Neuroanatomy: Meninges and Cerebrospinal Fluid
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Questions and Answers

What is the main function of the meninges?

  • To facilitate the flow of cerebrospinal fluid
  • To house blood vessels supplying the CNS
  • To provide structural support to neurons
  • To protect the brain and spinal cord (correct)

    • Which layer of the meninges is the thick outer layer?

  • Duramater (correct)
  • Piamater
  • Arachnoid membrane
  • Subarachnoid space

    • What does CSF stand for, and what is its primary role?

  • Cerebrospinal fluid, to regulate intracranial pressure (correct)
  • Cerebral systemic fluid, to facilitate blood flow
  • Cerebral spinal fluid, to nourish neurons
  • Central spinal fluid, to act as a structural framework

    • Which of the following conditions can result from a blockage in CSF flow?

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

    What type of cells are neuroglia, and what is their primary function?

    <p>Glial cells that protect and support neurons</p> Signup and view all the answers

    Which cells are responsible for maintaining the blood-brain barrier?

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

    In which area is the subarachnoid space located?

    <p>Between the piamater and the arachnoid membrane</p> Signup and view all the answers

    What occurs when there is failure of reabsorption of CSF?

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

    Which neurotransmitter is primarily secreted by excitatory projection neurons?

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

    What is the function of acetylcholinesterase at the neuromuscular junction?

    <p>Breaks down acetylcholine</p> Signup and view all the answers

    Which receptors are known for their slower response and involve GPCR mechanisms?

    <p>Metabotropic receptors</p> Signup and view all the answers

    What triggers the release of calcium ions during muscle contraction?

    <p>Action potential propagation</p> Signup and view all the answers

    Which of the following substances can block NMDA receptor channels?

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

    What type of ions do GABA A receptors allow to flow when activated?

    <p>Chloride ions</p> Signup and view all the answers

    What is the primary role of neuromodulators in the nervous system?

    <p>Regulate neurotransmitter availability</p> Signup and view all the answers

    Which neurotransmitter is considered a driver in the peripheral nervous system?

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

    Which structures serve as the dorsal and ventral boundaries of the thoracic cavity?

    <p>Thoracic vertebrae and sternum</p> Signup and view all the answers

    What is the primary function of the diaphragm during respiration?

    <p>To contract and increase thoracic pressure</p> Signup and view all the answers

    Which of the following nerves is responsible for the sympathetic innervation of the pelvic region?

    <p>Hypogastric nerve</p> Signup and view all the answers

    What is the relationship between the detrusor muscle and the control of micturition?

    <p>It contracts under parasympathetic control.</p> Signup and view all the answers

    In reflex arcs, which component is responsible for transmitting signals from receptors to the integration center?

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

    Which of the following structures is NOT considered part of the abdominal cavity?

    <p>Pelvic inlet</p> Signup and view all the answers

    What is the main distinction between somatic and autonomic reflexes?

    <p>Autonomic reflexes innervate glands and smooth muscles.</p> Signup and view all the answers

    Which opening of the diaphragm allows for the passage of the esophagus?

    <p>Esophageal hiatus</p> Signup and view all the answers

    What effect does the sympathetic division have on blood vessels?

    <p>It leads to vasoconstriction.</p> Signup and view all the answers

    Which cranial nerve is responsible for pupil constriction?

    <p>CN III - Oculomotor</p> Signup and view all the answers

    What is the role of agonist drugs in the context of receptors?

    <p>They bind to receptors and enhance the response.</p> Signup and view all the answers

    Which of the following is a function of the parasympathetic division?

    <p>Stimulating digestion.</p> Signup and view all the answers

    What neurotransmitter is released by adrenergic fibers?

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

    Which effect does the sympathetic nervous system have on the digestive tract?

    <p>Decreased activity and secretions.</p> Signup and view all the answers

    What is the function of sympathomimetic drugs?

    <p>They enhance the effects of the sympathetic nervous system.</p> Signup and view all the answers

    Which cranial nerves are primarily involved in the parasympathetic division?

    <p>CN III - Oculomotor, CN VII - Facial.</p> Signup and view all the answers

    What is the main consequence of a suprascapular nerve injury?

    <p>Denervation atrophy of supraspinatus and infraspinatus muscles</p> Signup and view all the answers

    Which nerve is primarily responsible for innervating the quadriceps muscle?

    <p>Femoral nerve</p> Signup and view all the answers

    What would be the expected symptom of radial nerve dysfunction?

    <p>Inability to extend the elbow, carpus, and digits</p> Signup and view all the answers

    Which structure is targeted in a palmar digital nerve block?

