Nervous
System
• Enzymes – control the rate of biochemical reactions. The two kinds of biochemical reactions are digestion and synthesis. We focused on enzymes as being vital to the function of your digestive system.
• Antibodies – seek out antigens, disable and mark them for destruction. Each antigen has a different shape, so there must be a different antibody for each foreign invader organism. Antibodies are vital to the function of the immune system.
• Hormones – chemical messages from one cell to another (far away). Hormones signal their target cells to change their behavior. The target cells are the only cells affected because they have the matching receptors to the shape of the hormone molecule. Hormones are vital to the function of the endocrine system.
• Neurotransmitters – chemical messages from one neuron to another across the synapse, or the space between two neurons (very very small). Neurotransmitters are vital to the function of the nervous system.
• Body Temperature
• Amount of Carbon Dioxide in the blood
• Blood Sugar
• Hydration
• Blood Pressure
The nervous system monitors both the internal and external environments of the body and when conditions change and homeostasis is threatened, the endocrine system is signaled to respond to the change in order to restore homeostasis.
Monitoring and responding to threats to homeostasis is referred to as negative feedback. When information is received (feedback) that suggests that homeostasis has been threatened (that's a negative situation), your body needs to respond to maintain a healthy internal environment.
Both systems:
Communicate with other systems, coordinating their functions
Use chemical messages that have specific receptors on target cells
Differences between Endocrine and Nervous Systems:
Responses to endocrine signals are slower and last a longer time.
Responses to nervous impulses are more rapid and last a very short time.
• Central Nervous System: Brain and Spinal Cord
• Peripheral Nerves: Nerves are bundles of individual nerve cells (NEURONS).
Neurons function very similarly to electrical wires, sending electrical signals throughout your body, just as fast. Researchers can actually measure the strength of these signals in milliVolts. Some neurons can be quite long, running from the base of your spinal cord to the tips of your toes. Neurons do not have the ability to divide and reproduce.
Neurons can send signals, also called nerve impulses, to other neurons or to organs such as muscles and endocrine glands. They do not pass their electrical signal on by touching other cells, they send chemical messengers across the very short distance between them. These protein messages are called neurotransmitters, and the space between neurons is called the synapse. In order for the signal to cause a response in the target cell, there must be a receptor with a complementary shape to the neurotransmitter on the target cell's membrane.
Hormones circulate everywhere in the body and are received only by specific target cells that carry the complementary receptors on their cell membranes. For example, when in danger your adrenal glands on top of your kidneys release adrenaline. Adrenaline is a signal only for your heart muscle, so only those cells will have receptors in their membranes that match the shape of the adrenaline molecule.
One of the most important human hormones is insulin, which regulates the amount of sugar in the blood. This must be closely regulated; too much can lead to high blood pressure, too little can lead to loss of consciousness or even death. Here's how it works:
When blood sugar increases (after a meal usually), neurons in the pancreas detect the increase and other cells of the pancreas secrete insulin into the blood.
Glucose is too large a molecule to diffuse through the membrane of a cell without help. There are protein passageways in the membrane that are specifically designed to allow glucose to enter the cell, but they have a "door" that must be opened. INsulin is the signal that binds to these "doors" and opens them, allowing glucose IN to the cells.
When glucose leaves the blood and enters cells, the body's blood sugar levels decrease. The neurons in the pancreas continue to monitor the blood and they detect the decrease in blood sugar. Once the levels return to normal, the pancreas stops releasing insulin. If insulin production is not stopped, then blood sugar levels would continue to decrease to dangerously low levels.
overview of how glands and hormones work