Task 3. Investigate static and stato-kinetic reflexes in guinea pig.



To put guinea pig to the table, to pay the attention to animal’s pose, head location, moving reactions. To turn over the animal on his back and to lie with his abdomen up. To pay attention to movement character, their order and definite animal pose.

To put guinea pig on board, to raise and to rock the animal, in turn raising board anterior or posterior end. Pay attention to fore-limbs (anterior extremities) status and movement, head status. To put down or to raise the board very fast, while observing anterior extremities status at the beginning and at the end of the movement, animal head status.

To put giunea pig on rotating chair, to perform rotations in horizontal plane to the right or to the left, to pay the attention to animal pose shift in course of movement, to head movement in course of rotation. To indicate, what happens at the rotation beginning and at rotation stoppage.

 

5. Literature recommended:

1. Lecture course.

2. Mistchenko V.P., Tkachenko E.V. Methodical instructions on Normal Physiology on practical classes for dental and medical students.-Poltava, 2005.-P. 49-50.

3. Ganong W.F. Review of Medical Physiology.-21st ed.-2003.-Section II.

4. Guyton A.C. Textbook of Medical Physiology.-NY, 1992.-P. 636-638.

 

Materials for self- control:

A. Control questions:

1. Midbrain reflectory function.

2. Vestibular apparatus, irritation conditions for otholitic and ampullar vestibulary receptors.

3. Decebrational rigidity.

4. Statho- and statho-kinetic reflexes.

5. Midbrain role in oral cavity functions regulation.

6. Midbrain vegetative reflexes.

7. Midbrain ascendant and descendant conductory ways.

 


LESSON 15
Cerebellum, diencephalon, subcortex nuclei physiology, their role in organism motor functions regulation

The topic studied actuality.

Dentists can get in touch with such cerebellum pathological states: hyperkineses – myoclonuses (fast fascillations of separate muscular groups) of swallowing musculature, soft palate and pharynx wall; speech disorder - scanding- accents are not on necessary syllable but is divided with equal intervals; at circulation disorder in cerebellum (at arteria closure – Vallenberg-Zaharchenko syndrome) – sensitivity is disorded on face, soft palate and vocal cord are paralyzed.

Structural organization of a cerebellum.

It is located above medulla oblongata and pons cerebri. It consists of two hemispheres, vermis and three pedunculi pairs (nervous fibers).

The hemispheres are divided into anterior and posterior lobes. They consist of cortex of a cerebellum and nuclei (nervous cells).

Upper peduncles connect it with midbrain, medium peduncles – with the pons, inferior peduncles – with medulla oblongata.

Neuronic structure of cerebellar cortex 

The cortex consists of three layers:

· 1-st – molecular: dendrites of Purkinje cells, piriform cells (Purkinje's cells), bodies of basket cells, stellate cells.

· 2-nd – ganglionic: bodies of piriform cells;

· 3-rd – granular: bodies of association [intercalary, internuncial] neurons.

Two types of afferent fibers (climbing and mossy) come to cortex.

There are nuclei in white matter of hemisphere and vermis of cerebellum: fastigial (3), globosus (1), emboliformis (4), dentatus nuclei (2).

Pedunculi of cerebellum are conductive tracts.

Upper (1) are directed to corpora quadrigemina of midbrain;

medium (3) bind cerebellum to pons;

inferior (7) bind with medulla oblongata.

Somatotopic projection in a cortex of vermis and hemispheres of a cerebellum

Collector of afferent impulses in cerebellum is fastigial nucleus, which sends them to piriform neurones (Purkin’e cells) of cerebellar cortex according to a somatic projection. Upper extremities are represented in anterior departments of hemispheres, inferior ones are represented in back departments, head and neck are represented in anterior parts of vermis cortex and trunk is represented in posterior part. The proximal parts of extremities are projected more medially, distal parts – more laterally, hemispheres are responsible for coordination of locomotions of extremities, vermis – of trunk.

Functions of cerebellum

1. Center of movements coordination.

2. Control of posture and muscle tone.

3. Senso-motor coordination of posture and purposive movements.

4. Participation in arbitrary locomotions and coordination of fast (phasic) and slow (tonic) components of motor act.

5. Coordination of fast purposive movements.


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