BASAL GANGLIA (NUCLEUS).pptx

BASAL GANGLIA (NUCLEUS) UNO, VICTOR KANU  INTRODUCTION Basal ganglia are subcortical masses of gray matter inside cerebral hemisphere. They are also known as basal nuclei Basal ganglia or basal nuclei are embedded in the central white core of cerebral hemisphere(telenc...

BASAL GANGLIA (NUCLEUS) UNO, VICTOR KANU  INTRODUCTION Basal ganglia are subcortical masses of gray matter inside cerebral hemisphere. They are also known as basal nuclei Basal ganglia or basal nuclei are embedded in the central white core of cerebral hemisphere(telencephalic in origin) at the level of diencephalon. Though basal ganglia are concerned with control of posture and voluntary movements, they do not have any direct input or output connections with spinal cord.  Component of the basal ganglia 1. Caudate nucleus 2. Lentiform nucleus 3. Amygdaloid nucleus (body) 4. Claustrum. Subthalamic nuclei, substantia nigra and red nucleus are correlated and co-listed with the components of basal ganglia clinically only because all these masses of gray matter are the centers for extrapyramidal system.  CORPUS STRIATUM  The corpus striatum is situated lateral to the thalamus and is almost completely divided by a band of nerve fibres, the internal capsule, into the caudate nucleus and the lentiform nucleus.  The term striatum is used here because of the striated appearance.  It is produced by the strands of gray matter passing through the internal capsule and connecting the caudate nucleus to the putamen of the lentiform nucleus. CORPUS STRIATUM The caudate nucleus and the lentiform nucleus together constitute the corpus striatum. This consists of two functionally distinct parts. The caudate nucleus and the putamen form one unit called the neostriatum, while the globus pallidus forms the other unit, the paleostriatum. Phylogenetically, amygdaloid nuclear complex and claustrum are considered as archistriatum.  The Caudate Nucleus  The caudate nucleus is a C-shaped mass of grey matter  It consists of a large head, a body and a thin tail.  The nucleus is intimately related to the lateral ventricle. The head of the nucleus bulges into the anterior horn of the ventricle and forms the greater part of its floor  The body of the nucleus lies in the floor of the central part and the tail in the roof of the inferior horn of the ventricle  The anterior part of the head of the caudate nucleus is fused, inferiorly, with the lentiform nucleus. This region of fusion is referred to as the fundus striati. CAUDATE NUCLEUS AND RELATED STRUCTURES  The fundus striati is continuous, inferiorly, with the anterior perforated substance  The anterior end of the tail of the caudate nucleus ends by becoming continuous with the lentiform nucleus.  It lies in close relation to the amygdaloid complex.  The body of the caudate nucleus is related medially to the thalamus, and laterally to the internal capsule which separates it from the lentiform nucleus  AMYGDALOID NUCLEUS The amygdaloid nucleus is situated in the temporal lobe close to the uncus. Through its connections, it can influence the body’s response to environmental changes. In the sense of fear, for example, it can change the heart rate, blood pressure, skin color, and rate of respiration.  CLAUSTRUM The claustrum is a thin sheet of gray matter that is separated from the lateral surface of the lentiform nucleus by the external capsule. Lateral to the claustrum is the subcortical white matter of the insula.  The function of the claustrum is unknown.  SUBSTANTIA NIGRA AND SUBTHALAMIC NUCLEI The substantia nigra of the midbrain and the subthalamic nuclei of the diencephalon are functionally closely related to the activities of the basal nuclei. The neurons of the substantia nigra are dopaminergic and inhibitory and have many connections to the corpus striatum. The neurons of the  CONNECTIONS OF CORPUS STRIATUM Afferent Connections The striatum (caudate and lentiform nuclei) receive afferents from the following: The entire cerebral cortex via corticostriate fibres. The intralaminar nuclei of the thalamus via thalamostriate fibres. The pars compacta of the substantia nigra via nigrostriate fibres. Noradrenergic fibres are received from the locus coeruleus. Serotoninergic fibres are received from the raphe nuclei (in the reticular formation of the midbrain).  CONNECTIONS OF CORPUS STRIATUM Efferent Connections The main output of the striatum is concentrated upon the pallidum and on the substantia nigra (pars reticularis). Fasciculus lenticularis arises from the inner segment of the globus pallidus and enters the subthalamic region. Ansa lenticularis arises from both the inner and outer segments of the globus pallidus.  CONNECTIONS OF THE GLOBUS PALLIDUS Afferent Fibres Striatopallidal Fibres Striatopallidal fibres pass from the caudate nucleus and putamen to the globus pallidus. Efferent Fibres Pallidofugal Fibres Pallidofugal fibres are complicated and can be divided into groups: 1) the ansa lenticularis, which pass to the thalamic nuclei; (2) the fasciculus lenticularis, which pass to the subthalamus; (3) the pallidotegmental fibers, which terminate in the caudal tegmentum of the midbrain; and (4) the pallidosubthalamic fibers, which pass to the subthalamic nuclei.  PRINCIPLES OF FUNCTION OF THE BASAL GANGLIA The basal nuclei are joined together and connected with many different regions of the nervous system by a very complex number of neurons. Basically, the corpus striatum receives afferent information from most of the cerebral cortex, the thalamus, the subthalamus, and the brainstem, including the substantia nigra. The information is integrated within the corpus striatum, and the outflow passes back to the areas listed above The outflow from the basal nuclei is channeled through the globus pallidus, which then influences the activities of the motor areas of the cerebral cortex or other motor centers in the brainstem Thus, the basal nuclei control muscular movements by influencing the cerebral cortex and have no direct control through descending pathways to the brainstem and spinal cord FUNCTIONAL CONNECTIONS OF THE BASAL NUCLEI  FUNCTIONS OF THE BASAL NUCLEI The basal nuclei control muscular movements by influencing the cerebral cortex. The basal nuclei assist in the regulation of voluntary movement and the learning of motor skills. Writing the letters of the alphabet, drawing a diagram, passing a football, using the vocal cords in talking and singing, and using the eye muscles when looking at an object are a few examples where the basal nuclei influence the skilled cortical motor activities. The basal nuclei not only influence the execution of a particular movement, but also help prepare for the movements. BLOOD SUPPLY OF THE BASAL NUCLEI  The basal nuclei are supplied by: Lenticulostriate branches of middle and anterior cerebral arteries. Anterior choroidal branch of internal carotid artery.  Disorders of movement in Basal ganglia disease 1. Hyperkinetic: Excessive abnormal movement i.e. chorea, athetosis, ballism 2. Hypokinetic: Slow movements i.e. akinesia, bradykinesia.  HYPERKINESIA Chorea: Rapid involuntary “ dancing” movements Athetosis: Continuous , slow writhing movements. Ballism (Hemiballismus): Involuntary flailing , intense and violent movements  HYPOKINESIA Akinesia: Difficulty in initiating movement Braykinesia :Slowness of movement.  Parkinson Disease  Parkinson disease is a progressive disease of unknown cause that commences between the ages of 45 and 55 years.  It is associated with neuronal degeneration in the substantia nigra and, to a lesser extent, in the globus pallidus, putamen, and caudate Parkinson’s disease. Section through the midbrain demonstrating nucleus. depigmentation in the substantia nigra due to loss of melanin (arrow).  SIGNS AND SYMPTOMS Parkinson Disease Patients have the following characteristic signs and symptoms: 1. Tremor 2. Rigidity 3. Bradykinesis 4. Postural disturbances 5. There is no loss of muscle power and no loss of sensibility. Since the corticospinal tracts are normal, the superficial abdominal reflexes are normal, and there is no Babinski response.