The Midbrain (learning outcome 2)

mesencephalon

The mesencephalon is the midbrain, and it has two major components:

• Tectum (roof)

• Tegmentum (covering)

The Tectum

• Located in Dorsal portion of mesencephalon (at the back of mesencephalon)

• Two main structures:

  Superior colliculi =

  Inferior colliculi =

Superior colliculi =

• Part of visual system/visual reflexes

 

• receive input from the retina and are involved in visual reflexes as well as help orient us towards moving stimuli in our peripheral vision.

Inferior colliculi =

• Part of auditory system

 

Inferior, underneath superior

Tegmentum

• Beneath the Tectum

Contains several structures:

 

• Part of the Reticular Formation (large region of the brainstem, containing many nuclei), (sleep and arousal, attention, muscle tone, movement, reflexes)

receives sensory information by means of various pathways and projects axons to the cerebral cortex, thalamus, and spinal cord.

 

 

Periaqueductal Gray Matter

•  (Controls sequences of movements for species typical behaviour, like fighting , reproducing etc )

• Grey because of all the cell bodies

 

 

Red Nucleus and Substantia Nigra (motor system - Parkinson's disease= tremors , stiff muscle… )

 

Substatia Nigra

•  motor system

• - Parkinson's disease= tremors , stiff muscle…

 

🔴Red nucleus → sends movement signals down to spinal cord

 

Substantia nigra → works with basal ganglia to control/smooth movement

 

Red Nucleus

sends movement signals down to spinal cord

Substatia Nigra

• motor system

• - Parkinson's disease= tremors , stiff muscle…

 Substantia nigra → works with basal ganglia to control/smooth movement

 

 

👉 The red nucleus helps send motor commands to the spinal cord, while the substantia nigra regulates movement via the basal ganglia, and its degeneration causes Parkinson’s disease.

 

• Nuclei related to controlling eye movements