The nervous system is the elements within an animal or organism that is concerned with the reception of stimuli, transmission of nerve impulses or the activation of muscle mechanisms. The reception of stimuli is the function of special sensory cells.

   Every Nerve Cell has a central portion that contains the Nucleus, which is known as the cell body. Inside the nerve cell are axons and dendrites. Dendrites are short extensions of the cell body which is involved in the reception of the stimuli. Dendrites receive impulses from other neurons. A neuron is a long cell that has a thick area containing the nucleus.  Neurons can be capable of slow and generalized activity or highly efficient and rapidly conducting units. The axon is usually a single elongated extension that is really important when it comes to the transmission of nerve impulses from one cell to another. Those impulses travel electrically along the cell membrane to the end of the axon.

   Some animals that have a Vertebrate have a bony spine and skull where the central part of the nervous system is housed. The peripheral part extends throughout the remainder of the body. The brain and spinal cord are continuous through the opening in the base of the skull. Both are in contact with the other parts of the body through nerves. 

   The part of the nervous system that is found in the skull is called the Brain. The brain is approximately three pounds and made up of pinkish-grey jellylike tissue which is made up of one hundred billion nerve cells or neurons. The brain controls movement, sleep, hunger and thirst. The brain also controls emotions like love, hate, fear, anger and sadness. The brain receives and interprets other signals that are sent from other parts of the body and the external environment.

   The part of the nervous system found in the spine is called the Spinal Cord. The spinal cord sends transmissions and descending impulses from the brain to the cord.  The spinal cord in an adult extends to the skull down to the rear, below this starts to taper off as a narrow thread with nervous matter. The cord is encased in a triple sheath of membranes. The spinal cord also relays impulses to muscles, blood vessels and glands.

   Muscle response can also be called Reflex. In it’s simplest form of the stimulation of a nerve through a sense organ or a receptor which is then followed by the transmission of stimulus. Usually when reflex happens the stimulus passes through one or two intermediate cells which then modifies the action and sometimes it involves the action of the whole organism. Impulses can be carried from processes of cells to motor endings within the muscles.