Lecture: Chapter 18 – Brain and the Cranial Nerves
October 15, 2018
[BRAIN] = portion of the CNS that is contained within the cranium.
→ 100 billion neurons + 10-15 trillion neuroglia make up the brain (each neuron forms 1000
synapses with other neurons).
The brain is the center for registering sensations, correlating them with one another and with
store information, making decisions, and taking actions. it is also the center for intellect,
emotions, behaviour, and memory.
• Major Parts of the Brain:
The adult brain consists of 4 major parts: brainstem, cerebellum, diencephalon, and cerebrum.
[Brainstem] = medulla oblongata, pons + midbrain. it Is continuous with the spinal cord
[Cerebellum] = posterior to the brainstem, “little brain”.
[Diencephalon] = thalamus, hypothalamus, and epithalamus.
[Cerebrum] = supported on the diencephalon and the brainstem; the largest part of the brain.
• Protective Coverings of the Brain:
Overview: bone, meninges, and fluid.
The cranium and the cranial meninges surround and protects the brain.
[Cranial Meninges] are the same as around the spinal cord; they consist of:
a. Outer dura mater
b. Middle arachnoid mater
c. Inner pia mater
The cranial dura mater has 2 layers, compared to the single layer of the spinal dura mater –
external layer is the “periosteal layer”, and the internal layer is the “meningeal layer”. These
two dural layers around the brain are fused together except where they separate to enclose the