Human Brain: Brain Stem.

 

Brain Stem.

• Lower part of the brain.

• Located in front of the cerebellum and ends in the spinal cord.

• It consists of,

1. MidBrain

2. Pons

3. Medulla Oblongata.

1. MidBrain:

• Also called “Mesencephalon” in Greek Mesen means middle and cephalon means brain hence “The Middle Brain”.

• Starts from diencephalon to pons.

• Anterior part contains a pair of tracts called “Cerebral Peduncles”.

• Posterior part, called “Tectum”, contains four elevations called “Cerebral Colliculus”.

• Superior colliculi are responsible for ``Visual Activity”.

• Inferior colliculi are responsible for “Auditory Activity”.

• It also contains a dark pigmented area called “Substantia nigra” the degeneration of neurons in this area is the prime cause of “Parkinson's Disease.”

• Midbrain contains two pairs of cranial nerves,

• Oculomotor nerve. (III Cranial Nerve)

• Trochlear nerve. (IV th Cranial Nerve)

2. Pons:

• Present above medulla oblongata and in front of the cerebellum.

• It connects parts of the brain with one another.

• It contains a “Respiratory center” which operates with the association of areas of Medulla Oblongata.

• Contains four pairs of cranial nerves.

• Trigeminal Nerve (V th cranial nerve).

• Abducens Nerve (VI th cranial nerve).

• Facial Nerve (VII th cranial nerve).

• Vestibulocochlear Nerve (VIII th cranial nerve).

3. Medulla Oblongata:

• Lowermost part of the brain.

• It ends in the spinal cord.

• Important part as contains several regulatory centers like,

• Cardiovascular Center: Deals with heart rate, regulation of blood pressure.

• Rhythmicity Area: Deals with maintaining the rhythm of breathing.

• Vasomotor area: Maintaining blood pressure.

• Swallowing center.

• Sneezing Center.

• Cough Center.

• Hiccuping Center.

• Also contains four pairs of cranial nerves.

• Vestibulocochlear nerve. (VIII th Cranial Nerve)

• Glossopharyngeal nerve. (IX th Cranial Nerve).

• Vagus Nerve. (Xth Cranial Nerve).

• Accessory Nerve (XIth Cranial Nerve).

• Hypoglossal Nerve (XII th Cranial Nerve).

Commonly Asked Questions.

1. Write a short note on Brain Stem.

2. Give functions of Medulla oblongata.