Parts of the Brain

The human brain is a complicated three-dimensional organ that includes many different parts, areas and structures (composed mainly of nervous tissues but also including e.g. vascular structures for blood supply), hence it cannot be adequately represented by a diagram of just one view or section.

The brain is part of the central nervous system (CNS), which includes the nervous structures of both the brain and the spine.

Diagram of Parts of the Brain

The diagram above shows the locations in the brain of the thalamus, hypothalamus, optic chiasma, infundibulum (also called the infundibular stem and the pituitary stalk), pituitary gland (also called the pituitary body), mamillary body, pons Varolii, medulla oblongata, cerebellum, cerebral aqueduct, pineal gland (also called the pineal body), corpus callosum and the central sulcus.

Brief notes about the structures labelled on this simple diagram of the brain

• Thalamus
  Located towards the centre of the brain are two thalami (thalami is the plural word, thalamus is the singular word), one on each side of the top of the spinal cord / brain. They are symetrical masses of grey-matter that relay nerve signals between the cerebral cortex (see further down this page) and the other parts of the CNS (brain and spinal cord). See the image on the right.
• Hypothalamus
  Sometimes described as the 'control centre' of the body, the hypothalamus contains centres that control body temperature ("thermoregulation"), hunger and hence eating, and water balance and hence thirst. It also produces two hormones, ADH and oxytocin, which are then secreted from the posterior pituitary See also more about the hypothalamus
• Optic chiasma
  When labelled on a diagram of the midsagittal section of the brain, the location of the optic chiasma (also called the optic commissure) appears to be a small dot or approx. circular area. This may be mis-leading because the optic chiasma is actually an X-shaped structure (as viewed from above or below) that is formed by the two optic nerves, one from each eye, crossing over just above and anterior to the pituitary gland so that the optic nerve from the right eye passes to the left-hemisphere of the visual cortex and vice-versa.
• Infundibular stem (also called the infundibulum and the pituitary stalk)
  A funnel-shaped channel that extends downwards from the hypothalamus to the posterior lobe of the pituitary. It contains hypophyseal portal veins connecting capillaries in the hypothalamus to capillaries in the anterior pituitary, and Axons of neurosecretory cells extending from the hypothalamus to the posterior pituitary. See also the pituitary gland
• Pituitary gland (also called the pituitary body)
  This serves as a link between the central nervous system and the endocrine system. Hormones secreted by the pituitary gland include FSH which is important for regulation of the reproductive system and ADH which regulates water retention by the kidneys. - See also the pituitary gland
• Mamillary body
  There are two mamillary bodies - i.e. a pair of rounded swellings. They are located in the floor of the hypothalmus, immediately posterior to (behind) the pituitary gland.
• Pons Varolii
  This is the part of the brainstem that links the medulla oblongata with the thalamus. It ontains numerous nerve tracts between the cerebral cortex and the spinal cord, and several nuclei of grey matter - see also parts of the CNS
• Medulla oblongata (sometimes referred to simply as the medulla)
  This is the connection between the spinal cord and the brain. It is important for essential ("vital") reflexes e.g. re. breathing, heart rate and regulation of blood vessels, and other ("non-vital") reflexes e.g. re. swallowing, salivation, blinking, coughing, sneezing - see also parts of the CNS
• Cerebellum
  This is the largest part of the hindbrain. It has an outer grey cortex and a core of white matter. The cerebellum co-ordinates balance and movement using sensory information from receptors in many different parts of the body e.g. it controls the synchronization of activity in groups of muscles under voluntary control for sport, dance or creating music. It is also important for posture for which it uses sensory information from the inner-ear. See also parts of the CNS
• Cerebral aqueduct (also callled the aqueduct of Sylvius)
  This is a narrow channel containing cerebrospinal fluid (CSF). It connects the third and fourth ventricles of the brain.
• Pineal gland (also called the pineal body)
  The anatomical name of the pineal gland is the epiphysis. It is a pea-sizes mass of nerve tissue that functions as an endocrine gland, secreting the hormone melatonin - see also more about the pineal gland
• Corpus callosum
  This is a broad band of nervous tissue connecting the two cerebral hemispheres (i.e. the right- and left- "halves" of the brain), estimated to contain around 250 million nerve fibres.

The Cerebrum, also known as the Cerebral Cortex

The cerebrum, which consists of grey matter, is the largest and most highly developed part of the human brain. It has motor areas that control voluntary movement, sensory areas that interpret information from sensory receptors around the body, and association areas that connect the motor and sensory parts.

Structure of the cerebrum:

The cerebral cortex is divided into two hemispheres each of which is sub-divided into four lobes, the frontal lobe, the parietal lobe, the temporal lobe and the occipital lobe. Particular areas of the cerebral cortex process specific types or categories of sensory, motor and integrative signals. Of the many functional areas of the cerebrum, only the forebrain (frontal cortex) and the visual centre are labelled above. The structure of the cerebrum includes many folds called gyri (singular, gyrus). Grooves between the folds are called either fissures in the cases of deep grooves, or sulci (singular, sulcus) in the cases of shallow grooves.

Labelled on the diagram above:

• The forebrain (frontal lobe)

  This is the most anterior region of the cerebrum. It is associated with retaining (i.e. memory of) emotions and is responsible for mental functions such as planning ahead, decision-making, attention span, and inhibition. Various changes in behaviour and mental health have been reported as possible effects of damage to the frontal lobe of the brain. Possible consequences that have been suggested include apathy, aggression and extreme sexual behaviour, and other disturbed emotions.

• The visual area (occipital lobe)

  This receives and interprets impulses from the optic nerve that convey visual information e.g. re. the shape, colour and movement of visual stimuli. The visual centre within the brain also has connector neurons that convey signals re. both visual accomodation and the pupil reflex. See also the eye and human vision

These notes are part of a general description of the human brain that is likely to be appropriate for students of first-level courses (e.g. AS and A-Level Human Biology, ITEC Anatomy and Physiology and other Health Science subjects) and for students researching this for general interest.