Nervous System Quiz
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Questions and Answers

What are the two main categories used to categorize divisions of the nervous system?

  • Motor and Sensory
  • Central and Peripheral
  • Somatic and Autonomic
  • Structural and Functional (correct)

    • Which structures make up the central nervous system (CNS)?

  • Cerebellum and brainstem
  • Somatic and autonomic pathways
  • Cranial and spinal nerves
  • Brain and spinal cord (correct)

    • What type of nerves are responsible for carrying impulses away from the central nervous system?

  • Afferent nerves
  • Efferent nerves (correct)
  • Cranial nerves
  • Sensory nerves

    • Which of the following structures is NOT a division of the cranial fossa?

    <p>Lateral Fossa</p> Signup and view all the answers

    What role does the pia mater play in protecting the brain?

    <p>Adheres closely to the brain and supplies blood vessels</p> Signup and view all the answers

    Which layer of the meninges contains two layers and forms venous sinuses between them?

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

    What is the function of the subarachnoid space?

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

    What structure helps alleviate increased intracranial pressure by shunting blood?

    <p>Subgaleal space</p> Signup and view all the answers

    What is the primary component of cerebrospinal fluid (CSF) that regulates its flow?

    <p>Carbon dioxide</p> Signup and view all the answers

    Which structure provides an alternative pathway for blood flow to the brain?

    <p>Circle of Willis</p> Signup and view all the answers

    What is the typical volume of cerebrospinal fluid (CSF) that circulates in the ventricles and subarachnoid space?

    <p>125 to 150 mL</p> Signup and view all the answers

    Which artery primarily supplies the frontal, parietal, and temporal lobes of the brain?

    <p>Middle Cerebral Artery</p> Signup and view all the answers

    Where is cerebrospinal fluid (CSF) predominantly produced?

    <p>Lateral ventricles</p> Signup and view all the answers

    What happens to CSF pressure when a person moves from a supine position to an upright position?

    <p>It doubles</p> Signup and view all the answers

    Which of the following components of CSF is at normal values of 50–75 mg/dL?

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

    Which space exists between the dura mater and the skull?

    <p>Epidural space</p> Signup and view all the answers

    What type of cells create a barrier similar to the blood-brain barrier in the choroid plexuses?

    <p>Ependymal cells</p> Signup and view all the answers

    Which artery is responsible for supplying the basal ganglia and corpus callosum?

    <p>Anterior Cerebral Artery</p> Signup and view all the answers

    What is the role of arachnoid villi in the central nervous system?

    <p>Reabsorb cerebrospinal fluid into venous circulation</p> Signup and view all the answers

    Which clinical effect is associated with a blockage in the Middle Cerebral Artery?

    <p>Language impairment (aphasia)</p> Signup and view all the answers

    What maintains stable cerebral blood flow despite variations in perfusion pressures?

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

    What is the primary function of the corticospinal tract?

    <p>Carries motor commands to the spinal cord</p> Signup and view all the answers

    Which cranial nerve is primarily responsible for controlling most eye movements?

    <p>Oculomotor Nerve (CN III)</p> Signup and view all the answers

    What condition may result from the blockage of the cerebral aqueduct?

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

    What function does the substantia nigra primarily serve?

    <p>Produces dopamine for motor control</p> Signup and view all the answers

    Which structure is responsible for balancing and maintaining posture?

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

    What is the main role of the pons?

    <p>Acts as a bridge for communication between the cerebellum and brainstem</p> Signup and view all the answers

    What does decussation refer to in the context of the medulla?

    <p>The crossing of motor pathways to the opposite side</p> Signup and view all the answers

    Which part of the autonomic nervous system (ANS) typically stimulates organ functions?

    <p>Sympathetic Nervous System</p> Signup and view all the answers

    What type of control does the cerebellum exhibit over motor functions?

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

    What is a function of the medulla oblongata?

    <p>Controlling reflex activities like heart rate</p> Signup and view all the answers

    Which tract connects the cortex to cranial nerve nuclei in the brainstem?

    <p>Corticobulbar Tract</p> Signup and view all the answers

    What primary function does the autonomic nervous system serve?

    <p>Regulates involuntary bodily functions</p> Signup and view all the answers

    Which of the following substances can cross the blood-brain barrier (BBB)?

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

    What role does the basal ganglia play in the brain?

    <p>Coordination of movement</p> Signup and view all the answers

    Which lobe of the brain is primarily responsible for processing auditory information?

    <p>Temporal Lobe</p> Signup and view all the answers

    What is the primary function of the primary motor area (Brodmann Area 4)?

    <p>Execution of voluntary movements</p> Signup and view all the answers

    Damage to Broca's speech area results in which condition?

    <p>Expressive aphasia</p> Signup and view all the answers

    Which structure is essential for coordinating activities between the two cerebral hemispheres?

    <p>Corpus Callosum</p> Signup and view all the answers

    What type of fibers facilitate communication between motor and sensory areas in the brain?

    <p>Association fibers</p> Signup and view all the answers

    Which area of the brain is involved in goal-oriented behavior and short-term memory?

    <p>Prefrontal Area</p> Signup and view all the answers

    What does the extrapyramidal system primarily control?

    <p>Involuntary reflexes</p> Signup and view all the answers

    Which structure is known for synthesizing dopamine?

    <p>Substantia Nigra</p> Signup and view all the answers

    What condition is characterized by motor control issues due to disruptions in the extrapyramidal system?

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

    Where is the primary visual cortex located?

    <p>Occipital Lobe</p> Signup and view all the answers

    Which part of the brain is responsible for the reception and interpretation of speech?

    <p>Wernicke Area</p> Signup and view all the answers

    What is the function of the internal capsule in the brain?

    <p>Connecting sensory and motor pathways</p> Signup and view all the answers

    What is the primary function of the amygdala within the limbic system?

    <p>Involved in emotional processing</p> Signup and view all the answers

    Which structure is primarily responsible for long-term memory formation?

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

    What role does the hypothalamus play in the autonomic nervous system?

    <p>Regulates involuntary bodily functions</p> Signup and view all the answers

    The epithalamus is involved in which function?

    <p>Regulation of circadian rhythms</p> Signup and view all the answers

    Which part of the midbrain is responsible for visual and reflexive responses?

    <p>Superior colliculi</p> Signup and view all the answers

    What is the primary function of the thalamus in the diencephalon?

    <p>Processing and relaying sensory information</p> Signup and view all the answers

    Which structure within the limbic system is involved in integrating smell with emotional responses?

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

    What significant role does the red nucleus play in the body?

    <p>Coordinates motor signals</p> Signup and view all the answers

    Which of the following is NOT a division of the diencephalon?

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

    What is a primary role of the hypothalamus in emotional expression?

    <p>Regulating hormone release</p> Signup and view all the answers

    The inferior colliculi in the midbrain are primarily involved in which type of processing?

    <p>Auditory processing</p> Signup and view all the answers

    What anatomical feature connects the hippocampus to other parts of the limbic system?

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

    Which of the following structures is NOT part of the limbic system?

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

    Which part of the midbrain is responsible for coordinating movement in response to sensory input?

    <p>Red nucleus</p> Signup and view all the answers

    What is the primary function of the somatic nervous system?

    <p>Controlling voluntary muscle movement</p> Signup and view all the answers

    What are afferent pathways responsible for?

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

    Which cells are responsible for the formation of the myelin sheath in the CNS?

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

    Lower motor neurons originate in which part of the nervous system?

    <p>Gray matter of the brainstem and spinal cord</p> Signup and view all the answers

    What is the consequence of upper motor neuron damage?

    <p>Initial paralysis followed by partial recovery</p> Signup and view all the answers

    What are the two types of pathways that connect the CNS to muscles?

    <p>Afferent and efferent pathways</p> Signup and view all the answers

    Which structure in the spinal nerves helps in sensory signal distribution?

    <p>Posterior rami</p> Signup and view all the answers

    What is the function of neuroglia in the CNS?

    <p>Support and protect neurons</p> Signup and view all the answers

    How many pairs of cranial nerves are there in the human body?

    <p>31 pairs</p> Signup and view all the answers

    What role do neurotransmitters play in neural communication?

    <p>Influence other neurons by transmission of signals</p> Signup and view all the answers

    Which of the following statements about motor units is true?

    <p>The neuromuscular junction is where motor neurons and muscle fibers communicate</p> Signup and view all the answers

    Where do spinal nerves exit in relation to their corresponding vertebrae?

    <p>Spinal nerves exit in correspondence with the vertebra above their exit point from the thoracic region downward</p> Signup and view all the answers

    What type of nerve fibers form networks called plexuses?

    <p>Mixed fibers from anterior rami</p> Signup and view all the answers

    What is the primary function of the sympathetic nervous system?

    <p>Mobilizes energy stores during stress or emergencies</p> Signup and view all the answers

    Where are the nerve cell bodies of the parasympathetic nervous system located?

    <p>In cranial nerve nuclei and the sacral region</p> Signup and view all the answers

    What type of fibers predominantly carry impulses in the peripheral autonomic nerves?

