Nervous System Overview

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Questions and Answers

Which of the following is responsible for the involuntary control of organ systems/internal viscera?

Autonomic nervous system (correct)

Central nervous system

Peripheral nervous system

Somatic nervous system

What is the primary function of microglia in the CNS?

To form myelin in the CNS

To line CSF-filled cavities in the CNS

To fill spaces between neurons

To remove debris within the CNS (correct)

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

Motor neurons

Sensory neurons

Interneurons (correct)

Pseudounipolar neurons

What is the term for the process by which an action potential jumps from node to node in a myelinated axon?

Saltatory conduction Signup and view all the answers

Which of the following neurotransmitters is synthesized from tryptophan?

Serotonin Signup and view all the answers

What is the term for the structures that hold chemical neurotransmitters in chemical synapses?

Vesicles Signup and view all the answers

Which of the following is NOT a type of glial cell found in the CNS?

Schwann cells Signup and view all the answers

Which of the following systems is responsible for regulating voluntary motor control of skeletal muscle?

Somatic nervous system Signup and view all the answers

What is the term for the gap between the terminal end of one neuron and the beginning of another neuron?

Synaptic cleft Signup and view all the answers

Which of the following is an example of a sensory neuron?

Neuron that transmits information from sensory receptors to the CNS Signup and view all the answers

What is the primary cause of euphoria?

Increases in dopamine Signup and view all the answers

What is the most common type of ischemic stroke?

Thrombotic stroke Signup and view all the answers

What is the primary goal of thrombolytic treatment in stroke patients?

To restore perfusion to the penumbra Signup and view all the answers

What is the most common cause of spontaneous subarachnoid hemorrhage?

Trauma Signup and view all the answers

What is the term for small vessel disease that leads to lacunar stroke?

Perivascular edema/inflammation of arterial walls Signup and view all the answers

What is the term for the central core of irreversible ischemia/necrosis?

Ischemic core Signup and view all the answers

What is the term for the area of salvageable damage surrounding the ischemic core?

Penumbra Signup and view all the answers

What is the most common location for saccular (berry) aneurysms?

Anterior circulation Signup and view all the answers

What is the term for the tangle of abnormal arteries and veins with no intervening capillary bed?

Arteriovenous malformation Signup and view all the answers

What is the most common type of cerebral edema?

Vasogenic edema Signup and view all the answers

What is the primary function of acetylcholinesterase in the synapse?

To break down acetylcholine into its constituent parts Signup and view all the answers

Which of the following neurotransmitters is involved in the regulation of respiratory rate in the medulla?

GABA Signup and view all the answers

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

Depolarization of the cellular membrane Signup and view all the answers

Which of the following neurotransmitters is not involved in the autonomic nervous system?

GABA Signup and view all the answers

What is the role of monoamine oxidase in the synapse?

To break down dopamine and other catecholamines Signup and view all the answers

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

Excitatory Signup and view all the answers

What is the mechanism of action of MAO inhibitors, which are used as antidepressants?

Inhibiting the breakdown of dopamine by monoamine oxidase Signup and view all the answers

What is the role of benzodiazepines in ethanol withdrawal?

To increase the activity of GABA receptors Signup and view all the answers

What is the primary component of the extracellular beta-amyloid deposits found in Alzheimer's disease?

Peptides produced by breakdown of more mature proteins Signup and view all the answers

Which of the following symptoms is NOT a cardinal symptom of Alzheimer's disease?

Tremors Signup and view all the answers

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

Increase the concentration of Acetylcholine Signup and view all the answers

What is the most common cause of an epidural hematoma?

Trauma, especially with skull fractures Signup and view all the answers

What is the primary function of cerebrospinal fluid in the brain and spinal cord?

To exerts pressure and support nearby structures Signup and view all the answers

What is the pH of cerebrospinal fluid?

7.3 Signup and view all the answers

What is the flow of cerebrospinal fluid from the ventricles?

From the right and left lateral ventricles to the third ventricle Signup and view all the answers

What is NOT a normal component of cerebrospinal fluid?

