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The midbrain or mesencephalon is the uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons. [2] It consists of the cerebral peduncles , tegmentum , and tectum . It is functionally associated with vision, hearing, motor control, sleep and wakefulness, arousal ( alertness ), and temperature regulation.
Anatomically, as the name suggests, the MLR is located in the mesencephalon (or midbrain), ventral to the inferior colliculus and near the cuneiform nucleus. [6] Although identifying the exact anatomical substrates of the MLR has been subject to considerable debate, the pedunculopontine nucleus (PPN), cuneiform nucleus, and midbrain ...
2 Midbrain (mesencephalon) 3 Forebrain (prosencephalon) Toggle Forebrain (prosencephalon) subsection. 3.1 Diencephalon. ... "Brain Anatomy and How the Brain Works".
It forms the floor of the midbrain (mesencephalon) whereas the tectum forms the ceiling. [2] It is a multisynaptic network of neurons that is involved in many subconscious homeostatic and reflexive pathways. It is a motor center that relays inhibitory signals to the thalamus and basal nuclei preventing unwanted body movement. [citation needed]
Caudally, it is continuous with the fourth ventricle at the junction of the mesencephalon and pons. [3] The midbrain tegmentum is situated anteriorly to the cerebral aqueduct. [3] The portion of the tegmentum posterior to the aqueduct is the tectum. [1] The superior and inferior colliculi that make up the corpora quadrigemina are situated ...
Unlike many nuclei within the central nervous system (CNS), the mesencephalic nucleus contains no chemical synapses, neurons instead being electrically coupled. [4] Neurons of this nucleus are pseudounipolar, receiving proprioceptive afferent information from the mandible and sending efferent projections to the trigeminal motor nucleus to mediate the monosynaptic jaw jerk reflex.
The mesencephalon is the second of the three primary vesicles, and does not further differentiate into a secondary brain vesicle. This will become the midbrain. The third primary vesicle, the rhombencephalon (hindbrain) will further differentiate into two secondary vesicles, the metencephalon and the myelencephalon.
The cerebral peduncles (In Latin, ped-means 'foot'.) are the two stalks that attach the cerebrum to the brainstem. [1] They are structures at the front of the midbrain which arise from the ventral pons and contain the large ascending (sensory) and descending (motor) tracts that run to and from the cerebrum from the pons.