Human Nervous System

How does regulatory system work? Human body requires a device to coordinate all of the activities, so that all parts of the body can work together. The ability that enables various activities to work all together without overlapping is called regulatory system. There are two types of body system that work together as regulatory system, namely nervous system and endocrine system.

Human Nervous system

Nervous system is the organ system which regulates or controls other organ systems. It is also responsible for knowledge and memory of a human. The smallest functional unit which composes human nervous system is neuron (nerve cell) which consists of cell body (pericarion), dendrite, and axon. In one cell body, there is only one axon, while the number of dendrite existing in a cell body can reach about 200.

Based on the structure, nerve cell can be distinguished into three types, which are as follows.

1. Motor nerve cell (efferent) comprises of motor nerve fibers which have the function to transmit impulse from brain or spiral cord to peripheral nerve and to activate the muscle.
2. Sensory nerve cell (afferent) comprises of sensory nerve fibers which have the function to transmit impulse from peripheral nerve toward the brain. The impulse is in the form of taste and sensation stimulations.
3. Mixed nerve cell (commisural) functions to connect central nerve in brain with the spinal cord.
4. Association nerve cell (commisural) functions to connect central nerves in the brain with the spinal cord.

The interconnection between nerve cells is formed in central nervous system or in the ganglion (nerve node). In reality, however, nerve fibers of neuron are not actually connected to each other, they are separated by a connector called synapse. Therefore, when impulse transmits from one nerve to another, It has to pass through synapses and dendrite activation of the next cells.

Synapse functions as a connecting site between neurons or between neuron and effector. Synapse consists of three parts, presynapse, pascasynapse, and synapse vesicle, which separates presynapse and pascasynapse.

Based on the nerve impulse that passes it trough, synapse is distinguished into electrical synapse and chemical synapse and chemical synapse.

1. Electrical synapse is the synapse that is passed through by electric current impulse in between the neurons. Electrical synapse is formed between two dendrites, axon and dendrite, or two axons.
2. Chemical synapse is the synapse that is passed through by chemical impulse called neurotrassmiter. Neurotrasmitter is a hormone produced by neuron and secreted into synapse vesicles. Chemical synapse is usually found between neuron and effector.

The communication between neurons occurs when one electrical impulse passes through the axon toward the synapse end. One electrical impulse will generate vesicle containing neurotransmitter to move toward presynapse membrane, then the vesicle membrane will fuse with presynapse membrane and release neurotransmitter molecules into synapse vesicles. The neurotransmitter molecules will bind with receptor of pascasynapses and stimulate it to transmit impulse to another neuron

The nerve cell which is not carrying impulse contains electric current. The outer part of cell membrane has positive charge while the inner part has negative charge. The cell is called polarized cell. When is impulse passes through. Afterward, polarization will return to the initial condition. Polarity alteration is influenced by sodium-potassium balance. Impulse flow along nerve cells uses electrochemical energy.

Human nervous system (vertebrate in general) consist of central nervous system and peripheral nervous system.

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