Analyzers. Role of cavity of mouth in the purposeful conduct

Physiology of hearing

1 – cochlear nerve; 2 – ventral cochlear nucleus; 3 – dorsal cochlear nucleus; 4 – olivar complexes; 5 – accessory nucleus; 6 – lateral lemniscus; 7 – lower hillocs of quadrigeminal body; 8 – medial genicular body; 9 – auditory cortex/

Semicircular canal function Ampula is enlargement at one end of semicircular canal. It has a small crest on top of which is a gelatinous mass known as cupula. Hair cells have two kinds of cilia – kinocilium and stereocilia. Kinocilium is large cilium located at one end of hair cell. Stereocilia are small. When stereocilia are bent towards kinocilium, hair cell is depolarized, i.e. stimulated.

When stereocilia are bend away from kinocilium, hair cell is hyperpolarized, i.e. inhibited. It occurs because acceleratory force acts to flow of fluid in semicircular canals during circular motion of the head or whole the body. Hair cells are located along crista ampularis and protect their cilia in cupula. Hair cells are secondary sensor cells, which synapse with neurons. Axons of these nerve cells compose vestibular nerve.

Nociceptive system

Also different changes in human organism followed by pain are observed: increase of muscle tone, accelerated heartbeat, increase of blood pressure, intensification of sweating, dilatation of pupils and elevation of glucose and cuprum level in plasma, activation of hemostasis. It considered to cause the majority of both visceral and biochemical reactions by excitation of sympathetic nervous system, which is presented by neurons of hypothalamus, hypophisis and cells in medullar substance of adrenal glands.

Afferent nociceptive impulses are collected into central nervous system by two kinds of nervous fibers: quick a-delta myelinated nerve fibers and C-fibers without myelin. The ascending fibers are included in spinothalamic tract, which passes through the spinal cord and reach medulla oblongata. Here there are second order sensory neurons of spinomesencephalic tract. Fibers of spinothalamic tract synapse with third-order neurons in the thalamus, which in turn project to the postcentral gyrus of the contralateral cerebral hemisphere.

Location of pathway terminations video