    <p>Efferent fibers</p> Signup and view all the answers

    Which type of neurotransmitter is released by most postganglionic sympathetic fibers?

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

    What distinguishes the preganglionic fibers of the parasympathetic nervous system from those of the sympathetic system?

    <p>They are longer and travel close to the organs they innervate</p> Signup and view all the answers

    Which of the following accurately describes the location of cell bodies in the sympathetic nervous system?

    <p>Thoracic and lumbar spinal cord</p> Signup and view all the answers

    What role do catecholamines play in the autonomic nervous system?

    <p>Stimulate adrenergic receptors</p> Signup and view all the answers

    Which structure in the autonomic nervous system acts as modified postganglionic neurons?

    <p>Adrenal medulla</p> Signup and view all the answers

    What is typically the function of α1 adrenergic receptors?

    <p>Stimulates excitation and vasoconstriction</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the autonomic nervous system's structure?

    <p>Composed entirely of myelinated fibers</p> Signup and view all the answers

    What occurs during the 'fight or flight' response induced by the sympathetic nervous system?

    <p>Mobilization of energy stores and increased alertness</p> Signup and view all the answers

    Which of the following plexuses innervates the heart?

    <p>Cardiac Plexus</p> Signup and view all the answers

    Which nerve is responsible for a significant portion of parasympathetic innervation in the viscera of the thorax and abdomen?

    <p>Vagus nerve (X)</p> Signup and view all the answers

    Which neurotransmitter is involved in cholinergic transmission within the autonomic nervous system?

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

    What is the conus medullaris?

    <p>The cone-shaped end of the spinal cord.</p> Signup and view all the answers

    Which section of the spinal cord is responsible for autonomic functions?

    <p>Lateral horn</p> Signup and view all the answers

    What is primarily composed of nerve cell bodies in the spinal cord?

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

    What is the primary function of the spinal cord?

    <p>Conducting reflexes and transmitting nerve impulses.</p> Signup and view all the answers

    Which vessel supplies blood to the spinal cord?

    <p>Vertebral arteries</p> Signup and view all the answers

    Why are spinal cord injuries classified as CNS pathologies?

    <p>They primarily affect sensory-motor pathways in the CNS.</p> Signup and view all the answers

    What can excessive intracranial pressure (IICP) lead to?

    <p>Compromised neuronal oxygenation.</p> Signup and view all the answers

    What denotes the first stage of increased intracranial pressure?

    <p>Vasoconstriction and venous compression.</p> Signup and view all the answers

    What type of brain injury is characterized by initial trauma?

    <p>Primary brain injury</p> Signup and view all the answers

    Which of the following statements about cerebrospinal fluid (CSF) is incorrect?

    <p>CSF is produced by peripheral nerves.</p> Signup and view all the answers

    What structure anchors the conus medullaris to the coccyx?

    <p>Filum terminale</p> Signup and view all the answers

    Which statement about peripheral nervous system injuries is true?

    <p>They can somewhat regenerate if the injury is not severe.</p> Signup and view all the answers

    What role do interneurons in the poster horn of the spinal cord serve?

    <p>Sensory signal integration.</p> Signup and view all the answers

    What effect does systemic arterial vasoconstriction have during increased intracranial pressure?

    <p>Increases blood pressure to overcome ICP.</p> Signup and view all the answers

    Which of the following conditions would be classified differently based on the nervous system impacted?

    <p>Spinal cord injury vs. peripheral neuropathy</p> Signup and view all the answers

    What is considered the central area of irreversible ischemia and necrosis during an acute ischemic stroke?

    <p>Core Region</p> Signup and view all the answers

    Which cellular event is a direct consequence of energy disruption following ischemia?

    <p>Ion imbalance</p> Signup and view all the answers

    Which of the following is NOT a proposed mechanism for vasospasm following subarachnoid hemorrhage?

    <p>Increased nitric oxide</p> Signup and view all the answers

    What is the window of opportunity to restore blood flow in the ischemic penumbra?

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

    Which condition is associated with increased intracranial pressure and may lead to secondary brain injury?

    <p>Subarachnoid Hemorrhage</p> Signup and view all the answers

    What primary mechanism characterizes ferroptosis in cell death following ischemic stroke?

    <p>Accumulation of lipid peroxides</p> Signup and view all the answers

    Which symptom is NOT typically associated with a ruptured vessel during a hemorrhagic stroke?

    <p>Loss of taste</p> Signup and view all the answers

    Which of the following refers to the syndrome of progressive neurologic deterioration occurring after SAH?

    <p>Delayed Cerebral Ischemia</p> Signup and view all the answers

    What role does cerebrospinal fluid (CSF) play in the brain's protection?

    <p>It cushions the brain from injury.</p> Signup and view all the answers

    Which mechanism involves the activation of caspase-1 during cell death?

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

    What is a common early manifestation of leaking vessels in the context of brain injury?

    <p>Episodic headaches</p> Signup and view all the answers

    What is a potential consequence of oxidative damage in the brain following ischemic stroke?

    <p>Cellular apoptosis</p> Signup and view all the answers

    Which description best fits necroptosis as a mechanism of cell death?

    <p>Regulated by RIPK1 and RIPK3</p> Signup and view all the answers

    What complication arises from the breakdown of the blood-brain barrier after hemorrhagic events?

    <p>Secondary hydrocephalus</p> Signup and view all the answers

    What occurs when the neck is passively flexed in the presence of certain neurological conditions?

    <p>Neck pain and increased rigidity</p> Signup and view all the answers

    What is the main purpose of the Hunt and Hess grading system?

    <p>To classify the severity of subarachnoid hemorrhage</p> Signup and view all the answers

    Which of the following complications is associated with increased intracranial pressure after a subarachnoid hemorrhage?

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

    What occurs during Stage 3 of increased intracranial pressure (ICP)?

    <p>ICP approaches arterial pressure, leading to hypoxia.</p> Signup and view all the answers

    Which process describes the formation of the peripheral nervous system during embryologic development?

    <p>Formation of the neural crest from mesodermal cells</p> Signup and view all the answers

    When does the cerebrospinal fluid (CSF) begin to form during fetal development?

    <p>5th week</p> Signup and view all the answers

    Which of the following describes a thrombotic stroke?

    <p>A clot forms in narrowed arteries due to atherosclerosis.</p> Signup and view all the answers

    What is the primary consequence of the loss of autoregulation during increased ICP?

    <p>Small increases in brain volume cause dramatic ICP increases.</p> Signup and view all the answers

    At what developmental stage do the spinal meninges begin to form?

    <p>Days 20 – 35</p> Signup and view all the answers

    What typically occurs if the rostral neuropore fails to close during fetal development?

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

    How does increased ICP lead to brain tissue herniation?

    <p>Through the loss of blood vessel diameter adjustments.</p> Signup and view all the answers

    What is a significant risk period for rebleeding after an initial bleeding episode in subarachnoid hemorrhage?

    <p>First 72 hours</p> Signup and view all the answers

    What is the primary treatment for acute ischemic stroke?

    <p>Intravenous thrombolysis using alteplase.</p> Signup and view all the answers

    Which mechanism is primarily disrupted in ischemic stroke leading to energy failure in the brain?

    <p>Sodium-potassium pump malfunction.</p> Signup and view all the answers

    Which of the following structures develops from the anterior part of the neural tube?

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

    What results from the obstruction of blood supply during an ischemic stroke?

    <p>Necrosis and neuronal death.</p> Signup and view all the answers

    What occurs as the cerebral hemispheres develop in the embryo?

    <p>Formation of nerve fiber connections</p> Signup and view all the answers

    Which type of cells give rise to the neurons and macroglial cells in the spinal cord?

    <p>Neuroepithelial cells</p> Signup and view all the answers

    What common risk factor is associated with the occurrence of ischemic strokes?

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

    What structure is responsible for communication between the two hemispheres of the brain?

    <p>Corpus callosum</p> Signup and view all the answers

    What clinical sign indicates rapid deterioration in Stage 3 of increased ICP?

    <p>Central neurogenic hypoventilation.</p> Signup and view all the answers

    Which pathophysiological event is primarily responsible for neuronal death after ischemic stroke?

    <p>Excitotoxicity and oxidative stress.</p> Signup and view all the answers

    What anatomical feature develops from the alar and basal plates in the medulla?

    <p>Both A and B</p> Signup and view all the answers

    What adverse effect can result from thrombolytic therapy in ischemic stroke treatment?

    <p>Hemorrhagic transformation.</p> Signup and view all the answers

    What happens to cerebral blood flow when ICP matches or exceeds systemic arterial pressure?

    <p>Cerebral blood flow ceases.</p> Signup and view all the answers

    What characteristic is associated with pupils during Stage 3 of increased ICP?

    <p>Pupils are small and sluggish.</p> Signup and view all the answers

    What critical physiological process is lost during Stage 4 of increased ICP?

    <p>Autoregulation of cerebral blood flow.</p> Signup and view all the answers

    What is a common cause of communicating hydrocephalus?

