Our body's building blocks are neurons; which basically are tiny nerve cells. There are three types of neurons; motor, sensory, and interneurons. Motor neurons carry outgoing information from the brain and spinal cord to muscle and glands. Sensory send information from the sensory receptors to the brain and spinal cord. Lastly, interneurons are neurons within the brain and spinal cord that communicate internally, and intervene between the sensory and motor inputs.
Parts of a Neuron
- Dendrites: receive messages from other cells
- Axon: passes messages away from the cell body to other neurons, muscles, or glands
- Myelin Sheath: covers the axon of some neurons, and helps speed neural impulses
- Terminal branches: form junctions with other cells
- Cell body: cell's life support center
Neurons transmit messages when stimulated by signals from our senses or when triggered by chemical signals from neighboring neurons. When they want to communicate, it forms an action potential. An action potential is the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell.
British physiologist Sir Charles Sherrington noticed that neural impulses were taking a long time to travel a neural pathway. Sherrington then discovered the meeting point between neurons, called a synapse.
The Nervous System
Our body’s speedy electro-chemical communications network is called our nervous system. The brain and spinal cord form the central nervous system (CNS), which communicates with the body’s sensory receptors, muscles, and glands via the PNS.
- Somatic Nervous System: enables voluntary control of our skeletal muscles; also called the skeletal nervous system
- Autonomic Nervous System: controls the glands and the muscles of the internal organs
- Sympathetic Nervous System: arouses
- Parasympatheic Nervous System: calms
The Endocrine System
The Endocrine System is the body's "slow" chemical communication system; a set of glands that secrete hormones into the blood stream. Hormones are chemical messengers that are produced by endocrine glands that travel through the bloodstream. Compared to the nervous system, the communication is slow, but the effect is long lasting. Their job is to keep everything in balance while responding to stress, exertion, and our own thoughts.
- Adrenal Glands: release epinephrine and norepinephrine; providing us with a surge of energy for fight or flight response.
- Pituitary Gland: releases hormones that influence growth and the release hormones by other endocrine glands.