regions

    Basal Ganglia and Thalamus

    • Basal ganglia:
      • Group of gray matter nuclei deep in the forebrain connected to the cortex, thalamus, and brain stem
      • Control muscle tone, posture, and large muscle movements
      • Include:
        • Caudate nucleus
        • Putamen
        • Globus pallidus
    • Thalamus:
      • Relay center for sensory information
      • Associated with sensory input, emotions, memory, and motor planning

    Neurotransmitters and Synapses

    • Review of action potentials: when a stimulus depolarizes the cellular membrane, triggering a cascade of events that allows the cell to fire
    • Chemical synapses:
      • Presynaptic and postsynaptic cells are separated by a thin synaptic cleft
      • Signaling occurs through the release of neurotransmitters from the presynaptic neuron in response to an action potential
      • Neurotransmitters bind to receptors on the postsynaptic membrane, causing a change in the postsynaptic neuron
    • Neurotransmitters:
      • Chemical messengers that allow the action potential to cross the synaptic cleft
      • Examples:
        • Acetylcholine
        • Norepinephrine
        • Dopamine
        • Serotonin
        • GABA (gamma-aminobutyric acid)
      • Excitatory vs inhibitory effects on the postsynaptic neuron

    Cerebrovascular Disease

    • Refers to a group of conditions that affect blood flow and blood vessels in the brain
    • Most common is stroke/CVA, which can be ischemic or hemorrhagic

    Stroke and Transient Ischemic Attack (TIA)

    • Stroke:
      • Abrupt onset of focal or global neurologic impairment
      • Can be ischemic (87%) or hemorrhagic (13%)
      • Types of ischemic strokes:
        • Thrombotic
        • Embolic
        • Lacunar
        • Hypoperfusion
    • Transient ischemic attack (TIA):
      • Episode of neurologic dysfunction lasting < 1 hour
      • Due to transient focal cerebral ischemia
      • Causes of TIA:
        • Embolic
        • Lacunar
        • Large artery, low flow

    Pathophysiology of Infarction

    • Infarction occurs when occlusion leads to loss of blood supply and ischemia, causing cell death
    • Infarction leads to necrosis and swelling (cerebral edema) in 48-72 hours
    • Ultimately causes disintegration of tissue and glial scarring

    Ischemic Core vs Penumbra

    • Ischemic core: central area of irreversible ischemia/necrosis
    • Penumbra: surrounding area of borderline ischemic tissue that is potentially salvageable
    • Restoration of perfusion to the penumbra can prevent necrosis and loss of function

    Clinical Correlation: Thrombolytics and Thrombectomy

    • Goal in stroke treatment is to intervene early enough to restore perfusion to the penumbra
    • Thrombolytics (e.g., tenecteplase) can be used to restore perfusion
    • Thrombectomy can be used to physically remove the thrombus in patients who are not candidates for thrombolytics or have a large vessel occlusion### Nerve Repair
    • Mature neurons in the CNS (Central Nervous System) have a permanent loss of function after injury, whereas peripheral nerves (PNS) can repair.
    • In the CNS, damaged tissue forms a glial scar, restricting future regeneration, whereas in the PNS, Wallerian degeneration occurs, with the distal nerve segment degenerating and the proximal segment growing back.
    • The process of nerve repair in the PNS depends on factors such as location, type of injury, degree of inflammatory response, and scar tissue.

    Neurons: Axons

    • Axons are long projections from the cell body that carry nerve impulses away from the cell body.
    • Myelinated neurons have a myelin sheath wrapped around the axon, which is an insulating layer that speeds up transmission.
    • Nodes of Ranvier are interruptions in the myelin sheath, allowing for saltatory conduction.

    White vs Gray Matter

    • White matter is composed of myelinated axons, organized into tracts that bring information to or take it from the cortex.
    • Gray matter is composed of unmyelinated cell bodies, found on the cortical surface and doing the work.

    Neuroglia (Glial Cells)

    • Neuroglia, or "nerve glue," are non-neuron cells that make up the support system of the nervous system.
    • Types of neuroglia include:
      • Oligodendrocytes: deposit myelin within the CNS.
      • Astrocytes: fill spaces between neurons and surround blood vessels in the CNS.
      • Microglia: remove debris within the CNS.
      • Ependymal cells: line CSF-filled cavities in the CNS and create CSF.

    Demyelinating Diseases

    • Diseases can be classified into two types:
      • Leukodystrophies: diseases of myelin formation or maintenance due to intrinsic (genetic) causes.
      • Myelinoclastic: diseases of normally formed myelin caused by extrinsic causes (toxins, chemicals, autoimmune disorders).
    • Pathophysiology of demyelinating diseases: loss of the myelin sheath leads to impaired signal conduction, causing progressive neurological dysfunction.

