Overview of the Central Nervous System

Meliton Silva, class 2006

Objectives

1. Start to get familiar with the Nervous System -what is looks like; how we study it.

2. Describe the components and functions of the Central Nervous System.

3. Recognize shapes and internal characteristics of different levels

4. Understand the clinical significance of this information.

Chris Cohan, Ph.D.Dept. of Pathology/Anat SciUniversity at Buffalo© 2017http://neuroscience.uth.tmc.edu/s2/chapter01.html

#1. The Nervous System has Peripheral and Central Divisions.

Peripheral Nervous System• all spinal, cranial nerves• all autonomic nerves• all ganglia of spinal, cranial, autonomic nerves

Parts of the CNS•The CNS consists of the

brain + spinal cord

•Brain = •Cerebral hemispheres•Cerebellum•Brainstem

•Brainstem= medulla, pons, midbrain

You will review these components in the Brain Museum this week.

#2. Each CNS component has unique features and functions.

Cerebral Hemispheres

• 2 hemispheres; each has a lateral and medial surface• Gyrus - folded, raised area• Sulcus/Fissure - a depression• Lobes - frontal, parietal, occipital, temporal• Components: telencephalon + diencephalon

lateral medial

telencephalon

Functions of Cerebral Hemispheres

Cerebral Hemispheres:• Sensory Perception

• Cognition

• Emotion

• Language

• Voluntary Movement

Brainstem

• Components: midbain, pons, medulla

• Contains: cranial nerves II-XII

midbrain

pons

medulla

Functions of Brainstem

Brainstem:• Cranial Nerves• Communication Highway• Vital Autonomic Centers

• Heartbeat• Vascular tone• Respiratory rhythm

midbrain

pons

medulla

Cerebellum• Coordinates movement

• learning movements

• (cognition)

Spinal Cord• Segments

• Cervical - 8

• Thoracic - 12

• Lumbar - 5

• Sacral - 5

• Functions

• incoming sensory info

• outgoing motor info

• autonomic information

shape

3 layers:• Dura - outermost, toughest layer

• Arachnoid - middle layer

• Pia - thinnest layer on surface of CNS.

• Create important spaces between layers

• for blood vessels and nerves

• for cerebrospinal fluid

#3. CNS is covered by 3 connective tissue layers, the meninges.

Clinical Significance1. Head trauma can tear blood vessels

associated with the meninges, causing life threatening epidural, subdural, or subarachnoid hematomas.

2. Infections can spread to the meninges and cause inflammation known as meningitis.

Because the brain is in a space confined by the skull, the introduction of anything new can be life-threatening.

#4. The brain is hollow. It contains a system of connected spaces, the ventricles, filled with cerebrospinal fluid.

VentriclesThere are 4 ventricles:

1. Two lateral ventricles2. Third ventricle3. Fourth ventricle

• Ventricles produce cerebrospinal fluid, which ultimately exits the ventricles into a meningeal space where it acts as a reservoir for the brain and spinal cord.

See web site tutorials

Clinical Significance1. In a lumbar puncture, cerebrospinal fluid is

removed from a region around the spinal nerves to diagnose CNS disorders.

2. If the flow of fluid in the ventricular system is blocked, it causes hydrocephalus. The ventricles enlarge, causing a dangerous increase in intracranial pressure.

#5. Nerve cells are the functional units of the nervous system. Their function depends upon glial cells.

Nerve cells have unique structural featuresrequired for their role in communication.

Nerve cells communicate at synapses, which allow them to form pathways and process information.

Synaptic communication depends on release of neurotransmitters.

Glial cells are intimately associated with nerve cell metabolism, signaling, protection and repair.

Most drug therapies based on this

Clinical SignificanceDiseases such as multiple sclerosis attack glial

cells that produce myelin surrounding nerve axons, impairing conduction of electrical signals.

Many neurological and psychiatric disorders (Parkinson’s Disease, schizophrenia, depression) result from abnormal release of neurotransmitters. Treatments for these disorders involve drugs that alter synaptic transmission.

#6. The nervous system is highly organized. Axons are bundled and separated from nerve cell bodies.

spinal cord

Areas with axons appear different from areas with cell bodies.

• The natural color of axons is white (white matter) due to myelin

• Cell bodies appear darker (grey matter)

To help distinguish these areas better, in sections, nervous tissue is stained. Myelin (axons) is black.

White matter

Grey matter

Grey matter

White matter

Cerebral hemispheres Brainstem Spinal Cord

The positions of white and and grey matter change throughout the nervous system.

white matter

grey matter

#7. The CNS is studied anatomically, pathologically, radiologically, clinically by comparison of different planes of section.

Coronalplane

Coronal, horizontal, sagittal planes allow comparison of internal structures and their relationships.

coronal horizontal sagittalMRI

Anatomical DirectionsCerebral hemispheres, brainstem,

spinal cord have different shapes and orientation to each other.

Anatomical terms can be used in different ways for orientation.

inferiorventral

Anatomical ShapesCross-sections of brainstem/spinal cord allow us to view internal

components. Cross-sections from different regions have different shapes, which are clues to their position.

#8. The CNS requires a continuous supply of blood to maintain its high metabolic activity.

Blood Supply• Source: Internal Carotid and

Vertebral Arteries

• ICA and Vertebral circulation anastomose in Circle of Willis

• Cerebral Arteries supply hemispheresAnterior Cerebral ArtMiddle Cerebral ArtPosterior Cerebral Art

Blood SupplyCerebral arteries supply distinct

areas on surface of hemispheres:

• Stroke = loss of blood supply to a region of the brain. Causes specific sensory and motor deficits related to that region.

Anterior Cerebral Art.

Middle Cerebral Art.

Posterior Cerebral Art.

Where We Are Going

• The nervous system is a communications network of highly organized pathways.

• NS disorders involve specific locations of damage, which cause deficits in function.

• These deficits can be explained and even predicted if you understand the arrangement of pathways inside the CNS.

Goals1. Recognize CNS divisions

2. Understand general functional roles

3. Recognize locations, shape and internal anatomy.

4. Questions are a natural part of learning. Please ask!