Understanding the Nervous System: Neurons, Impulses, and Receptors

Understanding the Nervous System

The nervous system is responsible for processing received information and generating appropriate responses. It connects with sensory receptors that receive stimuli and effector organs that execute the response.

Sensory Receptors

Receptors are specialized cells that capture stimuli and translate them into nerve impulses. Neurons are somewhat modified or non-nerve cells that connect chemically or electrically with other neurons.

Types of Receptors:

• Exteroceptors: Detect external stimuli.
• Interoceptors: Detect internal stimuli.
• Proprioceptors: Detect body position and movement.

Types of Neurons

Neurons can be classified in several ways:

By Number of Extensions:

• Monopolar: One extension.
• Bipolar: Two extensions.
• Multipolar: Multiple extensions.

By Function:

• Sensory Neurons: Capture and transmit sensory stimuli.
• Motor Neurons: Produce motor responses to stimuli.
• Interneurons: Conduct impulses between neurons.

Glial Cells

Glial cells, collectively called neuroglia, support and guide neurons. They eliminate some neurons, provide nutrients from the blood, and supply them to the neurons that need them.

Schwann Cells and Myelin Sheath

Schwann cells are glial cells that produce a fatty substance called myelin. They wrap around the axons of some neurons and form a myelin sheath, which increases the speed of nerve impulse conduction.

Nerve Impulse Generation

A nerve impulse is usually caused by alterations in the neuron's body due to a stimulus, which responds by releasing neurotransmitters. These chemical messages cause a change in the axon membrane that triggers the transmission of electrical signals.

Synaptic Transmission

Communication from one neuron to another occurs at the synapse, allowing alteration and communication between neurons. This interaction may be electrical or chemical. The electrical impulse can pass directly from one neuron to another.

Presynaptic to Postsynaptic Communication

To transmit the nerve impulse, the arrival of the impulse to the terminal bulbs causes the displacement of presynaptic vesicles to the neuronal membrane and their subsequent opening. Neurotransmitters are released into the synaptic space and then diffuse to membrane receptors, where they bind. This binding allows sodium to permeate the membrane of postsynaptic elements, resulting in depolarization of the second neuron, which then conducts a nerve impulse.