Understanding the Endocrine and Nervous Systems
The Endocrine System
The endocrine system functions as a coordinator, producing chemical messengers called hormones that control the body’s growth, development, and nutrient content. It is also important in the regulation of behavior. The endocrine system consists of a set of glands that secrete their products into the bloodstream.
Human Hormones
Hormones are natural substances, either lipid or protein-based, that travel through the bloodstream. They function as “chemical messengers” that regulate different functions in the body at a distance. They exert their action on cells, controlling and coordinating operations.
- They are very effective. Only a very small amount of a hormone is needed to fulfill its function.
- Their production is controlled. An excess or deficit of a hormone can cause illness.
- They are specific. Each hormone exerts its action on certain cells that respond specifically to it.
How Hormones Act
Hormones are produced by glands and released into the bloodstream. The action of hormones is characterized by its own specificity: although hormones reach all organs of the body, they exert their action only on a few. This phenomenon occurs because only the target organ cells have specific proteins on their outer membrane that recognize the hormone, triggering a response. These proteins are called hormone receptors and are specific to each hormone. When a hormone encounters its receptor, it binds to it through a mechanism similar to a key and a lock, triggering a biological response. For example, adrenaline regulates heart rate and respiration. The binding of adrenaline to adrenergic receptors in heart cells causes an increase in heart rate.
Hormonal Balance
The endocrine glands produce hormones at a rate that varies depending on the body’s needs. Endocrine activity is controlled by the pituitary gland, the director of the hormonal system. The pituitary is a small gland located at the base of the brain, which controls the functioning of other glands.
Nervous System
The nervous system processes messages from outside and inside the body and produces messages that control body functions. It coordinates the responses of the osteo-articular-muscular, immune, and endocrine systems. Depending on the organs that compose them, a central nervous system and a peripheral nervous system are distinguished.
Central Nervous System
The central nervous system is formed by the spinal cord and brain. It is protected by membranous envelopes called the meninges, the bones of the skull, and the vertebrae.
The Synapse
The contact between two neurons is called a synapse. Synapses involve a presynaptic neuron, from which the impulse is generated at the source of the axon, and a postsynaptic neuron, which receives impulses from different presynaptic neurons in its dendrites. At the end of the axon of the presynaptic neuron is a structure called the synaptic button, which contains vesicles with chemicals called neurotransmitters.
Reflex Arc
This refers to the path that a stimulus takes to generate a response. The stimulus reaches the sensory neuron, and the connection neuron generates a response. An example of a reflex is when we get something in our eye, like trash, and we close it quickly.