    <p>Subarachnoid hemorrhage</p> Signup and view all the answers

    What would most likely result from impairment in the blood-brain barrier leading to vasogenic edema?

    <p>Leakage of plasma proteins into extracellular spaces</p> Signup and view all the answers

    What is an effective treatment approach for managing cerebral edema?

    <p>Osmotherapy using mannitol</p> Signup and view all the answers

    Which congenital defect is characterized by the failure of skull closure leading to herniation of brain tissue?

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

    What leads to increased intracranial pressure in cases of hydrocephalus?

    <p>Imbalance between cerebrospinal fluid production and absorption</p> Signup and view all the answers

    What type of edema is caused by the failure of active transport systems in brain cells without disrupting the blood-brain barrier?

    <p>Cytotoxic (metabolic) edema</p> Signup and view all the answers

    Which type of hydrocephalus is caused by an obstruction preventing cerebrospinal fluid flow into the subarachnoid space?

    <p>Obstructive (non-communicating) hydrocephalus</p> Signup and view all the answers

    What complication is commonly associated with untreated cerebral edema?

    <p>Brain herniation</p> Signup and view all the answers

    Which condition may prevent the closure of the neural tube during early fetal development?

    <p>Inadequate folic acid supplementation</p> Signup and view all the answers

    What is primarily responsible for producing cerebrospinal fluid within the lateral ventricles?

    <p>Choroid plexus</p> Signup and view all the answers

    What characterizes interstitial edema in the brain?

    <p>CSF movement into extracellular brain spaces</p> Signup and view all the answers

    What is a significant complication of hydrocephalus related to cerebral function?

    <p>Enlargement of head without facial distortion</p> Signup and view all the answers

    Which maternal factor can prevent neural tube defects during pregnancy?

    <p>Folic acid supplementation</p> Signup and view all the answers

    What mechanism leads to vasogenic edema in the brain?

    <p>Breakdown of blood-brain barrier</p> Signup and view all the answers

    What is the primary reason acetylcholine receptor antibodies are significant in Myasthenia Gravis?

    <p>They disrupt acetylcholine receptor function.</p> Signup and view all the answers

    Which subgroup of Myasthenia Gravis is characterized by only ocular muscle symptoms throughout the disease course?

    <p>Ocular MG</p> Signup and view all the answers

    Which factor is considered a risk for developing Multiple Sclerosis?

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

    What type of hypersensitivity reaction is associated with Myasthenia Gravis?

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

    Which demographic group has the highest incidence of MuSK antibody type Myasthenia Gravis?

    <p>African American women in their 40s</p> Signup and view all the answers

    In the context of Multiple Sclerosis, what does demyelination primarily affect?

    <p>Oligodendrocyte cells</p> Signup and view all the answers

    Which clinical manifestation is most commonly associated with the early stages of Myasthenia Gravis?

    <p>Facial droop</p> Signup and view all the answers

    What results from the binding of IgG antibodies in Myasthenia Gravis?

    <p>Destruction of the postsynaptic membrane</p> Signup and view all the answers

    Which type of Multiple Sclerosis involves continuous progression without periods of remission?

    <p>Primary Progressive</p> Signup and view all the answers

    What is a common feature of muscle symptoms in Myasthenia Gravis?

    <p>Fatigue and weakness that fluctuate</p> Signup and view all the answers

    Which diagnostic procedure is commonly used for Multiple Sclerosis?

    <p>Lumbar puncture</p> Signup and view all the answers

    How do corticosteroids assist in the treatment of Multiple Sclerosis?

    <p>By reducing inflammation</p> Signup and view all the answers

    What is the effect of thymectomy in some Myasthenia Gravis patients?

    <p>Variable reduction in symptoms</p> Signup and view all the answers

    Which form of Multiple Sclerosis is characterized by a single neurologic episode lasting 24 hours or less?

    <p>Clinically Isolated Syndrome</p> Signup and view all the answers

    Study Notes

    Nervous System Divisions

    • The nervous system is divided into structural and functional categories
    • Structural categories include the central nervous system (CNS) and the peripheral nervous system (PNS)
    • Functional categories include the somatic nervous system and the autonomic nervous system (ANS)
    • The CNS consists of the brain and spinal cord
    • The PNS is comprised of cranial and spinal nerves that carry impulses towards (afferent - sensory) and away from the CNS (efferent - motor)

    Cranium Overview

    • The cranium protects the brain
    • It is composed of eight bones: frontal, parietal (two), temporal (two), ethmoid, sphenoid, and occipital.
    • The galea aponeurotica is a fibrous band providing extra protection
    • The subgaleal space connects with dural sinuses and can shunt blood to alleviate increased intracranial pressure

    Cranial Floor

    • The cranial floor is irregular and contains foramina for cranial nerves, blood vessels, and the spinal cord
    • The anterior fossa houses the frontal lobes
    • The middle fossa contains temporal lobes and the base of the diencephalon
    • The posterior fossa contains the cerebellum
    • The fossae serve as landmarks for locating intracranial lesions

    Meninges Overview

    • Meninges are three protective membranes surrounding the brain and spinal cord: dura matter, arachnoid, and pia mater
    • The dura mater has two layers that form venous sinuses between them
    • The outer layer of the dura matter forms the periosteum of the skull
    • The inner layer of the dura mater creates rigid membranes supporting and separating brain structures
    • The falx cerebri dips between cerebral hemispheres and is anchored at the crista galli
    • The tentorium cerebelli separates the cerebellum from the cerebral structures above
    • The arachnoid is a spongy, web-like layer that loosely follows the contours of the brain
    • The subdural space is located between the dura mater and arachnoid and contains small bridging veins, disruption of which leads to a subdural hematoma
    • The subarachnoid space is located between the arachnoid and pia mater and contains cerebrospinal fluid (CSF)
    • The pia mater is a delicate layer that closely adheres to the brain and spinal cord and provides support for blood vessels serving brain tissue
    • Choroid plexuses, which produce CSF, arise from the pia mater
    • The spinal cord is anchored to vertebrae via extensions of the meninges
    • Meninges extend beyond the spinal cord's end (at L1/L2) to the lower sacrum
    • CSF circulates down to the lumbar cistern, an expanded area of the subarachnoid space
    • Notable cisterns include the cerebellomedullary cistern (cisterna magna) and the pontine cistern
    • The extradural (epidural) space exists between the dura mater and the skull, skull fractures can sever vessels in this space, leading to epidural hematomas

    Cerebrospinal Fluid (CSF) Summary

    • CSF is a clear, colorless fluid resembling blood plasma and interstitial fluid
    • It provides buoyancy and protection for the brain and spinal cord, absorbing jolts and preventing strain on meninges, nerve roots, and blood vessels
    • Approximately 125 to 150 mL of CSF circulates in the ventricles and subarachnoid space, with around 600 mL produced daily.
    • CSF is primarily produced by ependymal cells in the choroid plexuses of the lateral, third, and fourth ventricles, which are vascularized by the pia mater.
    • The choroid plexuses create a barrier similar to the blood-brain barrier through tight junctions.
    • CSF pressure is about 80 to 180 mm of water in a supine position, doubling when upright.
    • Flow begins in the lateral ventricles, moving through the interventricular foramen to the third ventricle, then through the cerebral aqueduct to the fourth ventricle.
    • CSF can exit the fourth ventricle via lateral or median apertures into the subarachnoid space.
    • CSF is continuously produced and reabsorbed into the venous circulation via arachnoid villi which protrude through the dura mater into the venous sinuses
    • The villi act as one-way valves, allowing CSF to flow into the blood while preventing blood from entering the subarachnoid space.

    Blood Supply to The Brain Summary

    • The brain receives 800–1000 mL/min of blood flow.
    • Carbon dioxide (CO2) is the primary regulator of blood flow in the central nervous system (CNS).
    • Blood supply to the brain comes from the internal carotid arteries and the vertebral arteries.
    • The internal carotid artery provides a larger proportion of the brain's blood flow.
    • The circle of Willis is an arterial circle that helps maintain blood flow in the brain

    Blood Flow Overview:

    • The brain receives about 20% of cardiac output, equating to 800 to 1000 mL of blood per minute.
    • Autoregulation maintains stable cerebral blood flow despite variations in perfusion pressures
    • Carbon dioxide acts as a key regulator of blood flow, functioning as a potent vasodilator to ensure sufficient supply.

    Arterial Supply

    • The brain is supplied by the internal carotid arteries and vertebral arteries.
    • Internal carotid arteries originate from the common carotid arteries and enter the cranium at the base of the skull.
    • Internal carotid arteries pass through the cavernous sinus, branching into the anterior and middle cerebral arteries.
    • Vertebral arteries emerge from the subclavian arteries and traverse the cervical vertebrae.
    • Vertebral arteries enter the cranium through the foramen magnum and unite at the pons-medulla junction to form the basilar artery.
    • The basilar artery divides into paired posterior cerebral arteries at the midbrain level.

