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The Human Brain

Study hint: Read chapter 18 in your textbook carefully before you begin this part of Lecture 7. Follow the organization in your Syllabus as you note the typical, ventricular space, associated nerves, and the major structures of each of the divisions of the brain in the drawings and photographs in your textbook. Memorize the names, the Roman numerals, and the functions of each cranial nerve, as well as the foramen through which each nerve leaves the cranial cavity. Make up your own flow diagram of the circulation of the cerebrospinal fluid; and know the parts of the blood-brain barrier.

The brain is a fascinating organ. I could spend the entire course talking only about its many structures and their functional significance. Your first priority is to become familiar with the brain's major divisions. The adult brain is divided into 5 major regions with embryological significance. Each major division of the brain contains a space or cavity called a ventricle and associated cranial nerves.


Telencephalon Paired Lateral Ventricles CN I passes through the cribriform plate of the ethmoid bone to synapse in the olfactory bulb.
CN II courses from the orbit.

The telencephalon contains the cerebral cortex, the highest level of consciousness. The philosophical statement "I know that I know" occurs at this level of the nervous system. Yet, this level also contains structures that are not "cortex". These are subcortical regions called the basal ganglia. View this region in the special dissections in lab. The region referred to as the forebrain includes both the telencephalon and the diencephalon.

Directional Terms Inside the Cranial Cavity

Directional Terms Outside the Cranial Cavity
Anterior

Posterior

Superior

Inferior

 Anterior

Posterior

Superior

Inferior

Diencephalon Third Ventricle CN II and the Optic Chiasm

"I know but I don't know what I know" is the best way to describe the diencephalon. The four major parts of this region of the brain are the epithalamus (aka pineal gland aka epiphysis cerebri), thalamus, the hypothalamus, and the subthalamus (not listed in your Syllabus). The thalamus is a major, bidirectional relay center between the cerebral cortex and the spinal cord, for example. The hypophysis cerebri also known in some textbooks as the "master gland" is an endocrine gland with a complicated embryological history. The posterior pituitary gland is actually an outgrowth of the hypothalamus.


Mesencephalon Cerebral Aqueduct of Sylvius CN III, CN IV

The mesencephalon (aka midbrain) is the most superior portion of the brainstem, a region of the brain consisting of the mesencephalon, metencephalon and myelencephalon. The mesencephalon is an important reflex center. The very important pupillary light reflex, a favorite of law enforcement officers (LOL) is centered in this region of the brain.


Metencephalon Fourth Ventricle CN V, CN VI, CN VII, CN VIII

The metencephalon refers to the pons and cerebellum or little brain. The cerebellum is an unconscious, motor center. It receives sensory information from your muscles and sets up computer programs that you can run without thinking. Can you close your eyes and drink a glass of water without spilling it? I can! Can you touch your index finger to the tip of your nose with your eyes closed? I hope you can!  :)


Myelencephalon Fourth ventricle rostrally
Central canal caudally		 CN IX, CN X, CN XI, CN XII
Special topic: Innervation of the Tongue

The myelencephalon is the medulla oblongata. This area of the brain contains the arousal centers that wake us up every morning and keep us alert throughout the day. It also contains the ascending and descending tracts that connect the brain and the spinal cord.


Which cranial nerves are sensory(s) or motor(m) or both(b)?    Warning--This is definitely not politically correct!


What are the parts of the blood-brain barrier?




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