Quick Fact! The synapse is a point at which two neurons connect with each other. Allowing the transfer of impulse from one neuron to the other is the function of a synapse. The neurotransmitters which carry out the transfer of impulse are Noradrenaline and Acetylcholine.

Different Functions of the Nervous System

Central Nervous System

Functions of Brain The human brain is formed of the cerebrum, cerebellum, limbic system and brain stem. Cerebrum It is a part of the brain, sub-divided into four lobes namely frontal, parietal, temporal and occipital. • Frontal Lobe: The frontal lobe is associated with functions like reasoning, language, planning, etc. • Parietal Lobe: Recognition, orientation and perception of stimuli are the different functions of the parietal lobe. • Temporal Lobe: Speech, memory, auditory stimuli, etc. are the areas of functioning of the brain where the temporal lobe comes into play. • Occipital Lobe: This part of the brain performs the function of visual processing. Cerebellum This part of the brain is mainly involved in motor control. Language, concentration, pleasure responses, etc. are some of the other areas of functioning of the cerebellum. • Thalamus: This part of the cerebellum performs various motor and sensory functions. • Amygdala: The amygdala is mainly associated with emotional responses, memory and fear. • Hypothalamus: It is mainly responsible for regulating the body temperature. The hypothalamus is compared to a device called thermostat. Apart from controlling the body temperature, hypothalamus also plays an important role in controlling thirst, hunger and emotions. The suprachiasmatic nucleus (SCN) present in the hypothalamus controls the sleep-wake cycle of the body. • Hippocampus: The hippocampus enables us to learn new things. It is also associated with memorizing; in fact, the hippocampus helps in transforming short-term memories into permanent ones. Limbic System The limbic system controls our emotional responses and also helps in memorizing and learning. Brain Stem The brain stem performs different functions like sensing the vibrations, recognizing fine touch, pain, crude touch, itching, etc. This part of the brain is also associated with proper functioning of the respiratory and cardiac systems. Hind Brain Coordination of body movements and homeostasis are both carried out by the hind brain. The hind brain is formed of the medulla, cerebellum and pons. Basal Ganglia Body balance and movements are controlled by the basal ganglia. Medulla Oblangata This part of the brain controls breathing, blood pressure and heart rate.

Spinal Cord Functions The spinal cord plays an important role in connecting the peripheral nervous system with the brain. Here are the different functions performed by the spinal cord. • Movement of shoulders, elbow flexing and the movement of raising the arm are all carried out by the cervical spinal nerves 5 & 6. • The thoracic spinal nerve 1 and cervical spinal nerve 7 are responsible for the movements of wrist and other small muscles in the hand. • The movement of trunk and intercostal muscles lying above the waist is carried out by the thoracic spinal nerves 1-6. • The hamstring muscles of the knees can be flexed with the help of lumbar spinal nerves 4 & 5 and the spinal sacral nerves 1 & 2. • Adduction is a movement in which the muscle in question is brought closer to the middle sagittal plane of our body. The lumbar spinal nerves 2, 3 and 4 bring about the movement of thigh adduction. • Abduction is a movement in which a particular muscle or group of muscles move in the direction opposite to that in adduction. The lumbar spinal nerves 4 & 5 and sacral spinal nerve 1 allow the movement of thigh abduction. • The sacral spinal nerves 1 & 2 and lumbar spinal nerve 5 help in the plantar flexion movement of the foot and also in flexing the toes. • The movement of abdominal muscles is controlled by nerves starting from the thoracic spinal nerve 7 to lumbar spinal nerve 1. • Flexing of thighs is brought about by the lumbar spinal nerves 1, 2, 3 and 4. • The cranial spinal nerves 6 & 7 are responsible for the extension movement of wrists & elbows and also the pronation of wrists.

Reflex Arc It is a unit of the nervous system which responds to stimuli. The reflex arc can work in association with the spinal cord & brain and independently as well. Blinking of eyes is one of the examples of the functioning of reflex arc.

Peripheral Nervous System

The primary function of the peripheral nervous system (PNS) is to connect the limbs and other organs of the body with the central nervous system. The peripheral nervous system sends information processed in the central nervous system to the glands and muscles of the body. An appropriate response is then activated by these glands and muscles. Motor neurons send instructions to these muscles or glands. The PNS is sub-divided into somatic and autonomic nervous system. Somatic Nervous System This nervous system controls all the voluntary movements of our body by means of skeletal muscles; reflex arc is an exception to it. There are 3 kinds of somatic nerves described below. • Spinal Nerves: These nerves carry information obtained from the sensory organs to the spinal cord. • Association Nerves: They bring about the integration of sensory input and motor output. • Cranial Nerves: These are the nerves of the somatic system which transfer the information entering into and emerging from the brain stem. Autonomic Nervous System This nervous system is also known as visceral or involuntary nervous system. Digestion, perspiration, respiration, urination, pupillary dilation, etc. are the processes controlled by this nervous system. The autonomic nervous system responds involuntarily, i.e. it does not have to depend on the brain to activate the responses. The autonomic nervous system is sub-divided into sympathetic and parasympathetic nervous system. The former helps increase the activity of the autonomic nervous system while the latter acts in the reverse manner. Enteric Nervous System It is a sub-division of the autonomic nervous system. The enteric nervous system (ENS) controls the gastro-intestinal system. Although the ENS is a part of the autonomic nervous system, it is also capable of functioning independently. Ischemia can hamper the functioning of ENS. Ischemia is basically a problem in which blood supply to body tissues is restricted. This in turn deprives the tissues of oxygen and glucose. The end result is that cellular metabolism gets affected.

Functions of Receptors

Sensory receptors of the nervous system play an important role in extracting information from the environment and sending it back to the central nervous system. The sensory neurons carry information from sensory receptors to the central nervous system.

The central nervous system collects information from sensory receptors and processes it. The work of transferring and interpreting this information is done by the interneurons.

The receptors are classified into three types i.e. exteroceptors, interoceptors and proprioceptors. Here are the functions of these receptors. • Exteroceptors are used by the nervous system for detecting different types of smells, for listening, seeing, touching, tasting and feeling. • The signals associated with blood pressure, alimentary canal, bladder and osmotic pressure of the blood plasma are received by interoceptors. • The movement and position of body parts is tracked by proprioceptors.

The kind of stimulus received by receptors is one of the criteria used in classifying the receptors. Chemical receptors, mechanoreceptors and thermoreceptors are the different kinds of receptors classified on the basis of the given criteria. • The thermoreceptors which consist of warm receptors and cold receptors are excited by rising and falling temperatures respectively. • Mechanoreceptors carry information about mechanical stimulation to the central nervous system. • The chemical receptors are sub-divided into olfactory, gustatory and glucose detectors that are responsible for detecting smell, taste and glucose respectively. The glucose detectors are also responsible for providing information about the acid-base balance in the body.