Have you ever got your hand or any parts of your body touched a hot object? Of course, if that happens you will immediately withdraw from it. A living organism is able to react to the changes in the environment or surroundings. Any change in the environment that cause an organism to react is called stimulus, and an organism’s reaction to a stimulus is called response.
Now, this is the work of one of the most important systems in our body, The Nervous System. Nervous system is an organ system containing a network of specialized cells called neurons. The Nervous system is also divided into two parts, the central nervous system (CNS) that contains of the brain, spinal cord, and retina. The second one is the peripheral nervous system that consists of the cranial nerve from the brain and the spinal nerve from the spinal cord and sense organ.
The sense organs that receive stimuli, is called receptors. They inform the Central Nervous System of any change our surroundings, by producing electrical messages called nerve impulses. A nerve impulse is transmitted within a fraction of a second. In response to this stimulus, the CNS will send nerve impulses to the muscle, thus resulting an effect of action. The muscles are then called effectors.
The nervous system is made out of nervous tissues. There are the Sensory neuron, Motor neuron, and the Relay neuron. The sensory neuron is for sending the nerve impulses that is sent from the receptor to the brain or to the spinal cord. Motor neuron transmits nerve impulses from the central nervous system to the effectors or the effector. Relay neuron is for transmitting nerve impulses from the sensory neuron to the motor neuron.
Motor neuron are made out of Dendron, cell body, axon, Myelin Sheath, Neurilemma, Node of Ranvier, Dendrites of an axon, and Motor end Plate. Each and every single one of them has their own function. The sensory neuron has a circular cell body; it has only one long Dendron and a short axon.
Next is the Synapse and Motor end Plate. What are they you may ask? Well, Synapse is a junction between two neurons or a junction between a neuron and an effector such as a gland or muscle. Motor end Plate formed where the end branch of an axon encounter the muscle fibers. Nerve impulses are transmitted across the Motor end plate by chemicals that stimulate the muscle.
There are two regions in the brain and spinal cord. The Grey matter, that is located at the central part of the spinal cord and in the inner part of the brain, and The White matter, which is located in the outer part of the spinal cord and in the central part of the brain.
There’s also another thing that you should know about the Nervous system, and that is the Voluntary action and the reflex action. Action that is controlled by our will is called voluntary action; this voluntary action may and may not involve a receptor or sensory neuron. While Reflex action is an immediate response to a specific stimulus without conscious control. A reflex action is an involuntary action, which means that our body moves without us (or our brain) commanding them to, a movement that is not based on our will.
There are two types of reflex action, The spinal and cranial nerve reflexes. All this action occurs without any conscious effort, in fact sometimes it might be difficult to prevent them to react. The spinal reflex are controlled by the spinal cord, and cranial reflex are controlled by the brain (unconsciously) and usually occurs in the head region.
The nervous pathway is called the reflex arc. The reflex arc are consist of a receptor or sense organ, a sensory neuron, a relay neuron, a motor neuron, and an effector.
And that’s it about Nervous system, and to summarize all this you can watch this video right here: http://www.youtube.com/watch?v=yeGyUXywnFI
~By: Nasya Joan