Communication and the nervous system
The nervous system is a network of nerve cells and fibres that controls voluntary and involuntary actions and transmits signals between body parts. It is the major controlling, regulatory, and communicating system in the body. It is the centre of all mental activity including thought, learning, and memory. Together with the endocrine system, the nervous system is responsible for regulating and maintaining homeostasis.
Nerve signals are electrical in nature and therefore the nervous system is fast. Nervous signals can move as fast as 150 meters per second.
The nervous system can be divided into two parts:
Central nervous system: Central nervous system (CNS) consists of the brain and the spinal cord. The brain serves as the centre of the nervous systemand is located inside the skull. The spinal cord extends from the base of the skull to the lumbar region. It is the most important structure between the body and the brain.The spinal cord is protected by the bony vertebral column.
Peripheral nervous system: The peripheral nervous system (PNS) consists of nerves and ganglia outside of the brain and spinal cord. It connects the central nervous system (CNS) to the limbs and organs and serves as a communication relay going back and forth between the brain and the extremities. Sensory or afferent nerves provide the brain with input from organs and tissues. Motor or efferent nerves transmit output from the brain to muscles and glands (effector organs).
The sensations of pain, touch, heat and cold are due to stimulation of specialized nerve ending receptors in the skin. Receptors of another kind are present in muscles and joints. These receptors detect changes in position and orientation of the body and help in maintaining posture and balance.
Receptors of yet another kind are situated in internal organs. Thesehelp inregulating vital functions of the body such as pumping of the heart, blood pressure and the rate of respiration. When these receptors are stimulated, impulses move to the brain through the sensory nerves. Nerve impulses are electrical in nature.
Nerve cells also have to communicate with one another as more than one nerve is involved in the process of initial stimulus and the resulting physiological reaction. Nerves communicate with one another by releasing neurotransmitters in the gaps between them. Neurotransmitters are the chemicals which allow the transmission of signals from one neuron to the next across synapses.
Sensory nerves carry impulses from different parts of the body to the brain. The brain processes the incoming information and analyses and collated it. It then sends impulses along the efferent nerves and regulates body functions. Body functions are generally regulated through negative feedback mechanisms.
Reflex actions: A reflex action is an involuntary and nearly instantaneous movement in response to a stimulus. Examples of reflex actions include withdrawal of a finger when it comes into contact with a hot surface and constriction of the pupil in response to bright light.
Next: The Endocrine System