IMP points of CNS physiology (MASS REFLEX in SPINAL animals th afferants swing from one reflex center to the other... matlab aik center activate ho to wo doosray ko b activate ker daita hai... for example noxious stimulus to the skin will activate autonomic center and the evacuation of bladder or recctum takes place... BP swings from very high to very low THALAMIC SYNDROME Also called Dejirine Roussy syndrome.. occurs after stroke(ischemic or hemmorhagic ) in thalamus. After stroke there is loss of sensation on the opposite side of the body with tningeling. Later after some weaks or months the numbness developes to intractable and sever pain which Is disproportionate to normal physiologic stimuli… (this condition is called ALLODYNIAor DYSASTHESIA) This syndrome e is most commonly preceded by numbness in the affected side. In these cases, numbness is replaced by burning and tingling sensations, widely varying in degree of severity. Allodynia means hypersensitivity to sensations associated with a stimulus that would normally not cause pain Dysasthesia is defined as pain due to thalamic lesioning • AXON HILLOCK: initial thickened segment of cell body from which the axon originates • First portion of axon is called initial segment • Myelination is produced by wrapping of SCHWANN cell around the axon. Unmylinated axons do have the Schwann cells that donot wrap around. • Nerve cells are secretory cell. They differ from other secretory cells in that the secretion are evacuated away from the cell bodies from the axonal terminals • Nerve conduction is an active self propagative process • Fibers most susceptible to hypoxia are B>A>C • Fibers most susceptible to pressure A>B>C • Fibers most susceptible to local anesthesia C >B>A • Glial cells are 10 to 50 times more than nurons • There are two types of astrocytes fibrous and protoplasmic a. Fibrous astrocytes: contain many intermediate filaments and r found in white matter b. Protoplasmic astrocytes: found in grey matter and have granular cytoplasm. • Refractory period is of nerve fibers… not of muscle fibers. this is why titanic contraction occurs in muscles due to repeated stimulation • There are two types of muscle fbers. Type I and II a. Type I: slow, oxdative,red. They have moderate calcium pumping capacity of sarcoplasmic reticulum. They have moderate diameter and glycolytic capacity but high oxidative capacity. b. Type II: fast, glycolytic white. They have high calcium pumping capacity of sarcoplasmic reticulum. large diameter and high glycolutic activity but low oxidtice capacity • Synaptic vesical fusion involves the interlocking of v-snare protein(synaptobrevin) n vesicle and t-snare protein(syntaxin) on cell membrane • Bell megendie law: states that in spinal cord the dorsal roots are sensory and ventral are motor • Organs situated outside the blood brain barrier(collenctively called CIRCUMVALLATE ORGANS) a. Post pituitary and adjacent area of median eminence of hypothalamus b. Area postrema c. Organum vasculosum of lamina terminalis(OVLT) d. Subfornical organs
Posted on: Sat, 08 Nov 2014 14:26:22 +0000