    Cerebellum and Brainstem Supply

    • The posterior inferior cerebellar artery, anterior inferior cerebellar artery, and superior cerebellar artery supply the cerebellum and brainstem, originating from the basilar artery.
    • The basilar artery also gives rise to small pontine arteries.

    Arterial Classification

    • Superficial arteries are large arteries on the brain's surface and their branches
    • Projecting arteries are smaller branches that penetrate into the brain (Nutrient arteries)

    Circle of Willis

    • This structure provides an alternate pathway for blood flow if one artery is obstructed (collateral flow)
    • Formed by the posterior cerebral arteries, posterior communicating arteries, internal carotid arteries, anterior cerebral arteries, and anterior communicating arteries.
    • The anterior, middle, and posterior cerebral arteries extend from the circle to supply different brain regions, with the border zone representing areas between major arterial territories.

    Cerebral Artery Functions and Clinical Implications Summary

    • Anterior Cerebral Artery (ACA) supplies: basal ganglia, corpus callosum, medial surface of cerebral hemispheres, superior surfaces of frontal and parietal lobes
    • Middle Cerebral Artery (MCA) supplies: frontal, parietal, and temporal lobes, primarily cortical surfaces
    • Posterior Cerebral Artery (PCA) supplies: part of the diencephalon (thalamus, hypothalamus), temporal lobe, and occipital lobe

    Anterior Cerebral Artery (ACA) Clinical Implications

    • Hemiplegia (weakness on one side of the body) on the contralateral side.
    • Greater weakness in lower extremities compared to upper extremities.

    Middle Cerebral Artery (MCA) Clinical Implications

    • Aphasia (language impairment) in the dominant hemisphere.
    • Contralateral hemiplegia.

    Posterior Cerebral Artery (PCA) Clinical Implications

    • Visual loss.
    • Sensory loss.
    • Contralateral hemiplegia if the cerebral peduncle is affected.

    Blood-Brain Barrier (BBB) Summary

    • The BBB is a selective barrier that prevents potentially harmful substances in the blood from entering the brain's interstitial spaces or cerebrospinal fluid (CSF).
    • The BBB is composed of endothelial cells in brain capillaries with tight junctions.
    • It is supported by astrocytes, pericytes, and microglia.
    • The BBB allows certain substances (e.g., glucose, lipid-soluble molecules, electrolytes) to cross into and out of the brain via transport molecules.
    • It impacts drug therapy, as some antibiotics and chemotherapeutic agents can penetrate the BBB more effectively than others.

    Blood-Brain Barrier (BBB) Clinical Implications

    • Breakdown of the BBB can lead to the entry of toxic molecules and pathogens, contributing to neuroinflammation and neurodegeneration.
    • The choroid plexus epithelium and arachnoid membrane also contribute to barrier functions.

    Brain Divisions

    • The brain has three major divisions: forebrain, midbrain, and hindbrain.
    • The forebrain includes the cerebrum, thalamus, and hypothalamus.
    • The midbrain is also called the mesencephalon and is part of the brainstem.
    • The hindbrain consists of the pons, medulla oblongata, and cerebellum.

    Central Nervous System

    • Telencephalon (Cerebral Hemispheres) consist of the cerebral cortex and basal ganglia.

    Cerebral Cortex

    • Largest portion of the brain.
    • Surface covered with convolutions called gyri.
    • Grooves between gyri are termed sulci, and deeper grooves are called fissures.
    • Contains an outer layer of gray matter (neuron cell bodies, unmyelinated).
    • Organized into columns that receive, integrate, store, and transmit information.
    • Located in the frontal, parietal, temporal, and occipital lobes.

    Basal Ganglia

    • Composed of several nuclei.

    White Matter

    • Lies beneath the cerebral cortex.
    • Composed of myelinated nerve fibers (axons).
    • Tracts.

    Frontal Lobe Boundaries

    • Posterior margin is at the central sulcus (fissure of Rolando).
    • Borders inferiorly on the lateral sulcus (Sylvian fissure).

    Prefrontal Area

    • Responsible for:
      • Goal-oriented behavior (e.g., concentration).
      • Short-term and recall memory.
      • Elaboration of thought.
      • Inhibition of limbic areas of the CNS.

    Premotor Area (Brodmann Area 6)

    • Involved in programming motor movements.
    • Contains cell bodies that are part of the basal ganglia system.

    Frontal Eye Fields

    • Located in the lower portion of Brodmann Area 8 on the middle frontal gyrus.
    • Control eye movements.

    Primary Motor Area (Brodmann Area 4)

    • Located along the precentral gyrus.
    • Forms the primary voluntary motor area.
    • Exhibits somatotopic organization (homunculus) correlating specific body regions with brain areas.
    • Electrical stimulation causes specific muscle movements.

    Pyramidal System

    • Axons from the precentral gyrus form this system.
    • Includes:
      • Corticobulbar tract: Provides voluntary control of head and neck muscles (synapses in the brainstem).
      • Corticospinal tracts: Descend into the spinal cord for voluntary control of muscles throughout the body.
    • Controls function on the opposite side of the body (contralateral control).

    Broca's Speech Area

    • Located on the inferior frontal gyrus (Brodmann Areas 44, 45).
    • Usually found in the left hemisphere.
    • Responsible for motor aspects of speech.
    • Damage results in expressive aphasia (difficulty forming words).

    Parietal Lobe

    • Bordered by the central, parietooccipital, and lateral sulci.
    • Contains the major area for somatic sensory input along the postcentral gyrus (Brodmann areas 3, 1, 2).
    • Adjacent to the primary motor area (precentral gyrus).
    • Association fibers facilitate communication between motor and sensory areas.
    • Involved in sensory association (storage, analysis, interpretation of stimuli).

    Occipital Lobe

    • Located caudal to the parietooccipital sulcus and superior to the cerebellum.
    • Contains the primary visual cortex (Brodmann area 17), receiving input from the retinas.
    • Remainder involved in visual association (Brodmann areas 18, 19).

    Temporal Lobe

    • Lies inferior to the lateral fissure and consists of the superior, middle, and inferior temporal gyri.
    • Contains the primary auditory cortex (Brodmann area 41) and related association area (Brodmann area 42) within the lateral sulcus.
    • Houses the Wernicke area (posterior portion of Brodmann area 22) responsible for reception and interpretation of speech.
      • Dysfunction can lead to receptive aphasia or dysphasia.
    • Involved in memory consolidation and olfaction (sense of smell).

    Insula (Insular Lobe)

    • Located hidden within the lateral sulci between the temporal and frontal lobes.
    • Processes sensory and emotional information and routes it to other brain areas.

    Corpus Callosum

    • A mass of white matter pathways beneath the longitudinal fissure.
    • Connects the two cerebral hemispheres via sensory and motor contralateral projections.
    • Essential for coordinating activities between the hemispheres.

    Basal Ganglia (Basal Nuclei) System

    • Major group of subcortical nuclei.
    • Key components include:
      • Caudate Nucleus
      • Putamen
      • Globus Pallidus
    • Lentiform Nucleus: Formed by the putamen and globus pallidus, named for its lentil-like shape.
    • Striatum: Comprised of the caudate nucleus, putamen, and nucleus accumbens.
    • Substantia Nigra: Functionally part of the basal ganglia; synthesizes dopamine, a precursor to norepinephrine.

    Basal Ganglia Functions

    • Critical for voluntary movement.
    • Involved in cognitive and emotional functions.
    • The nucleus accumbens plays a role in pleasure and reward pathways.

    Internal Capsule

    • Thick layer of white matter.
    • Contains axons of afferent (sensory) and efferent (motor) pathways.
    • Passes to and from the cerebral cortex through the center of the cerebral hemispheres.
    • Located between the caudate and lentiform nuclei.

    Extrapyramidal System

    • The basal ganglia, along with their interconnections with:
      • Thalamus
      • Premotor cortex
      • Red nucleus
      • Reticular formation
      • Spinal cord
    • Considered part of the extrapyramidal system, which is involved in:
      • Motor control.
      • Causing involuntary reflexes and coordinated movements.
      • Stabilizing motor control.

    Extrapyramidal System Diseases

    • Parkinson Disease: Characterized by disruptions in the extrapyramidal system leading to motor control issues.
    • Huntington Disease: Also disrupts the extrapyramidal system, causing involuntary or exaggerated motor movements.

    Limbic System Overview

    • A group of interconnected structures located between the telencephalon and diencephalon, surrounding the corpus callosum.

    Limbic System Key Components

    • Amygdala: Involved in emotional processing and responses.
    • Hippocampus: Essential for memory formation and learning.
    • Fornix: A C-shaped bundle of fibers that connects the hippocampus to other parts of the limbic system.
    • Hypothalamus: Regulates autonomic and endocrine functions, influencing bodily responses to emotions.
    • Related Autonomic Nuclei: Help coordinate autonomic responses with emotional states.

    Limbic System Functional Aspects

    • Acts as an extension or modification of the olfactory system, highlighting the importance of smell in emotional responses.
    • Influences both the autonomic and endocrine systems, facilitating bodily responses to emotional stimuli.

