Matt Patterson - Oil on Canvas
The Nervous System
The organs of the nervous system as a whole include the brain and spinal cord, the nerves of the body, the specialized sense organs like the eyes and ears, and the microscopic sense organs found in the skin. The brain and spinal cord are together called the central nervous system or CNS, and the nerves of the body are the peripheral nervous system or PNS. A subdivision of the PNS is the autonomic nervous system or ANS, which consists of structures that regulate the body’s automatic or involuntary functions (like heart rate, contractions of the stomach and intestines, and secretion of chemical compounds by glands).
The two types of cells found in the nervous system are called Neurons, or nerve cells and Glia or Neuroglia, which are specialized connective tissue cells. Neurons conduct impulses and glia support neurons. There are three types of neurons, classified by the direction in which they transmit impulses. Sensory neurons transmit impulses to the spinal cord and brain from all parts of the body. Motor neurons transmit impulses in the opposite direction, away from the brain and spinal cord. Interneurons conduct impulses from sensory neurons to motor neurons.
Lea Morgan - Biological Illustration
A nerve is a group of peripheral nerve fibers bundled together, and nerves are called the white matter of the PNS because they have a protective sheath, called Myelin, which is white. A nerve impulse is a wave of electrical activity that travels along the surface of a neuron or nerve cell. Pressure, temperature, and chemical changes are the usual stimuli. The Synapse is the place where impulses are transmitted from one neuron to the next. The structure of the synapse contains a very small amount of Neurotransmitter, chemicals by which neurons communicate. Specific neurotransmitters are located in groups of neurons and released in specific pathways. Some examples of neurotransmitters include Acetylcholine, norepinephrine, dopamine, and serotonin. Two morphinlike neurotransmitters called Endorphins and Enkephalins inhibit conduction of pain impulses.
When we cope with stress of any kind, like strenuous exercise or experiencing strong emotions, the sympathetic nervous system is activated. This coping mechanism is also known as the fight-or-flight response, and it involves many organs of the body. The parasympathetic nervous system, in contrast, usually involves response by just one organ, and operates under normal, everyday conditions.
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The Skeletal System The Muscular System The Nervous System The Digestive System The Respiratory System |
The Endocrine System The Lymphatic System The Urinary System The Reproductive System |
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