1. The Neural System:

The neural system, also known as the nervous system, is a complex network of specialized cells that play a fundamental role in controlling and coordinating bodily functions. It is responsible for receiving, processing, and responding to various stimuli, allowing organisms to interact with their environment and maintain internal balance.

2. The Neuron - Structural and Functional Unit:

The neuron, often called a nerve cell, is the structural and functional unit of the neural system. Neurons are specialized cells that transmit electrochemical signals, known as nerve impulses or action potentials, from one part of the body to another. Each neuron has three main parts: the cell body (soma), dendrites, and an axon.

3. Axon:

The axon is a long, slender projection extending from the neuron’s cell body. It serves as a conducting pathway for nerve impulses, allowing them to travel away from the cell body and toward other neurons, muscles, or glands. The axon is covered by a myelin sheath, which acts as an insulator and speeds up the transmission of nerve impulses.

4. Generation and Conduction of Nerve Impulse:

The generation and conduction of a nerve impulse are essential for communication within the nervous system. Nerve impulses are initiated when a stimulus triggers a change in the electrical charge across the neuron’s membrane. This change, known as an action potential, travels down the axon to transmit information.

5. Three Kinds of Neurons:

In the neural system, there are three main types of neurons:

• Sensory Neurons: These neurons transmit sensory information from sensory receptors (e.g., in the skin, eyes, ears) to the central nervous system (CNS).
• Interneurons: Found exclusively in the CNS, interneurons act as connectors and process information between sensory and motor neurons.
• Motor Neurons: Motor neurons transmit signals from the CNS to effectors, such as muscles and glands, to produce a response.

6. The Key Important Fact About Ion Channels:

Ion channels play a crucial role in the generation and conduction of nerve impulses. These specialized proteins are embedded in the neuron’s membrane and control the flow of ions (charged particles) across the membrane. Ion channels are vital for maintaining the resting membrane potential and initiating action potentials.

7. Transmission of Impulses:

The transmission of impulses from one neuron to another occurs at specialized junctions called synapses. Neurotransmitters, chemical messengers, are released from the axon terminals of one neuron and received by the dendrites of the next neuron. This transmission is essential for information transfer between neurons.

8. Synaptic Transmission Across a Chemical Synapse:

At a chemical synapse, the process of synaptic transmission involves several key steps:

• Action potential reaches the axon terminal.

• Voltage-gated calcium channels open, allowing calcium ions to enter the neuron.

• Calcium ions trigger the release of neurotransmitters into the synaptic cleft.

• Neurotransmitters bind to receptors on the postsynaptic neuron, leading to a change in its membrane potential.

• If the membrane potential reaches the threshold, a new action potential is generated in the postsynaptic neuron.