Red blood cells Signup and view all the answers

What is the primary characteristic of cytotoxic cerebral edema?

Abnormal accumulation of fluid in brain cells leading to cell swelling Signup and view all the answers

Which type of nerve can repair itself after an injury?

PNS nerves Signup and view all the answers

What is the term for the degeneration of the distal end of a nerve fiber after an injury?

Wallerian degeneration Signup and view all the answers

What is the primary cause of leukodystrophies?

Intrinsic genetic defects Signup and view all the answers

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

Impaired signal conduction Signup and view all the answers

Which of the following is an example of a leukodystrophy?

Metachromatic leukodystrophy Signup and view all the answers

What is the primary mechanism of demyelination in multiple sclerosis?

Autoimmune response against myelin Signup and view all the answers

What is the role of macrophages in the pathophysiology of multiple sclerosis?

Presenting antigens to T-cells Signup and view all the answers

What is the term for the process of T-cells crossing the blood-brain barrier and recognizing myelin proteins as foreign?

Diapedesis Signup and view all the answers

What is the characteristic finding on imaging in multiple sclerosis?

White matter lesions on the brain and spinal cord Signup and view all the answers

What is the primary mechanism of remission in relapsing-remitting multiple sclerosis?

Recognition of inflammatory T-cells by regulatory T-cells Signup and view all the answers

What is the primary goal of treatment in multiple sclerosis?

Slowing the rate of demyelination Signup and view all the answers

What is the typical delay in symptom onset after rapid correction of chronic hyponatremia?

2-6 days Signup and view all the answers

Which structure in the basal ganglia receives dopamine signals from the substantia nigra and sends motor signals to the cortex?

Putamen Signup and view all the answers

What is the primary function of the indirect pathway in the basal ganglia?

Inhibiting voluntary motor movement Signup and view all the answers

What is the primary mechanism of demyelination in progressive multifocal leukoencephalopathy?

JC virus infection Signup and view all the answers

Which of the following is a characteristic of Huntington's disease?

Hyperkinesia and chorea Signup and view all the answers

What is the term for the process by which astrocytes and oligodendrocytes die after rapid correction of chronic hyponatremia?

Osmolyte depletion Signup and view all the answers

What is the term for the abnormal, involuntary movements seen in Huntington's disease?

Chorea Signup and view all the answers

What is the typical outcome of central pontine myelinolysis?

Irreversible symptoms Signup and view all the answers

What is the primary mechanism of re-myelination in the central nervous system?

Myelin sheath repair by oligodendrocytes Signup and view all the answers

Which of the following is a treatment for Parkinson's disease?

Levodopa/Carbidopa Signup and view all the answers

What is the primary function of the basal ganglia?

Initiating voluntary motor movements Signup and view all the answers

What is the primary cause of central pontine myelinolysis?

Rapid correction of chronic hyponatremia Signup and view all the answers

What is the result of the degeneration of dopamine-producing neurons in the substantia nigra?

Decreased dopamine levels in the brain Signup and view all the answers

What is the response in the brain when hyponatremia is corrected?

Water moves from intracellular to extracellular space Signup and view all the answers

What is the primary method of preventing central pontine myelinolysis?

Slow correction of chronic hyponatremia Signup and view all the answers

What is the term for the 'relay station' that receives and sends motor signals to and from the cortex?

Thalamus Signup and view all the answers

Which of the following is a characteristic feature of Parkinson's disease?

Tremors at rest Signup and view all the answers

What is the primary function of dopamine in the basal ganglia?

Initiating voluntary motor movements Signup and view all the answers

What is the primary purpose of a lumbar puncture?

To collect a sample of CSF and measure intracranial pressure Signup and view all the answers

In a patient with meningitis, what is the expected finding in CSF analysis?

Elevated WBCs, decreased glucose Signup and view all the answers

What is the primary mechanism of autoregulation of cerebral blood flow in response to increased intracranial pressure?

Compensatory vasodilation to maintain cerebral perfusion Signup and view all the answers

What is the clinical consequence of unrelieved increased intracranial pressure?

