The Nervous System

The Nervous System: An Overview

  • The nervous system regulates the body’s responses to its environment and controls all body functions.
  • It is divided into the central nervous system (CNS) and the peripheral nervous system (PNS).
  • The CNS comprises the brain and spinal cord, while the PNS includes all nerves outside the CNS.
  • It operates via a network of nerve cells known as neurons, each consisting of a cell body, axon, and dendrites.

Neurons and Neurotransmitters

  • Neurons are specialised cells that carry electrical signals, or impulses, around the body.
  • They communicate via small gaps called synapses, where electrical signals are converted into chemical signals called neurotransmitters.
  • An action potential triggers the release of neurotransmitters into the synapse, initiating the signal’s continuation.
  • Neurotransmitters attach to receptors on the next neuron, causing a new action potential.

Central Nervous System (CNS)

  • The brain controls higher functions like emotions, creativity, memory, and learning.
  • It processes sensory information from sense organs to make decisions about how the body should respond.
  • The spinal cord is a major pathway for impulses passing up to the brain or down from the brain to the rest of the body.
  • It also controls some automatic responses known as reflex actions.

Peripheral Nervous System (PNS)

  • The PNS connects the CNS to every other part of the body.
  • It contains two main types of neuron: motor neurons and sensory neurons.
  • Motor neurons carry signals from the CNS to muscles or glands, leading to a response.
  • Sensory neurons carry signals from sensory receptors to the CNS for processing.

Autonomic and Somatic Nervous Systems

  • The PNS is further divided into the autonomic and somatic systems.
  • The autonomic system controls involuntary actions like heart rate and digestion.
  • It’s divided into the sympathetic and parasympathetic systems, which often have opposite effects on organs.
  • The somatic system controls voluntary actions involving skeletal muscles.

Disorders of the Nervous System

  • A variety of disorders can affect the nervous system, including Alzheimer’s disease, Parkinson’s disease, and multiple sclerosis.
  • These disorders can result in symptoms ranging from muscle weakness and movement problems to changes in mood, memory, and behaviour.
  • Alzheimer’s disease is characterised by the formation of plaques and tangles in the brain, leading to cell death.
  • Parkinson’s disease is caused by a deficiency of the neurotransmitter dopamine, causing symptoms such as tremors and rigidity.
  • In multiple sclerosis, the immune system attacks the protective covering of nerve fibers, resulting in communication problems between the brain and the rest of the body.