Category Archives: Central Nervous System PHYSIOLOGY

THALAMUS

Thalamus in Greek means “Ante chamber” or “Inner chamber“. It was discovered way back in the 2nd Century AD, when Galen traced the optic-nerve fibers to an oval mass closely associated with the ventricles. It is considered as head ganglion of all sensory systems.It integrates & processes all sensory impulses. All sensory pathways (EXCEPTION – OlfactoryContinue reading “THALAMUS”

HYPOTHALAMUS

A diencephalic (bilateral) structure. It represents less than 1 % of the brain mass. Small in size but has two way communicating system with all levels of limbic system. Subdivision & nuclei of Hypothalamus CONNECTIONS Hypothalamus is connected to several areas of brain to serve several functions autonomic , visceral etc. Apart from neural connectionContinue reading “HYPOTHALAMUS”

LIMBIC SYSTEM

LIMBIC –> Border/ Girdle. derived from limbus meaning RING. Previously called Rhinencephalon due to its relation to olfaction. Apart from Olfaction, it plays important roles in behaviour, emotion,motivational drives, memory as well as regulation of visceral functions –> Hence referred as –> VISCERAL BRAIN Limbic system is not a separate structure. It refers to aContinue reading “LIMBIC SYSTEM”

DESCENDING MOTOR PATHWAYS / DESCENDING TRACTS

Connect the neurons in, cerebral cortex , Midbrain, Pons, Medulla & Cerebellum with motor neurons (LMN) at various levels. Axons of UMN synapse on spinal : Alpha motor neuron,gamma motor neuron, Spinal interneuron, Sensory afferents TRADITIONALLY TRACTS ARE CLASSIFIED AS: RECENT CLASSIFICATION : Hans Kupyres – 1981,85. CORTICOSPINAL TRACT / PYRAMIDAL TRACT Most important andContinue reading “DESCENDING MOTOR PATHWAYS / DESCENDING TRACTS”

MOTOR CORTEX

PRIMARY MOTOR CORTEX Largest of all motor areas Lies in the precentral Gyrus –> Area 4 of Brodmann extending from medial surface to lateral sulcus. low electrical –> Specific & repeatable movement. HOMONCULUS (little man) –> Drawn by Penfield & Rasmussen 1950. Body is upside down legs most medially pharynx lateral most. SIZE OF REPRESENTATIONContinue reading “MOTOR CORTEX”

ORGANISATION OF MOTOR SYSTEM

NEURAL CONTROL OF MOVEMENT Movement is crucial to all organisms. its performed in higher animals by contraction of & relaxation of the muscles. Motor system exists in Brain to translate out thought, sensation, emotion & feeling into MOVEMENT. SENSORY SYSTEM –> transforms physical energy into neural signals MOTOR SYSTEM –> NEURAL signal is converted toContinue reading “ORGANISATION OF MOTOR SYSTEM”

Basal Ganglia

FUNCTIONS OF BASAL GANGLIA PLANNING & PROGRAMMING –> Discharge starts even before commencement of movement. EXECUTION OF MOTOR TIMING, INTENSITY & SEQUENCES –> Basal Ganglia gets input from cortex projects back to cortex (Prefrontal, premotor, Supplementary motor area). These Corticospinal & Corticobulbar neurons influence Proximal & Distal limb. MUSCLE TONE –> Inhibits tone, decreases stretch reflexContinue reading “Basal Ganglia”