Chapter 14: The Brain

Overview

• The brain is a major focus of study within biological science, covered in one chapter of a standard A&P textbook.
• This chapter will cover major structures, CSF circulation, and basic functions of brain parts.
• The brain's function in coordinating the central nervous system will be discussed.
• Detailed topics will be further explored in future coursework and labs.

Brain Structures

General Overview

• Superior and Lateral Views: Brain viewed from top and side.
• Brain Segments:
  • Cerebrum: Most recognized part, divided into right and left hemispheres by the longitudinal fissure.
  • Cerebellum: Integrated into multiple functions.
  • Brain Stem: Critical role in functions.

Key Features

• Bilateral Symmetry: Mirror image left and right sides.
• Gyri and Sulci:
  • Gyri (singular: gyrus): ridges.
  • Sulci (singular: sulcus): grooves.
  • Important landmarks include central sulcus and lateral sulcus/fissure.

Lobes of the Cerebrum

• Frontal Lobe: Separated by central sulcus.
• Parietal Lobe: Behind frontal lobe.
• Temporal Lobe: Below the lateral sulcus.
• Occipital Lobe: Rearmost part.

Important Gyri

• Postcentral Gyrus: Primary somatic sensory cortex.
• Precentral Gyrus: Primary motor cortex.

Directional Terminology

• Rostral: Towards nose.
• Caudal: Towards tail.
• Aligns with anterior/ventral and posterior/dorsal terminology.

Brain Sections

• Sagittal Section: Divides brain into left and right sides, showing cerebrum, cerebellum, and brain stem.

Meningeal System

Meninges Layers

• Dura Mater: Tough outer layer with periosteal and meningeal layers.
• Arachnoid Mater: Spider-web like, potential subdural space.
• Pia Mater: Delicate inner layer, follows brain contours closely.
• Subarachnoid Space: Filled with cerebrospinal fluid (CSF).

Dural Folds

• Falx Cerebri: Between cerebral hemispheres.
• Tentorium Cerebelli: Separates cerebrum and cerebellum.
• Falx Cerebelli: Between cerebellar hemispheres.

Sinuses

• Venous Sinuses: Collect venous blood, including superior and inferior sagittal sinuses.

Cerebrospinal Fluid (CSF)

Ventricular System

• Ventricles: Hollow chambers in the brain.
  • Lateral Ventricles: Large, ram's horn shape.
  • Third Ventricle: Central.
  • Fourth Ventricle: Between cerebellum and brain stem.
• Cerebral Aqueduct: Connects third and fourth ventricles.

CSF Production and Circulation

• Choroid Plexus: Produces CSF, located in ventricles.
• Circulation Route:
  1. Produced in lateral ventricles.
  2. Flows through interventricular foramina to third ventricle.
  3. Flows through cerebral aqueduct to fourth ventricle.
  4. Exits ventricular system via apertures to subarachnoid space.
  5. Circulates around brain and spinal cord.

CSF Reabsorption

• Arachnoid Granulations: Absorb CSF into superior sagittal sinus.
• Daily CSF Production: Approximately 500 ml, with about 150 ml in circulation at any time.
• Function: Provides nutrient delivery and waste removal, research ongoing into its role in sleep and brain health.