ANATOMY AND PHYSIOLOGY OF

BRAINSTEM

BRAINSTEM Consists of: Midbrain Pons Medulla oblangata.

Superiorly continuous with forebrain. Inferiorly continuous with spinal cord. Posteriorly pons and medulla is

seperated by fourth ventricle.

Midbrain, pons and medulla connected to cerebellum by superior,middle and inferior cerebellar peduncle resp.

CRANIAL NERVES EMERGING FROM BRAINSTEM

3 and 4 – midbrain 5-pons 6,7,8-junction of pons and medulla. 9,10,11,12-medulla

The tissue in the floor of the aqueduct,between the 3rd and 4th ventricles of brain contains ARAS

(Ascending Reticular Activating System)

ARAS: extends throughout the brainstem from the spinal cord to the subthalamus.

Determines arousal

Damage to ARAS or areas of cerebral hemisphers- disturbance of normal conciousness.

If this area is dead- Person will be irreversibly unconcious and apnoeic.

MIDBRAIN

MIDBRAIN

CEREBRAL PEDUNCLE TECTUM

TEGMENTUM SUBSTANTIA NIGRA

CRUS CEREBRI

PONS lies between midbrain above and

medulla below in front of cerebellum. Include neural pathways that conduct

signals from brain down to cerebellum and medulla and that carry signals upto thalamus.

Contains nuclei that deals with respiration, swallowing, bladder control, hearing,equilibrium, eye movts. facial sensation, facial expressions etc.

MEDULLA OBLANGATA Located in the hind brain anterior to

cerebellum. Contains cardiac , respiratory, vomiting

and vasomotor centers and thus deals with breathing, heartrate, blood pressure.

FUNCTIONS OF BRAINSTEM

A properly functioning paramedian tegmental area of brainstem-precondition for full consiousness.Enables cerebral hemispheres to work in integrity.

Responsible for respiratory drive.

Maintenance of blood pressure.

All motor output travel through the brainstem.

Vision,smell,all the sensory traffic arrives through the brainstem.

Mediates cranial nerve reflexes.

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