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The cerebrum is the seat of intelligence, consciousness, and will power, and it controls reasoning, thinking, learning, and memorising.The pathway of a nerve impulse is: Stimulus → Sense Organ → Central Nervous System → Effector Organ → Response.The human nervous system is divided into the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).The nerve impulse passes across the synapse as a chemical message released from the terminal branches of the axon to the dendrites of the adjacent neuron.The Autonomic Nervous System controls the involuntary actions of visceral organs and the activities of smooth muscles in the alimentary canal and blood vessels.The two coordinating systems are the nervous system, which exercises neural control through electrochemical impulses, and the endocrine system, which exercises chemical control through hormones.The cerebellum coordinates voluntary movements of the body, controls voluntary muscles, and maintains body balance during physical activities.A nerve is a bundle of nerve fibres (axons) wrapped together in a protective sheath of connective tissue.The brain is enclosed and protected by a bony brain case known as the cranium or skull.The three main parts of a neuron are the cell body (cyton), the branching dendrons (with dendrites), and the long single extension called the axon.In the spinal cord, the gray matter is centrally located in an H-shape with white matter on the outside, which is the exact reverse of the brain’s arrangement where gray matter is on the outside and white matter is inside.A response is the reaction or behavior shown by a living organism as a result of an external or internal stimulus.The sympathetic nervous system has a stimulatory effect that prepares the body for violent action during adverse situations, whereas the parasympathetic nervous system has an inhibitory or calming effect that brings body activities back to normal.Interneurons in the brain or spinal cord interpret incoming sensory impulses and convert them into outgoing motor impulses.An injury to the medulla oblongata can cause death because it coordinates vital, life-sustaining involuntary activities such as heartbeat and breathing movements.The five sense organs are the eyes, ears, nose, tongue, and skin.Spinal nerves arise from the spinal cord, supply different parts of the body excluding the head, and are all of the mixed type.Sensory nerves bring impulses from sense organs to the brain or spinal cord, while motor nerves carry impulses from the brain or spinal cord to effector organs like muscles or glands.The folds (gyri) and grooves (sulci) increase the surface area of the gray matter, allowing it to accommodate a large number of neurons.The myelin sheath insulates the axon and speeds up the conduction of nerve impulses.
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Chapter: 07. Nervous System
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