Psychology Study Material: Brain Stem and Cerebellum: Medulla Oblongata

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Brain Stem and Cerebellum

Located underneath the limbic system the brain stem, containing four structures, is found in all vertebrates.

Brain Stem and Cerebellum

It contains four structures:

  • Medulla
  • Pons
  • Reticular formation
  • Thalamus

Responsible for basic survival functions such as breathing, heartbeat, and blood pressure.

Medulla/Medulla Oblongata

  • Located at the top of the spinal cord and continuous with it.
  • Damage to Medulla can be fatal as it is the centre responsible for vital functions i.e.. , respiration, heartbeat, and blood pressure.
  • Contains ascending & descending tracts that communicate between the spinal cord & various parts of the brain.
  • At medulla, nerves ascending from the body and descending from the brain cross over; hence the left side of the body is connected to the right side of the brain and vice versa.

Contains 3 vital centres:

  • Cardio inhibitory centre: regulates heart rate.
  • Respiratory centre: regulates the basic rhythm of breathing.
  • Vasomotor centre: regulates the diameter of blood vessels.

Pons

  • Pons = Latin word for bridge
  • Bridge connecting spinal cord with brain and parts of brain with each other.
  • The pons seems to serve as a relay station carrying signals from various parts of the cerebral cortex to the cerebellum.
  • Nerve impulses coming from the eyes, ears and touch receptors are sent on the cerebellum.
  • The pons also participates in the reflexes that regulate breathing.
  • It has parts that are important for the level of consciousness and for sleep.

Reticular Formation

  • The reticular formation is a region running through the middle of the hindbrain and into the midbrain.
  • A dense network of nerve cells.
  • It keeps the brain alert even during sleep.
  • It makes the cerebral cortex attend to new stimulation by arousing it.
  • Long fibrous tracts of reticular formation run into the thalamus.
  • Needed for arousal from sleep & to maintain consciousness.
  • Serious damage to reticular formation may result into a coma.

Thalamus

  • The pair of egg-shaped structures located at the top of the brainstem.
  • Incoming sensory information is channelled to the appropriate area of the cerebral cortex by thalamus, so that it is processed there.
  • Thalamus acts like a relay station … . the brain՚s sensory switchboard: it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla.
  • It receives information from the sensory neurons and routes it to the higher brain regions that deal with vision, audition, taste and touch.

Cerebellum

  • “Cerebellum” comes from the Latin word for “little brain” . The cerebellum is located behind the brain stem.
  • Cerebellum is somehow similar to the cerebral cortex: the cerebellum is divided into hemispheres and has a cortex that surrounds these hemispheres.
  • It carries 10 % of the weight of the brain.
  • It contains as many neurons as in the rest of the brain.
  • Its function is to coordinate body movements i.e.. coordination, maintenance of posture & balance.
  • Damage to cerebellum results into jerky and uncoordinated body movements.

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