THE BRAIN

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THE BRAIN FIVE SENSES

• By, Dr. Shamanthakamani Narendran, M.D.

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THE BRAIN

• The adult human brain weighs an average of 1.4
  kg, or about 2 percent of the total body weight. 
  
• Despite this relatively small mass, the brain
  contains approximately 100 billion neurons.
• Functioning as a unit, these neurons make up the
  most complex and highly organized structure on
  Earth. 

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THE BRAIN

• The brain is responsible for many of the
  qualities that make each individual
  unique-thoughts, feelings, emotions, talents,
  memories, and the ability to process information.
  
• Much of the brain is dedicated to running the
  body, the brain is responsible for maintaining
  Homeostasis by controlling and integrating the
  various systems that make up the body.

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1. The brain is the main switching unit of the
   central nervous system It is the place to which
   impulses flow and from which impulses originate.
2. The spinal cord provides the link between the
   brain and the rest of the body.
3. The brain has three main parts
4. The cerebrum
5. The cerebellum
6. The brain stem

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• The Brain is a highly organized ORGAN that
  contains approximately 100 billion neurons and
  has a MASS of 1.4 Kilograms.
• The Brain is Protected by a BONY Covering called
  the SKULL.
• The Brain is also WRAPPED in
• THREE LAYERS of
• CONNECTIVE TISSUE
• known as the MENINGES.

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• Connective Tissue connects one tissue to another.
  
• The INNER most layer, which covers and is bound
  to the surface of the brain, is called PIA MATER.
  It is a FIBEROUS LAYER made up of many Blood
  Vessels which carry FOOD and OXYGEN to the Brain.
  
• The OUTER Layer, called the DURA MATER, is
  composed of Thick Connective Tissue.

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• The ARACHNOID is the THIN, elastic, weblike layer
  between the PIA MATER and the DURA MATER. Between
  the Pia Mater and the Arachnoid is a space filled
  with CEREBROSPINAL FLUID.

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• Cerebrospinal Fluid separates the middle and
  inner Meninges and fills four interconnected
  VENTRICLES, or Cavities in the Brain. Within the
  Ventricles, Cerebrospinal Fluid acts as a
  Transport Medium for substances that are
  important to Brain Function.

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• The Cerebrospinal Fluid is a clear liquid that
  PROTECTS the Brain from mechanical injury by
  acting as a Shock Absorber.
• In order for the Brain to perform its functions,
  it must have a constant supply of Food and
  Oxygen.
• If the Oxygen supply to the brain is cut off even
  for a few minutes, the brain will usually suffer
  enormous damage. Such damage may result in DEATH.

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PARTS OF THE BRAIN

• THE CEREBRUM

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• THE CEREBRUM IS THE CONTROL CENTER OF THE BRAIN.
• The LARGEST and most PROMINENT part of the Human
  Brain is the CEREBRUM. 85 OF THE WEIGHT OF A
  HUMAN BRAIN.
• The Cerebrum is responsible for all the VOLUNTARY
  (CONSCIOUS) ACTIVITIES OF THE BODY. It is the
  site of INTELLIGENCE, LEARNING AND JUDGMENT.

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• IT FUNCTIONS IN LANGUAGE, CONSCIOUS THOUGHT,
  MEMORY, PERSONALITY DEVELOPMENT, VISION, AND
  OTHER SENSATIONS.
• The Cerebrum takes up most of the space in the
  cavity that houses the Brain. (SKULL)
• The CEREBRUM IS DIVIDED INTO TWO HEMISPHERES, THE
  LEFT AND RIGHT CEREBRAL HEMISPHERES.

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There is a DEEP GROVE that separates the Two
Hemispheres. The Hemispheres are Connected in a
region known as the CORPUS CALLOSUM. The right
and left cerebral

• hemispheres are linked by a bundle of neurons
  called A TRACT tells each half of the brain what
  the other half is doing.

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• The MOST Obvious FEATURE on the surface of each
  hemisphere are NUMEROUS FOLDS.
• These FOLDS and the GROOVES INCREASE the Surface
  Area of the Cerebrum. The Ridges are called GYRI,
  and the grooves are called SULCUS.
• The Cerebrum, which looks like a wrinkled
  mushroom, is positioned over the rest of the
  brain.

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• It contains thick layers of Unmyelinated Neurons,
  which look GRAY. ("GRAY MATTER")

The increased surface area permits the large
number of neurons to fit easily within the
confines of the Skull.
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• Each Hemisphere of the Cerebrum is divided into
  Four regions called LOBES.
• These LOBES are named for the SKULL BONES that
  cover them, FRONTAL, PARIETAL, TEMPORAL, AND
  OCCIPITAL LOBES.

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• The RIGHT hemisphere is associated with
  creativity and artistic ability. The LEFT
  hemisphere is associated with analytical and
  mathematical ability.

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• Sometimes blood vessels in the brain are blocked
  by blood clots, causing a disorder called A
  STROKE. During a Stroke, circulation to an area
  in the brain is blocked and the brain tissue
  dies. A severe Stroke in one side of the brain
  may cause PARALYSIS of the other side of the
  body.

