Part I Brain Anatomythe basics :Part I Brain Anatomythe basics David M. Pagnanelli, M.D.


Slide 2:Introduction


The nervous system is divided into the; :The nervous system is divided into the; central nervous system peripheral nervous system A component of the Peripheral Nervous System is the Autonomic Nervous System.


This session is directed at a component of the Central Nervous System,The Brain :This session is directed at a component of the Central Nervous System,The Brain


Slide 5:3D visual


An Overview :An Overview In a 150 pound human the brain accounts for only 2% of the body weight This side view of a human brain demonstrates the many crumpled convolutions of the brain surface. The dark blue streaks on the surface are veins. You can see the very large cerebrum at the top of the photo and the smaller cerebellum below it. The under surface of the brain has a very different appearance. You can see the many nerves entering and exiting from it, as well as the brain stem and cerebellum Looking at the top of the brain, see the space, or fissure, dividing the brain into right and left halves In the liver, any given area performs the exact same function as another. In the brain, although similar in appearance, each area has a unique function


Thinking inside the box :Thinking inside the box


Brain Surface Area :Brain Surface Area Total surface area of the cerebral cortex = 2,500 cm2 (2.5 square feet). In order to fit it in the skull, it is crumpled up.


The brain is divided into two halves or hemispheres. The large upper part is called the Cerebrum. The lower part is comprised of the Brain Stem and Cerebellum :The brain is divided into two halves or hemispheres. The large upper part is called the Cerebrum. The lower part is comprised of the Brain Stem and Cerebellum brain stem cerebrum cerebellum Although the two halves may look alike their functions are very different


The Cerebrum :Grey matter is composed of cell bodies of the neurons White matter is the axons and dendrites of the neurons – bundles of “cables” connecting regions of the brain and spinal cord. Deep within the brain are large clusters of neuron cell bodies called nuclei or ganglia. They are also grey matter The Cerebrum


Slide 11:The brain is situated in a very rigid boney casing, the skull.


The Skull :The Skull


The Skull :Foramen Magnum The underside of the skull has several holes (foramen) for the passage of nerves and blood vessels. The large hole (Foramen Magnum) is for passage of the spinal cord The Skull Inside view Under surface


Slide 14:Although the brain comprises only about 2% of the body weight it uses about 20% of the body's blood supply and consumes 15-20% of the oxygen Brain Circulation The human brain contains around 400 miles of blood vessels. An example of the blood vessels in a human brain, with the brain tissue removed


Slide 15:Brain Circulation Each area of brain is almost totally dependent upon the specific artery supplying that areas blood. So when the artery is blocked, that area of brain dies.


What is a brain made of? :What is a brain made of? Like all other organs of the body, the brain is made up of cells. These cells, like all others, have a nucleus, membranes, DNA, etc. The uniqueness in these cells is the long extensions of the cell membranes.


These cell extensions are specialized :These cell extensions are specialized Dendrites Axon; this one is insulated (orange) A neuron is a nerve cell. The brain is made up of approximately 100 billion neurons. Neurons have specialized projections called dendrites and axons. Dendrites bring information to the cell body and axons take information away from the cell body.


Neurons come in many shapes and sizes :Neurons come in many shapes and sizes The axon of a motor neuron in the spinal cord that innervates a muscle in the foot can be about 3 feet in length. Length of a Giraffe sensory axon, from toe to neck, is 15 feet.


Neuron shapes can be very complex :Neuron shapes can be very complex


Neuron Connections,The Synapse :Neuron Connections,The Synapse Neurons communicate with each other through chemical connections called synapses A single neuron can have between 1,000 and 10,000 synapses in contact with it. Electrochemical impulses travels at different speeds within different types of neurons. Transmission can be as slow as 0.5 meters/sec or as fast as 120 meters/sec. (equivalent to 268 miles/hour)


The Synapse :The Synapse Although the neurons appear to be touching, they are separated by small gap called a synapse Total number of synapses in cerebral cortex is about 60 trillion. This is equal to about a half-billion synapses per cubic millimeter.


Slide 22:Imagine, that in addition to each neuron, there are 50 times as many glial cells, and many blood vessels filling the space between them.


Other cells in the brain :Other cells in the brain The neurons make up less than 8% of the cells in the brain. There several types of glial cells; Insulate the neurons (myelin) Oligodendrocytes Nourish and support the neurons Astrocytes Produce Spinal Fluid Ependymal Cells Remove debris Microglia The majority of the remaining cells are called “Glia”, which means glue. There 10-50 times as many Glia cells as neurons.


Glial Cells :Glial Cells


The Ventricles :The Ventricles The ventricles are cavities in our brains, where most of the cerebrospinal fluid (CFS) is made is made.


The Ventricles :The animation illustrates a 3D view if the ventricles, as though a cast was made. The Ventricles


Coverings of the Brain :Coverings of the Brain Dura


Dural Partitions :Dural Partitions The Tentorium separates the cerebrum from the brain stem and cerebellum In a few regions, the dura creates large partitions, separating large parts of the brain The Falx separates the two hemispheres


Arachnoid :Arachnoid The Arachnoid is like a sheet of cellophane that is draped over the brain. It does not dip into the valleys of the brain contour. There is a space between the Arachnoid and the brain called the subarachnoid space. In this space is the spinal fluid and the blood vessels


Pia :Pia The Pia is represented by the very thin pink line that is outlining the exact surface of the brain. The Pia is a single layer of cells that coat the brain surface, much like linoleum on a floor The arrows outline the space between the arachnoid and pia; the subarachnoid space


Cerebrospinal FluidCSF :Cerebrospinal FluidCSF CSF is actively secreted by the brain. CSF is constantly being made, circulates and is reabsorbed into the blood stream. Total volume of cerebrospinal fluid = 125-150 ml The entire volume of cerebrospinal fluid turns over 3 to 4 times per day CSF is made at a rate of about 30cc per hour The CSF resides in the subarachnoid space


For Brain FunctionandBasic Physiologygo to Anatomy& PhysiologyPart II :For Brain FunctionandBasic Physiologygo to Anatomy& PhysiologyPart II