    <p>DIP joint and sole of the foot</p> Signup and view all the answers

    How does femoral nerve paralysis manifest clinically?

    <p>Inability to extend the stifle</p> Signup and view all the answers

    What does a lateral digital nerve block specifically target?

    <p>The lateral aspect of the foot</p> Signup and view all the answers

    Which nerve is affected in Sweeney condition causing lateral shoulder instability?

    <p>Suprascapular nerve</p> Signup and view all the answers

    What sensory area is solely supplied by the common fibular nerve?

    <p>Dorsal pes</p> Signup and view all the answers

    Study Notes

    Meninges

    • The meninges are protective membranes that enclose the brain and spinal cord.
    • Inflammation of the meninges is known as meningitis.
    • Pachymeningitis refers to inflammation of the dura mater, the thick outer layer of the meninges.
    • Leptomeningitis refers to inflammation of the arachnoid membrane and pia mater, the thin middle and inner layers of the meninges.

    Blood-Brain Barrier

    • The blood-brain barrier is a barrier between the plasma within the CNS vessels and the extracellular fluid (ECF).
    • The blood-brain barrier acts to protect the brain from harmful substances.

    Subarachnoid Space

    • The subarachnoid space is located between the arachnoid and pia mater, containing cerebrospinal fluid (CSF).

    Cerebrospinal Fluid (CSF)

    • CSF is a clear, colorless fluid that circulates throughout the brain and spinal cord.
    • CSF samples can be collected from the lumbar cistern, an enlargement of the SAS at the caudal cerebellum and dorsal brainstem.
    • CSF is rich in glucose and contains low concentrations of white blood cells (WBCs).
    • CSF plays a role in regulating intracranial pressure.

    Ventricular System

    • The ventricular system consists of a series of interconnected cavities within the brain filled with CSF.
    • The lateral ventricles are the first and second ventricles, located on either side of the brain.
    • The mesencephalic aqueduct connects the third ventricle to the fourth ventricle.

    CSF Flow

    • CSF flows from the lateral ventricles through the interventricular foramen into the third ventricle.
    • CSF then flows through the mesencephalic aqueduct into the fourth ventricle.
    • CSF then flows into the subarachnoid space via foramina found within the fourth ventricle.
    • Blockages or a failure of CSF reabsorption can result in hydrocephalus.
    • CSF is absorbed through veins to regulate intracranial pressure.

    Cells of the Nervous System

    • Neuroglia, also known as glial cells, are small cells that surround and support neurons.

    Neuroglia in the Peripheral Nervous System

    • Satellite cells are found in the PNS.

    Neuroglia in the Central Nervous System

    • Astrocytes are star-shaped glial cells that provide structural support to the CNS.
    • Oligodendrocytes are branched cells in the CNS that wrap around axons to form myelin.

    Neuron Communication

    • Neurons communicate with each other via neurotransmitters (NTs).
    • Synaptic transmission of NTs is a complex process involving docking, priming, fusion, recycling, and degradation.
    • Release of NTs is calcium-dependent and regulated by SNARE proteins.
    • Signal termination occurs due to NT degradation, re-uptake, and diffusion.

    Neuromuscular Junction (NMJ)

    • The NMJ is a specialized synapse between a motor neuron and a muscle fiber.
    • Acetylcholine (ACh) is the NT released at the NMJ.
    • Following ACh release, depolarization of the sarcolemma triggers a cascade of events leading to muscle contraction.

    Neurotransmitter Systems

    • Excitatory projection neurons release glutamate.
    • Inhibitory interneurons release GABA.
    • Neuromodulator systems consist of clusters of neurons in subcortical and brainstem nuclei that release NTs throughout the nervous system.

    Neurotransmitters (NTs)

    • Central Nervous System (CNS)
      • Drivers: glutamate, glycine, GABA
      • Modulators: acetylcholine, dopamine, norepinephrine, serotonin
    • Peripheral Nervous System (PNS)
      • Drivers: acetylcholine
        • Sympathetic preganglionic neurons
        • Parasympathetic preganglionic neurons
      • Modulators:
        • Norepinephrine (sympathetic postganglionic neurons)
        • Acetylcholine (parasympathetic postganglionic neurons)

    NT Receptors

    • Ionotropic Receptors (ion channels):
      • NMDA (N-methyl-D-aspartate) receptors: these receptors are permeable to Na+, K+ and Ca++, and also voltage-gated, blocked by Mg++.
        • NMDA receptor antagonists include: ketamine, dextromethorphan, dextrorphan, and ethanol
      • AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptors: these receptors are permeable to Na+ and K+
      • GABA receptors: agonists include benzodiazepines, antagonists include bicuculline.
    • Metabotropic Receptors (G protein-coupled receptors):
      • These receptors are associated with slower responses compared to ionotropic receptors
      • Glutamate receptors
        • mGluR receptors are involved in regulating glutamate availability
        • These receptors can affect both presynaptic and postsynaptic potentials.
      • GABA receptors
        • GABA-B receptors modulate K+ and Ca++ conductance.

