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Web links:

Human Cerebral Cortex: lobes, gyri and sulci (fissures):

http://www.marymt.edu/~psychol/brain.html
 
 

Brain Atlases

From: http://www9.biostr.washington.edu/

http://www.med.harvard.edu/AANLIB/home.html
 
 

Neuro Syllabus:

Check chapters related to anatomy of the Nervous System. Some figures are not available on the Internet.

To the naked eye, the Nervous system can be divided into two major parts (Figs. 3.1; 3.2):

1. The Central Nervous System, CNS, protected by bone, divided into:

            Brain, located in the skull

            Spinal cord, located in the spine.

2. Peripheral nervous system, PNS, which is not protected by bone, divided into:

            The somatic nervous system,

                       interacts with the external environment:

                        -Receives information: sensory function, afferent. (mnemonic: arrive)

                        -Mediates motor responses: motor function, efferent. (mnemonic: exit)

            Autonomic nervous system. Regulates organs and glands.

                       afferent (sensory) pathways from the organs to the CNS

                        efferent (motor) pathways from the CNS to the organs.

                                    Two kinds of efferent nerves

                                    1. Sympathetic nerves, for threatening (emergency) situations (escape, fight, etc)

by stimulating and mobilizing energy resources.

Emerge from the lumbar (small of the back) and thoracic (chest area) regions of the spinal cord.

                                    2. Parasympathetic nerves, conserve energy (self-sustaining).

Emerge from the brain and sacral (lower back) regions of spinal cord.
 

                                   Most organs receive both innervations. For example,

Heart rate is increased by the sympathetic system, and slowed down by the parasympathetic system.

Activity of organ is the result of the balance between sympathetic and parasympathetic effects.

The PNS consists of

            31 pairs of nerve that project from the spinal cord, and

            12 pairs that project from the brain (cranial nerves).

Some cranial nerves are purely sensory (afferent), examples:

olfactory (first cranial nerve)

optic nerves (second cranial nerves)

others are purely motor, for instance,

The 3, 4 and 6 pairs of cranial nerves are purely motor, move the eye, but most contain sensory and motor fibers.

Meninges: Coverings of the brain.

            dura mater, arachnoid and pia mater

Cerebral Ventricles. Remnants of the central canal. (FIG. 3.3).

The lateral ventricles (first and second ventricles),

and the third and fourth ventricles.

The third ventricle connects with the fourth by the cerebral aqueduct
 

CSF, cerebro spinal fluid, in the subarachnoidal space, cerebral ventricles, and central canal in spinal cord.

Produced at the choroid plexus in the ventricles (see Fig. 3.4).

 Network of capillaries (small blood vessels) that protrude into ventricles.

Absorbed in sinuses: cavities lined by dura matter and filled with venous blood, which drains into veins of the neck (jugular veins).

Blockade of the flow of CSF produces hydrocephalus (water head).

MOVIE CSF CIRCULATION

The Blood Brain Barrier (Fig. 3.9). Endothelial cells are tightly joined to one another, and many molecules, including some drugs to fight cancer or Parkinson, cannot pass into the brain. Glucose molecules are actively transported through cerebral blood vessel walls.

Why do we need it?

WHAT, THEN, IS THE BRAIN? CELLS OF THE NERVOUS SYSTE.

 The brain, perhaps the most complex system.

What is the functional organization of the nervous system?

1. Reticular doctrine: Is the brain a reticular structure, a syncithium? NO.

2. Neuron doctrine: The Neuron is the functional unit of the nervous system.

Camilo Golgi invented Golgi stain in the 1870's (19th century) (Fig. 3.11, 3.31).

Santiago Ramon Y Cajal

The neuron is a very specialized cell (FIG. 3.5; 3.6). It consists of:

Body or soma, dendrites, axon, axon hillock, axon terminal, synaptic button.

The cell membrane is a lipid bilayer with proteins embedded in it ( Fig. 3.7)

Myelin is a fatty sheath that covers the axon (Fig. 3.5).

Node of Ranvier: gaps in the myelin (Fig. 3.5)

The brain has about 100 billion neurons and about 100 trillion connections between them.

Neurons can be clasified according to:

1. Number of processes (FIG. 3.8)                2. Function:

Unipolar                                             Afferent (sensory)

Bipolar                                                Efferent (motor)

Miltipolar                                             Interneuron.

Not all living systems have these three kinds of functional neurons.

One-stage system (sensory-motor neuron): sea anemones (hydras).

Two-stage system (sensory and motor neurons): jellyfish.

Three-stage system (sensory-interneuron-motor): from mollusks (e.g., mussels) on.

Figure of stage systems

Accumulation of neurons are called nuclei (nucleus) in the CNS and ganglia (ganglion) in the PNS. Bundles of axons form tracts in the CNS and nerves in the PNS.

GLIA: In addition to neurons, the brain is made of glial cells. Glial cells are about 10 times more numerous than neurons.

Functions of glia

1. Structural support.

2. Nutritive functions and general housekeeping functions.

3. Help in forming the blood-brain barrier.

4. guidance for neuron migration during development.

5. Producing the insulating myelin for faster nervous conduction.                                                        

Oligodendrocites in brain (central nervous system)

Schwann cells in nerves (peripheral nervous system).

Macroglia: three kinds.

Oligodendrocites--produce myelin in CNS (FIG. 3.9).

Schawann cells-- produce myelin in PNS  (FIG. 3.9).

Astrocytes, which participate in nutrition and blood-brain barrier (FIG. 3.10).

Microglia: Engulf and remove cellular debris and trigger inflammatory responses.

Neuroanatomical techniques

Golgi reveals structure of neurons (Figs. 3.11; 3.31),

Nissl stain uses dyes like cresyl violet. It stains all cells, allowing to obtain information about the cellular architecture of neural tissue (cell layers) and to estimate number of neurons (Fig. 3.12).

Electron microscope. The limit of magnification for light microscopes is about 1,500. Electron microscopes allow much higher magifications (Fig. 4.10).

Neuronal pathways. Neurons are able to talk through long distances because they can have very long axons. How do scientists find out where the axons go, and what kind of circuits they form?

Anatomical techniques: Injections of anatomical tracers (horseradish peroxidase HRP, fluorescent tracers) and analysis of the

-retrograde transport.

-anterograde transport.

Physiological techniques

Neuroanatomical directions and planes (FIG. 3.14, 3.15, 3.16).

THE MAJOR SUBDIVISIONS OF THE CENTRAL NERVOUS SYSTEM

There are 6 major parts to the central nervous system (Fig. 3.19; 3.20)

Early in development, the CNS consists of

            3 vesicles: forebrain, midbrain and hindbrain, and the spinal cord.

Later, 6 subdivisions of the CNS can be recognized:

Forebrain                                          1) Telencephalon (Fig. 3.25, 3.27, 3.28, 3.29)

                                                           2) Diencephalon (Fig. 3.23)

Midbrain                                           3) Mesencephalon (Fig. 3.22)

Hindbrain                                         4) Metencephalon. (Fig. 3.21 )

                                                           5) Myelencephalon (Medulla) (Fig. 3.21)

Spinal cord                                        6) Spinal cord (Fig. 3.17, 3.18)
 
 

SUBDIVISIONS OF THE CENTRAL NERVOUS SYSTEM
(click on link for outline used in class **MUST USE INTERNET EXPLORER**)

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