Biology - The Nervous System (Brain, Spinal cord, Reflex action)

The Nervous System is divided into the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The CNS consists of the Brain and the Spinal Cord.

The basic unit of the nervous system is the Neuron (nerve cell), consisting of the Cyton (cell body), Dendrites, and a long Axon.

Transmission of nerve impulses occurs through a junction called the Synapse, where chemical neurotransmitters like Acetylcholine facilitate the signal transfer.

The Brain is protected by the cranium and three membranes called meninges, with Cerebrospinal Fluid ($CSF$) acting as a shock absorber.

The Cerebrum is the largest part of the brain, responsible for intelligence, memory, and voluntary actions.

The Cerebellum (little brain) is located below the cerebrum and coordinates muscular activities and maintains body balance and posture.

The Medulla Oblongata is the posterior-most part of the brain that controls involuntary actions like $heartbeat$, $breathing$, and $peristalsis$.

The Spinal Cord is the extension of the medulla, protected by the vertebral column, and serves as the center for reflex actions.

A Reflex Action is an automatic, sudden response to a stimulus without the conscious thought of the brain.

The Reflex Arc is the shortest pathway taken by a nerve impulse to complete a reflex action: $Stimulus \rightarrow Receptor \rightarrow Sensory \ Neuron \rightarrow Spinal \ Cord \rightarrow Motor \ Neuron \rightarrow Effector \rightarrow Response$.