Anatomy of Brain

Structure of the brain

  1. The brain is one of the largest, most complex organs in the human body, and is contained in the head, closely protected by the bones of the skull.
  2. Brain is the central organ of the nervous system and together with the spinal cord makes up the central nervous system.
  3. Brain is broadly divided into cerebrum or the cerebral cortex, cerebellum, and brainstem, each part performing different functions and put together contribute to the normal function of the brain.
  4. Cerebrum is the big dome-shaped part of the brain, occupying major part of the space in the skull. Cerebrum is divided into many lobes and controls sensory activity, motor activity, thoughts, and behavior.
  5. Cerebellum is a smaller part of the brain, located below the cerebrum and contributes to maintain balance & posture.
  6. Brainstem is the posterior and inferior part of the brain controlling the basic involuntary body functions, such as, heart rate, respirations, blood pressure control, and consciousness. At the base of brain, brainstem is continuous with the spinal cord.

Functions of different parts of brain

  1. Brain is broadly divided into cerebrum or the cerebral cortex, cerebellum, and brainstem, each part performing different functions and put together contribute to the normal function of the brain.
  2. Cerebrum is the big dome-shaped part of the brain, divided into many lobes, and occupies major part of the space in the skull.
  3. Cerebrum is the highest center in the sensory system, receiving sensory information, such as, touch, heat, cold, pain, vision, hearing, smell, and taste from the whole body. Cerebrum helps process and perceive the sensory information received.
  4. Cerebrum functions as the highest center of motor activity and controls voluntary body movements, such as, sitting, standing, stretching, jumping, walking, and running. Cerebrum also functions as the highest center of memory, thoughts, planning, emotions, behavior, and judgement.
  5. Cerebellum is a smaller part of the brain, located below the cerebrum and contributes to maintain balance & posture.
  6. Brainstem is the posterior and inferior part of the brain controlling the basic involuntary body functions, such as, heart rate, respirations, blood pressure control, and consciousness. The brain stem also controls the flow of messages between the upper brain or cerebrum and the rest of the body. At the base of brain, brainstem is continuous with the spinal cord.

Lobes of brain and their functions

  1. Cerebrum is the big dome-shaped part of the brain, occupying major part of the space in the skull.
  2. The cerebrum is equally divided into right and left halves, controlling the functions of both sides of the body.
  3. Each half of the cerebrum comprises of mainly frontal, parietal, occipital, and temporal lobes.
  4. Frontal lobe controls motor activity and voluntary body movements, such as, sitting, standing, stretching, jumping, walking, and running. Frontal lobe also controls higher cognitive functions, such as, memory, thoughts, planning, emotions, behavior, and judgement.
  5. Parietal lobe helps process and perceive sensory information related to touch, pressure, vibration, temperature differentiation of heat & cold, and taste from the entire body.
  6. Occipital lobe helps process visual information, such as, perception of color, distance, depth, spatial orientation, and object & face recognition.
  7. Temporal lobe helps process auditory information and is mainly important for hearing, speech & language recognition.

Ventricles of brain

  1. The ventricles of the brain are a set of connected cavities within the brain.
  2. In total, there are 4 ventricles in the brain. The first two are called lateral ventricles, then there is a third ventricle, and the last one is called the fourth ventricle.
  3. These cavities are lined by a network of blood vessels called choroid plexus and communicate with each other inside the brain.
  4. The blood vessels lining the ventricles filter the circulating plasma and help with production of cerebrospinal fluid, which helps with distribution of nutrition and removal of waste from the brain and spinal cord.
  5. As these cavities or ventricles are connected and communicating, CSF thus produced flows from one ventricle to the next.
  6. The ventricles finally drain the CSF from the brain into the spinal canal surrounding the spinal cord.

Cerebrospinal fluid

  1. The ventricles of the brain are a set of connected cavities within the brain that are lined by a network of blood vessels called choroid plexus.
  2. The blood vessels lining the ventricles filter the circulating blood and help with production of cerebrospinal fluid (CSF).
  3. As these cavities or ventricles are connected and communicating, CSF thus produced flows from one ventricle to the next.
  4. The ventricles finally drain the CSF from the brain into the spinal canal surrounding the spinal cord and into the storage spaces surrounding the brain. From these storage spaces, CSF is reabsorbed into circulation and is recycled.
  5. CSF mainly helps with distribution of nutrition and removal of waste from the brain and spinal cord.

