Which of the following is true regarding pyramidal tract fibres?
Ans:b (Initiate voluntary movement) Ref: Ganong 22nd ed/p.203Pyramidal tract is involved in voluntary contraction of muscle. Fine motor coordination is done by cerebellum.It is the basal ganglia that help to plan (programming) and coordinate complex voluntary movements. Pyrami- dal tract does not contain sensory fibres.The probable sequence of events in motor activity:-First there develops a will, but the area of brain where the will develops is uncertain.Programming- From the area where the will develops, impulses are sent to the motor cortex. These impulses are first programmed and the pro-grammed impulses now determine which area of motor cortex is to be stimulated. This programming is done in basal ganglia.-Activation of pyramidal system-The motor cortex is now fired, so that pyramidal tract fibres now become fired - Firing of LMN - contraction of skeletal muscles- action.* The extrapyramidal system is also concomitantly fired. This causes postural adjustment necessary for voluntary act.* When the voluntary motor activity is performed, the cerebellum receives input from both pyramidal and extrapyramidal system and controls both pyramidal and extrapyramidal activity.* Motor cortex fires --Impulses descends through pyramidal system. On their way they inform the cer- ebellum through corticopontocerebellar and olivocerebellar paths. * The cerebellum also receives feed back from various sources like muscles, joints and visual cortex, regarding whether the goal had been achieved or if there is any readjustment needed.* If any readjustment is needed the impulses are sent to area 4 or motor cortex through dentothalamo cortical and dentorubrothalamocortical paths.* Through them activities of area 4 can be adjusted. These readjustments make the voluntary actions automatic, highly precise and smooth.Corticospinal system or the pyramidal system is concerned with the voluntary control of muscular (motor) activity. Functions of brainCommands for voluntary movement originates- Cortical association areaPlanning & programming movement- Basal gangliaMotor commands from motor cortex to muscle is through- Corticospinal and- Corticobulbar tractsCoordination of movements- CerebellumSeat of emotions- Limbic system/ amygdalaRelay station for sensory or motor activity- ThalamusMemory- HippocampusPhysiology of memory storageShort term memory - immediate - prefrontal cortex- (no processing needed)Intermediate memory - recent - processing in hippocampus- neocortex (storage)Long tenn memory - remote - processing in hippocampus- neocortex (storage)
Fine control of motor movement
Initiate voluntary movement
Contain sensory fibres
Basal ganglia forms a part of it
Nervous System