    Limbic System Principal Effects

    • Mediates primitive behavioral responses such as survival instincts.
    • Governs visceral reactions to emotions (e.g., stress responses).
    • Involved in motivation and regulating mood.
    • Plays a significant role in feeding behaviors, influencing appetite and food preferences.
    • Contributes to biological rhythms, helping regulate sleep-wake cycles and other physiological processes.
    • Integrates the sense of smell with emotional and memory responses.

    Limbic System Connections and Mediation

    • The limbic system mediates emotion and long-term memory through its connections with the prefrontal cortex (often referred to as the limbic cortex).
    • This integration supports complex emotional responses and the storage and retrieval of memories associated with emotional experiences.

    Diencephalon

    • The diencephalon, also known as the interbrain, is located at the top of the brainstem and surrounded by the cerebrum.
    • It plays a crucial role in controlling vital functions and visceral activities and is closely associated with the limbic system.

    Diencephalon Divisions

    • The diencephalon consists of four main divisions:
      • Epithalamus
      • Thalamus
      • Hypothalamus
      • Subthalamus

    Epithalamus

    • Forms the roof of the third ventricle, a cavity in the brain.
    • Represents the most superior portion of the diencephalon.
    • Involved in the regulation of circadian rhythms and emotional responses.

    Thalamus

    • The largest component of the diencephalon, surrounding the third ventricle.
    • Acts as a major integrating center for afferent impulses (incoming sensory information) to the cerebral cortex.
    • Various sensations (e.g., touch, pain, temperature) are perceived at the thalamic level, but cortical processing is needed for interpretation.
    • Serves as a relay center for information from the basal ganglia and cerebellum to the appropriate motor areas of the brain, facilitating coordination and integration of motor functions.

    Hypothalamus

    • Located at the base of the diencephalon.
    • Functions to:
      • Maintain a constant internal environment (homeostasis), regulating various physiological parameters such as temperature, thirst, and hunger.
      • Implement behavioral patterns, influencing behaviors related to survival, such as feeding, mating, and aggression.
    • Contains integrative centers that control:
      • Autonomic Nervous System (ANS) function, regulating involuntary bodily functions.
      • Body temperature, through mechanisms such as sweating and shivering.
      • Endocrine function, by regulating hormone release from the pituitary gland.
      • Emotional expression, influencing how emotions are expressed behaviorally.
    • Exerts influence through both endocrine pathways (hormonal control) and neural pathways (direct nerve connections to various brain regions).

    Subthalamus

    • Located laterally flanking the hypothalamus.
    • Serves as an important component of the basal ganglia system for regulating motor activities.
    • Involved in coordinating voluntary movement and motor control.

    Midbrain (Mesencephalon) Overview

    • The midbrain is a small but critical part of the brain situated between the forebrain (cerebrum and diencephalon) and hindbrain (cerebellum and brainstem).
    • It plays essential roles in vision, hearing, motor control, sleep/wake cycles, arousal, and temperature regulation.
    • The midbrain is composed of three primary regions: tectum, tegmentum, and cerebral peduncles.

    Tectum

    • The tectum forms the roof of the midbrain and includes the corpora quadrigemina, which consists of two pairs of superior colliculi and two pairs of inferior colliculi.

    Superior Colliculi

    • Involved in:
      • Visual Processing: Integrates visual stimuli and facilitates eye movement coordination, especially tracking moving objects.
      • Reflexive Responses: Triggers reflexive head and eye movements in response to visual stimuli (e.g., orienting to a flash of light).
      • Multisensory Integration: Combines inputs from various sensory modalities to coordinate appropriate motor responses.

    Inferior Colliculi

    • Functions include:
      • Auditory Processing: Receives auditory information from the ears and integrates this with sensory input.
      • Head Orientation: Helps position the head in response to sound stimuli (e.g., turning the head to locate a sound).
      • Auditory Reflexes: Coordinates reflexive responses to auditory stimuli, such as turning towards a sudden loud noise.

    Tegmentum

    • Located beneath the tectum, forming the floor of the midbrain, and contains important nuclei and pathways.

    Tegmentum Key Components

    • Red Nucleus
      • Receives sensory information from the cerebellum and integrates it with motor signals.
      • Projects to the spinal cord through the rubrospinal tract, influencing motor control, particularly in flexor muscles.
    • Substantia Nigra
      • Contains dopaminergic neurons responsible for synthesizing and releasing dopamine.
      • Plays a critical role in movement regulation and is involved in the modulation of motor pathways.
      • Dysfunction or degeneration of this area is associated with Parkinson's disease, leading to motor control issues.

    Cerebral Peduncles

    • Large bundles of white matter located in the anterior portion of the midbrain
    • Composed of efferent (motor) fibers connecting the cerebral cortex to lower brain structures and the spinal cord
    • Key Tracts:
      • Corticospinal Tract: Carries motor commands from the motor cortex to the spinal cord, facilitating voluntary muscle movement throughout the body.
      • Corticobulbar Tract: Transmits motor signals from the cortex to cranial nerve nuclei in the brainstem, controlling facial and neck muscles.
      • Corticopontocerebellar Tract: Links the cortex to the pons and cerebellum, facilitating coordination and smooth execution of movements.
    • Notable Structures:
      • Nuclei of Cranial Nerves III and IV:
        • Oculomotor Nerve (CN III): Controls most eye movements, pupil constriction, and eyelid elevation.
        • Trochlear Nerve (CN IV): Controls the superior oblique muscle, which helps rotate the eye downwards and laterally.
      • Cerebral Aqueduct (Aqueduct of Sylvius):
        • A narrow canal that connects the third ventricle to the fourth ventricle, facilitating the flow of cerebrospinal fluid (CSF).
        • Blockage can lead to hydrocephalus, characterized by an accumulation of CSF in the ventricles, causing increased intracranial pressure.
    • Summary of Functions:
      • Integration Center: Acts as a crucial relay and integration center for sensory and motor information between the forebrain and the hindbrain.
      • Reflexive Actions: Coordinates reflexive movements related to visual and auditory stimuli.
      • Dopamine Production: The substantia nigra's production of dopamine is essential for regulating voluntary motor control.

    Hindbrain

    • Consists of two main divisions: the metencephalon and the myelencephalon.
    • Plays a crucial role in autonomic functions, motor control, and coordination.

    Metencephalon

    • Major Structures:
      • Cerebellum:
        • Composed of two hemispheres (left and right lobes) of gray and white matter.
        • Features a convoluted cortical surface, similar to the cerebrum.
        • Divided by a central fissure into two lobes, connected by a structure called the vermis.
        • Functions:
          • Responsible for reflexive and involuntary motor control.
          • Fine-tunes motor activity.
          • Balance and posture maintenance.
        • Neural Connections:
          • Connects to the medulla through the inferior cerebellar peduncle.
          • Connects to the midbrain via the superior cerebellar peduncle.
          • Connected to the pons through the middle cerebellar peduncles.
        • Control Mechanism:
          • Exhibits ipsilateral control.
      • Pons:
        • Positioned below the midbrain and above the medulla.
        • Characterized by its bulging appearance.
        • Functions:
          • Acts as a bridge for communication between the cerebellum and brainstem.
          • Facilitates communication between the two hemispheres of the cerebellum.
          • Contains the nuclei of cranial nerves V (trigeminal), VI (abducens), VII (facial), and VIII (vestibulocochlear).

    Myelencephalon

    • Major Structure:
      • Medulla Oblongata:
        • Forms the lowest part of the brainstem, connecting the brain to the spinal cord
        • Functions:
          • Autonomic Control: Regulates essential reflex activities such as:
            • Heart Rate
            • Respiration
            • Blood Pressure
            • Coughing, Sneezing, Swallowing, and Vomiting
          • Contains the nuclei for cranial nerves IX (glossopharyngeal), X (vagus), XI (accessory), and XII (hypoglossal).
          • Decussation of Motor Pathways: A major portion of descending motor pathways (e.g., corticospinal tracts) cross to the opposite side at the level of the medulla.
          • Sleep-Wake Regulation: Involved in processing sleep-wake rhythms.

    Autonomic Nervous System (ANS)

    • Regulates the body's internal environment and controls involuntary functions such as heart rate, digestion, and respiratory rate.
    • Further divided into the sympathetic and parasympathetic nervous systems, which have opposing effects on various organs and bodily functions.
    • Function: Coordinates and maintains a steady state among body organs.
    • Components: Includes components from both the central nervous system (CNS) and the peripheral nervous system (PNS).
    • Divisions:
      • Sympathetic Nervous System: Typically stimulates organs (e.g., increases heart rate).
      • Parasympathetic Nervous System: Generally inhibits or relaxes organ function (e.g., decreases heart rate).
    • Neural Pathways: Many ANS neurons travel within spinal nerves and certain cranial nerves, indicating the system's widespread activity throughout the body.
    • Visceral or Enteric System: A specialized part of the ANS that independently regulates the sensory and motor functions of the gastrointestinal tract.
    • Central Regulation: The CNS contains centers in the reticular formation for cardiovascular and respiratory control.
    • Structure: Made up of autonomic nerves, ganglia, and plexuses.

