No other fabric illustrates the concept of teamwork as well as nervous tissue. The transmission of information by nerve cells resembles a true relay race, in which one neuron is connected to another, each playing a role in the circuit they organize.
Three types of neurons can be recognized regarding their activity:
- Sensory neurons: transmit impulses from the sensory receptors (for example, in the sense organs) to other neurons in the pathway.
- Association neurons (interneurons): They get the message from the sensory neurons, process it, and transfer a command to the next nerve cells in the circuit. Some nerve circuits may not have this type of neuron.
- Effector neurons (or motors): they are the ones that transmit the message to the response effector cells, that is, muscle or glandular cells that respond by contraction or secretion, respectively.
Suppose you get a knock to the knee just below the kneecap or patella (names given to a bone in front of the knee).
The blow stimulates a receptor located inside the thigh muscle (the quadriceps). This receptor is attached to the dendrites of a sensory neuron - afferent - also called sensory neuron, which receives the message and forwards it to the cell body and from it to the axon. In turn, the sensory neuron axon establishes a synapse with a motor neuron - efferent (a response neuron).
The motor neuron axon is connected to the quadriceps muscle and forwards the "move" response. Immediately this muscle contracts and you move your leg. Note that moving your leg forward involves the work of only two neurons: the sensory and the motor. However, for this to happen, the posterior thigh muscle must remain relaxed.
Then, at the same time, the sensory neuron axon establishes a synapse with an interneuron (association neuron) which, in turn, makes a connection with a second motor neuron. The axon of this motor neuron travels to the posterior thigh muscle, inhibiting its contraction.
Nervous System Organization
Two major components are part of the human nervous system: central nervous system (CNS) it's the peripheral nerve system (PNS).
O central nervous system is formed by brain and for spinal cord. The brain is composed of several organs, including the two cerebral hemispheres (jointly known as the "brain"), the diencephalon, the cerebellum and the bulb. The brain and spinal cord are the places to which all information gathered by the organism is sent, whether originating from the external environment or from the organism itself. They are also the centers for processing this information and elaborating answers.
O peripheral nervous system includes the receivers throughout the body, besides the nerve ganglia and all nerves that arrive at the central organs bringing information or that originate from them, taking answers.