Forebrain : Its Anatomy & Function - Practice Questions & MCQ

Forebrain: Olfactory Lobe and Diencephalon

• It is the anterior part of the brain and largest among the three parts.
• The forebrain has two major divisions: 

              -  the diencephalon: it is lower, containing the thalamus and hypothalamus
              -  the telencephalon: it is on top of the diencephalon and contains the cerebrum
              -  the olfactory lobes 

• It is the large and complicated forebrain that distinguishes the human brain from other vertebrate brains.

Diencephalon:

• The diencephalon consists of two major regions called the thalamus and hypothalamus and two additional but smaller areas called the epithalamus and subthalamus. 
• It encloses third ventricle (brain cavity)

Thalamus:

• The thalamus constitutes the largest component of the diencephalon.
• It lies superior to the midbrain is composed prima­rily of grey matter.
• It is composed of a variety of nuclei that serve diverse functions. 
• In general, these nuclei serve as relays by which information is transmitted from different regions of the central nervous system (CNS) to the cerebral cortex.

Epithalamus

• Forming the roof of the diencephalon is a series of structures called the epithalamus. 
• It consists of pineal gland.

Hypothalamus

• On the ventral side hypothalamus forms the floor.
• The pituitary hangs below the hypothalamus by a stalk called the infundibulum.
• Two optic nerves cross each other to form optic chiasma in front of the pituitary.
• Hypothalamus integrates and controls the visceral activities. 
• It maintains homeostasis. 
• It provides anatomical connection between the nervous and endocrine systems by its relationship to the pituitary gland.
• Through connections with pituitary gland, it controls growth and sexual behaviour.
• Hypothalamus is thermoregulatory centre. Hence it is called “thermostat” of the body. 
• It is also associated with behavioural activities. 
• Appetite, thirst and satiety (feeling of being satisfied) centres are located in the hypothalamus. 
• It also influences respiration and heartbeat.

Olfactory lobes:

• The anterior part of the brain is formed by a pair of short club- shaped structures, the olfactory lobes. 
• They are fully covered by the cerebral hemispheres and are, therefore, only visible in the ventral view of the brain. 
• A pair of olfactory nerves arises from the olfactory lobes.