    Sympathetic Nervous System

    • Function: Mobilizes energy stores during stress or emergencies, commonly referred to as the “fight or flight” response.
    • Location of Cell Bodies: Innervated by cell bodies located in the spinal cord from the first thoracic (T1) to the second lumbar (L2) regions, hence termed the thoracolumbar division.
    • Preganglionic Axons:
      • Form synapses shortly after exiting the spinal cord in the sympathetic (paravertebral) ganglia.
      • Can travel in several ways:
        • Directly synapsing with postganglionic neurons at their level in the sympathetic chain ganglion.
        • Ascending to higher sympathetic chain ganglia before synapsing.
        • Descending to lower sympathetic chain ganglia before synapsing.
        • Passing through the sympathetic chain ganglion to synapse with collateral ganglia.
    • Postganglionic Neurons: Exit the collateral ganglia to innervate viscera located below the diaphragm.
    • Adrenal Medulla Innervation: Preganglionic sympathetic neurons that innervate the adrenal medulla travel through the splanchnic nerves without synapsing.

    Parasympathetic Nervous System

    • Function: Responsible for conserving and restoring energy during rest.
    • Location of Nerve Cell Bodies: Found in the cranial nerve nuclei and the sacral region of the spinal cord, collectively referred to as the craniosacral division.
    • Nerve Fiber Characteristics:
      • Preganglionic Fibers: Longer than those in the sympathetic division.
      • Cranial Nerves: Preganglionic parasympathetic nerves from the brainstem travel to the viscera in the head, thorax, and abdomen via cranial nerves, including:
        • Oculomotor (III)
        • Facial (VII)
        • Glossopharyngeal (IX)
        • Vagus (X)
      • Sacral Preganglionic Nerves: Originate in the sacral spinal cord, running separately or alongside some spinal nerves.
    • Synapses: Occur in terminal ganglia located near the target organs.
    • Nerve Plexuses: Similar to spinal nerves, autonomic nerves form plexuses.

    Summary of Neurotransmitter Actions in the Autonomic Nervous System

    • Neurotransmitters:
      • Both sympathetic preganglionic fibers and parasympathetic preganglionic and postganglionic fibers release acetylcholine (ACh).
      • Most postganglionic sympathetic fibers release norepinephrine (noradrenaline).
    • Catecholamines:
      • The catecholamines (epinephrine, norepinephrine, dopamine) produced in the adrenal medulla resemble those in the sympathetic nervous system.
      • Interact with various adrenergic receptors: α and β receptors are present on the effector organs.
    • Responses to Norepinephrine and Epinephrine:
      • Norepinephrine stimulates α1 and β1 receptors and selectively activates some β2 receptors.
      • Epinephrine stimulates all four types of adrenergic receptors.

    PERIPHERAL NERVOUS SYSTEM (PNS): Spinal Nerves and Cranial Nerves

    • Consists of nerves located outside the central nervous system (CNS).
    • Divided into two primary components:
      • Somatic Nervous System:
        • Controls voluntary muscle movement through efferent nerves (motor pathways).
        • Transmits sensory information via afferent nerves (sensory pathways).
      • Autonomic Nervous System:
        • Function: Regulates the body's internal environment and controls involuntary functions.
        • Divisions:
          • Sympathetic Nervous System: Mobilizes energy stores during stress or emergencies.
          • Parasympathetic Nervous System: Responsible for conserving and restoring energy during rest.
    • Nerve Composition:
      • Peripheral nerves are made up of individual axons and dendrites, most of which are encased in a myelin sheath that enhances signal transmission.
      • These axons and dendrites are grouped into bundles called fascicles.

    Upper and Lower Motor Neurons and Spinal Cord

    • Classification of Neurons:
      • Sensory neurons: Transmit impulses from peripheral sensory receptors to the CNS.
      • Associational or interneurons: Transmit impulses from neuron to neuron.
      • Motor neurons: Transmit impulses from the CNS to an effector organ.
    • Neuroglia ("nerve glue"), support for the CNS:
      • Astrocytes: Fill the spaces between neurons, surround blood vessels.
      • Oligodendroglia (oligodendrocytes): Deposit myelin.
      • Microglia: Remove debris.
      • Ependymal cells: Line CSF-filled cavities.

    Nerve Impulses

    • Neurons:
      • Generate and conduct electrical and chemical impulses.
      • Influence other nearby neurons by the release of neurotransmitters.
      • Communicate information to and from CNS.
      • Variable size and structure.
    • Neurotransmitters:
      • Norepinephrine, acetylcholine, dopamine, histamine, and serotonin.
    • Postsynaptic Effects:
      • Excited: Depolarized; excitatory postsynaptic potentials (EPSPs).
      • Inhibited: Hyperpolarized; inhibitory postsynaptic potentials (IPSPs).

    Protective Structures

    • Meninges:
    • Bone:
    • Axons:
      • May be divergent.
    • Myelin:
      • Segmented, lipid.
      • Insulating.
      • Forms myelin sheath.
      • Formed and maintained by Schwann cells.
    • Nodes of Ranvier:
      • Saltatory conduction

    Afferent Pathways

    • Definition: Transmit sensory information from peripheral receptors toward the cerebrum.
    • Termination: These pathways terminate in either the cerebral cortex or the cerebellar cortex, or both.

    Efferent Pathways

    • Definition: Relay information away from the cerebrum to the brainstem or spinal cord.
    • Types of Efferent Pathways:
      • Upper Motor Neurons:
        • Location: Contained entirely within the central nervous system (CNS).
        • Function:
          • Control fine motor movements.
          • Influence and modify spinal reflex arcs and circuits.
          • Form synapses with interneurons, which in turn synapse with lower motor neurons that project into the peripheral nervous system (PNS).
      • Lower Motor Neurons:
        • Location: Their cell bodies are located in the gray matter of the brainstem and spinal cord.
        • Function: Directly influence muscles.
        • Processes: Extend from the CNS into the PNS.

    Effects of Neuron Damage

    • Upper Motor Neuron Damage:
      • Consequence: Usually results in initial paralysis.
      • Recovery: Partial recovery may occur within days or weeks.
    • Lower Motor Neuron Damage:
      • Consequence: Leads to paralysis.
      • Recovery: Recovery is possible only if there is peripheral nerve damage followed by nerve regeneration.

    Motor Units

    • Definition: A motor unit consists of a motor neuron and the skeletal muscle fibers it stimulates.
    • Neuromuscular Junction: The junction between the axon of the motor neuron and the plasma membrane of the muscle cell, also known as the myoneural junction.

    Spinal Nerves

    • Overview: The human body has 31 pairs of spinal nerves.
    • Exit Points:
      • The first cervical nerve exits above the first cervical vertebra (C1).
      • All other spinal nerves exit below their corresponding vertebrae.
    • Structure:
      • Spinal nerves are mixed nerves, containing both sensory (afferent) and motor (efferent) neurons.
      • The structure resembles a tree with:
        • Roots: Arising as rootlets that combine into roots next to the anterior and posterior horns of the spinal cord.
        • Trunk: The convergence of the two spinal nerve roots at the intervertebral foramen, forming the spinal nerve trunk.
        • Branches: The spinal nerve then divides into anterior and posterior rami.
      • Rami:
        • Anterior Rami: Except for thoracic nerves, these form plexuses (networks of nerve fibers) that branch into peripheral nerves.
        • Posterior Rami: Distributed to specific body areas, sending sensory signals from defined locations associated with particular spinal cord segments.
    • Dermatomes:
      • Specific areas of cutaneous (skin) innervation corresponding to spinal cord segments are called dermatomes.
      • Dermatomes have a relatively regular pattern, but adjacent areas can receive innervation from more than one spinal nerve.

    Cranial Nerves

    • Overview: Like spinal nerves, cranial nerves are categorized as peripheral nerves.
    • Types: Most cranial nerves are mixed nerves, although some are purely sensory or motor.
    • Connection: Cranial nerves connect to nuclei in the brain and brainstem.

    Spinal Cord

    • Location & Protection:
      • Part of the central nervous system (CNS).
      • Lies within the vertebral canal and is protected by the vertebral column.
    • Functions:
      • Connects the brain and the body through a long nerve cable.
      • Facilitates somatic and autonomic reflexes.
      • Involved in motor pattern control.
      • Modulates sensory and motor functions.
    • Structure:
      • Begins at the medulla oblongata and ends at the first or second lumbar vertebra in adults.
      • Conus medullaris: Cone-shaped end of the spinal cord.
      • Cauda equina: Nerve bundle continuing from the conus medullaris.
      • Filum terminale: A filament anchoring the conus medullaris to the coccyx.
    • Spinal Sections: Divided into vertebral sections with corresponding paired nerves:
      • 8 cervical
      • 12 thoracic
      • 5 lumbar
      • 5 sacral
      • 1 coccygeal
    • Cross-Section Anatomy:
      • Gray matter: Forms a butterfly-shaped inner core.
        • Contains Nerve cell bodies
      • Central canal: Filled with cerebrospinal fluid (CSF) runs through the spinal cord.
      • Gray matter divided into three regions:
        • Posterior (dorsal) horn: Contains interneurons and axons from sensory neurons.
        • Lateral horn: Contains cell bodies related to the autonomic nervous system (ANS).
        • Anterior (ventral) horn: Contains nerve cell bodies for efferent (motor) pathways that exit via spinal nerves.
      • White matter covers gray matter
    • The primary functions of the spinal cord include:
      • Conducting somatic and autonomic reflexes.
      • Providing motor pattern control centers.
      • Modulating sensory and motor function.
      • Connecting the brain and body.
      • Serving as a pathway for sensory and motor information to travel to and from the brain.
      • Transmitting nerve impulses to and from the peripheral nervous system.

