Overview of the Brain

Overview of the brain

The brain is one of the largest organs in the body and regulates our everyday functioning. The brain receives, integrates and transmits information all around our body. There are certain regions of the brain that have different functional roles. The brain is encased and protected by the skull (also called the cranium) and can be divided into three main parts; the forebrain, midbrain and hindbrain.

Forebrain

The forebrain serves a range of functions including cognitive, sensory and motor functioning.

Much of the higher level functions occur in the cerebral cortex. The cerebral cortex is made up of gray matter, this is where majority of neuronal cell bodies lie. White matter tracts are made up of neuronal axonal projections, found below the cortex.

The functional lobes

The cerebral cortex can be divided into broad functional lobes, within these functional divisions there are further subdivisions that serve different functions.

Frontal lobe

The frontal lobe is involved in higher level executive functioning as well as sensory, emotional and motor functioning. The frontal lobe contains the motor cortex, which receive motor feedback information and also send out signals to control movement. It also contains the Brocas area, which is implicated in the expression of written and spoken language.

Parietal lobe

The parietal lobe is involved in the processing of sensory information, spatial and visual orientation in addition to speech, semantic and mathematical abilities.

Temporal lobe

The temporal lobe is involved in the understanding and integration of language, auditory perception and memory.

Occipital lobe

The occipital lobe is the visual processing centre of the brain.

Midbrain

The midbrain contains the mesencephalon and connects the forebrain to the hindbrain. The midbrain can be subdivided into the tectum and tegmentum. The tectum is located at the back of the midbrain and contains both the superior and inferior colliculi, which receive visual and auditory information, respectively.

Hindbrain

The hindbrain regulates vital involuntary autonomic functions that are essential for our survival, such as respiration, heart rate, sleep etc.

Key brain regions

The thalamus is an integrative centre in the brain and relays and filters sensory and motor information to other brain regions such as the cortex. It also regulates sleep cycles.

The basal ganglia are a group of neuronal structures that function to regulate all aspects of voluntary and involuntary behaviour including movement and motivation.

The pituitary gland controls the release of hormones by endocrine glands in the body. The pituitary gland also releases its own hormones that have direct or indirect effects on the body.

The meninges

The brain is protected by what is known as the meninges, these are membranous coverings that encase the brain and spinal cord. The meninges serve as a structural framework and protect the cerebral vasculature. Three membranes cover the brain and spinal cord; dura, pia and arachnoid mater.

Dura mater – The dura mater is the outermost layer and is extremely durable. It lines the cranium (skull) and holds the brain in place.

Pia mater – The pia mater is the innermost layer and adheres directly to the surface of the brain, it is predominantly impermeable to fluid and the only openings in the pia mater are for the entrance of blood vessels.

Arachnoid mater – The arachnoid mater is a layer of connective tissue that lies between the dura and the pia mater.