Brain and Cranial Nerves

• The brain has grey matter made up of unmyelinated neurons and white matter made up of myelinated neurons
• The outer regions of the brain are grey matter and the deeper regions are white matter, which is the opposite of the spinal cord
• Brain protection


  • Skin of scalp
  • Skull bones
  • Meninges (dura mater, arachnoid mater, pia mater)
  • Cerebrospinal fluid
• Falx cerebri


  Extension of dura mater found between the two cerebral hemispheres
• Falx cerebelli


  Extension of dura mater found between the two halves of the cerebellum
• Tentorium cerebelli


  Extension of dura mater found between the cerebrum and cerebellum
• Blood supply to the brain

  • Vertebral arteries
  • Common carotid arteries
  • Jugular veins
• The brain receives about 20% of the body's oxygen supply despite its relatively small size
• Blood-brain barrier


  Barrier formed by astrocytes to protect the brain from substances in the bloodstream
• Brain ventricles


  • Lateral ventricles
  • Third ventricle
  • Fourth ventricle
• Cerebrospinal fluid flow


  1. Made in choroid plexus

  2. Flows from lateral ventricles to third ventricle via interventricular foramen

  3. Flows from third ventricle to fourth ventricle via cerebral aqueduct

  4. Circulates around brain and spinal cord
• Cerebral spinal fluid flow

  1. Lateral ventricles

  2. Third ventricle

  3. Interventricular foramen

  4. Cerebral aqueduct

  5. Fourth ventricle

  6. Median aperture

  7. Lateral aperture

  8. Arachnoid villi
• Parts of the brainstem

  • Medulla oblongata
  • Pons
  • Midbrain
• Medulla oblongata


  Responsible for reflexes like heart rate changes, respiratory changes, coughing, sneezing, and hiccupping
• Pons


  Sends motor information from the cerebrum to the cerebellum, helps to alter breathing patterns
• Midbrain


  Sends motor information from the cerebrum to the cerebellum and spinal cord, sends sensory information from the spinal cord to the thalamus
• The reticular formation is a network of neurons that helps maintain consciousness and wakefulness
• Cerebellum


  Helps with skeletal muscle contraction coordination
• Damage to the cerebellum can cause clumsiness
• Brainstem


  Helps to send motor information from the cerebrum to the cerebellum
• Cerebellum


  Helps with skeletal muscle contraction coordination, keeps you coordinated
• Muscle contraction coordination


  1. One leg muscles contract while another leg muscles relax

  2. One leg dorsi flexes while another plantar flexes
• Alcohol consumption


  Disrupts the function of the cerebellum, causing clumsiness and loss of coordination
• Diencephalon


  Central portion of the brain located under the corpus callosum
• Parts of the diencephalon

  • Thalamus
  • Hypothalamus
  • Epithalamus
• Thalamus


  Receives and fine-tunes sensory information before sending it to the cerebrum
• Hypothalamus


  Regulates homeostatic activities and maintains homeostasis
• Epithalamus


  Contains the pineal gland which produces melatonin to regulate sleep-wake cycles
• Circumventricular organs of the diencephalon lack a blood-brain barrier, allowing the hypothalamus to monitor the bloodstream and maintain homeostasis
• Cerebrum


  Outer, superficial portion of the brain
• The cerebrum is divided by a deep longitudinal fissure, almost cutting the brain in half
• Sulci


  Shallow grooves on the surface of the cerebrum
• Gyri


  The actual brain surface itself
• Lobes of the cerebrum

  • Frontal lobe
  • Parietal lobe
  • Temporal lobe
  • Occipital lobe
  • Insula
• Frontal lobe


  Controls and initiates motor activities
• Parietal lobe


  Receives and processes sensory information
• Temporal lobe


  Processes auditory/hearing information
• Occipital lobe


  Processes visual information
• The corpus callosum is a white matter tract that facilitates communication between the left and right cerebral hemispheres
• Gray matter


  More superficial, outer portion of the brain