Diencephalon

It consists of:

• thalamus;

• hypothalamus;

• epithalamus.

Only thalamus deals with motor reactions. Other parts activity are linked with vegetative and behavioural reactions.

Thalamus – is a structure in which processing and integration of practically all signals coming into brain cortex are occurred. Such signals are originated from spine, midbrain, cerebellum, basal gangliums. There are more than 120 nuclei in it, forming complexes that are divided into: anterior, posterior, medial and lateral. Thalamus complicated structure, existance of interconnected specific, non-specific and associative nuclei allow to organize such motor acts as sucking, mastication, swallowing, loughing. Motor acts are integrated in thalamus with vegetative reflexes providing these movements.

Brain reticular formation

It is represented by neurons net with multiple connections practically with all brain parts. Its participation in movement: from it to spinal and cranio-cerebral nuclei motoneurons sygnals come which organize head, trunk status and pose. Reticular ways releasing spine motor systems activity are originated from all reticular formation parts. Ways coming from pons inhibit spine motoneurons activity (the latest innervate flexors and activate extensors motoneurons). Ways coming from medulla oblongata cause opposite effect. Reticular formation irritation leads to tremor, muscular hypertony or spinal reflexes inhibiting. It occurs when pose is necessary to be regulated and one movement must be changed by other one.

Cerebellum

Cerebellum sends efferent sygnals to spine and regulates muscular contractions force, permits durable tetanic muscular contraction, saving optimal muscular tone under rest and movement states, to measure arbitrary movements to perform fast transition from flexion to extension and on the contrary. It provides different muscles contractions synergy at complicated movements for example, in course of walking.

When cerebellum doesn’t regulate movements human being has different motor disorders.

• Astheny – muscular force contraction decreasing; fast muscles fatigue.

• Asthasy – loosing the ability to durable muscular contraction that makes standing, sitting difficult and even impossible.

• Athaxy – movements co-ordination disorders.

• Asynergy – co-operative movements disturbances (human being can’t sit from laying state without hands help).

• Dystony – muscular tone unarbitrary increasing or decreasing.

• Thremor – fingers, hand, head trembling under rest; this thremor is enforced during movement.

• Dysmetry – movements equality disorders expressed either in excessive or in insufficient movement.

• Dysarthry – speech disorder.

• Drunk walking – person is walking having arranged his leg widely, having shaked from one side to another.

• Adiadochokinesis – person can’t rotate fast his hands up and down.

• Writing disorders – megalography – very big letters.

At cerebellum injury medulla oblongata vestibular nuclei and reticular formation neurons are activated which stimulate spine motoneurons. Simultaneousely pyramidal neurons activity is decreased and thus their inhibitory influence to those spinal motoneurons is reduced. Finally, motoneurons cause muscular hypertonus having received stimulating sygnals from medulla oblongata while absence inhibitory sygnals from cortex.