    Blood Supply to the Spinal Cord

    • Vertebral arteries:
      • Anterior spinal arteries
      • Posterior spinal arteries
      • Branch off the aorta artery.

    Central vs. Peripheral Nervous System Pathologies

    • Central Nervous System (CNS): Includes the brain and spinal cord.
    • Peripheral Nervous System (PNS): Consists of nerves branching off from the CNS to innervate the body.
    • Traumatic Brain Injury (TBI): Injury to the brain, often resulting in primary and secondary damage.
    • Peripheral Neuropathies: Damage to peripheral nerves, causing localized deficits.
    • Spinal Cord Injuries (SCIs): Damage to the spinal cord, disrupting communication between the brain and body, leading to widespread neurological deficits.
    • Radiculopathies: Compression or irritation of nerve roots, causing pain, numbness, and weakness.
    • Seizure Disorders and Epilepsy: Abnormal electrical activity in the brain causing seizures.
    • Cerebrovascular Accident (CVA): Stroke caused by blockage (ischemic) or bleeding (hemorrhagic) in the brain.
    • Headache Syndromes: Pain in the head, often due to muscle tension, inflammation, or vascular issues.
    • Tumors: Abnormal growths in the brain or spinal cord.

    Brain Autoregulation

    • Autoregulation: The brain's ability to adjust blood vessel diameter to maintain constant cerebral blood flow (CBF) despite changes in systemic blood pressure.
    • Cerebral Perfusion Pressure (CPP): The pressure needed to perfuse the brain with blood (CPP = Mean Arterial Pressure (MAP) - Intracranial Pressure (ICP)).
    • Increased Intracranial Pressure (IICP): Pressure inside the skull greater than 20 to 25 mm Hg.
    • Stages of IICP:
      • Stage 1: Compensatory mechanisms (vasoconstriction, venous compression) maintain stable ICP.
      • Stage 2: Compensatory mechanisms fail, systemic vasoconstriction occurs, and neuronal oxygenation is compromised.
      • Stage 3: ICP approaches arterial pressure, leading to brain hypoxia, hypercapnia, and loss of autoregulation.
      • Stage 4: Brain herniates, leading to irreversible brain damage and death.
    • Failure of Autoregulation: In IICP, autoregulation fails, leading to a vicious cycle of increased pressure and reduced perfusion.

    Ischemic Stroke

    • Ischemic Stroke: Blockage of a cerebral artery, interrupting blood flow and oxygen supply to brain tissue.
    • Types of Ischemic Stroke: Thrombotic (clot forms in the artery), Embolic (clot travels from another location).
    • Pathophysiology:
      • Blockage of blood flow leads to energy failure in brain cells.
      • Excitotoxicity, oxidative stress, inflammation, and cell death contribute to neuronal damage.
    • Treatment: Intravenous thrombolysis with alteplase to dissolve clots.
    • Reperfusion Injury: Can occur after restoring blood flow due to the release of damaging molecules.

    Hemorrhagic Stroke, Focusing on Subarachnoid Hemorrhage (SAH)

    • Subarachnoid Hemorrhage (SAH): Bleeding into the space between the brain and its protective membranes.
    • Causes: Rupture of an aneurysm or arteriovenous malformation (AVM).
    • Pathophysiology:
      • Blood leaks into the subarachnoid space, increasing intracranial pressure (ICP).
      • Autoregulation is impaired, leading to reduced cerebral blood flow.
      • Blood-brain barrier disruption, inflammation, and brain edema.
    • Complications: Delayed cerebral ischemia (DCI), hydrocephalus, rebleeding.
    • Management: Control ICP, prevent vasospasm, surgical repair.

    Key Mechanisms of Cell Death Following Ischemic Stroke

    • Ferroptosis: Iron-dependent cell death caused by lipid peroxidation.
    • Phagoptosis: Engulfment of cells by other cells.
    • Parthanatos: Cell death triggered by poly(ADP-ribose) polymerase (PARP) overactivation.
    • Pyroptosis: Inflammatory form of cell death mediated by caspase-1.
    • Necroptosis: Regulated form of necrosis involving receptor-interacting protein kinase 1 (RIPK1) and RIPK3.

    Overview of Nervous System

    • Central nervous system (CNS): brain and spinal cord.
    • Peripheral nervous system (PNS): neurons outside the CNS connecting the brain & spinal cord to peripheral structures.
    • Autonomic nervous system (ANS): neurons innervating smooth muscle, cardiac muscle, glandular epithelium, and combinations of these tissues.

    Development of Nervous System

    • Begins during the 3rd week of embryonic development.
    • Neural plate and neural groove develop on the posterior aspect of the trilaminar embryo.
    • Neural tube differentiates into the CNS.
    • Neural crest gives rise to the PNS and ANS.
    • Cranial neuropore closes on day 25, caudal neuropore closes day 27.

    Development of Spinal Cord

    • Primordial spinal cord develops from the caudal part of the neural plate and caudal eminence.
    • Neural tube caudal to the 4th pair of somites forms the spinal cord.
    • Wall of the neural tube is composed of thick neuroepithelium.
    • Neuroepithelial cells constitute the ventricular zone (gives rise to neurons and macroglial cells).
    • Neuroepithelial cells from the ventricular zone differentiate into primordial neurons (neuroblasts, which form an intermediate zone between ventricular & marginal zones).
    • Outer parts of neuroepithelial cells comprise the marginal zone (becomes the white matter of the spinal cord).
    • Alar plate: afferent (sensory) functions.
    • Basal plate: efferent (motor) functions.
    • By 8 weeks, the spinal cord extends the entire length of the vertebral canal.
    • Eventually, the spinal cord ends at the 1st lumbar vertebra in adults.

    ### Spinal Meninges

    • Develop from mesenchymal cells and neural crest cells (days 20-35).
    • Dura mater: external layer.
    • Pia mater and arachnoid mater (leptomeninges): internal layers.
    • Subarachnoid space: fluid-filled space within the leptomeninges.
    • Cerebrospinal fluid (CSF) begins to form in the 5th week.

    Brain Development

    • Begins in the 3rd week when the neural plate and tube are developing.
    • Neural tube cranial to the 4th pair of somites becomes the brain.
    • Neural progenitor cells proliferate, migrate, and differentiate into specific areas of the brain.
    • Primary brain vesicles differentiate during weeks 3-5:
      • Forebrain (prosencephalon): divides into telencephalon and diencephalon.
      • Midbrain (mesencephalon): does not divide.
      • Hindbrain (rhombencephalon): partially divides into metencephalon and myelencephalon.
    • Neuroblasts in the basal plates of the medulla: efferent (motor) neurons.
    • Neuroblasts in the alar plates of the medulla: afferent (sensory) neurons.
    • Cerebral hemispheres are evident by 7 weeks.

    Cerebral Development

    • Commissures connect corresponding areas of the cerebral hemispheres.
    • Corpus callosum is the largest commissure, extending over the roof of the diencephalon.
    • Sulci (grooves) and gyri (convolutions) develop as the fetus grows, increasing the cerebral cortex surface area.

    Congenital Anomalies of Nervous System

    • Result from defective closure of the rostral neuropore during the 4th week of development.
    • Cranium Bifidum
    • Tethered Spinal Cord
    • Spina Bifida:
      • Spina Bifida Occulta
      • Spina Bifida with Meningocele
      • Spina Bifida with Myelomeningocele
    • Meroencephaly
    • Microcephaly: head circumference more than 2 standard deviations below the mean.

    ### Most Common Presentations of Neural Tube Defects

    • Anencephaly: rostral end of the neural tube fails to close, leading to incomplete brain development.
    • Spina bifida: neural tube remains open at the caudal end, resulting in incomplete spinal cord development.
    • Encephalocele: failure of skull closure resulting in herniation of brain tissue.

    ### Ventricular System

    • Communicating network of cavities filled with CSF.
    • CSF is produced from arterial blood by the choroid plexuses of the lateral and fourth ventricles.
    • CSF fills the ventricles and subarachnoid space, is absorbed across the arachnoid villi into the venous circulation, and drains into lymphatic vessels surrounding the cranial cavity and spinal canal.
    • Cycle of CSF production and reabsorption is constant.