    Sympathetic Nervous System (SNS)

    • The SNS innervates the thoracolumbar region of the spinal cord.
    • SNS fibers release norepinephrine (NE) to adrenergic receptors.
    • SNS activation leads to the "fight or flight" response.
    • Sympathomimetic drugs mimic the SNS.
    • Sympatholytic drugs oppose the SNS.

    Parasympathetic Nervous System (PNS)

    • The PNS innervates cranial and sacral regions of the nervous system.
    • The PNS promotes "rest and digest" functions.
    • The PNS is innervated by CN III, VII, IX, and X, and the sacral nerves S2-4.
    • The PNS uses acetylcholine (ACh) as its neurotransmitter.

    Thoracic Cavity

    • The thoracic cavity is bordered dorsally by the thoracic vertebrae and ventrally by the sternum.
    • The cranial inlet is formed by the first rib and costal cartilages.
    • The caudal outlet is bordered by T13, the 13th rib, and the xiphoid process.
    • The diaphragm separates the thoracic cavity from the abdominal cavity.

    Abdominal Cavity

    • The abdominal cavity is bordered dorsally by the lumbar vertebrae and hypaxial muscles, ventrally by the abdominal wall muscles, cranially by the diaphragm, and caudally by the pelvic inlet.
    • The diaphragm has three openings:
      • Aortic hiatus
      • Esophageal hiatus
      • Caval foramen

    Pelvic cavity

    • The pelvic cavity is cranial to the pelvic inlet.
    • The pelvic cavity is innervated by the hypogastric nerves (sympathetic) and pelvic nerves (parasympathetic).

    Micturition

    • Micturition is the process of urination.
    • The detrusor muscle (parasympathetically controlled) contracts to expel urine.
    • The internal urethral sphincter (sympathetically controlled) relaxes.
    • The external urethral sphincter (somatically controlled) relaxes.

    Reflex Arcs

    • Reflex arcs are neural pathways that mediate reflex actions.
    • Reflex arcs involve sensory neurons, interneurons (integration center), motor neurons, and effectors.
    • Somatic reflexes activate skeletal muscles.
    • Autonomic reflexes involve smooth muscles, cardiac muscles, and glands.
    • The hypothalamus is the main integrative center for both somatic and autonomic reflexes.

    Thoracic Limb Innervation

    • Digit I (radial nerve)
      • Lateral distal brachium
      • Dorsal proximal antebrachium
      • Dorsal manus
    • Digit V (ulnar nerve)
      • Ventral antebrachium
      • Caudal distal brachium and antebrachium
    • Musculocutaneous nerve
      • Dorsal brachium
      • Medial distal brachium
      • Proximal antebrachium

    Ungulate Limb Innervation

    • Thoracic Limb
      • Subscapular nerve
      • Suprascapular nerve
      • Cranial pectoral nerve
      • Musculocutaneous nerve
      • Median nerve
      • Ulnar Nerve
      • Radial nerve
      • Lateral thoracic nerve
      • Axillary nerve
      • Thoracodorsal nerve

    Thoracic Limb Nerve Blocks

    • Palmar nerve block
      • The palmar digital nerve block desensitizes the palmar foot, DIPJ, and sole of the foot.

    Pelvic Limb Innervation

    • Femoral nerve
      • Innervates the quadriceps muscle
    • Obturator nerve
      • Innervates the adductor muscles
    • Common fibular (peroneal) nerve
      • Innervates the extensor muscles of the digits
    • Tibial nerve
      • Innervates the flexor muscles of the digits
    • **Pudendal nerve **
      • Innervates the external anal sphincter muscle

    Femoral Nerve Paralysis

    • Femoral nerve paralysis can lead to an inability to extend the stifle joint.

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    Nervous System Functions PDF

    Description

    This quiz covers key concepts related to the meninges, blood-brain barrier, subarachnoid space, and cerebrospinal fluid (CSF). Participants will explore the structure and function of these essential components of the central nervous system. Test your knowledge on inflammation conditions and the protective roles of these membranes.

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