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Neurological Assessment and Monitoring 421

TABLE 16.3 Organisation of the brain

Division Description Functions
Forebrain
Cerebrum Largest and uppermost portion of Cortex (outer layer) is the site of conscious thought, memory,
the brain. Divided into two reasoning and abstract mental functions, all localised within
hemispheres, each subdivided specific lobes.
into the frontal, parietal, temporal
and occipital lobes.

Diencephalon Between the cerebrum and the Thalamus sorts and redirects sensory input; hypothalamus
brainstem. Contains the thalamus controls visceral, autonomic, endocrine and emotional
and hypothalamus. function, and the pituitary gland. Contains some of the centres
for coordinated parasympathetic and sympathetic stimulation,
temperature regulation, appetite regulation, regulation of
water balance by antidiuretic hormone (ADH), and regulation
of certain rhythmic psychobiological activities (e.g. sleep).
Brain stem Anterior region below the Connects cerebrum and diencephalon with spinal cord.
cerebrum: the medulla, pons, and
midbrain compose the brainstem.
Midbrain
Midbrain Below the centre of the cerebrum. Has reflex centres concerned with vision and hearing; connects
cerebrum with lower portions of the brain. It contains sensory
and motor pathways and serves as the centre for auditory and
visual reflexes.

Basal ganglia or corpus striatum The mass of grey matter in the An important role in planning and coordinating motor
midbrain beneath the cerebral movements and posture. Complex neural connections link the
hemispheres. Borders the lateral basal ganglia to the cerebral cortex. The major effect of these
ventricles and lies in proximity to structures is to inhibit unwanted muscular activity; disorders
the internal capsule. of the basal ganglia result in exaggerated, uncontrolled
movements.

Pons Anterior to the cerebellum. Connects cerebellum with other portions of the brain; contains
motor and sensory pathways; helps to regulate respiration;
axons from the cerebellum, basal ganglia, thalamus and
hypothalamus; portions of the pons also control the heart,
respiration and blood pressure. Cranial nerves V–VIII connect
the brain in the pons.

Hindbrain Contains a portion of the pons,
the medulla oblongata and the
cerebellum.
Reticular activation system (RAS) The reticular formation networks Activity of the cerebral cortex is dependent on both specific
run through the brainstem core, sensory input and non-specific activating impulses from the
known as the tegmentum. RAS, and is critical to the existence of the conscious state,
states of alertness and arousal.