Reflex Arc When dust falls in our eyes, the eyelids close immediately not waiting for our willingness; on touching a hot pan, the hand is withdrawn rapidly. Do you know how this happens? The spinal cord remains as a connecting functional nervous structure in between the brain and effector organs. But sometimes when a very quick response is needed, the spinal cord can effect motor initiation as the brain and brings about an effect.
This rapid action by spinal cord is called reflex action. It is a fast, involuntary, unplanned sequence of actions that occurs in response to a particular stimulus. The nervous elements involved in carrying out the reflex action constitute a reflex arc or in other words the pathway followed by a nerve impulse to produce a reflex action is called a reflex arc (Figure . ).
Functional Components of a Reflex Arc Sensory Receptor - It is a sensory structure that responds to a specific stimulus. Sensory Neuron - This neuron takes the sensory impulse to the grey (afferent) matter of the spinal cord through the dorsal root of the spinal cord. Motor neuron Effector Muscle in arm Heat/Pain Receptors in skin Inter neuron Sensory neuron Spinal cord (CNS) Message to brain Figure . Reflex arc XI Std Biology-Zoology Chapter- two roots: ) a posterior dorsal root with a ganglion outside the spinal cord and ) an anterior ventral root with no external ganglion.
Somatic Neural System (SNS) The somatic neural system (SNS or voluntary neural system) is the part of the peripheral neural system associated with the voluntary control of body movements via skeletal muscles. The sensory and motor nerves that innervate striated muscles form the somatic neural system. Major functions of the somatic neural system include voluntary movement of the muscles and organs, and reflex movements. In adult, the total CSF volume is about ml and is replaced every hours.
About ml of CSF is formed daily. The choroid plexus helps cleanse the CSF by removing waste products. Autonomic Neural System The autonomic neural system is auto functioning and