A Study Of Anatomy And Psychology Essay

The procedure in provokeing the leg to backing a stair is a interwoven one which brings a huge step of technology inter-transfer between the brain and the eventual(prenominal) skeletal go across. There is initiation of the exertion at the brain which is transmitted via narrow white fiber tracts to the hip flexors via the medium spinal anaesthesia cord, involving a very building hard mechanism at the carrellular directThe initiation of the process is at the tug cortex (Ms I) of the brain. The primary beat back playing field is located at the precentral gyrus of the frontlet lobe. The bowl controlling the motion of the dismay branchs lies towards the superior surface of the brain. Wi little(a) this area lies the cell body of the primary neuron. These neurons are cognize as upper motor neurons (UMN). These UMNs receive modulating urge from the inputs from the cerebellum and the basal ganglia via the extrapyramidal pathways. These tracts strengthen the gross move ment initiated at the head-on cortex. In turn these areas are spiel by afferent signals from ascending spino cerebellar, and spino-thalamic pathways.The complex the signal initiated at the nucleus of the cell body is transmitted electronic totallyy via the axon of the myelinated neuron via the mode of salutatory conduction. The myelin sheath which surrounds the axon of piths that involve fast transport, breaks at intermediate regions known as Nodes of Ranvier. The electrical caprice moves in a jumping manner at these nodes impertinence transmission as a neural impulse, generated by the formation of a nerve execution potential. Like all excitable tissue, nerves maintain a resting tissue layer potential that is the difference of emf across the membrane of the neuron. In neurons this quantify is 70 mV.This voltage difference is maintained by the Na/K kernel on the membranes. This impulse generated at the axon hillock is transmitted via the depolarizing phase which allows so dium ions ingress into cells via initiation of the Na channels. This approach of Na in one service allows activation of other Na channels, cause depolarization of the adjacent region of the neuron. by and by repolarization occurs via the opening of K channels, which restores the membrane potential. therefrom this process continues which allows the transmission of impulse. Many such nerves together descend as the descending cortico spinal tract in the pyramidal system, which touch offs through the midbrain into the spinal cord, decussating at the level of midbrain( 90% of the parts decussating and forming the lateral pass spinothalamic tract) and again at the level of spinal cord ( the other 10%, forming the earlier spinothalamic tract) . It is the former which is responsible for the lower limb movements. The cortico-spinal tract travels in the anterior detusk cell of the spinal cord manger the lumbar level where they synapse with the spinal ventral root neuron (lower mot or neuron). A single post-synaptic neuron receives signals from many neurons.At the axon terminal, the propagation of impulses leads to release of neurotransmitters, which are stored in specialized vesicles. The released Ach diffuses into the synaptic offer and binds with receptors on the post synaptic membrane to produce excitatory post synaptic potentials. This leads to generation and propagation of impulse in nerves which are destined to furnish the neuro-muscular junction. At the neuro-muscular junction, Ach is released, which diffuses into the synovial cleft and binds to receptors in the motor end plate, and triggers a muscle action potential. The released Ach is destroyed by the acetylcholinestrase.At the level of the sarcolemma of the muscles, the muscle AP travels along T-tubules, opening Ca release channels in the sarcoplasmic reticulum. Ca binds to troponin-tropomysin complex, which releases the myosin heads, these then bind to the actin thin filaments, and draws them cl oser to the M line. Meanwhile saving the Z disc closer. This leads to muscle fibre densification. This is a self propagating sequence finally atomic number 82 to the contraction of ilio-psoas muscle, which causes the flexion of thigh on the pelvis. Each nerve fibre innervates many musle fibres ( about 150). This is the motor unit.The great the number of motor units recruited by the nerve action potential, the greater the force of contraction of the muscles. In the spinal cord, nerve impulse travels along the lumbar plexus (L1-L5) to innervate the iliopsoas ( hip flexion- ilio-inguinal nerve), biceps femors, semitendinosus and semimembranosus ( knee flexion sciatic nerve), ankle flexors ( EHl, EDL, TA tibial nerve), leading to the person climbing the step. This excitatory impulse is also associated with the production of inhibitory action potential ( hyperpolarizing impulse) in the antagonists (eg the glutei, which must disentangle to allow flexors to act.In the event of su mmit of the upper limb above the head, to lift a book, the impulse travels along the cortico spinal tract till the level of the cervical cord to synapse with the lower motor neurons of the brachial plexus ( C3-T1). From here the nerve impulses travel to shoulder elevators ( supraspinatus, deltoid, trapezius, and latissimus dorsi)- posterior cord ), cubitus extensor muscle ( triceps and anconeus radial nerve) wrist extensor ( ECRL, ECRB radial nerve), finger flexors ( FDS, FDP median value nerve and the ulnar nerve) and the intrinsics ulnar nerve and the median nerve)