brain

• Brain


  Large organ weighing 1.4 kg which lies within the cranial cavity
• Components of the brain

  • Cerebrum
  • Thalamus
  • Hypothalamus: Diencephalon
  • Midbrain
  • Pons
  • Medulla oblongata: The Brain Stem
  • Cerebellum
• Cerebrum


  • Largest part of the brain and it occupies the anterior and middle cranial fossae
  • Divided by a deep cleft, the longitudinal cerebral fissure, into right and left cerebral hemisphere, each containing one of the lateral ventricle
  • Two types of matter: Grey Matter (Superficial part of the cerebrum - Cerebral cortex) and White Matter (Deep inside the cerebrum - Nerve fibers)
• Corpus Callosum


  Mass of white matter that connects the two hemispheres of the brain
• Falx cerebri


  Structure that separates the two hemispheres of the brain and penetrates to the depth of the corpus callosum
• Gyri/Convolutions


  Infoldings or furrows of varying depth on the surface of the cerebral cortex
• Sulci/Fissures


  Spaces that separate the convolutions on the surface of the cerebral cortex
• Lobes of the cerebrum

  • Frontal Lobes
  • Parietal Lobe
  • Temporal Lobes
  • Occipital Lobe
• Central Sulci, Lateral Sulci, Parieto-occipital Sulci


  Boundaries that mark the divisions between the lobes of the cerebrum
• Cerebral Tracts


  • Association Tract
  • Commissural Tract
  • Projection Tract
• Basal Ganglia


  Group of cell bodies that lie deep within the brain and form part of the extrapyramidal tract<|>Act as relay stations with connections to many parts of the brain including motor area and thalamus<|>Functions: Initiation and fine control of complex movement, Learned coordinated activities such as posture and walking
• Primary Motor Area


  • Lies in the frontal lobe immediately anterior to the central sulcus
  • Cell bodies are pyramid shaped and they control skeletal muscle activity
  • Two neurons are involved in the pathway to skeletal muscle: Upper Motor Neuron (First) and Lower Motor Neuron (Second)
  • The motor area of the right hemisphere controls voluntary muscle movement on the left side of the body and vice versa
  • Damage to either of these neurons may result in paralysis
  • The areas of the cerebral cortex representing different parts of the body are proportional to the complexity of movement of the body part, not to its size
• Motor Speech (Broca's) Area


  • Situated in the frontal lobe just above the lateral sulcus
  • Controls the muscle movements needed for speech
  • Dominant in the left hemisphere in right-handed people and vice versa
• Somatosensory Area


  • Area immediately behind the central sulcus, where sensations of pain, temperature, pressure and touch, awareness of muscular movement and the position of joints are perceived
  • The size of the cortical areas representing different parts of the body is proportional to the extent of sensory innervations
• Auditory Area


  • Lies immediately below the lateral sulcus within the temporal lobe
  • Receives nerve impulses transmitted from inner ear by the cochlear part of the vestibular cochlear nerve (8th Cranial Nerve)
• Visual Area


  • Lies behind the parieto-occipital sulcus and includes the greater part of occipital lobe
  • Receives impulses carried by optic nerve (2nd Cranial Nerve)
• Olfactory Area


  • Lies deep within the temporal lobe, where impulses from the olfactory epithelium of the nose transmitted by the olfactory nerve (1st Cranial Nerve)
• Taste Area


  • Lies above the lateral sulcus in the deep layers of the somatosensory area
  • Receives and perceives impulses from the taste buds as taste
• Premotor Area


  • Lies in the frontal lobe, immediately anterior to the motor area
• Prefrontal Area


  • Extends anteriorly from the premotor area to include the remainder of the frontal lobe
  • Larger and more highly developed in humans than in other animals
• Sensory Speech (Wernicke's) Area

  • Situated in the temporal lobe, adjacent to the parieto-occipital area
• Parieto-Occipital Area


  • Lies behind the somatosensory area and includes most of the parietal lobe
• Diencephalon


  Connects the cerebrum and the midbrain, consists of several structures situated around the third ventricle
• Thalamus


  • Consists of two masses of grey and white matter situated within the cerebral hemisphere just below the corpus callosum
• Hypothalamus


  • Small but important structure weighing around 7g
  • Consists of nuclei
  • Situated below and in front of the thalamus, immediately above the pituitary gland
  • Linked to the posterior lobe of the pituitary gland by nerve fibers and to the anterior lobe by a complex system of blood vessels
• Pineal Gland


  • Also called the pineal body or epiphysis cerebri
  • Tiny, cone shaped gland in the brain that's located beneath the back part of the corpus callosum
  • In adults, it weighs about 0.1 grams
  • Part of the endocrine system
  • Consists of portions of neurons, neuroglial cells and specialized secreting cells called pinealocytes
• Midbrain


  • Situated around the cerebral aqueduct between the cerebrum above and the pons below
  • Consists of nuclei and nerve fibers, which connect the cerebrum with lower parts of the brain and with the spinal cord
• Pons


  • Situated in front of the cerebellum, below the midbrain and above the medulla oblongata
  • Cell bodies (grey matter) lie deeply, and the nerve fibers are on the surface
  • Consists mainly of nerve fibers that form a bridge between the two hemispheres of the cerebellum, and of fibers passing between the higher levels of the brain and the spinal cord
  • Contains a pneumotaxic area that operates in conjunction with the respiratory center in the medulla oblongata
• Medulla Oblongata


  • Most inferior region of the brain stem
  • Extending from the pons above, it is continuous with the spinal cord below
  • About 2.5cm long and lies just within the cranium, above the foramen magnum
  • Anterior and posterior surfaces are marked by central fissures
  • Outer surface is composed of white matter, which passes between the brain and the spinal cord and grey matter, which lies centrally
  • Some medullary nerves relay information from the special senses of hearing and balance to higher centers in the brain
  • Vital centers, consisting of groups of cell bodies (nuclei) associated with autonomic reflex activity, lie in its deeper structure: Cardiovascular Centre, Respiratory Centre, Reflex Centre of vomiting, coughing, sneezing and swallowing
• Cerebellum


  • Situated behind the pons and immediately below the posterior portion of the cerebrum occupying the posterior cranial fossa
  • Ovoid in shape and has two hemispheres, separated by a narrow median strip called the vermis
  • Grey matter forms the surface of the cerebellum, and the white matter lies deeply