Herniation of the brain tissue through openings in the skull Signup and view all the answers

What is the primary indication for external ventricular drains in patients with space-occupying lesions?

To monitor ICP and drain CSF Signup and view all the answers

What is the primary difference between obstructive and communicating hydrocephalus?

Location of CSF obstruction Signup and view all the answers

What is the primary treatment option for obstructive hydrocephalus?

Ventriculoperitoneal shunt Signup and view all the answers

What is the term for the accumulation of excess CSF in the ventricular system due to loss of surrounding brain tissue?

Hydrocephalus ex vacuo Signup and view all the answers

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

Shearing and tearing of neuronal axons Signup and view all the answers

What is the term for the lesions seen on neuroimaging in patients with diffuse axonal injury?

Multiple small lesions within white matter tracts Signup and view all the answers

What is the primary mechanism of autoimmune response in Guillain-Barré syndrome?

Molecular mimicry between Campylobacter jejuni and peripheral nerve cells Signup and view all the answers

Which of the following is a characteristic clinical manifestation of Guillain-Barré syndrome?

Symmetric, ascending weakness starting in the legs Signup and view all the answers

What is the main medication used to treat Guillain-Barré syndrome?

Intravenous immunoglobulin (IVIG) Signup and view all the answers

What is the anatomical structure responsible for compression of the median nerve in Carpal Tunnel Syndrome?

Transverse carpal ligament Signup and view all the answers

Which of the following is a characteristic feature of Charcot-Marie-Tooth disease?

High-arched feet due to muscular imbalance Signup and view all the answers

What is the primary pathophysiological mechanism of Charcot-Marie-Tooth disease?

Demyelination of peripheral nerves Signup and view all the answers

Which of the following is a characteristic symptom of Myasthenia Gravis?

Progressive skeletal muscle weakness and fatigability Signup and view all the answers

What is the primary mechanism of autoimmune response in Myasthenia Gravis?

Antibody-mediated blockade of the acetylcholine receptor Signup and view all the answers

Which of the following is a characteristic feature of Guillain-Barré syndrome?

Symmetric, ascending weakness starting in the legs Signup and view all the answers

What is the primary role of IVIG in the treatment of Guillain-Barré syndrome?

Neutralizing the autoantibodies Signup and view all the answers

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

Blocking the release of glutamate believed to play a role in neuronal injury Signup and view all the answers

What is the most common complication of diabetes?

Diabetic Peripheral Neuropathy Signup and view all the answers

What is the term for the process by which the autonomic nervous system automatically adjusts its activity to match the needs of the body?

Homeostasis Signup and view all the answers

What is the primary component of the peripheral nervous system that is responsible for transmitting sensory information to the central nervous system?

Afferent nerves Signup and view all the answers

What is the primary cause of death in patients with Amyotrophic Lateral Sclerosis (ALS)?

Respiratory failure Signup and view all the answers

What is the primary mechanism of nerve damage in Diabetic Peripheral Neuropathy?

All of the above Signup and view all the answers

What is the term for the sensation of 'first pain' in the transmission of pain signals?

Sharp, immediate pain Signup and view all the answers

What is the primary function of the dorsal columns in the spinal cord?

Transmission of light touch and vibration signals Signup and view all the answers

What is the term for the type of neuron that is responsible for transmitting motor signals to muscles?

Motor neuron Signup and view all the answers

What is the primary difference between the somatic and autonomic nervous systems?

The autonomic nervous system is responsible for regulating involuntary functions, while the somatic nervous system is responsible for regulating voluntary functions Signup and view all the answers

What is the primary mechanism of pathogenesis in myasthenia gravis?

Autoantibodies blocking acetylcholine receptors in the neuromuscular junction Signup and view all the answers

A patient with myasthenia gravis presents with difficulty breathing. What is the most likely cause of this symptom?

Weakness of the diaphragm muscle Signup and view all the answers

What is the mechanism of action of acetylcholinesterase inhibitors in the treatment of myasthenia gravis?

