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Learning Objectives

• Identify and explain major anatomical structures and functions of the brain.
• Describe the ventricles and their openings.
• Explain the formation and circulation of cerebrospinal fluid.
• Explain the structure and arrangement of the meninges.
• Identify and explain the major anatomical structures and functions of the spinal cord.

Overview of the Nervous System

• The nervous system performs tasks in three basic steps:
  • Reception: Sense organs receive information about changes within the body and the external environment and transmit coded messages to the central nervous system (CNS).
  • Processing: The CNS processes this information, relates it to past experiences, and determines an appropriate response.
  • Response Initiation: The CNS issues commands to muscles and gland cells to execute the response.

Overview of the Brain

• Major Subdivisions:
  • Cerebrum
  • Diencephalon
  • Cerebellum
  • Brainstem

The Cerebrum

• Consists of two hemispheres: the left and right, separated by the Longitudinal Fissure.
  • Fissures: Deep grooves in the brain.
  • Each hemisphere has specialized functions with some exceptions (e.g., language is primarily associated with the left hemisphere).

Cerebral Structure

• The surface has Gyri (ridges) and Sulci (shallow grooves), which increase surface area.
• Composed of Gray Matter (cell bodies & dendrites, outer layer called the Cortex) and White Matter (myelinated axons).

The Cerebral Cortex

• Involved in:
  • Awareness
  • Sensory perception
  • Voluntary motor initiation
  • Communication
  • Memory
  • Understanding
• Contains three types of functional areas:
  • Motor Areas: Control voluntary movement.
  • Sensory Areas: Conscious awareness of sensation.
  • Association Areas: Integrate diverse information.

Functional Regions of the Cerebral Cortex

Frontal Lobes

• Functions involve thinking, reasoning, planning, personality and emotions (Prefrontal Cortex).
• Areas in the frontal lobe:
  • Primary motor cortex (precentral gyrus)
  • Premotor area (planning movements)
  • Broca’s Motor Speech Area (formulates spoken response).

Parietal Lobes

• Involved in:
  • Primary somatosensory cortex (general sensory information)
  • Somatosensory association cortex (integrates sensory input).

Temporal Lobes

• Functions in: auditory processing, word recognition and comprehension (Wernicke’s area), memory, taste, and olfactory processing.

Occipital Lobes

• Involved in processing visual information.

Insula Lobe

• Associated with emotional responses and related behaviors.

Diencephalon

• Comprises:
  • Thalamus: Relay station for sensory information (except olfaction).
  • Hypothalamus: Controls the autonomic nervous system and regulates homeostasis (e.g., blood pressure, temperature, hunger).
  • Epithalamus: Contains the pineal gland which regulates biological rhythms (melatonin production).

Brainstem

• Consists of:
  • Midbrain: Involved in visual and auditory reflexes.
  • Pons: Connects different parts of the brain, involved in sleep and respiratory functions.
  • Medulla Oblongata: Regulates autonomic functions (cardiovascular and respiratory centers).

Cerebellum

• Functions:
  • Coordinates voluntary movements and balance.
  • Interprets sensory input from muscle receptors, maintaining equilibrium.

Meninges

• Three Layers:
  • Dura Mater: Outermost, tough layer.
  • Arachnoid Mater: Middle layer, delicate with web-like extensions; contains cerebrospinal fluid (CSF).
  • Pia Mater: Innermost layer, tightly adheres to the brain and contains blood vessels.
• Functions: Protect the CNS, contain CSF, and form partitions in the skull.

Cerebrospinal Fluid (CSF)

• Forms a liquid cushion around the brain.
  • Functions: Buoyancy, protection from trauma, nourishment, and chemical signaling.
• Produced by the Choroid Plexus in the ventricles and circulates through the CNS, returning to the venous bloodstream.

The Spinal Cord

• Extends from the foramen magnum to L1 or L2 vertebra.
  • Provides two-way communication between brain and body and is a major reflex center.
• Contains Gray Matter (central region, butterfly shape) and White Matter (myelinated axons organized into ascending and descending tracts).
• Gray Matter Divisions:
  • Dorsal Horn: Sensory neurons.
  • Ventral Horn: Motor neurons.
• Disorders:
  • Trauma can lead to loss of function (paralysis). Complete transections result in total loss of sensory and motor function below the injury level; can lead to paraplegia or quadriplegia.

Conclusion

• The central nervous system, including the brain and spinal cord, encompasses complex structures and functions essential for overall bodily functions, motor control, and sensory processing. Understanding these systems is crucial for diagnosing and treating neurological disorders.