If I was boiling a pot of water and reached over to turn the burner off. In doing so, my arm brushes against the hot kettle and I get burned. From the perspective of my nervous system there are several things that take place.
Pain is detected in my arm by a nerve cell, or sensory neuron, that carries messages from the senses toward the central nervous system. The central nervous system consists of my brain and spinal cord. When I feel the pain, neurons have been triggered near the soma and cross their threshold. Then it travels from the dendrite and soma, to the branching end of the axon. Axons are made up of fiber and carry messages through my brain and central nervous system. I have about 3 million miles of axons in my brain. The axons in my body branch out into smaller fibers which have bulb-shaped ends, also known as axon terminals. The information is transferred from neuron to neuron by way of these axon terminals because it allows a connection to other neuron’s dendrite and soma. When enough neurons are excited they cross their threshold and create nerve impulses. A nerve impulse occurs when a neuron’s molecules open up and allow ions from another neuron to affect its electric charge by way of ion channels, or tunnels piercing all the way to the axon membrane.
Since I was burned, many neurons suddenly became positively charged which raised the resting potential of the neurons in the place I was burned to action potentials. The potential changes from having a negative electric charge to having a positive electric charge, which creates action potentials, or nerve impulses. When enough neurons become action potentials, a nerve impulse shoots down the axons at a rapid speed. Electrically charged molecules within a neuron, flow in and out of the axon, sending the message that I have been burned throughout my body.
Some axons are coated with a fatty layer called myelin. Small gaps in the myelin help nerve impulses move faster. Instead of passing down the entire length of the axon through each neuron, the action potential leaps from gap to gap. An action potential reaches the tips of the axon terminals, and neurotransmitters are released into the synapse. This is the space between neurons where messages are passed.
Neurotransmitters are chemicals that alter activity in neurons. What happens when chemical molecules cross over a synapse? A receptor site, or receiving area, on the next neuron senses the neurotransmitters, and either the neuron excites the activity of the neurotransmitters. When enough neurons are excited a neural network within the central nervous system is produced. Our spine is made up of bundles of axons covered with myelin and consists of peripheral nervous system nerves. The spine connects these nerves to the brain.
The pain of being burned is detected by a sensory neuron which immediately fires off a message to my spine. Inside my spine, the neuron synapses with a connector neuron which activates a motor neuron and carries the message from the central nervous system to muscles and glands. Muscle fibers are made up of effector cells that make it capable of initiating responses. The muscles then contract and cause me to pull my hand back. This is done without the use of the brain because the pain provoked an automatic response, or reflex arc, within my spinal cord. A reflex arc is a nerve impulse that travels to the spinal cord and then to the muscle, causing it to contract and pull my hand back.
I don’t cuss, I cry instead.
Coon, D., & Mitterer, J. O. (2008). Introduction to Psychology: Gateway to Min and Behavior. Retrieved from www.coursmart.com.