Gospel of Neuro

Overview of the Nervous System

  • The nervous system consists of approximately 86 billion neurons.

  • The importance of studying the nervous system:

    • Controls all body functions.

    • Various clinical implications.

    • Understanding nervous system anatomy aids in diagnosing and treating illnesses.

Importance of Studying Nervous System Anatomy

  • Clinical Relevance:

    • Vital for diagnosing various clinical conditions.

      • Examples of clinical cases:

      • Vestibular diseases

      • Trigeminal neuritis

      • Facial nerve paralysis

      • Radial nerve paralysis

  • Procedures Utilizing the Nervous System:

    • Cerebrospinal fluid (CSF) collection

    • Epidural anesthesia (high and low)

Epidural Anesthesia

  • Types of Epidural Anesthesia:

    • High Epidural Anesthesia

    • Low Epidural Anesthesia

  • Uses for Low Epidural Anesthesia:

    • Treating perineal lacerations, rectal tears, and rectovaginal fistulas.

Diagnosing Diseases with CSF Collection

  • Conditions Diagnosed with CSF:

    • Equine Protozoal Myelitis (EPM)

    • Meningitis

    • Protozoal diseases

Classification of Neurons

  • Importance of classifying neurons to better understand the 86 billion neurons:

    • To simplify and understand their roles, we classify based on two criteria:

      • Anatomical (location)

      • Functional (physiology)

Classification by Anatomy

  • Divided into:

    • Central Nervous System (CNS)

      • Comprising:

      • Brain

      • Spinal cord

    • Peripheral Nervous System (PNS)

      • Comprising:

      • Spinal nerves

      • Cranial nerves

Two Criteria for Anatomical Classification

  1. Constituents of the nervous system:

    • Central Nervous System: Brain and spinal cord.

    • Peripheral Nervous System: Spinal nerves, cranial nerves.

  2. Development:

    • CNS develops from the neural tube.

    • PNS develops from the neural crest.

    • The distinction of neuronal location is either in the CNS (skull and spinal cord) or the PNS (remainder of body).

Neural Regeneration

  • Ability to regenerate:

    • CNS: Lacks the ability to regenerate.

    • PNS: Exhibits some regenerative capabilities.

Supporting Cells

  • CNS Supporting Cells:

    • Astrocytes: Provide structural support and help with the blood-brain barrier.

    • Oligodendrocytes: Form myelin sheath.

    • Microglia: Act as immune cells of the brain.

  • PNS Supporting Cells:

    • Schwann cells: Form myelin in PNS.

    • Satellite cells: Support ganglia.

Functional Classification of the Nervous System

  • Neurons classified by function:

    • Sensory Neurons: Carry signals to the CNS.

    • Motor Neurons: Carry signals away from the CNS.

Two Types of Motor Neurons

  • Somatic Motor Neurons: Control skeletal muscles.

  • Visceral Motor Neurons: Control organs.

Understanding Neuron Functions

  • Functional Requirements for Neuronal Activity:

    1. Stimulus required (e.g., mechanical, thermal, chemical).

    2. Sensory receptors receive stimuli.

    3. Adjusting or Integrating neuron.

    4. Motor response (e.g., muscle contraction, secretion).

Types of Neurons

  1. Unipolar Neurons: One axon and many dendrites, primarily sensory neurons.

  2. Bipolar Neurons: One axon and one dendrite, found in the retina.

  3. Multipolar Neurons: One axon with many dendrites, primarily motor neurons.

Development of the Nervous System

  • Key stages in development:

    1. Zygote develops into two layers - morula, leading into:

    2. Blastula - two layers of cells.

    3. Gastrula - three layers of cells:

    • Ectoderm (nervous system origin)

    • Mesoderm

    • Endoderm

  • Formation of the nervous system:

    • Derived from neuroectodermal epithelium.

    • Differentiation involves formation of three vesicle brain structure, followed by development into a five-vesicle structure.

Blood Supply to the Nervous System

  • The nervous system consumes roughly 20% of cardiac output despite being only 2% of body weight.

    • This indicates a high demand for nutrients and oxygen due to active neuronal firing.

Blood Supply Key Points

  • Arterial Blood Supply:

    • Major suppliers:

      • Internal carotid artery: supplies more than 80% of brain blood flow.

      • Vertebral artery: supplies the remaining 20%.

    • Key arteries and their importance:

      • Rostral Cerebellar Artery: supplies cerebellum - important for balance.

      • Middle Cerebral Artery: supplies lateral parts of the brain - significant risk for strokes.

  • The blood-brain barrier maintains selective permeability, controlling substances that enter the CNS.

Structure of Blood Supply

  • Blood supply comes from:

    • Internal Carotid Artery

      • Supplies the rostral part of the brain.

      • Includes middle and rostral cerebral arteries.

    • Vertebral Basilar Artery

      • Supplies the caudal part of the brain.

Key Points About Arteries

  • Branches of Arteries:

    • The left and right common carotid arteries split into internal and external branches.

    • The subclavian arteries give rise to vertebral arteries, which merge to form the basilar artery supplying the posterior circulation.

Risks Associated With Blood Supply

  • Risk of ischemic strokes due to large vessel size (e.g., middle cerebral artery).

  • Factors influencing blood flow:

    • High activity possibly leading to embolisms due to blood clot formation in larger vessels.

Summary of Blood Circulation Pathway

  • Start at the heart and proceed through:

    1. Aortic Arch

    2. Common Carotid and Subclavian Arteries

    3. Internal Carotid and External Carotid Arteries

    4. Vertebral Arteries meeting at Basilar Artery.

  • The basilar artery assists in completing the circle of Willis enhancing collateral blood supply.

Final Thoughts

  • Organization and proper understanding of the brain’s arterial supply are essential for diagnosing and managing neurological conditions effectively.