Human Coordination Systems: Nervous and Endocrine
Coordination Systems
People perform different functions: we move, breathe, digest food, excrete waste substances, and so on. To perform all these functions, we need to interact with the environment, both externally and internally. Using the function of relationship, people, like all other living things, receive information and prepare responses.
To perform the function of relationship, people need to have a coordination system that allows us to detect changes that occur in the environment, analyze them, and respond by developing appropriate responses. This is achieved through two systems:
- The nervous system: It consists of nerve tissue, produces quick and short-lived responses. It acts through nerve impulses that travel along nerves.
- The endocrine system: It consists of endocrine glands and produces very slow but durable responses. It acts through chemical messengers called hormones that travel through the blood to the cell or body, acting on it.
Both systems run and regulate all bodily activities, and are closely interrelated, acting in an integrated manner.
Elements Involved in Coordination
In both systems of coordination, a process occurs from when we receive a stimulus to when we provide a response. This involves different components, which sequentially are:
- Receiver: A structure capable of perceiving stimuli and transmitting them to the nerve centers. The sense organs are receptors that pick up stimuli from outside the body. A stimulus is any change, both outside and inside the body, capable of provoking a response from the body. It can be pain, a sound, etc.
- Nerve center: The body responsible for receiving information received by the receivers, processing it, and preparing and transmitting a series of responses to the effector organs.
- Effector: The body responsible for carrying out the response. There may be two types of effectors, which develop two different response rates:
- Muscle: Produces a motor response, which involves movement.
- Gland: Causes a secretory response, involving the secretion of some substance.
Components of the Nervous System
The nervous system consists of two cell types: neurons and glial cells.
Neurons
Neurons receive and transmit signals. The transmission of these signals is performed by nerve impulses and occurs as a result of certain changes in the plasma membrane of the neuron. The nerve impulse always travels in the same direction. It is generated in a dendrite by way of electric waves, runs throughout the neuron, and out the axon.
Neurons are not touching each other, but between them, there is a buffer zone called synapses. Typically, synapses are established between the terminal branches of the axon of one neuron and the dendrites or cell body of another. The transmission of nerve impulses across the synapse is made by chemical mediators called neurotransmitters. When the nerve impulse reaches the end of the axon, neurotransmitters are released at the synaptic cleft extensions. They bind to the membrane of the dendrite or cell body of the next neuron, which makes this initiate a new nerve impulse.
In their role, neurons are classified into three types:
- Sensory neurons: Carry information captured by the receivers to the central nervous system, i.e., to the brain and spinal cord.
- Motor neurons: Send the information from the central nervous system to the effectors, causing muscle contraction or secretion of the glands.
- Association neurons or interneurons: They are part of the central nervous system. Sensory neurons are connected with the motor neurons.
Glial Cells
Glial cells are interspersed among the neurons, which they protect, isolate, or feed. The main glial cells are astrocytes, which nourish neurons, and Schwann cells, which are wrapped around the axons of certain neurons, forming the insulating cover of myelin.