Preventing the breakdown of acetylcholine by acetylcholinesterase Signup and view all the answers

What is the purpose of plasmapheresis in the treatment of myasthenia gravis?

Removing autoantibodies from the blood Signup and view all the answers

What is the effect of repeated stimulation on the neuromuscular junction in myasthenia gravis?

Progressive depletion of acetylcholine from nerve terminals Signup and view all the answers

What is the purpose of IV immunoglobulin in the treatment of myasthenia gravis?

Giving antibodies that block the action of anti-AChR antibodies Signup and view all the answers

What is the primary mechanism of neuronal cell death in secondary brain injury?

Free-radical injury to cell membranes Signup and view all the answers

What is the hallmark symptom of concussion?

Confusion and amnesia with or without loss of consciousness Signup and view all the answers

What is the most common cause of meningitis in infants?

Group B streptococcus Signup and view all the answers

What is the primary goal of steroid therapy in bacterial meningitis?

To reduce inflammation Signup and view all the answers

What is the term for the progressive neurological disorder that often presents like dementia, caused by repetitive closed-head injuries?

Chronic traumatic encephalopathy Signup and view all the answers

What is the most common location for focal cerebral contusions?

Basal frontal and temporal areas Signup and view all the answers

What is the primary mechanism of secondary brain injury?

Cascade of molecular injury mechanisms Signup and view all the answers

What is the term for the infection of the brain parenchyma itself?

Encephalitis Signup and view all the answers

Study Notes

Central Nervous System (CNS) and Peripheral Nervous System (PNS)

CNS: brain and spinal cord
PNS: cranial nerves and spinal nerves
PNS pathways divided into:
- Ascending (afferent): carries sensory information towards CNS
- Descending (efferent): motor neurons travel away from CNS to innervate effector organs

Neurons

Electrically excitable cells
Cellular components:
- Microtubules: transport substances (like neurotransmitters)
- Neurofibrils: structure support
- Nissl substances: granules made of rough ER, responsible for protein synthesis
Structural classification:
- Unipolar, pseudounipolar, bipolar, multipolar (most common)
Functional classification:
- Sensory neurons: impulses from sensory receptors to CNS (afferent pathway)
- Motor neurons: impulses from CNS to effector organs (efferent pathway)
- Interneurons (associational neurons): transmit impulses between neurons (>99% of all neurons)

Neuroglia (Glial Cells)

CNS: astrocytes, microglia, oligodendrocytes, ependymal cells
PNS: Schwann cells
Function: support and maintain neurons
Types:
- Astrocytes: fill spaces between neurons
- Microglia: remove debris within CNS (brain macrophages)
- Oligodendrocytes: form myelin in CNS
- Ependymal cells: line CSF-filled cavities in CNS and create CSF

Chemical Synapses

Signaling from one cell to the next occurs through release of neurotransmitters
Presynaptic neuron: releases neurotransmitters into synaptic cleft
Postsynaptic neuron: receives neurotransmitters through receptors

Neurotransmitters

"The language that allows the action potential to cross the synaptic cleft"
Types:
- Acetylcholine: regulates muscle contraction, memory, and cognition
- Norepinephrine: involved in attention, arousal, and stress response
- Dopamine: involved in reward, motivation, and movement
- Serotonin: regulates mood, appetite, and sleep
- GABA (gamma-aminobutyric acid): main inhibitory neurotransmitter in CNS

Cerebrovascular Disease

Refers to a group of conditions that affect blood flow and blood vessels in the brain
Types:
- Ischemic stroke: occurs when blood vessels become blocked or narrowed
- Hemorrhagic stroke: occurs when blood vessels rupture

Ischemic Stroke

Abrupt onset of focal or global neurologic impairment
Types:
- Transient ischemic attack (TIA): episode of neurologic dysfunction lasting < 1 hour
- Thrombotic stroke: occurs when a blood clot forms in a blood vessel
- Embolic stroke: occurs when a blood clot forms in another part of the body and travels to the brain
- Lacunar stroke: occurs when small blood vessels in the brain are blocked
- Hypoperfusion stroke: occurs when blood flow to the brain is reduced