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• The Cerebrum consists of TWO SURFACES
• The FOLDED OUTER SURFACE is called the CEREBRAL
  CORTEX and consists of GRAY MATTER (UNMYELINATED
  NEURONS).
• The INNER SURFACE is called the CEREBRAL MEDULLA,
  which is made up of bundles of MYELINATED AXONS.
  THE WHITE MATTER.
• The Myelin gives the White Matter its White
  Color.

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THE CEREBELLUM

• The CEREBELLUM is the SECOND LARGEST part of the
  Brain, and is located at the back of the Skull.
  It coordinates muscle movements.

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• The Cerebellum coordinates and balances the
  actions of Muscles so that the body can move
  gracefully and efficiently.
• The Cerebellum CONTROLS BALANCE, POSTURE, and
  COORDINATION.
• The Cerebellum receives sensory impulses from
  muscles, tendons, joints, eyes, and ears, as well
  as input from other brain centers.

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• It processes information about position and
  controls posture by keeping skeletal muscles in a
  constant state of partial contraction.
• The Cerebellum Coordinates rapid and ongoing
  movements.
• This is a small CAULIFLOWER SHAPED Structure.

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• A Major part of learning how to perform physical
  activities seems to be related to training the
  Cerebellum to coordinate the proper muscles.
  Because the function of the Cerebellum is
  INVOLUNTARY (not under conscious control),
  learning a completely new physical activity can
  be very difficult.

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THE BRAIN STEM

• The BRAIN STEM CONNECTS the BRAIN to the SPINAL
  CORD.

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• The brain stem, which maintains life support
  systems, consist of the diencephalon,  medulla
  oblongata, pons, and the midbrain.
• The Brain Stem Controls Vital Body Processes.
• The Brain stem not only coordinates and
  integrates all INCOMING INFORMATION it also
  serves as the place of entry or exit for ten of
  the Twelve Cranial Nerves.

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• The Upper Brain Stem, the Diencephalon, contains
  important relay centers for information entering
  an exiting the brain.
• The Lower Brain Stem consists of the MEDULLA
  OBLONGATA, PONS, AND MIDBRAIN.
• The Lowest Part of the Brain Stem is the Medulla
  Oblongata (Sometimes just called the Medulla).

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• The Medulla contains WHITE MATER that conducts
  impulses between the Spinal Cord and Brain.
• The MEDULLA controls involuntary functions that
  include, breathing, blood pressure, heart rate,
  digestion, swallowing, and coughing.
• Another important part of the Medulla is a GROUP
  of CELLS known as THE RETICULAR ACTIVATING SYSTEM
  or RETICULAR FORMATION (RAS).

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• The Reticular Activation System (RAS) actually
  helps to alert, or awaken, the upper parts of the
  Brain, including the Cerebral Cortex. Such
  actions keep the Brain alert and conscious.
• The RAS also helps to control respiration and
  circulation and serves as a filtering system for
  incoming sensory signals. For example, we awaken
  to the sound of an alarm clock, to a bright light
  flash, or to a painful pinch because activity in
  the RAS that arouses the Cerebral Cortex.

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• Just above the Medulla, the brainstem enlarges to
  form the PONS. PONS mean BRIDGE, and this area of
  the brain stem contains mostly white matter that
  provides a link between the cerebral cortex and
  the cerebellum. Above the PONS and continuous
  with it is the MIDBRAIN, the smallest division of
  the lower brain stem.

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DIENCEPHALON

• THE THALAMUS AND HYPOTHALAMUS
• The Thalamus and Hypothalamus are found in the
  part of the brain between the Brain Stem and
  Cerebrum.
• The Thalamus, which is composed of Gray Matter,
  serves as a SWITCHING STATION FOR SENSORY INPUT.
  With the Exception of SMELL, each Sense Channels
  its Sensory Nerves through the Thalamus.

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• The Thalamus passes information to the proper
  region of the Cerebrum for further processing.
• Immediately Below the Thalamus is the
  Hypothalamus, which is the CONTROL CENTER for
  hunger, thirst, fatigue, anger, and body
  temperature.
• Parts of the Diencephalon and the Cerebrum are
  included in an important group of connected Brain
  Centers called the LIMBIC SYSTEM.

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• The Limbic System includes the Thalamus, the
  Hypothalamus, some deeper parts of the Cerebral
  Cortex, and centers in the Temporal Lobes.
• The Limbic system plays an important role in
  emotions, memory, and motivation, among other
  things.

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BRAIN GROWTH IN FETUS
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SENSORY SYSTEMS

• Human experience is effected by both internal and
  external stimuli. 
• Humans are able to distinguish among many
  different types of stimuli by means of a highly
  developed system of SENSE ORGANS. 
• Sensory Systems represent an integration of the
  functions of the Peripheral Nervous System and
  the Central Nervous System.

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• The Sensory Division of the Peripheral Nervous
  System gathers information about the Body's
  Internal Conditions and External Environment.
• Sensory Systems translate light, sound,
  temperature, and other aspects of the Environment
  to Electrical Signals and transmit these signals,
  in the form of Action Potentials, to the Central
  Nervous System, where they are Interpreted.