Nervous and Hormonal Coordination Systems in the Body

Coordination Systems: Nervous and Hormonal

When a body is small (one cell or more), its component cells are capable of capturing different environmental stimuli and responding to them. When the body is complex and has organs and organ systems, they must act together to perform their roles effectively. The nervous and hormonal systems carry out the coordination function.

Nervous System

Structure of the Neuron: Neurons are highly specialized cells that make up the different tissues and organs of the nervous system. These cells have different morphologies but share common features:

• Soma: Contains the nucleus and cytoplasm with all organelles.
• Axon: A long, unbranched extension with a widened end called the synaptic button.
• Dendrites: Highly branched, short extensions that project from the soma.

Axons are surrounded by a lipid layer called myelin. An axon and its myelin sheath form a nerve fiber. Many nerve fibers are grouped together to form nerves. A simile would be an electric cable, where the copper filaments represent nerve fibers, grouped and surrounded by a plastic cover, representing the nerve. Neurons do not regenerate.

Neuron Function

Neurons transmit information to one another in the form of nerve impulses, which are electrical in nature. The nerve impulse travels down the axon of one neuron to the synaptic button. From there, it jumps to the dendrites of another neuron. Dendrites pass the impulse to the soma, and then to the axon, continuing to another neuron. This leap of nerve impulses from one neuron to another is called a synapse.

At the synapse, the nerve impulse causes the synaptic button to release neurotransmitters. These neurotransmitters reach the dendrites of another neuron, triggering a new nerve impulse. Millions of new synapses are created throughout life.

Central Nervous System

The central nervous system consists of the brain and spinal cord.

• The Brain: A skull-shaped organ that fits perfectly within the skull, weighing around 1 to 1.5 kilograms.
• Cerebrum: A major part of the brain, divided into two hemispheres (right and left). It presents outwards-facing folds called gyri and inward folds called sulci. The brain is not solid; it has several cavities filled with cerebrospinal fluid. The brain is formed externally by gray matter and internally by white matter. Its function is to process and coordinate information from the external environment, generate responses, and store information (memory).
• Cerebellum: Located below the cerebrum, also known as the "tree of life." It coordinates muscle movement and balance.
• Medulla Oblongata: Located below the cerebellum. It controls involuntary functions like breathing, blood flow, and bowel movements.
• Spinal Cord: A tube that begins below the medulla oblongata. This tube is hollow, and its interior contains spinal fluid. Within the medulla are the cell bodies of neurons (gray matter), and on the outside are the nerve fibers that enter or leave it (white matter). Thirty-one pairs of spinal nerves exit the spinal cord. Its function is to carry messages to the brain and transmit orders to various organs.