Pathophysiology of Infarction

Infarction occurs when occlusion leads to loss of blood supply and ischemia
Ischemic core vs. penumbra: central core of irreversible ischemia/necrosis surrounded by zone of borderline ischemic tissue

Hemorrhagic Stroke

Occurs when blood vessels rupture
Types:
- Intracerebral hemorrhage: occurs when a blood vessel in the brain ruptures
- Subarachnoid hemorrhage: occurs when a blood vessel on the surface of the brain ruptures
- Subdural hemorrhage: occurs when a blood vessel between the brain and skull ruptures

Stroke Syndromes

Middle cerebral artery (MCA) stroke: occurs when the MCA is blocked
Posterior circulation (vertebrobasilar) stroke: occurs when the posterior circulation is blocked

Demyelinating Disorders

Leukodystrophies: inherited metabolic disorders that affect myelin formation or maintenance
Myelinoclastic diseases: diseases that destroy normally formed myelin
Types:
- Multiple sclerosis (MS): an autoimmune disease that affects the CNS
- Progressive multifocal leukoencephalopathy (PML): a rare and opportunistic infection
- Central pontine myelinolysis (osmotic demyelination syndrome): caused by rapid correction of chronic hyponatremia### Central Pontine Myelinolysis
Caused by rapid correction of chronic hyponatremia
Astrocytes and oligodendrocytes die 24 hours after initial insult
Symptoms: para or quadriparesis, behavioral disturbances, movement disorders, seizures, lethargy, confusion, and coma
Prevention: slowly correct chronic hyponatremia to allow cells to adapt to osmotic changes

Alzheimer's Disease

Neurodegenerative disease
Most common cause of dementia
Two pathologic hallmarks: extracellular beta-amyloid deposits (plaques) and intracellular neurofibrillary tangles
Diagnosis: insidious onset and progressive course of cognitive decline
Cardinal symptoms: memory impairment, executive functioning impairment, language deficits, visuospatial abnormalities, apathy, social disengagement, and irritability
Treatment: cholinesterase inhibitors (e.g., donepezil, rivastigmine) to increase concentration of acetylcholine and slow progression of symptoms

Meninges and Cerebrospinal Fluid

Epidural hematoma: bleeding between skull and dura
Subdural hematoma: bleeding between dura and arachnoid
Subarachnoid hemorrhage: bleeding between arachnoid and pia
CSF: clear fluid produced by ependymal cells of the choroid plexus in the lateral, third, and fourth ventricles
CSF flow: produced in ventricles, flows through foramina, and reabsorbed by arachnoid granulations
Functions: exerts pressure, provides cushioning, and protects against trauma

Ventricular System

CSF ends up in the superior sagittal sinus and is reabsorbed by arachnoid granulations
Ventricular system: CSF produced in ventricles and flows through foramina
Make up of CSF: pH ~ 7.3, glucose level 2/3 of plasma, and very little protein

Clinical Correlation - CSF Analysis

Lumbar puncture: sample of CSF and measurement of intracranial pressure
Abnormalities: bacteria, RBCs, WBCs, elevated glucose, and protein levels

Hydrocephalus

Accumulation of excess CSF in the ventricular system
Types: obstructive (blockage of CSF flow) and communicating (overproduction of CSF)
Normal pressure hydrocephalus: adult syndrome of progressive dementia, gait disorders, and urinary incontinence
Main treatment option: VP shunt

Traumatic Brain Injury

Caused by external force
Pathophysiology: primary brain injury (diffuse axonal injury, focal cerebral contusions, and intracranial hemorrhage) and secondary brain injury (free-radical injury, electrolyte imbalances, mitochondrial dysfunction, and inflammatory responses)
Clinical manifestations: concussion, altered mental status, and memory loss
Concussion: mild traumatic brain injury, temporary impairment of neurologic function

