The nervous system consists of the brain, spinal cord and nerves. It is a complex system serving as a communication centre of the entire human body. It controls and coordinates all body parts. It is responsible for memory, thinking, reason, learning, emotions, drives, creativity, intuition, consciousness, sensation and movement. It also controls visceral functions and the whole endocrine system.

The nervous tissue is made up of two types of cells, neurons and neuroglia. Neurons transmit impulses, while neuroglia protect and nourish neurons. There are three types of neurons. Motor neurons transmit the information from the central nervous system to the effectors, e.g. muscles. Sensory neurons send the information from the receptors in the sensory organs and the skin to the brain. Interneurons transport impulses within the central nervous system.

Each neuron consists of the soma (cell body) with a nucleus, dendrites and an axon. A dendrite receives the message and carries it into the cell. One neuron can have hundreds of dendrites. In contrast, an axon carries the message away from the neuron. Each neuron has usually one axon. The axon is covered in myelin. This substance protects the axon and it also speeds up the impulse transmission. At the end of the axon there are axon terminals (endings) connecting to the dendrites of other neurons. The place of connection is called a synapse.

The nervous system is functionally divided into two parts, the central and peripheral nervous system. The CNS is formed by the brain and the spinal cord, while the PNS is made up of the cranial and spinal nerves. The peripheral nervous system can be further divided into the somatic and the autonomic nervous systems. The first one controls the voluntary functions, such as muscles. The other one controls all visceral (involuntary) functions. The autonomic nervous system consists of the sympathetic and parasympathetic nervous system. The sympathetic system increases the vital functions when we face stress (e.g. pulse, respiratory rate and blood pressure). The parasympathetic one decreases these functions when our body is at rest (e.g. while sleeping).

The brain is located in the cranium and it is protected by three membranes called meninges (dura mater, arachnoid, pia mater). Between these meninges there is cerebrospinal fluid, which protects and nourishes the nerve tissue, keeps it healthy and removes all waste products.

The largest part of the brain is called the cerebrum. This part makes us who we are: our intelligence, memory, personality, emotions, speech, and ability to feel and move. Specific areas of the cerebrum process specific type of information. These areas are called lobes: the frontal, parietal, temporal and occipital. The frontal lobes are concerned with speech, thinking, imagination, planning and reason, the parietal lobes with movement and sensory impulses coming from the skin and sensory organs, the occipital lobes with vision and the temporal lobes with hearing and memory.

The cerebrum is divided into the right and left hemispheres. These are joined by the part called corpus callosum. The left hemisphere controls the right side of the body and it is considered to be logical and analytical. The right hemisphere controls the left side of the body and it is thought to be more intuitive and creative.

Below the cerebrum sit the thalamus, hypothalamus and pituitary gland. The thalamus looks like two eggs. It works as a main relay station of the brain. It carries messages from the sensory organs like the eyes, ears, nose and fingers to the cerebral cortex. Around the thalamus, there are structures forming a limbic system, which is responsible for our sexual drive, behaviour, emotions, instincts and intuition.

The hypothalamus is located below the thalamus. It controls the pulse, thirst, appetite, sleep patterns, and other processes in our bodies that happen automatically. It forms a link between the nervous and endocrine systems because it is connected to the pituitary gland. This gland produces hormones that control our growth, metabolism, digestion, sexual maturity, water and mineral balance in the body and response to stress.

The pons, medulla oblongata and midbrain are often called together the brainstem. The brainstem takes in, sends out, and coordinates all of the brain's messages. It also controls many of the body's automatic functions, such as breathing, heart rate, blood pressure, and some reflexes like swallowing and vomiting.

The cerebellum is also called the ´little brain´ because it looks like a small version of the cerebrum. It is responsible for balance, movement and coordination.

The spinal cord runs down the vertebral column. It is covered by the same three meninges and the cerebrospinal fluid like the brain. The spinal cord passes the nerve impulses from the PNS to the CNS and the other way round. However, it can bypass the brain in reflex actions.

On a cross-section, the cord looks like a butterfly. The butterfly is in the middle and it is formed by the grey matter. In contrast, the outer layer is made up of the white matter.

The peripheral nervous system is made up of cranial and spinal nerves. These provide communication between the CNS and the peripheral organs. Unlike the brain and the spinal cord, the nerves are not protected by bones, meninges or cerebrospinal fluid, so they are exposed to injuries.

There are 12 pairs of cranial nerves and 31 pairs of spinal nerves. The cranial nerves connect to the brain directlly, not through the spinal cord. They carry sensory impulses from the area of the head and neck into the brain and motor commands out of the brain.

Spinal nerves emerge from the spinal cord. Each nerve divides into dorsal and ventral branches. The dorsal branches control the rear part of the body, while the ventral branches serve the front and sides. Nerves can join together and form plexuses. There are four main spinal nerve regions. The cervical region commands the head, chest and arms. The thoracic region serves the chest and abdomen. The lumbar region controls the lower abdomen and legs. The sacral region is responsible for legs, buttocks and genitals.

Each nerve can conduct impulses in only one direction. Sensory nerves conduct impulses toward the CNS (afferent) and the motor nerves conduct impulses from the CNS to the peripheral organs (efferent).

We divide the PNS into the somatic and autonomic subsystems. The somatic nervous system carries impulses to and from the parts of the body such as skeletal muscles and skin. They control voluntary movement. The stimuli are detected by receptors in the skin, sensory organs and skeletal muscles. Impulses are then transmitted by sensory neurons into the CNS. Inside the CNS, the sensory information is interpreted and the response is conducted by motor neurons to the skeletal muscles, which contract.

The autonomic nervous system regulates the activities of smooth (visceral or involuntary) muscles of organs, the heart, blood vessels and glands. When receptors detect changes in organs, impulses are conducted to the CNS. In the brain, a response is developed. Impulses are then carried to effectors, such as glands, heart and smooth muscles and they perform the command.

The autonomic nervous system is functionally divided into the sympathetic and parasympathetic nervous systems. In general, the sympathetic NS controls activities that help the body cope with stress. In contrast, the parasympathetic NS controls activities that support the body while at rest.