Nervous System Overview

The Nervous System

• The nervous system has two main parts:
  • Central Nervous System (CNS): Composed of the brain and spinal cord, acting as the central processing unit (CPU)
  • Peripheral Nervous System (PNS): Consists of spinal nerves, their branches, and a network in internal organs. It acts as the input and output system for the CNS. The PNS carries signals between the CNS and other parts of the body.

Functional Units: Neurons

• The basic building block of the nervous system is the neuron.
• The human body contains over 100 billion neurons.
• Each neuron is comprised of a cell body, various branches (dendrites), and a main branch called the axon.
• The axon is the functional unit for transmitting signals.

Neuron Structure and Function

• Cell body: Responsible for metabolic processes within the neuron.
• Axon: The main conductor of impulses, transmitting signals away from the cell body.
• Dendrites: The input zone of the neuron, receiving signals from other neurons.

Nerve Cell Bodies

• Nuclei: Clusters of nerve cell bodies located inside the central nervous system (CNS).
• Ganglia: Clusters of nerve cell bodies situated outside the CNS.

Main Function: Conduction

• Neurons transmit information through electrical signals called action potentials.
• Information flows through neurons with dendrites collecting incoming electrical signals, the cell body integrating these signals, and the axon generating an outgoing signal to another neuron or effector cell.

Action Potential Transmission Methodology

• Specific gates in the axon membrane allow positively charged ions to pass, changing the membrane charges inside and outside the axon.
• There is a fast inward flow of sodium ions, which results in depolarization.
• Repolarization is a fast outward flow of potassium ions.

Glial Cells (Support Cells)

• Glia cells are support cells that surround and assist neurons.
• They provide structural and metabolic support, and insulation for neurons.
• In peripheral nerves, Schwann cells provide myelination.
• In the CNS, oligodendrocytes provide myelination.

Myelin Sheath

• Made by glia cells
• Acts as insulation (a fatty sheath)
• Allows faster transmission of action potentials by saltatory conduction, jumping from node to node.

Multiple Sclerosis (MS)

• A disease that damages the myelin sheath.
• Loss of myelin disrupts nerve signal transmission, causing various symptoms.
• MS has different classifications (ranging from benign to progressive forms)

Synapses

• Synapses are the junctions between neurons and/or neurons to muscle or glands.
• The synaptic gap is too wide for the action potential to cross, hence signal transmission occurs via chemicals called neurotransmitters.
• Neurotransmitters are released from the presynaptic neuron, cross the gap and bind with receptors in the postsynaptic neuron, triggering an action potential.

Transmitter Removal from Synapse

• Neurotransmitters are removed from the synapse by:
  • Enzymatic degradation
  • Reuptake into the presynaptic cell

Drugs

• External drugs can affect the nervous system by mimicking, increasing or blocking neurotransmitters.
• Drugs can alter neurotransmission by binding to receptors, affecting the release or degradation of neurotransmitters.

Explore the key components of the nervous system, including its two main parts: the Central Nervous System and the Peripheral Nervous System. Learn about the functional units, neurons, and their structures such as cell bodies, axons, and dendrites. This quiz highlights how signals are transmitted within the nervous system.