CNS Infections

Meningitis: infection of the meninges
Encephalitis: infection of the brain parenchyma
Clinical manifestations: fever, neck stiffness, and altered mental status
Treatment: empiric antibiotics and antivirals, and steroids to reduce inflammation

Basal Ganglia

Group of subcortical nuclei responsible for motor control
Functions: initiating voluntary motor movement and regulating movement
Made up of the substantia nigra, caudate nucleus, and putamen

Movement Disorders

Huntington's disease: rare autosomal dominant genetic disorder
Clinical manifestations: dementia, psychiatric symptoms, and chorea movements
Treatment: focused on symptom management

Parkinson's Disease

Degenerative disorder of the substantia nigra
Clinical manifestations: pill-rolling tremor, rigidity, shuffling gait, and bradykinesia
Treatment: levodopa/carbidopa to replace dopamine

Amyotrophic Lateral Sclerosis (ALS)

Progressive neurodegenerative disorder of upper and lower motor neurons
Clinical manifestations: muscle atrophy, weakness, and paralysis
Treatment: focused on symptom management

Peripheral Nervous System

Direct extension of the central nervous system
Components: autonomic nervous system and somatic nervous system
Functions: monitors and reacts to external stimuli

Diabetic Peripheral Neuropathy

Most common complication of diabetes
Clinical manifestations: progressive loss of sensation, numbness, and pain
Pathophysiology: distal symmetric polyneuropathy, ischemia, and buildup of advanced glycation end products

Guillain-Barré Syndrome

Autoimmune destruction of the schwann cells surrounding peripheral nerves
Clinical manifestations: symmetric, ascending weakness, and numbness
Diagnosis: clinical diagnosis, EMG, and nerve studies
Treatment: supportive care, pain control, and IVIG

Carpal Tunnel Syndrome

Compression of the median nerve as it travels through the wrist
Clinical manifestations: numbness, tingling, and pain in the hand and forearm
Prevention: supportive care, and corticosteroid injections### Carpal Tunnel
The carpal tunnel is formed by the transverse carpal ligament superiorly and the carpal bones inferiorly.
The median nerve passes through the carpal tunnel along with nine flexor muscle tendons.
The median nerve provides motor and sensory innervation to the hand.
Compression of the median nerve leads to ischemia and mechanical disruption.

Innervation of the Hand

The median nerve supplies the abductor pollicis brevis, the flexor pollicis brevis (superficial head), the opponens pollicis, and the first and second lumbricals.

Charcot-Marie-Tooth Disease (CMT)

CMT is a group of hereditary disorders that cause peripheral neuropathy in both sensory and motor neurons.
It is a “demyelinating” disorder of the peripheral nervous system.
Over time, neurons degenerate leading to muscle weakness/atrophy.
CMT affects longer nerves first, with symptoms typically beginning in the feet/lower legs and then the fingers, hands, and arms.
High arched feet are a common feature due to muscular imbalance (from atrophy).
Pathogenic variants in various genes lead to abnormalities in peripheral nerves or myelin.
Thin or misfolded myelin sheaths and hypertrophic myelination are characteristic of CMT.
Symptoms of CMT include hammertoe, foot drop, trips and falls due to gait disorders, and repeated ankle sprains.

Myasthenia Gravis

Myasthenia Gravis is an autoimmune disorder of the neuromuscular junction that manifests as progressive skeletal muscle weakness and fatigability.
The body makes autoantibodies to the acetylcholine receptor, reducing the number of available receptor sites.
Repeated stimulation leads to progressive neuromuscular fatigue and depletion of acetylcholine in the nerve terminal.
Clinical manifestations include generalized proximal limb weakness and fatigability with repeated activities, drooping of eyelids (ptosis), flattened smile, and difficulty breathing in severe cases.
Treatment options include acetylcholinesterase inhibitors, immunosuppressants like corticosteroids, plasmapheresis, and IV immunoglobulin.

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Description

This quiz covers the basics of the nervous system, including the central and peripheral nervous systems, their pathways, and divisions. Learn about the roles of ascending, descending, somatic, and autonomic nervous systems.