Chapter 14: The Brain and the Cranial Nerves

Lecture Overview

• Focus on the brain regions, spaces inside (ventricles), cranial nerves, anatomical and functional classifications.
• The brain is the largest part of the central nervous system, consisting of:
  • Cerebrum
  • Cerebellum
  • Diencephalon
  • Brain stem

Main Parts of the Brain

• Cerebrum

  • Largest part, two hemispheres.
  • Covered by cerebral cortex (gray matter) and filled with white matter.
  • Responsible for high mental functions: thought, memory, decision-making, planning.
  • Surface features: Gyri (elevations) and sulci (depressions), deeper grooves are fissures.

• Cerebellum

  • Second largest, coordinates body movements.
  • Also has two hemispheres and is covered by a cortex.

• Diencephalon

  • Located between cerebrum and cerebellum.
  • Includes thalamus (sensory relay) and hypothalamus (emotion, autonomic functions, hormone production).
  • Contains pituitary gland (hypophysial gland) connected to hypothalamus by infundibulum.

• Brainstem

  • Connects brain to spinal cord, consists of midbrain, pons, and medulla oblongata.
  • Midbrain processes visual and auditory information.
  • Pons connects cerebellum to brainstem.
  • Medulla oblongata regulates autonomic functions (heart rate, blood pressure, digestion).

Development and Ventricles

• Embryonic development: Prosencephalon, Mesencephalon, Rhombencephalon.
• Ventricles: spaces inside brain lined with ependymal cells, containing cerebrospinal fluid (CSF).
  • Four ventricles: two lateral, third, and fourth.

Protection and Blood Supply

• Protection

  • Skull bones and cranial meninges (Pia, Arachnoid, Dura mater).
  • CSF acts as a cushion, circulating in subarachnoid space.

• Blood-Brain Barrier (BBB)

  • Isolates brain from general circulation, selective permeability.
  • Created by tight junctions in endothelial cells, regulated by astrocytes.

• Blood Supply

  • Internal carotid arteries and vertebral arteries.
  • Stroke occurs when blood supply is interrupted.

Brain Regions in Detail

• Medulla Oblongata

  • Connects brain to spinal cord, controls reflexes and autonomic functions.
  • Cranial nerves IX-XII originate here.

• Pons

  • Connects midbrain to medulla, regulates respiratory rhythm.
  • Cranial nerves V-VIII originate here.

• Midbrain

  • Contains tectum and tegmentum, responsible for visual and auditory reflexes.
  • Cranial nerves III-IV originate here.

• Cerebellum

  • Coordinates balance, posture, and muscle movements (BPM: Balance, Position, Muscle movements).
  • Contains cerebellar cortex and Arbor vitae (white matter).

• Diencephalon

  • Thalamus: Relay station for sensory information.
  • Hypothalamus: Regulates endocrine and autonomic functions, produces ADH and oxytocin.

• Limbic System

  • Controls emotions and memory.

Summary

• The brain consists of the cerebrum, cerebellum, diencephalon, and brainstem, each with distinct functions and structures.
• Protection and support are provided by meninges and CSF.
• Blood supply and barriers maintain brain health and function.