    Multiple Sclerosis

    • A diffuse, progressive CNS autoimmune disease due to degeneration of CNS myelin, scarring, and loss of axons.
    • Onset usually between 20 and 40 years old, more common in genetically female patients.
    • Pathophysiology: immune cells (macrophages, T-cells, B-cells) attack myelin, leading to demyelination and axonal loss.
    • Clinical manifestations: relapsing-remitting, multifocal symptoms, and lesions on imaging.

    Alzheimer's Disease

    • A neurodegenerative disease, most common cause of dementia, and one of the leading sources of morbidity and mortality in the aging population.
    • Two pathologic hallmarks: extracellular beta-amyloid deposits (plaques) and intracellular neurofibrillary tangles.
    • Diagnosis: clinical criteria, including a history of insidious onset and progressive course of cognitive decline, exclusion of other etiologies, and documentation of cognitive impairments.

    Meninges, Cerebrospinal Fluid

    • The meninges are three layers of protection for the brain: dura mater, arachnoid, and pia mater.
    • The subarachnoid space contains CSF, produced by ependymal cells of the choroid plexus.
    • CSF has multiple roles, including exerting pressure, providing protection, and transporting hormones and removing waste.

    Hydrocephalus

    • Accumulation of excess CSF in the ventricular system, either due to overproduction or blockage of CSF flow.
    • Types: obstructive, communicating, and normal pressure.
    • Treatment: VP shunt, external ventricular drains.

    Head Trauma

    • Traumatic brain injury (TBI) is an alteration in brain function or other evidence of brain pathology caused by external force.
    • Pathophysiology: primary brain injury, including diffuse axonal injury and focal cerebral contusions.
    • Mechanisms of injury: direct impact, rapid acceleration/deceleration, penetrating injury, and blast waves.### Intracranial Hemorrhage
    • Epidural hematomas, subdural hematomas, or subarachnoid hemorrhage can occur as a result of TBI
    • Secondary brain injury occurs due to a cascade of molecular injury mechanisms that start at the time of injury and continue for hours to days
    • Mechanisms include free-radical injury to cell membranes, electrolyte imbalances, mitochondrial dysfunction, inflammatory responses, apoptosis, and secondary ischemia from vasospasm
    • These mechanisms lead to neuronal cell death and cerebral edema

    Concussion

    • Mild traumatic brain injury (mTBI) characterized by temporary impairment of neurologic function
    • Symptoms include memory loss, attention deficits, headache, and altered mental status
    • Neuronal dysfunction occurs due to metabolic insults from the trauma rather than an actual structural abnormality
    • Concussed cells become vulnerable, and if a second concussion is sustained during this period, damage can be irreversible
    • Hallmark symptoms are confusion and amnesia with or without loss of consciousness

    Chronic Traumatic Encephalopathy

    • Progressive neurological disorder that often presents like dementia and can also have motor disorders
    • Resulting from repetitive closed-head injuries, such as in boxers and football players

    CNS Infections

    • Meningitis: infection of the meninges resulting in inflammation
    • Can be caused by viruses, bacteria, or fungi
    • Viral causes include enteroviruses, HSV-1, HSV-2, and VZV
    • Fungal causes include cryptococcus and candida, usually seen in immunocompromised patients
    • Encephalitis: infection/inflammation of the brain parenchyma itself, not always distinguishable clinically from meningitis

    Bacterial Meningitis

    • Caused by virulence factors of a pathogen overcoming host defense mechanisms
    • Common pathogens include group B streptococcus, Neisseria meningitidis, Streptococcus pneumoniae, H. Influenza, and E. coli
    • Invasion of bacteria into the meninges can occur through the bloodstream, direct extension from local infection, or otitis media and sinusitis
    • Clinical manifestations include fever, neck stiffness, and altered mental status
    • Treatment includes empiric antibiotics and later narrowed based on culture results from CSF analysis

    Neurodegenerative & Movement Disorders

    • Basal Ganglia:
      • Group of subcortical nuclei responsible for motor control
      • Composed of the substantia nigra, caudate nucleus, and putamen
      • Functions include initiating voluntary motor movement, suppressing unwanted movement, and procedural learning
    • Substantia Nigra:
      • "Black Substance" containing high concentration of dopamine (neuromelanin)
      • Most of the dopamine in the brain is located here
      • Neurons project to the striatum, communicating through dopamine signaling
    • Indirect & Direct Pathways:
      • Basal ganglia receive information from the cortex and send motor signals back to the cortex through the thalamus
      • Dopamine signaling from the substantia nigra regulates movement through the indirect and direct pathways

    Movement Disorders

    • Group of neurologic conditions that cause abnormal movements
    • Can be either hyperkinetic (increased movements) or hypokinetic (decreased movements)
    • Can affect both voluntary and involuntary movements
    • Common disorders include ataxia, chorea, dystonia, tremor, Huntington's disease, and Parkinson's disease

