central nervous system (mesencephalon), Slides of Psychology

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CENTRAL

NERVOUS

SYSTEM :

MESENCEPHALON/

MIDBRAIN

Presented by: Madiha

CENTRAL NERVOUS SYSTEM

MIDBRAIN/MESENCEPHALON The mesencephalon or midbrain is the portion of the brainstem that connects the hindbrain and the forebrain. Function: Functions of the mesencephalon include:  (^) Controlling Responses to Sight  (^) Eye Movement  (^) Pupil Dilation  (^) Regulate Muscle Movement  (^) Hearing

STRUCTURES

Cont. Superior colliculi: The superior collicului is involved in preliminary visual processing and control of eye movements. Inferior colliculi: The inferior collicului is involved in auditory processing. It receives input from various brain stem nucle

Tegmentum: The tegmentum (from Latin for "covering") is a general area within the brainstem. It forms the floor of the midbrain (mesencephalon) Functions: It is a motor center that relays inhibitory signals to the thalamus and basal nuclei preventing unwanted body movement.

Cont. The tegmentum area includes various different structures, such as  The "rostral (=frontal/cranial/oral) end of the reticular formation,  (^) Several nuclei controlling eye movements,  (^) The periaqueductal gray matter ,  (^) The red nucleus and  (^) The substantia nigra.

Reticular formation: The reticular formation is the large structure consisting of many nuclei.The reticular formation receives sensory information by the means of various pathways and projects axons to the cerebral cortex, thalamus, and the spinal cord. Functions :  (^) It plays a role in sleep and arousal, attention, muscle tone, movement, and various vital reflexes.

Substantia nigra  The substantia nigra has nerve connections with the frontal lobes and other areas of the brain involved in motor function.  Cells in the substantia nigra also produce dopamine , a chemical messenger that helps to coordinate muscle movement.

Disease:  (^) Neurodegeneration of nerve cells in the substantia nigra results in a drop off of dopamine production.  (^) Significant loss in dopamine levels (60-80%) may result in the development of Parkinson's disease.  (^) Parkinson's disease is a nervous system disorder that results in the loss of motor control and coordination. Symptoms include tremors, slowness of movement, muscle stiffness, and trouble with balance.