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The History of the study of the Brain Early brain studies used the

method of phrenology. Phrenology – examination of

the skull where bumps and indentations are used to make a ‘mental map’ and were then related to the character of that person.

The end of World War II and the massive quantity of brain injuries leads many people to examine the brain on a deeper level.

New technologies like the MRI have allowed doctors to observe the brain in operation in incredible detail.

http://skepdic.com/phren.html

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Overview – The Nervous System

Central Nervous System (CNS) = Brain + Spinal Cord

Peripheral Nervous System = Nerves to rest of body

Sensory nerves carry messages from the body to the brain

Motor nerves carry messages from the brain to the body

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Central Nervous System - Anatomy & Function -

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The Human Spinal Cord

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The Spinal Cord The main pathway for information connecting the brain and

peripheral nervous system

- Conducts sensory information from the peripheral nervous system (both somatic and autonomic) to the brain.

- Conducts motor information from the brain to the various effectors (skeletal muscles, cardiac muscle, smooth muscle, glands).

Serves as a minor coordinating center responsible for some simple reflexes (e.g., withdrawal reflex).

The average spinal cord is 45 cm long in men and 43 cm long in women. The spinal cord weighs approximately 35 g.

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The Spinal Cord : Vertebrae

The human spinal cord is protected by the bony spinal column. The spinal column is made up of bones called vertebrae.

The spinal cord is located in the vertebral foramen and is made up of 30 segments: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccyx. A pair of spinal nerves exits from each segment of the spinal cord.

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Vertebra, cervical (neck)

Vertebra, thoracic (mid back) Vertebra, lumbar (low back)

Vertebral column

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The vertebral column provides structural support for the trunk and surrounds and protects the spinal cord.

The vertebral column also provides attachment points for the muscles of the back and ribs.

The vertebral disks serve as shock absorbers during activities such as walking, running, and jumping. They also allow the spine to flex and extend. Common injury: Ruptured Disk

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Complex lumbar spine fracture

Cervical dislocation Thoracic dislocation

Bullet in thoracic spinal canal

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Famous Spinal Cord Injuries

Mike Utley – 1991 Detroit Lions Offensive Lion fractured his 6th and 7th cervical vertebrae.

http://www.mikeutley.org/images/mike.gif

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Christopher Reeves “Well, I totally decimated my first

cervical vertebra and my second, and so my body and my spine and my head were not connected. Only my neck muscles were holding my head on, and fortunately I didn't suffer any brain damage, at least none that I can detect. [laughter] But, you know, that's what they tell me at any rate. But they literally had to put my head back on my body, and a wonderful surgeon, Dr. John Jane at the University of Virginia, was the one who operated on me, and they had to make it up. They had never done anything like this before, because this is what is called a hangman's injury, you know, like if you get dropped through the trap door and then cut down, sent to rehab and told to have a nice life.”

http://record.wustl.edu/archive/2000/12-01-00/photos/reeves.jpg

Cervical dislocation

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How does the brain protect itself?

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Four ways the brain protects itself:

1. Skull - 2. Meninges 3. Cerebrospinal Fluid 4. Blood Brain Barrier (BBB)

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Central Nervous System- The Coverings of the Brain

(Shocks)

Meninges

Both the brain and the spinal cord are covered in three continuous sheets of connective tissue, the meninges.- The dura mater (the dura): the outer layer- The arachnoid: the middle layer- The pia mater (the pia): the inner layer

“The meninges PAD the brain”

17 http://www.baltimoresun.com/media/photo/2004-05/12819309.jpg

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Central Nervous System- Cerebrospinal Fluid (CSF) -

The entire surface of central nervous system is bathed by a clear, colorless fluid, called cerebrospinal fluid (CSF). The CSF is contained within a system of fluid-filled cavities called ventricles.

The total volume of CSF is 125-150 ml

Normal resting pressure of the CSF is between 150-180 mmH2O.

Total production of CSF is about 400-500 ml/day (about 0.36 ml/min)

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Central Nervous System- Cerebrospinal Fluid (CSF) -

What does the CSF do? Protection: The CSF protects the brain from damage by

“buffering” the brain. Buoyancy: The pressure at the base of the brain is

reduced by immersing in the CSF. Excretion of waste products: The one-way flow from the

CSF to the blood takes potentially harmful metabolites, drugs and other substances away from the brain.

Endocrine medium for the brain: The CSF serves to transport hormones to other areas of the brain.

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Central Nervous System

- Blood-Brain Barrier (BBB) -

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What is the Blood-Brain Barrier (BBB) ?

The barrier exists between the blood and the brain

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BBB – History The late 19th century, Paul Ehrlich’s

experiment Certain dyes (e.g., a series of aniline derivatives) administered intravenously to small animals stained all the organs except the brain: The brain has a lower affinity for the dye than the other tissues.

In 1913, Edwin G. Goldman’s experiment

The dye trypan blue, directly injected into the cerebrospinal fluid of rabbits or dogs, readily stained the entire brain but did not enter the bloodstream to stain the other internal organs: The CNS is separated from the blood by a barrier of some kind.

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BBB – History The late 1960’s Electron microscopy confirmed the hypothesis that

brain capillaries provide the anatomical basis of the BBB

Recent studies - The BBB is present in all vertebrate brains - The BBB is laid down within the first 3 months of

human fetal life

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BBB – Function

“Neuroprotective Role”

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“Biological Shield” or “Safeguard”

BBB – Function

Physical Barrier

n To protect the brain tissues from “foreign substances” or “certain chemicals” in the blood that may injure the brain

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BBB – Function

“Neuroprotective Role”

“Obstacle to Drug Delivery”

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In order to cross the BBB in pharmacologically significant amounts, the therapeutic drugs must have the following characteristics:

Lipid soluble Have a molecular weight < 400 Daltons Not be a substrate for a BBB active efflux transporter

This class of drugs constitutes <2% of all potential small molecule drugs. Only few brain disorders, such as depression, schizophrenia, chronic pain, and epilepsy, respond to such drugs.

100% of large molecule drugs and 98% of small molecule drugs do not cross the BBB.

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Reflection

Of the four protective functions, which do you think would be most important in the field of psychology? Why?