    Huntington's Disease

    • Rare autosomal dominant genetic disorder
    • Clinical manifestations include dementia, psychiatric symptoms, and chorea movements
    • Progressive and ultimately fatal
    • Genetic mutation in the Huntingtin (HTT) gene causes triplet repeat expansion of a particular DNA sequence, leading to neuronal death and dysfunction
    • Treatment is focused on symptom management, usually aimed at suppressing chorea movements to improve quality of life

    Parkinson's Disease

    • Degenerative disorder of the substantia nigra
    • Progressive degeneration of dopamine-producing neurons in the substantia nigra
    • Symptoms include "pill-rolling" tremor at rest, rigidity, masked facies, shuffling gait, bradykinesia, and dementia
    • Clinical correlation: treatment is focused on replacing dopamine in the brain, usually with Levodopa/Carbidopa

    Amyotrophic Lateral Sclerosis (ALS)

    • Progressive neurodegenerative disorder of upper and lower motor neurons
    • Etiology is unknown, with some genetic susceptibility
    • Pathophysiology includes motor neuron degeneration and death, cortical motor neuron death, and spinal cord atrophy
    • Symptoms include muscle atrophy, weakness, and respiratory failure
    • Unfortunately, there is no cure, and the disease is usually fatal within five years of diagnosis

    Peripheral Nervous System

    • Direct extension of the central nervous system, monitoring and reacting to external stimuli
    • Two components: autonomic nervous system (ANS) and somatic nervous system
    • ANS helps maintain homeostasis, automatically adjusting the activity of the sympathetic and parasympathetic nervous systems to match the needs of the body
    • Somatic nervous system includes afferent (sensory) nerves and efferent (motor) nerves, traveling from the CNS to muscle for motor activation
    • PNS is outside of the skull and spinal vertebra, not protected by the blood-brain-barrier, and susceptible to toxic injury from circulating substances

    Guillain-Barré Syndrome

    • Autoimmune destruction of schwann cells surrounding peripheral nerves
    • Post-infectious autoimmune neuropathy, ~70% of patients have a preceding infection
    • Campylobacter jejuni is the most common preceding infection, found in undercooked poultry, causing GI illness (diarrhea)
    • Molecular mimicry mechanism: campylobacter jejuni membranes have a component similar to ganglioside, a component of peripheral nerves, leading to cross-reaction and attack of peripheral nerves

    Clinical Manifestations of Guillain-Barré Syndrome

    • Symmetric, ascending weakness is the hallmark, typically begins in the legs
    • Numbness, tingling, and weakness that can progress to paralysis
    • Symptoms generally progress over a period of 2 weeks

    Diagnosis and Treatment of Guillain-Barré Syndrome

    • Clinical diagnosis, typically based on preceding infection and characteristic presentation
    • EMG and nerve studies can be helpful if unclear
    • Supportive care, monitor for progression, respiratory status, and blood pressure
    • Main medication: IVIG (intravenous immunoglobulin), with specific criteria for use

    Carpal Tunnel Syndrome

    • Common condition causing numbness, tingling, and pain in the hand and forearm
    • Anatomic issue: compression of the median nerve as it travels through the wrist (carpal tunnel)
    • Presents as pain, paresthesia, and less commonly, weakness in the median nerve distribution
    • Congenital predisposition: some people have smaller carpal tunnels than others

    Charcot-Marie-Tooth Disease (CMT)

    • Group of hereditary disorders causing peripheral neuropathy in both sensory and motor neurons
    • Abnormalities in axons or production/maintenance of the myelin sheath
    • Demyelinating disorder of the peripheral nervous system
    • Symptoms typically begin in the feet/lower legs and then the fingers, hands, and arms
    • High arched feet due to muscular imbalance (from atrophy)

    Pathophysiology of Charcot-Marie-Tooth Disease

    • Pathogenic variants in genes that make proteins for peripheral nerve and myelin sheath maintenance
    • Abnormalities in peripheral nerves or myelin, leading to thin or misfolded myelin sheaths, alternating segments of demyelination, and axonal loss

    Myasthenia Gravis

    • Autoimmune disorder of the neuromuscular junction, manifesting as progressive skeletal muscle weakness and fatigability
    • Pathogenesis: autoantibodies to the acetylcholine receptor, binding to the receptor and interfering with neurotransmitter function
    • Clinical manifestations: generalized proximal limb weakness and fatigability, drooping of eyelids (ptosis), double vision (diplopia), flattened smile, and difficulty chewing and/or swallowing

    Treatment of Myasthenia Gravis

    • Acetylcholinesterase inhibitors to block the enzyme that breaks down Ach
    • Immunosuppressants like corticosteroids
    • Plasmapheresis to remove autoantibodies from the blood
    • IV immunoglobulin to give other antibodies that block the anti-AChR antibodies

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    This quiz covers the basics of the central and peripheral nervous systems, including the functions of cranial and spinal nerves, and the ascending and descending pathways.

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