    Neural Tube Defects

    • Congenital malformation occurring between the 20th and 28th day after conception.
    • Cells of the neural plate do not fold correctly to form the neural tube, resulting in incomplete closure.
    • The growing brain and spinal cord are then exposed.
    • Second to congenital heart defects as the most common serious birth defect.
    • Result from complex interactions of genes and environmental conditions (dietary factors, toxic exposures, hyperthermia).
    • May be preventable with prenatal maternal folic acid (FA) supplementation, avoiding prenatal exposure to known teratogens.

    Chiari Malformation

    • A malformation of the brainstem and cerebellum.

    ### Partial or Complete Agenesis of Corpus Callosum

    • Absence or incomplete development of the corpus callosum.

    ### Lissencephaly

    • A rare condition in which the brain's surface is smooth, lacking the normal folds (gyri) and grooves (sulci).

    ### Hydrocephalus

    • Significant enlargement of the head, but the face is of normal size.
    • Usually associated with intellectual disability.
    • Results from impaired circulation and absorption of CSF or (rarely) from increased production.
    • Imbalance between CSF production and absorption, with accumulation of CSF in the cranial cavity.
    • Increased size of the ventricles and elevation of intracranial pressure produces the clinical manifestations of hydrocephalus.
    • Communicating (non-obstructive hydrocephalus): impaired cerebrospinal fluid re-absorption without obstruction between the ventricles and subarachnoid space or overproduction of CSF (rare).
    • Noncommunicating (obstructive hydrocephalus): caused by a CSF-flow obstruction ultimately preventing CSF from flowing into the subarachnoid space (either due to external compression or intraventricular mass lesions).

    ### Types of Cerebral Edema

    • Increase in fluid content within brain tissue, leading to an enlargement of extracellular or intracellular volume.

    • Distortion of blood vessels, displacement of brain tissues, increased intracranial pressure (IICP), and potential brain herniation are the main harmful effects of cerebral edema.

      • Vasogenic Edema (most common type):
        • Caused by increased capillary permeability from the blood-brain barrier breakdown.
        • Plasma proteins leak into extracellular spaces, drawing water and increasing brain water content.
        • Begins at the injury site, spreading in white matter due to easier separation of myelinated fibers.
        • Leads to further edema because of ischemia and increased IICP.
        • Symptoms: Focal neurological deficits, disturbances in consciousness, and severe increases in ICP.
        • Resolves by slow diffusion of fluid back into the bloodstream.
      • Cytotoxic (Metabolic) Edema:
        • Directly affects brain cells (neurons, glial cells, and endothelial cells) due to toxic factors.
        • Causes failure of active transport systems without disrupting the blood-brain barrier.
        • Most often caused by ischemia/hypoxia.
        • Cells lose potassium and gain sodium, causing water to move into the cells, leading to intracellular swelling.
        • Occurs primarily in the gray matter and can further exacerbate vasogenic edema by compromising endothelial tight junctions.
      • Interstitial Edema:
        • Occurs with noncommunicating hydrocephalus (obstructive type).
        • Caused by increased cerebrospinal fluid (CSF) volume, leading to CSF movement into extracellular brain spaces.
        • Primarily affects white matter, reducing its size due to myelin lipid loss.
        • Increases hydrostatic pressure within the white matter.

    ### Treatment of Cerebral Edema

    • Oxygen therapy to optimize brain oxygenation.
    • Osmotherapy (e.g., mannitol) to reduce brain water content.
    • Diuretics to remove excess fluid.
    • CSF drain tube placement to decrease intracranial pressure.
    • Systemic blood pressure maintenance through fluid management to ensure adequate cerebral perfusion.
    • Steroids (dexamethasone) for cerebral edema caused by brain tumors.

    Myasthenia Gravis (MG)

    • Progressive neuromuscular junction disorder.
    • Autoimmune disease in which antibodies disrupt acetylcholine receptors at the neuromuscular junction, affecting nerve impulse transmission.

    ### Risk Factors for MG

    • Possible genetic link: 27% of cases have a family history of autoimmune disorders.
    • Genetic markers (HLA-B8, DR3) are linked to a high risk of developing MG.
    • Late onset: Males over 65.
    • Early onset: Women ages 20-30.
    • African American women in their 40's had the highest incidence of the MuSK subtype.
    • 30% of cases of people with Thymomas get Myasthenia Gravis.

    Normal Physiology

    • Nerve impulses at the neuromuscular junction are transmitted by neurotransmitters released from the presynaptic terminal of the axon.
    • These neurotransmitters bind to the acetylcholine receptor on the myocytes, eliciting muscle contraction.

    Pathophysiology of MG

    • Hypersensitivity reaction – Type 2 (B cell mediated).
    • IgG antibodies act as autoantibodies against nicotinic acetylcholine receptors (AChR).
    • Targets:
      • AChR (Acetylcholine receptors) – most common.
      • MuSK (Muscle specific kinase).
      • LRP4 (Lipoprotein receptor-related protein 4).
    • Binding of these antibodies activates the complement system, leading to membrane attack complex (MAC) formation and destruction of the postsynaptic membrane.

    Thymus' Role in MG

    • The thymus may have a deficiency in intrinsic complement regulatory proteins in some patients.
    • This deficiency allows the proliferation of Acetylcholinergic antibody-producing cells, leading to:
      • Thymoma of the medullary areas of the thymus.
      • Circulation of Acetylcholine receptor (AchR) antibody.
      • Germinal center formation in the thymus, which makes more acetylcholinergic antibody-producing cells (causing a persistent autoimmune response to acetylcholine receptors despite thymectomy in some patients).

    Clinical Markers of MG

    • Ocular and facial muscles tend to be first affected at the tissue level, progressing to generalized body weakness later.
    • Destruction and blocking of neurotransmitter receptor sites lead to incomplete muscular depolarization and the inability to repeat depolarization after a few impulses at the cellular level.
    • Anticholinergic-receptor (AchR) or muscle-specific kinase (MuSK) antibody tests can confirm elevated levels of these antibodies in the blood, supporting an MG diagnosis.

    Clinical Manifestations of MG

    • Muscle fatigue and weakness: fluctuates and can affect eye, face, mouth, throat, neck, respiratory, arm, and leg muscles.
    • Facial droop: Inability to make facial expressions.
    • Diplopia.
    • Ptosis.
    • Swallowing and speaking problems: includes choking and drooling.
    • Trouble breathing deep and coughing.
    • Symptoms worsen throughout the day in early stages.

    Subtypes of MG

    • Early Onset G: Target antigen is AchR, peaks in patients 30-50 years of age, but often experienced much earlier. Symptoms are generalized and ocular. Juvenile MG is rare.
    • Late Onset MG: Target antigen is AchR, peaks between 50-69 years old. Symptoms are generalized and ocular.
    • Transient Neonatal MG: Present at birth due to maternal antibodies, but antibodies disappear along with symptoms.
    • Ocular MG: Only experience ocular muscle symptoms for the entirety of the MG course. Older Japanese and American populations experience this more.
    • MusK antibody type MG: 10-15% of cases have muscle-specific Kinase antibodies and not AchR antibodies.
    • Seronegative MG: No detectable circulating antibody against AchR or MuSK.

    ### Multiple Sclerosis (MS)

    • Autoimmune disease leading to the breakdown of myelin, loss of axons, and plaque formation.
    • MS affects oligodendrocyte cells.

    ### Risk Factors for MS

    • Exact cause is unknown, but possible gene-environment involvement.
    • Smoking, vitamin D deficiency, obesity, and Epstein-Barr Virus are possible risk factors.

    ### Pathophysiology of MS

    • Inflammation, demyelination, myelin repair, loss of oligodendrocytes, and scar formation are the key characteristics of the disease.

    ### Clinical Manifestations of MS

    • Vision problems
    • Difficulty walking
    • Fatigue
    • Bowel and bladder dysfunction
    • Dysarthria
    • Cognitive changes

    ### Types of MS

    • Relapsing-Remitting
    • Primary Progressive
    • Secondary Progressive
    • Progressive Relapsing

    Other Subcategories of MS

    • Clinically Isolated Syndrome: a single episode of neurologic symptoms lasting 24 hours or less.
      • May be related to demyelination.
      • May not develop into MS.
    • Fulminant: an acute form of MS that rapidly progresses.
    • Benign: mild form of MS with rare relapses.

    Diagnosis and Treatment of MS

    • Lumbar puncture (LP), S/S, MRI, and evoked potential studies are used for diagnosis.
    • No cure: treatment includes corticosteroids, immunosuppressants, and immune system modulators.
    • Lifestyle modifications: avoiding smoking, extreme heat exposure, and fatigue/stress, engaging in exercise are recommended.

    ### MS Summary

    • Chronic autoimmune disease with no cure.
    • Inflammation, demyelination, myelin repair, loss of oligodendrocytes, and scar formation characterize MS.
    • The four different types of MS are classified by how the clinical manifestations present in individuals.

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    Test your knowledge on the divisions of the nervous system, focusing on the structures of the central nervous system (CNS) and the protective layers surrounding the brain. This quiz explores essential concepts related to cranial fossa, meninges, and their functions.

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