The Human Nervous System

labeled parts of the human nervous systemLike other higher vertebrates, the human nervous systems has two main parts – the central nervous system (CNS) and the peripheral nervous system (PNS).

The central nervous system consists of the brain and the spinal cord. Its function is to send messages from the brain to other cells in the body and back again.

First, let’s look at the brain – or cerebrum. It is covered by an outer layer called the cerebral cortex. The cerebral cortex is much more complex in humans than in other mammals which also have a cerebral cortex.

Four main sections make up the cerebral cortex. They are described below:

1. The frontal lobe is located at the front of the brain. Expressive language, reasoning, motor control, and higher level understanding happen here. Other lobes of the brain send messages to the frontal lobe allowing the brain and body to carry our movements.

labeled lobes of the brain2. The parietal lobe is the middle section of the brain and is responsible for processing certain sensory messages such as touch, pressure, and pain.

3. The occipital lobe is the back of the brain. Vision – interpreting visual stimuli – is a main function of this lobe.

4. The temporal lobe is the brain’s bottom section. The hippocampus, which is a small curved formation in the brain associated with learning, memory, and emotion, is located in this lobe which is also responsible for hearing or interpreting sounds.

sympathetic nervous system labeled partsBesides the brain, which is protected by the skull and cerebrospinal fluid, the central nervous system also includes the spinal cord which is protected by the vertebrae.

The peripheral nervous system is mostly made of nerves situated throughout the body. Motor neurons are involved with voluntary movement while involuntary functions are regulated by the autonomic nervous system within the PNS. The autonomic system is separated into three different systems – the sympathetic nervous system and the parasympathetic nervous system which both deal with involuntary functions and the enteric nervous system with controls the gastrointestinal system.

Nerve cells are called neurons. They send signals via electrochemical waves which travel along axons which are long thin fibers. Chemicals called neurotransmitters are released at junctions called synapses. Other specialized cells within the nervous system are glial cells which provide structural and metabolic support.