M

Neuroanatomy: Structure and Functions of the Brain and Spinal Cord

Structure of the Brain and Spinal Cord

  • Hemispheres

    • The brain consists of two large parts, known as hemispheres.
    • Left Hemisphere: Controls the right side of the body.
    • Right Hemisphere: Controls the left side of the body.

  • Brain Stem

    • Involved in basic life functions.
    • Not a distinct structure, but a general region in the nervous system.

Gray and White Matter

  • Gray Matter

    • Inner color of the nervous tissue, found in the cerebral cortex, consists mainly of neuron cell bodies.

  • White Matter

    • Outermost layer, composed of myelinated axons that speed up signal transmission.
    • Functions as the highway for sending signals to various parts of the brain and spinal cord.

  • Cerebral Cortex

    • Outer layer of the brain responsible for processing sensory and motor information.
    • Divided into lobes, each associated with different functions:
    • Frontal Lobe: Contains the motor cortex, responsible for motor control.
    • Temporal Lobe: Involved in olfactory and auditory processing.
    • Parietal Lobe: Integrates multiple senses excluding smell, taste, and vision.
    • Occipital Lobe: Primarily responsible for vision.

Brain Functions

  • Motor and Sensory Cortices

    • Motor Cortex: Controls voluntary movements; specialized movements become automatic after practice.
    • Sensory Cortex: Responsible for processing sensory information (taste, smell, vision, etc.) and associating it with emotions and memories.

  • Contralateral Control

    • Each hemisphere affects the opposite side of the body (e.g., right brain injury leads to left side paralysis).

Hemispheric Specializations

  • There's a notion of "left-brained" (logical, mathematical) and "right-brained" (creative) individuals.
    • Left Brain: Focused on logic, language, and analytical skills.
    • Right Brain: Manages creativity and artistic skills.

Basal Nuclei

  • Small islands of gray matter within the brain involved in sorting sensory information.
  • Functions as a relay station for sensory information coming from the body to the appropriate lobe for processing.
  • Damage can lead to diseases such as Parkinson's disease, which impairs the sorting of information.

Major Structures of the Brain

  • Thalamus: Acts as a relay station for sensory and motor signals.
  • Hypothalamus: Serves as the main control center for the autonomic nervous system (emotions, body temperature, etc.).
  • Cerebellum: Coordinates voluntary movements and is crucial for balance and motor learning.

Meninges

  • Three protective membranes cover the brain and spinal cord:
    • Dura Mater: Outermost, thick protective layer; contains dural sinuses where CSF drains.
    • Arachnoid Mater: Middle layer with blood vessels and subarachnoid space filled with CSF.
    • Pia Mater: Innermost delicate layer, sits directly on the brain surface.

Cerebrospinal Fluid (CSF)

  • Formed in the choroid plexus, which are specialized tissues found in the ventricles of the brain.
  • Circulates around the brain and spinal cord, providing cushioning and support.
  • Flow pathway:
    1. CSF is produced in the choroid plexus.
    2. Fills the lateral ventricles and third ventricle.
    3. Enters the subarachnoid space and flows through the cerebral aqueduct to the fourth ventricle.
    4. Moves to the central canal of the spinal cord.

Common Clinical Applications

  • Meningitis: Infection leading to inflammation and pressure on the brain.

    • Symptoms include headache, fever, and neck stiffness.

  • Hydrocephalus: Accumulation of CSF due to blockage, causing increased pressure on the brain.

  • Concussions/Contusions: Result from trauma causing the brain to hit the skull, leading to bruising or swelling.

  • Alzheimer's: Associated with tau protein tangling in axons, leading to neuron degradation and memory loss.