1.6 The Central Nervous System

Brain and Spinal Cord

The central nervous system (CNS) consists of the brain and spinal cord. It processes information from the body and environment, integrates it, and sends commands out. The spinal cord relays signals between the brain and peripheral nervous system and controls simple reflexes without needing brain input.

Neurons and Glial Cells

Neurons are specialized cells that transmit electrical and chemical signals throughout the CNS. Glial cells support neurons by providing structural support, insulation (via myelin), nutrients, and removing waste. Glial cells also assist in forming the blood-brain barrier, protecting the CNS from harmful substances.

Neural Communication Basics

Neurons communicate at synapses using neurotransmitters, chemicals released from the axon terminal that cross the synaptic gap to bind receptor sites on the next neuron. This process underlies all CNS functioning, from reflexes to complex thought, and can be disrupted by drugs or disease affecting neurotransmission.

Key terms

Central Nervous System (CNS)

The brain and spinal cord; processes and integrates information from the body and environment.

Spinal Cord

Relays messages between brain and body; controls reflexes independently of the brain.

Glial Cells

Support cells that insulate, nourish, and protect neurons; help form the blood-brain barrier.

Blood-Brain Barrier

A protective barrier that prevents harmful substances in the blood from entering brain tissue.

Neurotransmitters

Chemical messengers released at synapses that bind to receptor sites to transmit signals between neurons.

Try an AP-style question

The central nervous system consists of…

1. the sensory organs
2. all nerves in the body
3. the autonomic system
4. the brain and spinal cord