Pyramidal and extrapyramidal tracts cerebellar ataxia - intension tremor http://www.youtube.com/watch?v=5eBwn22Bnio parkinsons - TRAP - subst.nigra http://www.youtube.com/watch?v=ECkPVTZlfP8 http://www.youtube.com/watch?v=-3l6diJ2oZ4&feature=related http://www.youtube.com/watch?v=pOhBtTYfSE4 athetosis - pallidum http://www.youtube.com/watch?v=J_wIDm1_ax4 Huntington disease - chorea - putamen http://www.youtube.com/watch?v=OveGZdZ_sVs

Pyramidal and extrapyramidal tracts

Paralyza – uplne Pareza – neuplne ochrnuti

The low decerebrate human is usually comatose and shows extensor spasticity as in the later stages of spinal transection, but of more severity. The low decerebrate animal cannot stand by itself despite the heightened extensor tone, partly because it lacks vestibular control to maintain upright posture. It cannot right itself if turned upside down; it cannot walk; and it cannot regulate its temperature or endocrine function. In decorticate rigidity, the hypertonicity is usually unidirectional, predominantly in the anti-gravity muscles. Thus, in the upper limbs, extension is resisted, and in the lower limbs, flexion is resisted. clasp(pen)-knife Decerebrate posturing: the patient’s back arches backwards, elbows and legs extended (indicative of a midbrain lesion). Decerebrate posturing is slightly worse and indicates significant brain stem damages. Decorticate posturing: the patient’s back arches backwards, elbows flexed and legs extended (suggesting a thalamic lesion).

Labyrinthe reflexes - decerebrate Neck reflexes Left-right Up-down Up – front flex, hind ext Down – front ext, hind flex Labyrinthe reflexes - decerebrate Dorsal position – extension Ventral – flexion Labyrinthe reflexes - decorticate Head righting

cerebellum three functional divisions, based on the principal sources of afferent fibres – mossy fiber pontine nuclei (motor cortex) spine vestibular nuclei In addition, all parts of the cerebellum receive fibres from the contralateral inferior olivary complex of nuclei in the medulla – climbing fibers, learning Superior olives – auditory system

cerebellum Spinal cord Motor cortex Vestibular ncl

The connections of the cerebellum are with the same side of the body and with the opposite cerebral hemisphere. 

Vestibulocerebellum = nodule and the two flocculi = Archicerebellum = (Fastigial nucleus) = from the vestibular ganglion and nuclei = balance = vertigo, nystagmus and an unsteady gait. Spinocerebellum = Paleocerebellum = Interposed nucleus = globose and emboliform nuclei = the vermis and adjacent cortex of the anterior lobe and of part of the posterior lobe = from spine = muscle tone = ataxia (alcohol) Pontocerebellum = Neocerebellum = Dentate nucleus = cerebellar cortex = from the pontine nuclei (from motor cortex) = voluntary = ipsilateral ataxia 2 3 1 hereditary spinocerebellar degenerations (such as Friedrich's ataxia) and degenerative disease due to too much ethanol imbibition

Basal ganglia (1) The basal ganglia are important to life nuclei in the brain interconnected with the cerebral cortex, thalamus and brainstem. Basal ganglia are associated with a variety of functions: motor control, cognition, emotions and learning. Parts: the striatum (putamen, caudate nucleus, nucleus accumbens) globus pallidus (internal and external segments) subthalamic nucleus (STN) substantia nigra (SN) - compacta (SNc), reticulata (SNr)

Red excitatory Blue inhibitory Magenta dopa SNr – subst. Nigra pars reticulata SNc – subst.nigra pars compacta Thalamus stimulates cortex, direct pathway stimulates thal (hyperkinetic), indirect inhibits (hypokinetic) In the direct pathway, cortical cells project excitatory inputs to the striatum, which in turn projects inhibitory neurons onto the cells of the SNr-GPi complex. The SNr-GPi complex projects directly onto the thalamus through the inhibitory ansa lenticularis pathway. The striatal inhibition of the SNr-GPi complex coupled with SNr-GPi inhibition of the thalamus therefore results in a net reduction of inhibition of the thalamus via the striatum. The thalamus projects excitatory glutamatergic neurons to the cortex itself. The direct pathway, therefore, results in the excitation of the motor cortex by the thalamus. Once stimulated, the cortex projects its own excitatory outputs to the brain stem and ultimately muscle fibers via the lateral corticospinal tract. The following diagram depicts the direct pathway: Cortex (stimulates) → Striatum (inhibits) → "SNr-GPi" complex (less inhibition of thalamus) → Thalamus (stimulates) → Cortex (stimulates) → Muscles, etc. → (hyperkinetic state) The indirect pathway also starts from neurons in the striatum. Once stimulated by the cortex, striatal neurons in the indirect pathway project inhibitory axons onto the cells of the globus pallidus externa (GPe), which tonically inhibits the subthalamic nucleus (STN). This inhibition (by the striatum) of the inhibitory projections of the GPe, results in the net reduction of inhibition of the STN. The STN, in turn, projects excitatory inputs to the SNr-GPi complex (which inhibits the thalamus). The end-result is inhibition of the thalamus and, therefore, decreased stimulation of the motor cortex by the thalamus and reduced muscle activity. The direct and indirect pathways are therefore antagonist in their functions. Following is a diagram of the indirect pathway: Cortex (stimulates) → Striatum (inhibits) → GPe (less inhibition of STN) → STN (stimulates) → "SNr-GPi" complex (inhibits) → Thalamus (is stimulating less) → Cortex (is stimulating less) →Muscles, etc. → (hypokinetic state) Main circuits of the basal ganglia. This diagram shows 2 coronal slices that have been superimposed to include the involved basal ganglia structures. The + and - signs at the point of the arrows indicate whether the pathway is excitatory or inhibitory, respectively, in effect. Green arrows refer to excitatory glutamatergic pathways, red arrows refer to inhibitory GABAergicpathways and turquoise arrows refer todopaminergic pathways that are excitatory on the direct pathway and inhibitory on the indirect pathway. The antagonistic functions of the direct and indirect pathways are modulated by the substantia nigra pars compacta (SNc), which produces dopamine. Special D1-receptors in the basal ganglia are excited by dopamine, favoring the direct pathway, whereas specialized D2-receptors in the basal ganglia are inhibited in presence of dopamine and favor the indirect pathway.[1] Through these mechanisms the body is able to maintain balance between excitation and inhibition of motion. Lack of balance in this delicate system leads to pathologies such as Parkinson's disease.

Parkinson's disease (2) Mnemonic device T - Tremor - Involuntary trembling of the limbs (resting tremor) R - Rigidity - Stiffness of the muscles A - Akinesia - Lack of movement or slowness in initiating and maintaining movement P - Postural instability - Characteristic bending or flexion of the body, associated with difficulty in balance and disturbances in gait

Parkinson's disease (2) Dopaminergic pathways of the human brain in normal condition (left) and Parkinson's disease (right). Red Arrows indicate suppression of the target, blue arrows indicate stimulation of target structure.

athetosis writhing movements pallidum hemibalism nc. subthalamicus subst. Nigra dopa tremor akinesia rigidity chorea putamen