Functions of cerebrospinal fluid

  • The ventricles of the brain are a set of connected cavities within the brain that are lined by a network of blood vessels called choroid plexus.
  • The blood vessels lining the ventricles filter the circulating blood and help with production of cerebrospinal fluid (CSF).
  • As these cavities or ventricles are connected and communicating, CSF thus produced flows from one ventricle to the next.
  • CSF finally drains from the brain into the spinal canal surrounding the spinal cord and into the storage spaces surrounding the brain. From these storage spaces, CSF is reabsorbed into circulation and is recycled.
  • While flowing along the ventricles, spinal canal, and the storage spaces surrounding the brain, CSF accomplishes some major functions such as:
  1. Nourishment: While flowing along the ventricles and the spinal canal, CSF helps with distribution of nutrition to the brain and spinal cord.
  2. Disposal of waste: While flowing along the ventricles and the spinal canal, CSF also helps with removal of waste from the brain & spinal cord and drains it back into circulation to be excreted from the body.
  3. Shock absorption & protection: In the storage spaces surrounding the brain and while flowing through the spinal canal surrounding the spinal cord, CSF helps protecting the brain and spinal cord as a cushion. This helps with limiting the risk of brain and spinal cord damage from head injuries & accidents.
  4. Protection of vital centers: There are some vital centers controlling heart rate, respirations, and blood pressure located at the base of brain. Brain is a heavier organ, which can mount extreme pressure on these vital centers and compromise their function. CSF surrounds the brain and helps with keeping the brain slightly floated. This can reduce the pressure the heavy brain can exert on the vital centers located at the base of brain, thus helping them to function normally.
  5. Also, the chemical composition of CSF helps with normal transmission of nerve impulse, thus promoting normal brain & spinal cord function.

Meninges

  1. Brain and spinal cord are surrounded by three coverings or membranes called meninges.
  2. These membranes are primarily protective in function. Surrounding the brain and spinal cord, these membranes protect the brain and spinal cord from any physical injury and damage.
  3. The dura mater is thick and touch outermost layer present immediately beneath the bones of skull and vertebrae. This layer is richly supplied with blood vessels and nerves.
  4. Arachnoid mater is the middle layer present beneath the dura mater and hardly has any blood vessels and nerves.
  5. Pia mater is the very thin innermost layer and is closely adhered to the brain & spinal cord. This layer also is richly supplied with blood vessels and nerves.
  6. Beneath the arachnoid mater, there is a space called subarachnoid space. This is the space between middle layer arachnoid mater and the innermost layer pia mater. This space is filled with fluid called cerebrospinal fluid, which helps with nourishment, shock absorption, and protection of vital centers in the brain.

Blood supply to brain

  1. Brain is one organ highly dependent on blood supply for oxygen and nutrient requirements.
  2. It is supplied by a rich network of blood vessels formed by arteries called common carotid arteries, vertebral arteries, and their branches.
  3. These blood vessels supply to different parts of the brain, which control different body functions.
  4. For example, frontal lobe controls motor activity and voluntary body movements, such as, standing, walking, running, and higher cognitive functions, such as, memory, planning, and judgement. Parietal lobe helps process and perceive sensory information related to touch, pressure, vibration, heat and cold. Occipital lobe helps process information pertaining to vision and temporal lobe helps process information pertaining to hearing. Base of brain controls basic involuntary body functions, such as, heart rate, respirations, blood pressure control, and consciousness.
  5. Blood supply to the brain could be compromised for many reasons, such as, low blood volume in the body, loss of blood from any injury or accident, and obstruction to blood flow due to clot formation.
  6. Any compromise in the blood supply to these parts of the brain can result in serious consequences.
  7. Reduced blood supply to the brain can result in varying symptoms such as, numbness, weakness, paralysis, poor vision & hearing, confusion, dizziness, and loss of consciousness, depending on the part of brain affected with the reduced blood supply