The Human Brain

The Brain

Is protected by the skull and three tough membranes known as meninges

The spaces between the brain and the skull are filled with cerebrospinal fluid, which acts as a shock absorber.

A concussion occurs if the brain is severely shaken and bumps against the skull.

The Brain, cont’d

Is a gas guzzler - it comprises 2% of the total body weight, yet uses 25% of the oxygen taken in by the body.

Major Parts of the Brain

Cerebrum - largest part of the brain (2/3), which sets humans apart from other animals. It is divided into left and right

hemispheres The outer layer is called the cerebral

cortex and is made of gray matter; the inner layer is white matter

The cerebral cortex carries out sensory functions, as well as memory, learning and thought

Two Hemispheres of Cerebrum

(top view)

Cerebrum

Major Parts of the Brain

Cerebellum - found at the back of the brain It is also divided into left and right

hemispheres with gray matter on the outside and white matter inside.

It controls all voluntary movements and plays a major role in balance and coordination

Cerebrum

Cerebellum

Major Parts of the Brain

Medulla Oblongata - found at the base of the brain, below the cerebellum It is made mainly of nerve fibers that

connect the spinal cord to other parts of the brain.

It controls many involuntary actions such as breathing, heartbeat, blood flow, and coughing.

Cerebrum

Cerebellum

Medulla Oblongata

Major Parts of the Brain

Corpus Callosum - found in the center of the cerebrum It is a bundle of nerve fibers in the inner

white matter. It makes a bridge-like connection

between the two hemispheres of the cerebrum so that information can pass between the two halves.

Cerebrum

Cerebellum

Medulla Oblongata

Corpus Callosum

Corpus Callosum

(bottom view)

Major Parts of the Brain

Pons - found just above the medulla oblongata It serves as a relay system, connecting

the spinal cord, medulla oblongata, cerebellum and cerebrum

Cerebrum

Cerebellum

Medulla Oblongata

Corpus Callosum

Pons

Major Parts of the Brain

Hypothalamus - found in the center of the cerebrum It controls body temperature, thirst and

hunger, sleep, and emotions. It is associated with maintaining

homeostasis. It also plays a role in the functioning of

the endocrine system.Thalamus – coordinates and

interprets sensory information and directs it to the cerebrum

Cerebrum

Cerebellum

Medulla Oblongata

Corpus Callosum

Pons

Hypo-thalamus

Thalamus

MaintainingHomeostasis

Major Parts of the Brain

Pituitary Gland - found below the hypothalamus. It is referred to as the master gland

because it controls all the other endocrine glands.

Cerebrum

Cerebellum

Medulla Oblongata

Corpus Callosum

Pons

Hypo-thalamus

Pituitary Gland

Thalamus

Meet Phineas Gage

The year is 1848. Phineas Gage is 25 years old. He is quiet, hard-working and responsible. He has been promoted to foreman and he and his team are blasting through rock to lay a railroad in Vermont. The correct procedure for blasting is to put dynamite down the hole, pour in some sand, and pack it down with a tamping iron. The dynamite would then be lit from a safe distance to blast the rock. Phineas forgot the sand and a spark from the tamping iron caused an accidental explosion. This caused the 3 foot tamping iron to be propelled through the bottom of his left cheekbone and out the top of his head. It flew in an arc across the sky and landed 100 feet behind him.

The amazing thing is that after a few moments of being unconscious, Phineas was sitting up and talking to his coworkers!

Phineas was alive but he was not the same man. The once mild-mannered, well-liked man had turned into a man with a violent temper, who swore all the time. He lost his job on the RR and had a hard time holding down a job at all. He eventually went travelling with the circus and telling his story. He took the famous tamping iron with him. He died about 12 years later from epileptic convulsions.

His body was buried in 1860 but exhumed in 1867. His skull and the tamping iron are now on display at Harvard University’s School of Medicine.

The accident destroyed much of Phineas’ left frontal lobe. His was the first case to suggest that parts of the brain might affect personality and behavior.

Lobes of the Cerebrum