Cerebellum And Brainstem

CEREBELLUM BRAINSTEM Cerebellum • The second largest brain structure, sits below the cerebrum. • Like the cerebrum, the cerebellum has an outer cortex of gray matter and two hemispheres. • It receives/relays information via the brain stem. • The cerebellum performs 3 major functions, all of which have to do with skeletal-muscle control: Functions: • • •

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Balance/ Equilibrium of the trunk Muscle tension, spinal nerve reflexes Fine motor control, eye movement. (Incoming information is transferred from the cerebral cortex via the pons. Outgoing information goes back to the cortex via the thalamus.) Cerebellar disease (abscess, hemorrhage, tumors, trauma) results in ataxia (muscle incordination), tremors, and disturbances of gait and equilibrium. This can also interfere with a person's ability to talk, eat, and perform other routine tasks.

i) ii)

Cerebellum coordinates voluntary movements so, that they are smooth balanced and accurate [function of neocerebellum] Controls tone, posture equilibrium [Archeo & paleocerebellum]

Diencephalon The diencephalon, located between the cerebrum and the midbrain, consists of several important structures, two of which are the: Thalamus: • •

Large, bilateral (right thalamus/left thalamus) egg-shaped mass of gray matter serving as the main synaptic relay center. Receives/relays sensory information to/from the cerebral cortex, including pain/pleasure centers.

Hypothalamus: • •

A collection of ganglia located below the thalamus and intimately associated with the pituitary gland. It has a variety of functions: ƒ senses changes in body temperature ƒ controls autonomic activities and hence regulates the sympathetic and parasympathetic nervous systems; ƒ links to the endocrine system/controls the pituitary gland ƒ regulates appetite ƒ functions as part of the arousal or alerting mechanism; and links the mind (emotions) to the body

Functions: • • • •

Voluntary movement/ motor integration Perception/ Sensory/mind-body integration Temperature Appetite

Brain Stem •

The medulla oblongata, pons, and midbrain (mesencephalon or cerebral peduncles) are often referred to collectively as the brain stem Control the most basic life functions.

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Of these three, the medulla is the most important. Diseases or injuries affecting medulla often prove fatal. All functions of the brain stem are associated with cranial nerves III-XII.

Functions: • • • •

Breathing/respiration (pons, medulla) Heart rate/ action (medulla) Blood pressure (vasoconstriction)/ blood vessel diameter (medulla) Reflex centers for pupillary reflexes and eye movements (midbrain, pons); and for vomiting, coughing, sneezing, swallowing, and hiccupping (medulla).